- 1964-67 Imperial Chemical Industries (Ltd): Technical Officer (Chemical Engineer)
- 1967-75 McGill University, Montreal (1967-70: Lecturer; 1970-72: Assistant Professor; 1972-75: Associate Professor)
- 1973-74 Università di Napoli: Visiting Professor in Industrial Chemistry and Chemical Plan
- 1975-76 Imperial College, London: Lecturer in Chemical Engineering
- 1976-81 University of Cambridge: Lecturer in Chemical Engineering
- 1978-81 Trinity College, Cambridge: Fellow (1980-81 Praelector)
- 1981- University of Surrey
- 1981-92: Professor of Chemical Engineering
- 1981-91: Head of Department of Chemical and Process Engineering
- 1992-05: Director of Centre for Environmental Strategy
- 1992-08: Professor of Environmental Technology
- 2008-: Emeritus Professor
Selected external appointments
- 1992-98 Member, UK Ecolabelling Board
- 1996-05 Member, Royal Commission on Environmental Pollution
- 1997- Member, International Expert Group on application of LCA to waste management
- 2000-10 Director, Blackrock-Merill Lynch New Energy Trust
- 2001 - Member, Rolls-Royce Environmental Advisory Board
- 2003-4 Member, Royal Society/Royal Academy of Engineering Working Group on Nanotechnology
- 2004-5 Specialist Adviser on Energy Efficiency to House of Lords' Science and Technology Committee
- 2004-9 Member, Forestry Commission Advisory Committee on Forest Research
- 2006-11 Member, Science Advisory Council of Department of the Environment, Food and Rural Affairs (DEFRA)
- 2006-11 Chair of the Advisory Committee of the Sustainable Development Research Network
- 2007-8 Member of Carbon Trust/BSI Steering Group on "Measurement of the
- embodied greenhouse gas emissions in products and services"
- 2009-10 President of the International Society for Industrial Ecology
- 2011- Executive Director of the International Society for Industrial Ecology
University roles and responsibilities
- Emeritus - research and p/g supervision
Environmental System Analysis, including Life Cycle Assessment, Industrial Ecology and Sustainable Energy Systems; Bioenergy; Sustainable Supply Chains; Engineering Ethics.
- National Industrial Symbiosis Programme (NISP)
- TSEC-Biosys research consortium (NERC)
The Planetary Boundaries (PB) framework represents a significant advance in specifying the ecological constraints on human development. However, to enable decision-makers in business and public policy to respect these constraints in strategic planning, the PB framework needs to be developed to generate practical tools. With this objective in mind, we analyse the recent literature and highlight three major scientific and technical challenges in operationalizing the PB approach in decision-making: first, identification of thresholds or boundaries with associated metrics for different geographical scales; second, the need to frame approaches to allocate fair shares in the ‘safe operating space’ bounded by the PBs across the value chain and; third, the need for international bodies to co-ordinate the implementation of the measures needed to respect the Planetary Boundaries. For the first two of these challