Microbial electrosynthesis (MES) is an innovative technology for electricity driven microbial reduction of carbon dioxide (CO2) to useful multi-carbon compounds. This study assesses the cradle-to-gate environmental burdens associated with acetic acid (AA) production via MES using graphene functionalized carbon felt cathode. The analysis shows that, though the environmental impact for the production of the functionalized cathode is substantially higher when compared to carbon felt with no modification, the improved productivity of the process helps in reducing the overall impact. It is also shown that, while energy used for extraction of AA is the key environmental hotspot, ion-exchange membrane and reactor medium (catholyte & anolyte) are other important contributors. A sensitivity analysis, describing four different scenarios, considering either continuous or fed-batch operation, is also described. Results show that even if MES productivity can be theoretically increased to match the highest space time yield reported for acetogenic bacteria in a continuous gas fermenter (148 g L−1 d−1), the environmental impact of AA produced using MES systems would still be significantly higher than that produced using a fossil-based process. Use of fed-batch operation and renewable (solar) energy sources do help in reducing the impact, however, the low production rates and overall high energy requirement makes large-scale implementation of such systems impractical. The analysis suggests a minimum threshold production rate of 4100 g m−2 d−1, that needs to be achieved, before MES could be seen as a sustainable alternative to fossil-based AA production.
The earlier in the development of a process a design change is made, the lower the cost and the higher the impact on the final performance. This applies equally to environmental and technical performance, but in practice the environmental aspects often receive less attention. To maximise sustainability, it is important to review all of these aspects through each stage, not just after the design. Tools that integrate environmental goals into the design process would enable the design of more environmentally friendly processes at a lower cost. This paper brings together approaches based on Life Cycle Assessment (LCA) including comparisons of design changes, hotspot analysis, identification of key impact categories, environmental break-even analysis, and decision analysis using ternary diagrams that give detailed guidance for design while not requiring high quality data. The tools include hotspot analysis to reveal which unit operations dominate the impacts and therefore should be the focus of further detailed process development. This approach enables the best variants to be identified so that the basic design can be improved to reduce all significant environmental impacts. The tools are illustrated by a case study on the development of a novel process with several variants: thermal cracking of mixed plastic waste to produce a heavy hydrocarbon product that can displace crude oil, naphtha, or refinery wax or be used as a fuel. The results justified continuing with the development by confirming that the novel process is likely to be a better environmental option than landfill or incineration. The general approach embodied in the toolkit should be applicable in the development of any new process, particularly one producing multiple products.
It is well accepted that the technical, financial and environmental performance of a chemical process is largely determined during design. Therefore, the development of tools that integrate environmental considerations would enable the design of more environmentally friendly processes at a lower cost. This research investigates how Life Cycle Assessment (LCA) can be applied at any stage in the design process to produce useful information for design, not just after the plant is operating, which is the norm for LCA. The tools have been applied to the development of a novel process (the RT7000): thermal cracking of mixed plastic waste to produce several hydrocarbon products with the potential to displace crude oil, naphtha, or refinery wax or be used as a fuel. To allow LCA to guide the design process, a toolkit methodology was developed including comparisons of design changes, hotspot analysis, identification of key impact categories, environmental break-even analysis, and decision analysis using ternary diagrams. The results of applying these tools justified continuing with the development by confirming that the novel process is likely to be a better environmental option than landfill or incineration. At the later stages of design, advanced tools such as process simulations become attractive and allow a more accurate estimation of material and energy flows. A simulation of the RT7000 in Aspen Plus® was developed that provided data for a wide range of feed compositions. The RT7000 continued to have lower environmental impact to incineration offering a saving equivalent to 969-1305 kgCO2/tonne plastic processed. It was also ascertained that variation in feed composition does influence environmental performance, but not enough to affect the outcomes of decision making. The general approaches used in this work to assess the RT7000 should be applicable to the development of any new process. Benefits and insights similar to those obtained in the case study can realistically be expected when these methodologies are applied to any new processes. Therefore the results have been published in the Journal of Cleaner Production (Gear et al., 2018)
The techno-economic potential of the UK poplar wood and imported oil palm empty fruit bunch derived bio-oil integrated gasification and Fischer-Tropsch (BOIG-FT) systems for the generation of transportation fuels and combined heat and power (CHP) was investigated. The bio-oil was represented in terms of main chemical constituents, i.e. acetic acid, acetol and guaiacol. The compositional model of bio-oil was validated based on its performance through a gasification process. Given the availability of large scale gasification and FT technologies and logistic constraints in transporting biomass in large quantities, distributed bio-oil generations using biomass pyrolysis and centralised bio-oil processing in BOIG-FT system are technically more feasible. Heat integration heuristics and composite curve analysis were employed for once-through and full conversion configurations, and for a range of economies of scale, 1 MW, 675 MW and 1350 MW LHV of bio-oil. The economic competitiveness increases with increasing scale. A cost of production of FT liquids of 78.7 Euro/MWh was obtained based on 80.12 Euro/MWh of electricity, 75 Euro/t of bio-oil and 116.3 million Euro/y of annualised capital cost.
The potential for generating renewable electricity from palm oil mill residues (POMR) has received policy support from the Malaysian Government for almost two decades. However, uptake of the technology is still relatively low. A significant issue dominating the discussion for many years is how to translate the renewable electricity generation potential from POMR into actual implementation. The research seeks to understand the opportunities and barriers for the use of POMR for a Renewable Electricity System (POMR-RES) in Peninsular Malaysia by assessing the technical, techno-economic and environmental feasibility of generating renewable electricity from palm oil mill residues focusing mainly on empty fruit bunches (EFB) and biogas. A combination of mathematical analysis and simulation using Aspen PlusTM software was employed to assess the technical feasibility of the system. Techno-economic analysis was combined with Life Cycle Assessment (LCA) to integrate the environmental impact perspective into the POMR-RES evaluation. The results show that EFB has better technical and techno-economic performance than the biogas. Furthermore, the on-site POMR-RES with an installed capacity of 5.70 MW or greater is technically feasible, economically viable and environmentally favourable. The electricity generated from a POMR-RES of this scale is sufficient to meet a mill’s operational electricity demand, the parasitic load of the POMR-RES and provide surplus electricity to the national grid. An economically feasible size POMR-RES are expected to provide: 1. a 20% return on investment (ROI) with five to seven-year payback period (PP). 2. a positive net present value (NPV) with break-even point (BEP) of five to seven-year. The electricity generated in POMR-RES emits 95% less GHG emissions compared with current Malaysian electricity grid average when the emission from LUC is excluded from the electricity generation process. Thirty-five mills in Peninsular Malaysia were identified as having sufficient EFB supply to operate at or above this economically feasible size with the total accumulated generation capacity of 200 MW. This accumulated capacity would account for 25% of the 2020 target for palm oil biomass under National Renewable Energy Policy and Action Plan. This research provides a positive case for generating local, renewable electricity from EFB that can be used as evidence and practical recommendations for various actors such as prospective investors, analysts, stakeholders, mill owners and policymakers and government agencies such as the Sustainable Energy Development Authority Malaysia (SEDA) for efficient and sustainable utilization of POMR. This study also makes a positive contribution towards achieving the national renewable energy target for additional renewable power supplies and as a contribution towards improved global sustainability.
Many manufacturing companies recognise the need to produce products that are cleaner, greener, and environmentally sustainable, yet they are only at the early stages of this transition in addressing the symptoms of unsustainability at their direct operations by reducing waste and the use of energy, water and material. The implementation of reductions in these areas can be disparate and minimal given the life cycle of a product. Bridging the gap between the rhetoric of sustainable manufacturing and reality requires a holistic, systems thinking approach to ensure the implementation of sustainability is unified and strategic. This paper presents a novel environmentally sustainable manufacturing framework that encompasses energy, water, waste, biodiversity, and people & community. It adopts a systems thinking perspective to address the factories ‘environmental life cycle impact to deliver factory and supply chain benefits. The insights from the application at a Nestlé confectionery factory are reported.
Life cycle Assessments (LCAs) of crude oil derived products such as fuels, petrochemicals and polymers benefit from robust inventories of emissions and consumptions of the specific ways in which the crude oil can be extracted and processed. It is known that there is variation of up to 30% or more in the Greenhouse gas (GHG) ‘footprint’ of different crude oils depending upon the different crude types, production systems, geographic location etc. It is also known that in a number of comparative LCA analyses between petrochemical products and bio-based alternatives there can be rather small differences (e.g. 10 – 20%) in the GHG emissions or other environmental impacts. The large potential range in emissions profile per unit of crude oil and the sometimes-small margin of difference between crude-oil based products and alternatives suggests that the specific route of crude production (and processing) will be an important factor in decision-making and policy centred on environmental criteria. The research in this thesis was conducted to examine the site-specific air emission data, with emphasis on VOCs, for crude oil production and how this could affect the results of LCAs of petrochemical products in comparison with the use of generic LCA database data to characterize the environmental profiles of such products. Company specific air emission data was collected from an upstream crude oil & gas company in Kuwait. The data collected was company available modelled data and new field measurements collected via the use of a mobile laboratory. This emission data was converted to specific substance emission values via Gaussian plume modelling and relating it to crude oil flows in the upstream facilities. Thereby new, specific LCI datasets for the air emissions of Kuwaiti crude oil were developed and deployed in LCAs to assess their effects on the environmental profiles of such crude oil and its end products. These LCAs demonstrated considerable heterogeneity in aspects of the environmental profile of the crude oils and example downstream end products driven by the specific LCI datasets for the various production systems examined.
Integrated gasification combined cycle (IGCC) power generation systems have become of interest due to their high combined heat and power (CHP) generation efficiency and flexibility to include carbon capture and storage (CCS) in order to reduce CO2 emissions. However, IGCC’s biggest challenge is its high cost of energy production. In this study, decarbonised coal IGCC sites integrated with CCS have been investigated for heat integration and economic value analyses. It is envisaged that the high energy production cost of an IGCC site can be offset by maximising site-wide heat recovery and thereby improving the cost of electricity (COE) of CHP generation. Strategies for designing high efficiency CHP networks have been proposed based on thermodynamic heuristics and pinch theory. Additionally, a comprehensive methodology to determine the COE from a process site has been developed. In this work, we have established thermodynamic and economic comparisons between IGCC sites with and without CCS and a trade-off between the degree of decarbonisation and the COE from the heat integrated IGCC sites. The results show that the COE from the heat integrated decarbonised IGCC sites is significantly lower compared to IGCC sites without heat integration making application of CCS in IGCC sites economically competitive.
The objective of this work was to design a heat integrated, cost-effective, and cleaner combined heat and power (CHP) generation plant from low-cost, fourth-generation biomass waste feedstocks. The novelty lies in the development of systematic sitewide heat recovery and integration strategies among biomass integrated gasification combined cycle processes so as to offset the low heating value of the biomass waste feedstocks. For the biomass waste based CHP plant technical and economic analysis, the process was based on low-cost agricultural wastes like straws as the biomass feedstock and further established for a more predominant biomass feedstock, wood. The process was modeled using the Aspen simulator. Three conceptual flowsheets were proposed, based on the integration of the flue gas from the char combustor, which was separately carried out from the steam gasification of biomass volatalized gases and tars, and carbon dioxide removal strategies. The cost of energy production included detailed levelized discounted cash flow analysis and was found to be strongly influenced by the cost of feedstock. On the basis of a combined energy generation of 340−370 MW using straw wastes priced at 35.3 £/t or 40 Euro/t, with 8.5% and 8.61% by mass moisture and ash contents, respectively, the cost of electricity generation was 4.59 and 5.14 p/(kW h) for the cases without and with carbon capture respectively, with a 10% internal rate of return and 25 years of plant life. On the basis of the carbon capture value assigned by the Carbon Credits Trading scheme, a much constrained viable price of 22 £/t of such agricultural waste feedstocks for CHP generation was obtained, while up to 60 £/t of waste feedstocks can be economically viable under the UK Climate Change Levy, respectively.
This paper, for the first time, reports integrated conceptual MBCT/biorefinery systems for unlocking the value of organics in municipal solid waste (MSW) through the production of levulinic acid (LA by 5wt%) that increases the economic margin by 110-150%. After mechanical separation recovering recyclables, metals (iron, aluminium, copper) and refuse derived fuel (RDF), lignocelluloses from remaining MSW are extracted by supercritical-water for chemical valorisation, comprising hydrolysis in 2wt% dilute H2SO4 catalyst producing LA, furfural, formic acid (FA), via C5/C6 sugar extraction, in plug flow (210−230°C, 25bar, 12s) and continuous stirred tank (195−215°C, 14bar, 20mins) reactors; char separation and LA extraction/purification by methyl isobutyl ketone solvent; acid/solvent and by-product recovery. The by-product and pulping effluents are anaerobically digested into biogas and fertiliser. Produced biogas(6.4MWh/t), RDF(5.4MWh/t), char(4.5MWh/t) are combusted, heat recovered into steam generation in boiler (efficiency:80%); on-site heat/steam demand is met; balance of steam is expanded into electricity in steam turbines (efficiency:35%).
This paper presents the first environmental life cycle analysis for a range of different confectionery products. A proposed Life Cycle Assessment (LCA) approach and multi-criteria decision analysis (MCDA) was developed to characterise and identify the environmental profiles and hotspots for five different confectionery products; milk chocolate, dark chocolate, sugar, milk chocolate biscuit and milk-based products. The environmental impact categories are based on Nestle's EcodEX LCA tool which includes Global Warming Potential (GWP), Abiotic Depletion Potential (ADP), ecosystems quality, and two new indicators previously not considered such as land use and water depletion. Overall, it was found that sugar confectionery had the lowest aggregated environmental impact compared to dark chocolate confectionery which had the highest, primarily due to ingredients. As such, nine key ingredients were identified across the five confectionery products which are recommended for confectionery manufacturers to prioritise e.g. sugar, glucose, starch, milk powder, cocoa butter, cocoa liquor, milk liquid, wheat flour and palm oil. Furthermore, the general environmental hotspots were found to occur at the following life cycle stages: raw materials, factory, and packaging. An analysis of five improvement strategies (e.g. alternative raw materials, packaging materials, renewable energy, product reformulations, and zero waste to landfill) showed both positive and negative environmental impact reduction is possible from cradle-to-grave, especially renewable energy. Surprisingly, the role of product reformulations was found to achieve moderate-to-low environmental reductions with waste reductions having low impacts. The majority of reductions was found to be achieved by focusing on sourcing raw materials with lower environmental impacts, product reformulations, and reducing waste generating an aggregated environmental reduction of 46%. Overall, this research provides many insights of the environmental impacts for a range of different confectionery products, especially how actors across the confectionery supply chain can improve the environmental sustainability performance. It is expected the findings from this research will serve as a base for future improvements, research and policies for confectionery manufacturers, supply chain actors, policy makers, and research institutes towards an environmentally sustainable confectionery industry.
Development of clean coal technology is highly envisaged to mitigate the CO2 emission level whilst meeting the rising global energy demands which require highly efficient and economically compelling technology. Integrated gasification combined cycle (IGCC) with carbon capture and storage (CCS) system is highly efficient and cleaner compared to the conventional coal-fired power plant. In this study, an alternative process scheme for IGCC system has been proposed, which encompasses the reuse of CO2 from the flue gas of gas turbine into syngas generation, followed by methanol synthesis. The thermodynamic efficiency and economic potential are evaluated and compared for these two systems. The performances of the systems have been enhanced through systematic energy integration strategies. It has been found that the thermodynamic and economic feasibilities have attained significant improvement through the realisation of a suitably balanced polygeneration scheme. The economic potential can be enhanced from negative impact to 317 M€/y (3.6 €/GJ). The results have demonstrated promising prospects of employing CO2 reuse technology into IGCC system, as an alternative to CCS system.
The biofuel mix in transport in the U.K. must be increased from currently exploited 3.33% to the EU target mix of 10% by 2020. Under the face of this huge challenge, the most viable way forward is to process infrastructure-compatible intermediate, such as bio-oil from fast pyrolysis of lignocellulosic biomass, into biofuels. New facilities may integrate multiple distributed pyrolysis units producing bio-oil from locally available biomass and centralized biofuel production platforms, such as methanol or Fischer–Tropsch liquid synthesis utilizing syngas derived from gasification of bio-oil. An alternative to bio-oil gasification is hydrotreating and hydrocracking (upgrading) of bio-oil into stable oil with reduced oxygen content. The stable oil can then be coprocessed into targeted transportation fuel mix within refinery in exchange of refinery hydrogen to the upgrader. This Article focuses on the evaluation of economic and environmental sustainability of industrial scale biofuel production systems from bio-oils. An overview of bio-oil gasification-based system evaluation is presented, while comprehensive process reaction modeling (with 40 overall bio-oil hydrocracking and hydrotreating reaction steps), simulation, integration, and value analysis frameworks are illustrated for bio-oil upgrading and refinery coprocessing systems. The environmental analysis shows that the former technologies are able to meet the minimum greenhouse gas (GHG) emission reduction target of 60%, to be eligible for the European Union (EU) Directive’s 2020 target of 10% renewable energy in transport, while at least 20% renewable energy mix from an upgrader is required for meeting the EU GHG emission reduction target. Increases in the price of biodiesel and hydrogen make coprocessing of stable oils from bio-oil upgrader using refinery facilities economically more favorable than final biofuel blending from refineries and create win–win economic scenarios between the bio-oil upgrader and the refinery. The range of the cost of production (COP) of stable oil (328 MW or 0.424 t/t bio-oil), steam (49.5 MW or 0.926 t/t bio-oil), and off-gas or fuel gas (72.3 MW or 0.142 t/t bio-oil) from a bio-oil (LHV of 23.3 MJ/kg) upgrader process is evaluated on the basis of individual product energy values and global warming potential (GWP) impacts. The minimum and the maximum annualized capital charges predicted by the Discounted Cash Flow (DCF) analysis correspond to 25 operating years and 10% IRR, and 10 operating years and 20% IRR, respectively. On the basis of this DCF strategy and 1200 $/t of hydrogen and 540 $/t of biodiesel market prices, the selling prices of 259.32 $/t, 34.85 $/t, and 174.27 $/t of the stable oil, steam, and fuel gas, respectively, from the upgrader to the refinery were obtained to create win–win marginal incentive for the upgrader and refinery systems, individually. If stable oil from a bio-oil upgrader can be launched as a product potentially to be used in refinery hydrocracker (at a competitive price of 490 $/t), for the production of renewable diesel, upgrader can be operated independently, such as purchase hydrogen from vendors at competitive price, with comparative marginal incentives. The bio-oil upgraders, either stand-alone or integrated, were designed to meet desired product specifications, diesel with specific gravity 0.825 and cetane number 57 and stable oil with API 30.1 and cetane number 28.7, for coprocessing through the refinery hydrocracker, respectively.
The heterogeneously catalyzed transesterification reaction for the production of biodiesel from triglycerides was investigated for reaction mechanism and kinetic constants. Three elementary reaction mechanisms Eley-Rideal (ER), Langmuir- Hinshelwood-Hougen-Watson (LHHW), andHattori with assumptions, such as quasi-steady-state conditions for the surface species andmethanol adsorption, and surface reactions as the rate-determining steps were applied to predict the catalyst surface coverage and the bulk concentration using a multiscale simulation framework. The rate expression based on methanol adsorption as the rate limiting in LHHW elementary mechanism has been found to be statistically the most reliable representation of the experimental data using hydrotalcite catalyst with different formulations.
A two-dimensional mathematical model has been developed for characterizing and predicting the dynamic performance of an air-cathode MFC with graphite fiber brush used as anode. The charge transfer kinetics are coupled to the mass balance at both electrodes considering the brush anode as a porous matrix. The model has been used to study the effect of design (electrode spacing and anode size) as well as operational (substrate concentration) parameters on the MFC performance. Two-dimensional dynamic simulation allows visual representation of the local overpotential, current density and reaction rates in the brush anode and helps in understanding how these factors impact the overall MFC performance. The numerical results show that while decreasing electrode spacing and increasing initial substrate concentration both have a positive influence on power density of the MFC, reducing anode size does not affect MFC performance till almost 60 brush material has been removed. The proposed mathematical model can help guide experimental/pilot/industrial scale protocols for optimal performance.
Purpose The aim of the paper is to assesses the role and effectiveness of a proposed novel strategy for Life Cycle Inventory (LCI) data collection in the food sector and associated supply chains. The study represents one of the first of its type and provides answers to some of the key questions regarding the data collection process developed, managed and implemented by a multinational food company across the supply chain. Methods An integrated LCI data collection process for confectionery products was developed and implemented by Nestlé, a multinational food company. Some of the key features includes: (1) management and implementation by a multinational food company, (2) types of roles to manage, provide and facilitate data exchange, (3) procedures to identify key products, suppliers and customers, (4) LCI questionnaire and cover letter, and (5) data quality management based on the pedigree matrix. Overall, the combined features in an integrated framework provides a new way of thinking about the collection of LCI data from the perspective of a multinational food company. Results The integrated LCI collection framework spanned across five months and resulted in 87 new LCI datasets for confectionery products from raw material, primary resource use, emission and waste release data collected from suppliers across 19 countries. The data collected was found to be of medium-to-high quality compared with secondary data. However, for retailers and waste service companies only partially completed questionnaires were returned. Some of the key challenges encountered during the collection and creation of data included: lack of experience, identifying key actors, communication and technical language, commercial compromise, confidentiality protection, and complexity of multi-tiered supplier systems. A range of recommendations are proposed to reconcile these challenges which include: standardisation of environmental data from suppliers, concise and targeted LCI questionnaires, and visualising complexity through drawings. Conclusions The integrated LCI data collection process and strategy has demonstrated the potential role of a multinational company to quickly engage and act as a strong enabler to unlock latent data for various aspects of the confectionery supply chain. Overall, it is recommended that the research findings serve as the foundations to transition towards a standardised procedure which can practically guide other multinational companies to considerably increase the availability of LCI data.
This paper presents material flow and sustainability analyses of novel mechanical biological chemical treatment system for complete valorization of municipal solid waste (MSW). It integrates material recovery facility (MRF); pulping, chemical conversion; effluent treatment plant (ETP), anaerobic digestion (AD); and combined heat and power (CHP) systems producing end products: recyclables (24.9% by mass of MSW), metals (2.7%), fibre (1.5%); levulinic acid (7.4%); recyclable water (14.7%), fertiliser (8.3%); and electricity (0.126 MWh/t MSW), respectively. Refuse derived fuel (RDF) and non-recyclable other waste, char and biogas from MRF, chemical conversion and AD systems, respectively, are energy recovered in the CHP system. Levulinic acid gives profitability independent of subsidies; MSW priced at 50 Euro/t gives a margin of 204 Euro/t. Global warming potential savings are 2.4 and 1.3 kg CO2 equivalent per kg of levulinic acid and fertiliser, and 0.17 kg CO2 equivalent per MJ of grid electricity offset, respectively.
Process to process material and heat integration strategies for bio-oil integrated gasification and methanol synthesis (BOIG-MeOH) systems were developed to assess their technological and economic feasibility. Distributed bio-oil generations and centralised processing enhance resource flexibility and technological feasibility. Economic performance depends on the integration of centralised BOIG-MeOH processes, investigated for cryogenic air separation unit (ASU) and water electrolyser configurations. Design and operating variables of gasification, heat recovery from gases, water and carbon dioxide removal units, water-gas shift and methanol synthesis reactors and CHP network were analysed to improve the overall efficiency and economics. The efficiency of BOIG-MeOH system using bio-oil from various feedstocks was investigated. The system efficiency primarily attributed by the moisture content of the raw material decreases from oilseed rape through miscanthus to poplar wood. Increasing capacity and recycle enhances feasibility, e.g.1350MWBOIG-MeOH with ASU and 90% recycle configuration achieves an efficiency of 61.5% (methanol, low grade heat and electricity contributions by 89%, 7.9% and 3% respectively) based on poplar wood and the cost of production (COP) of methanol of 318.1 Euro/t for the prices of bio-oil of 75 Euro/t and electricity of 80.12 Euro/MWh, respectively. An additional transportation cost of 4.28e8.89 Euro/t based on 100 km distance between distributed and centralised plants reduces the netback of bio-oil to 40.9e36.3 Euro/t.
Magnetite nanoparticles (MNPs) have several applications, including use in medical diagnostics, renewable energy production and waste remediation. However, the processes for MNP production from analytical-grade materials are resource intensive and can be environmentally damaging. This work for the first time examines the life cycle assessment (LCA) of four MNP production cases: (i) industrial MNP production system; (ii) a state-of-the-art MNP biosynthesis system; (iii) an optimal MNP biosynthesis system and (iv) an MNP biosynthesis system using raw materials sourced from wastewaters, in order to recommend a sustainable raw material acquisition pathway for MNP synthesis. The industrial production system was used as a benchmark to compare the LCA performances of the bio-based systems (cases ii-iv). A combination of appropriate life cycle impact assessment methods was employed to analyse environmental costs and benefits of the systems comprehensively. The LCA results revealed that the state-of-the-art MNP biosynthesis system, which utilises analytical grade ferric chloride and sodium hydroxide as raw materials, generated environmental costs rather than benefits compared to the industrial MNP production system. Nevertheless, decreases in environmental impacts by six-fold were achieved by reducing sodium hydroxide input from 11.28 to 1.55 in a mass ratio to MNPs and replacing ferric chloride with ferric sulphate (3.02 and 2.59, respectively, in a mass ratio to MNPs) in the optimal biosynthesis system. Thus, the potential adverse environmental impacts of MNP production via the biosynthesis system can be reduced by minimising sodium hydroxide and substituting ferric sulphate for ferric chloride. Moreover, considerable environmental benefits were exhibited in case (iv), where Fe(III) ions were sourced from metal-containing wastewaters and reduced to MNPs by electrons harvested from organic substrates. It was revealed that 14.4 kJ and 3.9 kJ of primary fossil resource savings could be achieved per g MNP and associated electricity recoveries from wastewaters, respectively. The significant environmental benefits exhibited by the wastewater-fed MNP biosynthesis system shows promise for the sustainable production of MNPs.
Bioelectrochemical systems (BESs) have been catalogued as a technological solution to three pressing global challenges: environmental pollution, resource scarcity, and freshwater scarcity. This study explores the social risks along the supply chain of requisite components of BESs for two functionalities: (i) copper recovery from spent lees and (ii) formic acid production via CO2 reduction, based on the UK’s trade policy. The methodology employed in this study is based on the UNEP/SETAC guidelines for social life-cycle assessment (S-LCA) of products. Relevant trade data from UN COMTRADE database and generic social data from New Earth’s social hotspot database were compiled for the S-LCA. The results revealed that about 75% of the components are imported from the European Union. However, the social risks were found to vary regardless of the magnitude or country of imports. “Labour and Decent Work” was identified as the most critical impact category across all countries of imports, while the import of copper showed relatively higher risk than other components. The study concludes that BESs are a promising sustainable technology for resource recovery from wastewater. Nevertheless, it is recommended that further research efforts should concentrate on stakeholder engagement in order to fully grasp the potential social risks.
In this work, a dynamic computational model is developed for a single chamber microbial fuel cell (MFC), consisting of a bio-catalyzed anode and an air-cathode. Electron transfer from the biomass to the anode is assumed to take place via intracellular mediators as they undergo transformation between reduced and oxidized forms. A two-population model is used to describe the biofilm at the anode and the MFC current is calculated based on charge transfer and Ohm's law, while assuming a non-limiting cathode reaction rate. The open circuit voltage and the internal resistance of the cell are expressed as a function of substrate concentration. The effect of operating parameters such as the initial substrate (COD) concentration and external resistance, on the Coulombic efficiency, COD removal rate and power density of the MFC system is studied. Even with the simple formulation, model predictions were found to be in agreement with observed trends in experimental studies. This model can be used as a convenient tool for performing detailed parametric analysis of a range of parameters and assist in process optimization.
As waste generation increases with increasing population, regulations become stricter to control and mitigate environmental emissions of substances, e.g. heavy metals: zinc and copper. Recovering these resources from wastes is the key interest of industries. The objective of this paper is the sustainability and feasibility evaluations of zinc recovery from waste streams. Sustainability and feasibility of a resource recovery strategy from wastes in a circular economy are governed by avoided environmental impacts and cost-effective transformation of an environmental contaminant into a valuable resource, e.g. as a coproduct by making use of an existing infrastructure as much as possible. This study, for the first time, gives a comprehensive overview of secondary sources and processes of recovering zinc, its stock analysis by country, regional and global divisions by a Sankey diagram, policies to regulate zinc emissions and avoided environmental impacts by zinc recovery. Two representative cases are further investigated for economic feasibility analysis of zinc recovery from 1) steelmaking dust and (2) municipal solid waste (MSW). The amount and value of zinc that can be generated from dust emitted from various steelmaking technologies are estimated. Additional revenues for the steelmaking industrial sector (with electric arc furnace), at the plant, national (UK), regional (EU) and global levels are 11, 12, 169 and 1670 million tonne/y, or 19-143, 20-157, 287-2203 and 2834-21740 million €/y, respectively. The second case study entails an integrated mechanical biological treatment (MBT) system of MSW consisting of metal recovery technologies, anaerobic digestion, refuse derived fuel (RDF) incineration and combined heat and power (CHP) generation. An effective economic value analysis methodology has been adopted to analyse the techno-economic feasibility of the integrated MBT system. The value analysis shows that an additional economic margin of 500 € can be generated from the recovery of 1 tonne of zinc in the integrated MBT system enhancing its overall economic margin by 9%.
This study presents a steady state, two dimensional mathematical model of microbial fuel cells (MFCs) developed by coupling mass, charge and energy balance with the bioelectrochemical reactions. The model parameters are estimated and validated using experimental results obtained from ve aircathode MFCs operated at different temperatures. Model analysis correctly predicts the nonlinear performance trend of MFCs with temperatures ranging between 20 oC - 40 oC. The two dimensional distribution allows the computation of local current density and reaction rates in the biolm, helping to correctly capture the interdependence of system variables and predict the drop in power density at higher temperatures. Model applicability for parametric analysis and process optimization is further highlighted by studying the effect of electrode spacing and ionic strength on MFC performance.
This study describes and evaluates a dynamic computational model for two chamber microbial electrosynthesis (MES) system. The analysis is based on redox mediators and a two population model, describing bioelectrochemical kinetics at both anode and cathode. Mass transfer rates of substrate and bacteria in the two chambers are combined with the kinetics and Ohm’s law to derive an expression for the cell current density. Effect of operational parameters such as initial substrate concentration at anode & cathode and the operation cycle time, on MES performance are evaluated in terms of product formation rate, substrate consumption and Coulombic efficiency (CE). For fixed operation cycle time of 3 or 4 days, the anode and cathode initial substrate concentrations show linear relationship with product formation rate; however MES operation with 2 day cycle time shows a more complex behaviour, with acetic acid production rates reaching a plateau and even a slight decrease at higher concentrations of the two substrates. It is also shown that there is a trade-off between product formation rate and substrate consumption & CE. MES performance for operation with cycle time being controlled by substrate consumption is also described. Results from the analysis demonstrate the interdependence of the system parameters and highlight the importance of multi-objective system optimization based on targeted end-use.
The selections of product portfolios, processing routes and the combination of technologies to obtain a sustainable biorefinery design according to economic and environmental criteria represent a challenge to process engineering. The aim of this research is to generate a simple but yet robust methodology that assists the process engineers to understand the environmental and economic behaviour of biorefinery systems. The novel Economic Value and Environmental Impact analysis (EVEI) methodology is presented in this paper. EVEI analysis is a tool that emerges from the combination of the value analysis method for the evaluation of economic potential and environmental footprinting for impact analysis. A quick illustration of the methodology in providing insights into the performances of a process network is given by taking a bioethanol plant as case study. The applicability to analyse biorefinery systems for selection of process pathway alternatives is demonstrated by using a Jatropha-based biorefinery case study. The systematisation of the methodology allowed its implementation and integration into a Computer Aided Process Engineering (CAPE) tool in the well known Excel® environment using the built-in VBA facility. This will accelerate the design process allowing focus on the analysis of results and devising alternatives from highly complex integrated process schemes. © 2012 Elsevier B.V.
The selection of product portfolios, processing routes and the combination of technologies to obtain a sustainable biorefinery design according to economic and environmental criteria represents a challenge to process engineering. The aim of this research is to generate a robust methodology that assists process engineers to conceptually optimise the environmental and economic performances of biorefinery systems. A novel economic value and environmental impact (EVEI) analysis methodology is presented in this paper. The EVEI analysis is a tool that emerges from the combination of the value analysis method for the evaluation of economic potential with environmental footprinting for impact analysis. The methodology has been effectively demonstrated by providing insights into the performance of a bioethanol plant as a case study. The systematisation of the methodology allowed its implementation and integration into a computer-aided process engineering (CAPE) tool in the spreadsheet environment. © 2013 The Institution of Chemical Engineers.
Copyright © 2014, AIDIC Servizi S.r.l.Energy saving within the manufacturing sector has a role to play in reducing global energy consumption and green house gas emissions. Despite heating applications being common throughout industry, there is currently no framework that provides practical guidance for energy optimisation in ovens. This paper presents a systematic approach to guide an engineer through five stages of optimisation. It begins with defining the problem and system boundaries, before developing a thorough understanding of the oven system through mass balance and energy analysis as well as identifying all process variables. Analysis of key process variables is conducted to develop process & product understanding and to identify key variables. Improvement of the system and then controlling for full implementation leads to successful conclusion of the project. Application of this methodology has been conducted on curing oven for masking tape manufacture. The optimisation results in a potential 4.7 % annual reduction of the plants energy consumption and off-setting 305 teCO2 from minimal capital expenditure. As the methodology can be tailored to accommodate individual optimisation options for each oven scenario, while still providing a clear pathway, it has potential to reduce energy within the wider manufacturing industry.
We present a correlation for determining the power density of microbial fuel cells based on dimensional analysis. Important operational, design and biological parameters are non-dimensionalized using a selection of scaling variables. Experimental data from various microbial fuel cell studies operating over a wide range of system parameters are analyzed to attest accuracy of the model in predicting power output. The correlation predicts nonlinear dependencies between power density, substrate concentration, solution conductivity, external resistance, and electrode spacing. The straightforward applicability without the need for any significant computational resources, while preserving good level of accuracy; makes this correlation useful in focusing the experimental effort for the design and optimization of microbial fuel cells.
Industrial ovens consume a considerable amount of energy and have a significant impact on product quality; therefore, improving ovens should be an important objective for manufacturers. This paper presents a novel and practical approach to oven improvement that emphasises both energy reduction and enhanced process performance. The three-phased approach incorporates product understanding, process improvement and process parameter optimisation. Cure understanding is developed using Dynamic Mechanical Analysis (DMA) and Lch-CIE colour tests, which together highlight the impact of temperature variation on cure conversion and resulting product quality. Process improvement encompasses thermodynamic modelling of the oven air to evaluate the impact of insulation on temperature uniformity and system responsiveness. Finally, process parameters, such as temperature, pressure negativity and air flow, are optimised to reduce energy consumption. The methodology has been effectively demonstrated for a 1MW festoon oven, resulting in an 87.5% reduction in cooling time, saving 202h of annual downtime and a reduction in gas consumption by 20-30%.
Generating electricity from biomass are undeniably gives huge advantages to the energy security, environmental protection and the social development. Nevertheless, it always been negatively claimed as not economically competitive as compared to the conventional electricity generation system using fossil fuel. Due to the unfair subsidies given to renewable energy based fuel and the maturity of conventional electricity generation system, the commercialization of this system is rather discouraging. The uniqueness of the chemical and physical properties of the biomass and the functionality of the system are fully depending on the availability of the biomass resources, the capital expenditure of the system is relatively expensive. To remain competitive, biomass based system must be developed in their most economical form. Therefore the justification of the economies of scale of such system is become essential. This study will provide a comprehensive review of process to select an appropriate size for electricity generation plant from palm oil mill (POM) residues through the combustion of an empty fruit bunch (EFB) and biogas from the anaerobic digestion of palm oil mill effluent (POME) in Peninsular Malaysia using a mathematical model and simulation using ASPEN Plus software package. The system operated at 4 MW capacity is expected to provide a return on investment (ROI) of 20% with a payback period of 6.5 years. It is notably agreed that the correct selection of generation plant size will have a significant impact on overall economic and environmental feasibility of the system.
Jhuma Sadhukhan, E Martinez-Hernandez, Richard J Murphy, DKS Ng, MH Hassim, Kok Siew Ng, WY Kim, IFMd Jaye, MY Leung, P Hang, V Andiappan (2017)Role of Bioenergy, Biorefinery and Bioeconomy in Sustainable Development: Strategic Pathways for Malaysia, In: Renewable & Sustainable Energy Reviews81(Part 2)pp. 1966-1987
Malaysia has a plethora of biomass that can be utilized in a sustainable manner to produce bio-products for circular green economy. At the 15th Conference of Parties in Copenhagen, Malaysia stated to voluntarily reduce its emissions intensity of gross domestic product by upto 40% by 2020 from 2005 level. Natural resources e.g. forestry and agricultural resources will attribute in achieving these goals. This paper investigates optimum bio-based systems, such as bioenergy and biorefinery, and their prospects in sustainable development in Malaysia, while analyzing comparable cases globally. Palm oil industry will continue to play a major role in deriving products and contributing to gross national income in Malaysia. Based on the current processing capacity, one tonne of crude palm oil (CPO) production is associated with nine tonnes of biomass generation. Local businesses tend to focus on products with low-risk that enjoy subsidies, e.g. Feed-in-Tariff, such as bioenergy, biogas, etc. CPO biomass is utilized to produce biogas, pellets, dried long fibre and bio-fertilizer and recycle water. It is envisaged that co-production of bio-based products, food and pharmaceutical ingredients, fine, specialty and platform chemicals, polymers, alongside biofuel and bioenergy from biomass is possible to achieve overall sustainability by the replacement of fossil resources. Inception of process integration gives prominent innovative biorefinery configurations, an example demonstrated recently, via extraction of recyclable, metal, high value chemical (levulinic acid), fuel, electricity and bio-fertilizer from municipal solid waste or urban waste. Levulinic acid yield by only 5 weight% of waste feedstock gives 1.5 fold increase in profitability and eliminates the need for subsidies such as gate fees paid by local authority to waste processor. Unsustainable practices include consumable food wastage, end-of-pipe cleaning and linear economy that must be replaced by sustainable production and consumption, source segregation and process integration, and product longevity and circular economy.
Biodiesel production is a very promising subject due to the relevance that it is environmental-friendly and an alternative diesel fuel for fossil fuel. Nowadays, most industrial applications of biodiesel production are performed by the transesterification of renewable biological sources based on heterogeneous catalysts, which requires separate reaction and separation processes. And the conversion of the reaction is restricted due to its equilibrium limitation. Thus, in this work, a simulated moving bed chromatographic reactor (SMBR) has been applied for the first time into the transesterification of biodiesel production, which allows us to carry out a simultaneous reaction and separation process and drive the transesterification reaction beyond its equilibrium. A detailed dynamic modeling of reaction as well as continuous adsorptive separation based on the surface reacting kinetic phenomena integrating with particle-level transport phenomena has been established firstly for a SMBR process design and optimization. This research offers a heuristic insight into the improvement of industrial production of biodiesel. A case study of the transesterification of tributyrin with methanol over hydrotalcite catalysts has been demonstrated to establish the effectiveness of this methodology.
In this contribution, we present a novel methodology for flexible design of industrial systems based on detailed differential value analysis (Sadhukhan, J. Ph.D. Dissertation, UMIST, Manchester, U.K., 2002). Evolving from graph theory this methodology performs better than conventional mathematical programming based optimisation approaches through systematic structural decomposition of large scale industrial systems into basic processing elements (paths and trees), which helps to reduce the size and the complexity of large combinatorial problems and comprehensively analyse the multiple objectives, set of optimal operating states and marginal contributions at elemental levels that are critical for flexible designs. © 2005 Elsevier B.V. All rights reserved.
Design of clean energy systems is highly complex due to the existence of a variety of CO abatement and integration options. In this study, an effective decision-making methodology has been developed for facilitating the selection of lowest energy or lowest cost intensity systems, from a portfolio of flowsheet configurations with different decarbonisation strategies. The fundamental aspect of the proposed methodology lies in thermodynamic feasibility assessment as well as quantification of CO emission treatment intensity using a graphical approach (CO emission balance diagram) for energy and economic performance analyses of integrated decarbonised systems. The relationship between the graphical representation and performances is established using blocks and boundaries on integrated systems. The effectiveness of the methodology has been demonstrated through a range of coal gasification based polygeneration and cogeneration systems, incorporating either of carbon capture and storage (CCS) or CO reuse options. © 2012 Elsevier Ltd.
Stricter environmental legislation on emissions, product qualities, and the increased availability of heavier and sourer crudes are the main driving forces for refineries to use gasification technologies for the "bottom of the barrel" disposal into production of hydrogen and clean energy. However, economic viability needs to be fully proven. This paper takes the challenge of integrating gasification to an overall refinery. To achieve this, a four stage optimization strategy is developed. In the screening and scoping stage, the energy integration opportunities are explored. In site level optimization, the overall integration among refinery and gasification is considered to maximize the margin. In process level optimization, appropriate integration among gasification, hydrogen, and utility systems is derived to minimize the investment. Finally, the simultaneous optimization of site and process levels is carried out to trade off between benefits and investment. By applying this methodology to a refinery case study, signific marginal improvement is achieved with minimal investment.
A methodology for detailed differential economic analysis of industrial systems based on an analytical optimization procedure is presented. Existing process integration methodologies for large scale industrial systems (refineries, petrochemicals, chemicals) where a number of processes, streams, and supporting systems are involved, do not provide economic value structure of individual components prior to optimization. Such problems are overcome through an economic analysis of streams and processes in a system. A novel optimization method called analytical optimization for process industries is developed. An overall integration strategy is then developed to capture the impacts of variable operating conditions and complex network connections in the detailed differential economic analysis of systems. The methodology is applied in the design and synthesis of an oil upgrading system. This is an abstract of a paper presented at the 7th World Congress of Chemical Engineering (Glasgow, Scotland 7/10-14/2005).
Development of clean coal technology is highly envisaged to mitigate the CO emission level whilst meeting the rising global energy demands which require highly efficient and economically compelling technology. Integrated gasification combined cycle (IGCC) with carbon capture and storage (CCS) system is highly efficient and cleaner compared to the conventional coal-fired power plant. In this study, an alternative process scheme for IGCC system has been proposed, which encompasses the reuse of CO from the flue gas of gas turbine into syngas generation, followed by methanol synthesis. The thermodynamic efficiency and economic potential are evaluated and compared for these two systems. The performances of the systems have been enhanced through systematic energy integration strategies. It has been found that the thermodynamic and economic feasibilities have attained significant improvement through the realisation of a suitably balanced polygeneration scheme. The economic potential can be enhanced from negative impact to 317 M€/y (3.6 €/GJ). The results have demonstrated promising prospects of employing CO reuse technology into IGCC system, as an alternative to CCS system. © 2011 Springer-Verlag.
A biorefinery involving internal stream reuse and recycling (including products and co-products) should result in better biomass resource utilisation, leading to a system with increased efficiency, flexibility, profitability and sustainability. To benefit from those advantages, process integration methodologies need to be applied to understand, analyse and design highly integrated biorefineries. A bioethanol integration approach based on mass pinch analysis is presented in this work for the analysis and design of product exchange networks formed in biorefinery pathways featuring a set of processing units (sources and demands) producing or utilising bioethanol. The method is useful to identify system debottleneck opportunities and alternatives for bioethanol network integration that improve utilisation efficiency in biorefineries with added value co-products. This is demonstrated by a case study using a biorefinery producing bioethanol from wheat with arabinoxylan (AX) co-production using bioethanol for AX precipitation. The final integrated bioethanol network design allowed the reduction of bioethanol product utilisation by 94%, avoiding significant revenue losses. © 2012 Elsevier Ltd.
Design of highly efficient multifunctional reaction processes for energy production is one of the main focus areas of Chemical Engineering. This article presents multiscale simulation frameworks for heterogeneously catalyzed reactors wherein numerous synthesis steps are integrated for high efficiency biodiesel production. The goal is the modeling of transport-adsorption-reaction-desorption phenomena through catalytic porous networks for efficient diffusion, reactions of desired pathways and elimination of side reactions and waste formation. Building upon exciting ongoing EPSRC funded research activities on 'Designer catalyst for high efficiency biodiesel production', this work proposes a simulation method to refine micro-meso porous kinetic and diffusive parameters to converge with the experimental results and for biodiesel synthesis in continuous oscillatory baffle reactor (OBR) from non-edible oils. © 2012 Elsevier B.V.
A novel framework integrating dynamic simulation (DS), life cycle assessment (LCA) and techno-economic assessment (TEA) of bioelectrochemical system (BES) has been developed to study for the first time wastewater treatment by removal of chemical oxygen demand (COD) by oxidation in anode and thereby harvesting electron and proton for carbon dioxide reduction reaction or reuse to produce products in cathode. Increases in initial COD and applied potential increase COD removal and production (in this case formic acid) rates. DS correlations are used in LCA and TEA for holistic performance analyses. The cost of production of HCOOH is €0.015–0.005g–1 for its production rate of 0.094–0.26kgyr–1 and a COD removal rate of 0.038–0.106kgyr–1. The life cycle (LC) benefits by avoiding fossil-based formic acid production (93%) and electricity for wastewater treatment (12%) outweigh LC costs of operation and assemblage of BES (–5%), giving a net 61MJkg-1HCOOH saving.
G Campbell, A Koutinas, R Wang, J Sadhukhan, C Webb (2006)Cereal potential, In: TCE(781)pp. 26-28
INST CHEMICAL ENGINEERS
It was established that olefin cracker and gasification technologies provide solutions to today's refineries by marketing unwanted, heavy, high sulfur, TAN materials though environmentally benign, highly valuable productions. To a refinery, these technologies offer reaction operations like hydrocracking, catalytic reforming etc. However, they convert the various fractions of oils including heavy, high sulfur, TAN oils to more valuable primary petrochemicals, hydrogen, power, and energy. Due to high investment and maintenance costs of these two processes their applications are limited to refineries. However, in recent years when the environmental legislations on fuel qualities and emissions demand a complete disposal of bottom fractions into sustainable products, while ensuring a steady economic gain, integration of these two technologies to refineries seems to be the most promising option. Economic justification is achieved in the following ways. A high valued product slate consisting of polymer grade olefins (ethylene, propylene), hydrogen, transportation fuels (gasoline, diesel), power and energy with significantly lower emissions is resulted from complete bottom of barrel disposal. No heavy products, fuel oils, residues are produced having lower value than crude oils. Today's refinery should ideally employ a limited number of selective technologies: crude distillation, hydrotreating, olefin cracking, resid processing (e.g. solvent deasphalting, delayed coking), integrated gasification combined cycle (IGCC). Use of advanced process integration tools and development of process technologies particularly in the areas of olefin cracking, IGCC offer additional prospects of economic growth in refineries. This is an abstract of a paper presented at the 7th World Congress of Chemical Engineering (Glasgow, Scotland 7/10-14/2005).
Biodiesel production is a very promising area due to the relevance that it is an environmental-friendly diesel fuel alternative to fossil fuel derived diesel fuels. Nowadays, most industrial applications of biodiesel production are performed by the transesterification of renewable biological sources based on homogeneous acid catalysts, which requires downstream neutralization and separation leading to a series of technical and environmental problems. However, heterogeneous catalyst can solve these issues, and be used as a better alternative for biodiesel production. Thus, a heuristic diffusion-reaction kinetic model has been established to simulate the transesterification of alkyl ester with methanol over a series of heterogeneous Cs-doped heteropolyacid catalysts. The novelty of this framework lies in detailed modeling of surface reacting kinetic phenomena and integrating that with particle-level transport phenomena all the way through to process design and optimisation, which has been done for biodiesel production process for the first time. This multi-disciplinary research combining chemistry, chemical engineering and process integration offers better insights into catalyst design and process intensification for the industrial application of Cs-doped heteropolyacid catalysts for biodiesel production. A case study of the transesterification of tributyrin with methanol has been demonstrated to establish the effectiveness of this methodology.
A method for the optimizing process networks of industrial systems and applications to refineries and petrochemicals was discussed. The analytical optimization procedure was designed based on comprehensive economic analysis of process networks for maximising the overall system economics. The anaytical optimization process network comprised of three steps including marketing integration, and the optimization of network flowsheet. Marginal correlations for elements and processing of streams were developed in terms of its market price, cost of production (COP) and value on processing (VOP),and market price.
The development of a generalized strategy for modeling and integration of an overall system, for detailed economic analysis of industrial systems, is described. Economic analysis of a system establishes the economic analysis of streams and processes with respect to the current system operation, network configuration, and market situation. An overall integration is developed to capture the impacts of real plant operations and the effects of network interactions in the detailed economic analysis of complex systems. The approach for economic analysis of a system is simple and provides a transparent and complete set of economic values for all basic components and correlates these values with the overall system economic margin.
A new method for optimising process networks is presented in this paper. The method uses economic analysis of existing systems based on the new value analysis method (Ph.D. Dissertation, UMIST, Manchester, UK, 2002) as the basis to derive the optimum network design. The analytical optimisation method comprises of three steps. Market integration is the first step that fully exploits the available market opportunities for selling and purchasing streams based on individual marginal contributions from productions and processing of streams. Market integration is an easy and straightforward way of achieving quick benefits. The second step deals with optimisation of network flowsheet/connections. The economic margins of various paths of network are used to determine the weaker paths and the stronger paths where the loads of weaker paths can be shifted. This load shifting among paths leads up to the overall benefits of a system, Finally, the non-profitable or less profitable process units are optimised to improve their individual marginal contributions. Analytical optimisation turns the traditional back box approach into a clear and transparent procedure and is simple to understand and easy to use. The application of analytical optimisation is demonstrated with industrial cases from refining. In the end, a generalised methodology has been illustrated on how to design the optimum flowsheet of a petrochemical complex in a changing market price scenario. © 2004 Elsevier Ltd. All rights reserved.
A generalized strategy for the modeling and integration of an overall system is developed for the purpose of detailed economic analysis of industrial systems. The work uses the basics of value analysis method (Sadhukhan, J. Ph.D. Dissertation, UMIST, Manchester, U.K., 2002) to identify major material streams and their elements of production and processing. These major material streams are evaluated for economics, and these economics are used to predict the economics of elements of production and processing expressed as profit functions of process units. However, in a complex network system, there exist a variety of streams forming a number of processing networks in addition to the core system of major material streams and utilities. To consider the effects of overall network interactions in the economics of major material streams and elements, these processing networks are modeled interchangeably as material or utility networks and integrated with the core system of major material streams and utilities. Further, these economics of streams and elements are used to establish the overall system economics and thereby capturing the effects of overall network interactions in the overall system economics. The insights developed to build economic models at various stages are illustrated with several examples and an industrial case study from a refinery. In addition to the economic analysis of an overall refining system, the refinery crude switch problem is used to demonstrate the application of system economic analysis to optimum feedstock selection.
Development of clean coal technology is highly envisaged to mitigate the CO2 emission level while meeting the rising global energy demands which require highly efficient and economically compelling technology. Integrated gasification combined cycle (IGCC) with carbon capture and storage (CCS) system is highly efficient and cleaner compared to the conventional coal-fired power plant. In this study, an alternative process scheme for IGCC system has been proposed, which encompasses the recycling and re-use of CO2 from the flue gas of gas turbine into a secondary syngas processing route, proceeding with conversion of syngas into methanol. The system modification requires extensive mass and energy integration strategies to ensure that the efficiency and economics of the system are achieved to a considerably high level. The thermodynamic and economic feasibilities of the modified IGCC system were found to attain tremendous improvements. The thermal efficiency has been increased from 54% to 89.3%, whilst the economic potential has been enhanced from 48.1 M€/y to 377.4 M€/y. These results have shown good future prospects for employing CO2 re-use technology into IGCC system, as an alternative to CCS system.
Biodiesel, an alternative diesel fuel, has become more attractive recently because of its environmental benefits and the increase in the petroleum price. Nowadays, most industrial applications of biodiesel production are performed by the transesterification of renewable biological sources based on homogeneous acid catalysts, which requires downstream neutralization and separation leading to a series of technical and environmental problems. However, heterogeneous catalyst can solve these issues, and be used as a better alternative for biodiesel production. Thus, a heuristic diffusion-reaction kinetic model has been established to simulate the transesterification of alkyl ester with methanol over a series of heterogeneous Cs-doped heteropolyacid catalysts. The novelty of this framework lies in detailed modeling of surface reacting kinetic phenomena and integrating that with particle-level transport phenomena all the way through to process design and optimisation, which has been done for biodiesel production process for the first time. This multi-disciplinary research combining chemistry, chemical engineering and process integration offers better insights into catalyst design and process intensification for the industrial application of Cs-doped heteropolyacid catalysts for biodiesel production. A case study of the transesterification of tributyrin with methanol has been demonstrated to establish the effectiveness of this methodology.
Several decarbonised polygeneration schemes exploiting carbon capture and storage (CCS) or CO reuse technologies for the generation of clean fuels, chemicals, electricity and heat have been systematically analysed for techno-economic feasibility. Process simulation, energy integration and economic analysis were undertaken to analyse the effect of process configurations and operating conditions on the economic potential (EP) and risks. CO capture and reuse producing methane using Sabatier's reaction shows less favourable economics compared to the counterpart CCS based scheme, both producing electricity, hydrogen, acetic acid and methanol in common. Post-combustion CO tri-reforming into methanol production in addition to electricity generation shows overall favourable economics compared to the counterpart integrated gasification combined cycle (IGCC) with CCS scheme. Thus, increasing product portfolio from energy products in a cogeneration plant to chemical products evolved from thermodynamic and process integration synergies increases the techno-economic viability. Bio-oil can be processed as an alternative low carbon feedstock. While bio-oil creates environmental incentives, its economic competitiveness can be enhanced by introducing credits on product prices. © 2013 Elsevier B.V.
This work tackles the carbon dioxide (CO2) emission problem in process sites, particularly in relation to the site utility systems. There are three basic decarbonisation routes to deal with the CO2 emission problem in energy production. These are pre-combustion, post-combustion and the oxy-combustion routes. For each route, different CO2 separation technologies can be exploited. This work has adopted different decarbonisation routes with both conventional CO2 separation technologies and novel pre-combustion routes. Unlike the CO2 emission problem of energy generation taken in isolation, the emissions from a utility site can be widely distributed. To challenge this problem, utility sites are integrated with decarbonised combined heat and power generation systems. By doing this, some of the utility products like power, steam and fuel can be substituted by products from the decarbonised power generation system. Consequently, reduced carbon dioxide emissions from the utility system can be achieved. Thus, a wide range of decarbonisation designs can be applied with power generation. Among them, pre-combustion with novel CO2 separation technology has the best performance. Integrating decarbonised combined heat and power generation systems can give significant potential for CO2 emission reduction to the utility site.
This review presents the developments in the mathematical models for various bioelectrochemical systems. A number of modeling approaches starting with the simple description of biological and electrochemical processes in terms of ordinary differential equations to very detailed 2D and 3D models that study the spatial distribution of substrates and biomass, have been developed to study BES performance. Additionally, mathematical models focused on studying a particular process such as ion diffusion through membrane and new modeling approaches such as artifcial intelligence methods, cellular network models, etc., have also been described. While most mathematical models are still focused on performance studies and optimization of microbial fuel cells, new models to study other BESs such as microbial electrolysis cell, microbial electrosynthesis and microbial desalination cell have also been reported and discussed in this review.
As the range of feedstocks, process technologies and products expand, biorefineries will become increasingly complex manufacturing systems. Biorefineries and Chemical Processes: Design, Integration and Sustainability Analysis presents process modelling and integration, and whole system life cycle analysis tools for the synthesis, design, operation and sustainable development of biorefinery and chemical processes. Topics covered include: Introduction: An introduction to the concept and development of biorefineries. Tools: Included here are the methods for detailed economic and environmental impact analyses; combined economic value and environmental impact analysis; life cycle assessment (LCA); multi-criteria analysis; heat integration and utility system design; mathematical programming based optimization and genetic algorithms. Process synthesis and design: Focuses on modern unit operations and innovative process flowsheets. Discusses thermochemical and biochemical processing of biomass, production of chemicals and polymers from biomass, and processes for carbon dioxide capture. Biorefinery systems: Presents biorefinery process synthesis using whole system analysis. Discusses bio-oil and algae biorefineries, integrated fuel cells and renewables, and heterogeneous catalytic reactors. Companion website: Four case studies, additional exercises and examples are available online, together with three supplementary chapters which address waste and emission minimization, energy storage and control systems, and the optimization and reuse of water. This textbook is designed to bridge a gap between engineering design and sustainability assessment, for advanced students and practicing process designers and engineers.
A discussion covers the challenge of engineering cereal-based biorefineries; argument that cereals are the best raw material option for a sustainable chemical industry; economic issues; success factors, e.g., process engineering innovations and the chemistry of extraction and transformation of cereal components; genetic modification of cereals; and implications on the education of process engineers.
The Feed-In-Tariff scheme in the UK has generated attractive economics in the investment for anaerobic digestion (AD) to convert sewage sludge into biogas and digested sludge for energy and agricultural applications, respectively. The biogas is a source of biomethane to replace natural gas in the gas grid system. Biogas can be utilised to generate combined heat and power (CHP) on-site, at household micro and distributed or community scales. These biogas CHP generation options can replace the equivalent natural gas based CHP generation options. Digested sludge can be transformed into fertiliser for agricultural application replacing inorganic N:P:K fertiliser. Biogas and digested matter yields are inter-dependent: when one increases, the other decreases. Hence, these various options need to be assessed for avoided life cycle impact potentials, to understand where greatest savings lie and in order to rank these options for informed decision making by water industries. To fill a gap in the information available to industry dealing with wastewater, the avoided emissions by various AD based technologies, in primary impact potentials that make a difference between various systems, have been provided in this paper.1m3 biogas can save 0.92m3 natural gas. An average UK household (with a demand of 2kWe) requires 180,000MJ or 5000Nm3 or 4.76t biogas per year, from 15.87t sewage sludge processed through AD. The proton exchange membrane fuel cell (PEM FC) is suitable for building micro-generations; micro gas turbine (Micro GT), solid oxide fuel cell (SOFC) and SOFC-GT hybrid are suitable for distributed generations upto 500kWe and occasionally over 500kWe; engine and ignition engine above 1MWe. These CHP technologies can be ranked from the lowest to the highest impacts per unit energy production: PEM FC is the environmentally most benign option, followed by SOFC, SOFC-GT, Engine or Micro GT and Ignition engine (with the highest impact potential), respectively. In terms of avoided global warming, acidification and photochemical ozone creation potentials, compared to equivalent natural gas based systems, the biogas based PEM FC micro-generation and Micro GT distributed systems achieve the greatest avoided emissions with the most cost-effectiveness. Application of digested sludge as fertiliser has more toxicity impacts, however, has greater avoided emissions in acidification and photochemical ozone creation potentials on the basis of inorganic N:P:K fertiliser, compared to the biogas production for the natural gas grid system. © 2014 Elsevier Ltd.
Jhuma Sadhukhan, Siddharth Gadkari, Elias Martinez-Hernandez, Kok Siew Ng, Mobolaji Shemfe, Enelio Torres-Garcia, Jim Lynch (2019)Novel macroalgae (seaweed) biorefinery systems for integrated chemical, protein, salt, nutrient and mineral extractions and environmental protection by green synthesis and life cycle sustainability assessments, In: Green Chemistry
Royal Society of Chemistry
Highly efficient macroalgae based chemical factories and environmental protection have been comprehensively studied for the first time to displace fossil resources to mitigate climate change impact. Wild macroalgae by (bio)phytoremediation and residual macroalgae by biosorption can be used to treat wastewaters, marine environment, soil and sludge. Cultured macroalgae can be processed through drying, milling, grinding, suspension in deionised water and filtration extracting sap of heavy metals; centrifugation of solids recovering nutrients; ion exchange resins of supernatants separating protein and polysaccharides; dialysis purifying protein from salts and pretreatment of polysaccharides producing a sugar platform. Protein profiling shows the presence of the essential amino acids as well as others as food additive, flavour enhancer and pharmaceutical ingredient. Sugars can be converted into a chemical: levulinic acid by controlled acid hydrolysis; 2,5-furandicarboxylic acid by heterogeneous catalytic reaction; succinic acid by tricarboxylic acid cycle; lactic acid by fermentation, with 3-5 times market value than bioethanol. Protein, sugar based chemical and inorganics give the highest to the lowest climate change impact savings of 12, 3 and 1 kg CO2 equivalent kg-1 product. Their cost of production is estimated at $2010 t-1, significantly lower than their market prices, making the integrated marine biorefinery system economically more attractive than lignocellulosic terrestrial biorefinery systems. Social life cycle assessment indicates that the highest to the lowest avoided social impacts will be from the displacements of animal based protein, sugars and minerals, in Indonesia, China and Philippines (producing 27 million tonnes per annum, 93% of global production), respectively.
Driven by the need to develop a wide variety of products with low environmental impact, biorefineries need to emerge as highly integrated facilities. This becomes effective when overall mass and energy integration through a centralised utility system design is undertaken. An approach combining process integration, energy and greenhouse gas (GHG) emission analyses is shown in this paper for Jatropha biorefinery design, primarily producing biodiesel using oil-based heterogeneously catalysed transesterification or green diesel using hydrotreatment. These processes are coupled with gasification of husk to produce syngas. Syngas is converted into end products, heat, power and methanol in the biodiesel case or hydrogen in the green diesel case. Anaerobic digestion of Jatropha by-products such as fruit shell, cake and/or glycerol has been considered to produce biogas for power generation. Combustion of fruit shell and cake is considered to provide heat. Heat recovery within biodiesel or green diesel production and the design of the utility (heat and power) system are also shown. The biorefinery systems wherein cake supplies heat for oil extraction and seed drying while fruit shells and glycerol provide power generation via anaerobic digestion into biogas achieve energy efficiency of 53 % in the biodiesel system and 57 % in the green diesel system. These values are based on high heating values (HHV) of Jatropha feedstocks, HHV of the corresponding products and excess power generated. Results showed that both systems exhibit an energy yield per unit of land of 83 GJ ha−1. The global warming potential from GHG emissions of the net energy produced (i.e. after covering energy requirements by the biorefinery systems) was 29 g CO2-eq MJ−1, before accounting credits from displacement of fossil-based energy by bioenergy exported from the biorefineries. Using a systematic integration approach for utilisation of whole Jatropha fruit, it is shown that global warming potential and fossil primary energy use can be reduced significantly if the integrated process schemes combined with optimised cultivation and process parameters are adopted in Jatropha-based biorefineries.
To reduce reliance on fossil fuel and environmental issues, alternative energy sources such as biomass are vital to be recovered and converted into value-added products. In sago industry, a huge amount of sago biomass (i.e., sago barks and fibres) is generated and discharged to the environment during sago starch extraction process (SSEP). In order to reduce environmental pollutants, the biomass can be utilised as feedstocks for energy, and bioethanol production. Therefore, Part 1 of these articles in series presents a techno-economic analysis to examine the feasibility of sago biomass-based combined heat and power (CHP) system ( Wan et al., 2015a ); and Part 2 is to examine the feasibility of integrated bioethanol production and energy systems. In this part, a conceptual integrated sago-based biorefinery (SBB) is envisioned and analysed based on the bioethanol plant study conducted by the National Renewable Energy Laboratory (NREL). Besides, techno-economic performance as well as environmental performance of this integrated SBB is evaluated via Aspen Plus software and a spreadsheet based yield prediction model. For the performance evaluation, various feedstocks such as sago fibres, barks and combined biomass (fibres and barks) are considered. In addition, techno-economic and environmental performance of the integrated SBB with on-site and off-site enzyme production as well as the impacts of labour cost on the economic performance of the integrated SBB is also evaluated. Based on the evaluation and analysis, the integrated SBB with combined biomass (fibres and barks) has the highest technical, economic and environmental performance amongst the sago biomass. A total of 4.75 t/d of bioethanol and 252 kW/d of electricity are expected to be produced; and reduction of 16.32 tCO2 equivalent/d of carbon dioxide emission is expected. In addition, the payback period of the integrated SBB with on-site enzyme production and using current available labour from SSEP is estimated as 6.6 years. Based on the analysis, it is noted that enzyme and labour costs are critical cost contributors to the new development of the integrated SBB and hence, a sensitivity analysis on such parameters is performed.
The sustainable biorefinery will only be realised with a focus on optimal combinations of feedstock-process technologies-products. For many years, industry has been looking to add value to the by-products of commercial agriculture, forestry and processing. More recently, as concerns about climate change have increased around the globe, the use of biomass as a carbon saving feedstock (compared to fossil feedstock) has led to the implementation of policies to encourage its use for bioenergy, biofuels and bio-based products. As biomass conversion technologies become reality at the commercial scale for a range of diverse end products, the need to establish bespoke biomass supply chains also becomes a reality and industrial developers will face many business-critical decisions on the sourcing of biomass and location of conversion plants (biorefineries). The research presented here, aims to address these issues through the development of a comprehensive database to aid biomass sourcing and conversion decision-making. The database covers origin, logistics, technical suitability (in this case for a proprietary organosolv pre-treatment process) and policy and other risk attributes of the system. The development of key criteria required by the business community to develop biomass supply chains for specific requirements is discussed.
Amandeep Kaur, Hitesh C. Boghani, Edward M. Milner, Richard L. Kimber, Iain S. Michie, Ronald Daalmans, Richard M. Dinsdale, Alan J. Guwy, Ian M. Head, Jonathan R. Lloyd, Eileen H. Yu, Jhuma Sadhukhan, Giuliano C. Premier (2019)Bioelectrochemical treatment and recovery of copper from distillery waste effluents using power and voltage control strategies, In: Journal of Hazardous Materials371pp. 18-26
Copper recovery from distillery effluent was studied in a scalable bioelectro-chemical system with approx. 6.8 L total volume. Two control strategies based on the control of power with maximum power point tracking (MPPT) and the application of 0.5 V using an external power supply were used to investigate the resultant modified electroplating characteristics. The reactor system was constructed from two electrically separated, but hydraulically connected cells, to which the MPPT and 0.5 V control strategies were applied. Three experiments were carried out using a relatively high copper concentration i.e. 1000 mg/L followed by a lower concentration i.e. 50 mg/L, with operational run times defined to meet the treatment requirements for distillery effluents considered. Real distillery waste was introduced into the cathode to reduce ionic copper concentrations. This waste was then recirculated to the anode as a feed stock after the copper depletion step, in order to test the bioenergy self-sustainability of the system. Approx. 60–95% copper was recovered in the form of deposits depending on starting concentration. However, the recovery was low when the anode was supplied with copper depleted distillery waste. Through process control (MPPT or 0.5 V applied voltage) the amount and form of the copper recovered could be manipulated.
Biodiesel is a renewable, environmentally friendly fuel. Commercially most biodiesel is produced from the esterification reaction of vegetable oil with methanol in the presence of a homogeneous catalyst 1. Heterogeneous catalysis however lowers the cost of production by reducing the number of downstream processes. There have been some experimental studies on hydrotalcite as a heterogeneous catalyst2, but little work has been done on the modelling of the process. To evaluate the industrial applicability of the heterogeneous catalyzed process, we have developed a multiscale model for hydrotalcite catalyzed transesterification using a hybrid Monte Carlo/mean field approach. The spatial distribution of species on the catalyst surface is an important factor in determining the reaction rate and this can be taken into account by the application of Kinetic Monte Carlo3. An Eley-Rideal type mechanism is used to model the reactions on the catalyst surface. The overall reaction rate expressions have been derived based on the assumption of quasi steady state conditions for the surface species. We have used a novel hybrid model based on elementary reaction steps to increase the accuracy and robustness of the overall reaction kinetic expression and hence the design of the reactor. This model can be further extended to determine optimum catalyst properties and bulk conditions.
The UK whole-wheat bioethanol and straw and DDGS-based combined heat and power (CHP) generation systems were assessed for environmental sustainability using a range of impact categories or characterisations (IC): cumulative primary fossil energy (CPE), land use, life cycle global warming potential over 100 years (GWP), acidification potential (AP), eutrophication potential (EP) and abiotic resources use (ARU). The European Union (EU) Renewable Energy Directive's target of greenhouse gas (GHG) emission saving of 60% in comparison to an equivalent fossil-based system by 2020 seems to be very challenging for stand-alone wheat bioethanol system. However, the whole-wheat integrated system, wherein the CHP from the excess straw grown in the same season and from the same land is utilised in the wheat bioethanol plant, can be demonstrated for potential sustainability improvement, achieving 85% emission reduction and 97% CPE saving compared to reference fossil systems. The net bioenergy from this system and from 172,370 ha of grade 3 land is 12.1 PJ y providing land to energy yield of 70 GJ ha y. The use of DDGS as an animal feed replacing soy meal incurs environmental emission credit, whilst its use in heat or CHP generation saves CPE. The hot spots in whole system identified under each impact category are as follows: bioethanol plant and wheat cultivation for CPE (50% and 48%), as well as for ARU (46% and 52%). EP and GWP are distributed among wheat cultivation (49% and 37%), CHP plant (26% and 30%) and bioethanol plant (25%, and 33%), respectively. © 2013 Elsevier Ltd.
The recovery of heat has long been a key measure to improving energy efficiency and maximising the heat recovery of factories by Pinch analysis. However, a substantial amount of research has been dedicated to conventional heat integration where low grade heat is often ignored. Despite this, the sustainability challenges facing the process manufacturing community are turning interest on low grade energy recovery systems to further advance energy efficiency by technological interventions such as heat pumps. This paper presents a novel heat integration framework incorporating technological interventions for both simple and complex factories to evaluate all possible heat integration opportunities including low grade and waste heat. The key features of the framework include the role of heat pumps to upgrade heat which can significantly enhance energy efficiency; the selection process of heat pump designs which was aided by the development of ‘Heat Pump Thresholds’ to decide if heat pump designs are cost-competitive with steam generation combustion boiler; a decision making procedure to select process or utility heat integration in complex and diverse factories; and additional stream classifications to identify and separate streams that can be practically integrated. The application of the framework at a modified confectionery factory has yielded four options capable of delivering a total energy reduction of about 32% with an economic payback period of about 5 years. In comparison, conventional direct and/or indirect heat integration without heat pumps showed an energy reduction potential of only 3.7–4.3%. Despite the long payback, the role of heat pumps combined with an integrated search by direct and indirect heat exchange from zonal to factory level can provide the maximum heat recovery. The framework has the potential to be applied across the process manufacturing community to inform longer-term energy integration strategies.
Despite some success with microbial fuel cells and microbial electrolysis cells in recovering resources from wastes, challenges with their scale and yield need to be resolved. Waste streams from biorefineries e.g. bioethanol and biodiesel plants and wastewaters are plausible substrates for microbial electrosynthesis (MES). MES integration can help biorefineries achieving the full polygeneration potentials, i.e. recovery of metals turning apparently pollutants from biorefineries into resources, production of biofuels and chemicals from reuse of CO2 and clean water. Symbiotic integration between the two systems can attain an economic and environmental upside of the overall system. We envision that electrochemical technologies and waste biorefineries can be integrated for increased efficiency and competitiveness with stillage released from the latter process used in the former as feedstock and energy resource recovered from the former used in the latter. Such symbiotic integration can avoid loss of 2 material and energy from waste streams, thereby increasing the overall efficiency, economics and environmental performance that would serve towards delivering the common goals from both the systems. We present an insightful overview of the sources of organic wastes from biorefineries for integration with MES, anodic and cathodic substrates and biocatalysts. In addition, a generic and effective reaction and thermodynamic modelling framework for the MES has been given for the first time. The model is able to predict multi-component physico-chemical behaviour, technical feasibility and best configuration and conditions of the MES for resource recovery from waste streams.
Due to the huge amount of sago biomass generated and discharged to the environment from sago industry without proper treatment, serious environmental impacts are caused. In order to reduce such environmental pollutants, sustainable conversion of biomass into value-added products is of paramount importance. However, up-to-date, sago-based biorefinery, which is a facility that converts sago biomass into value-added products via different conversion technologies, is yet to be implemented in sago industry. Therefore, this pair of articles presents techno-economic evaluation to examine the feasibility of sago-based biorefinery in Malaysia context. This is an essential and necessary initial step to encourage investors to evaluate and invest in sago-based biorefinery. In part 1 of this pair of articles, techno-economic analysis is conducted to examine the feasibility of sago biomass-based combined heat and power (CHP) system. In addition, a systematic generic fuzzy optimisation-based techno-economic evaluation framework is presented in Part 1 to determine the optimum CHP system with consideration of technical, environmental and economic aspects. Following the proposed approach, the optimum CHP system which using normal pressure boiler, generates 472 kW of net electricity from sago barks (10.2 odt/d) with a payback period of 3.51 years, and carbon saving of 5475 kgCO2/d. Note that in order to achieve the optimum result, making use of current labour from sago starch extraction process (SSEP), and off-site pre-treatment are needed. Besides, sensitivity analysis based on the existence of pre-treatment, variations in feedstock cost, boiler efficiency, and biomass feedstock is also conducted. Part 2 of this pair of articles is to further extend the techno-economic evaluation to examine the feasibility of integrated sago-based bioethanol production and energy systems ( Wan et al., 2015a ). In this pair of articles, a sago starch processing facility from Sarawak, Malaysia with a starch production capacity of 12 t/d is used for techno-economic evaluations
Biodiesel, an alternative diesel fuel, has become more attractive recently because of its environmental benefits and the increase in the petroleum price. Nowadays, most industrial applications of biodiesel production are performed by the transesterification of renewable biological sources based on homogeneous acid catalysts, which requires downstream neutralization and separation leading to a series of technical and environmental problems. However, heterogeneous catalyst could solve these issues, and be used as a better alternative for biodiesel production. Thus, a heuristic diffusion-reaction kinetic model has been established to simulate the transesterification of alkyl ester with methanol over a series of heterogeneous Cs-doped heteropolyacid catalysts. The novelty of this framework lies in detailed modeling of surface reacting kinetic phenomena and integrating that with particle-level transport phenomena all the way through to process design and optimisation. A kinetic model based on a three-step ‘Eley-Rideal' type of mechanism in the liquid phase is used in the simulation of reaction. The effect of diffusion inside a catalyst pellet is taken into account because of the mass transport inside the catalyst particles. This multi-disciplinary research offers better insights into catalyst design and process intensification for the industrial application of Cs-doped heteropolyacid catalysts for biodiesel production. A case study of the transesterification of tributyrin with methanol has been demonstrated to establish the effectiveness of this methodology.
Addressing a number of critical challenges caused by centralised production and large scale distribution infrastructures, local production systems designed in a synergistic manner could offer a possible pathway towards sustainability. The thesis focuses on the technical design of local production systems integrating local heterogeneous processes to satisfy local demands through efficient use of locally available renewable resources within technical and ecological constraints. A conceptual and quantitative multi-level framework, based on the Cumulative Exergy Resource Accounting methodology, was first developed for a better understanding of a local production system by considering the production and consumption of products or services as well as ecological processes. A general design framework comprising an optional preliminary design stage followed by a simultaneous design stage based on mathematical optimisation was then developed for solving the design problem towards minimum overall resource consumption. The preliminary design stage considers each supply subsystem individually and allows insights into the potential interactions between them. The simultaneous design stage has the capacity to include all design integration possibilities. A second, insight-based approach was further developed, which offers a new hierarchical and iterative decision and analysis procedure and incorporates design principles and ability to examine design decisions. The multilevel resource accounting framework was demonstrated on ethanol production from cane and successfully revealed how decisions at one level would affect other levels of the system. Both design approaches were illustrated on a case study for the design of local food-energy-water nexus. It showed the advantages of an integrated design of a system which makes use of local resources to meet its demands over a system relying on centralised supplies and over a design without considering integration opportunities between subsystems. The insight-based approach was also found to produce a comparable design to the simultaneous design approach while offering more valuable insights for decision makers.
The shipping industry represents a large sector with a wide range and significant scale of impacts. This underlines the need for sustainable decision making, which ensures the economic viability of operations in the long term, whilst reducing environmental impacts and health and safety risks. The demand for integrated tools that enable decision makers to integrate a holistic set of sustainability measures has already been pointed out in the literature, ideally considering the whole life cycle. In this Thesis, a multi-criteria decision support framework has been developed to evaluate the implementation of different material options on a life cycle basis. This comprises an evaluation of Life Cycle Costs (LCC), Environmental Impacts (EI) and Risk Assessment (RA) alongside each other, explicitly accounting for uncertainties in the inputs. Subsequently, all these aspects are integrated through a Multi-Criteria Decision Analysis (MCDA) approach, allowing to account for different perspectives and priorities of the decision maker. The framework was used to evaluate High-Strength Low-Alloy steel (HSLA) and advanced composites to replace conventional steel in ship structures. Results show the potential of these materials, indicating significant financial and emission savings over the life cycle, despite their higher initial costs. However, currently uncertainties and consequently risks are present and the approach shows how to account for these depending on the priorities of the decision maker. It is demonstrated that the approach provides structured decision support for sustainable material choices. The novelty lies in integrating different sustainability aspects in one coherent framework, taking a life cycle perspective. By doing this it is possible to integrate different types of data and explicitly account for different stakeholder perspectives and decision maker priorities. Another key feature is the clear visualisation of results, facilitating transparent communication to support the decision making process. Whilst the contribution of the research presented is demonstrated for the shipping sector, the potential of applying the framework and the methodology in other industrial applications is highlighted.
Global consumption for confectionery products are growing and is exerting enormous pressures on confectionery supply chains across the world to efficiently utilise natural resources towards becoming environmentally sustainable. However, there are a disparate range of studies investigating the environmental impacts of confectionery products, and more importantly how to improve environmental sustainability performance. In this thesis, the aim was to improve knowledge of opportunities for reducing environmental impact in confectionery manufacturing – from factory to supply chain – by developing methodological tools based on heat integration and Life Cycle Assessment (LCA). A range of novel methodologies were developed to advance heat integration and LCA knowledge, including (1) a heat integration framework combining direct and indirect heat exchange from zonal to multiple zones, possibly incorporating heat pump technology to enhance low grade heat recovery; (2) methodologies for systematically improving Life Cycle Inventory (LCI) data based on the role of multinational companies and for conducting effective LCA for confectionery products; and (3) a methodology to assess and quantify the environmental life cycle impacts of multi-product food factories. These methodologies have been applied at a multi-product confectionery factory, which has revealed significant findings: (1) combining direct and indirect heat integration from zonal to multiple zones can reduce factory energy by 4.04–6.05%, (2) heat pump technology can reduce factory energy by up to 29.2% but imposes design complexity and long economic paybacks up to 6.62 years, (3) fine bakery ware products on average was found to have the highest aggregated environmental life cycle impacts (higher than chocolate products by 7.1%, milk-based products by 18%, and sugar by 51.9%), and (4) combined improvement strategies of 50% energy reduction with 100% renewable energy, zero food waste to landfill (inc. 50% food waste reduction), and raw material changes to lower impacts can potentially reduce: Global Warming Potential by 65.82%, water depletion by 43.02%, abiotic depletion potential by 20.66%, land use by 17.45% and ecosystem quality by 7.24%. Overall, this research has culminated in several contributions to knowledge which substantially increases understanding of how to improve the environmental sustainability of confectionery manufacturing across the product, factory and supply chain level. The research will serve as a guide for future improvements, research and policies of confectionery manufacturers, supply chain actors, policy makers, and research institutes.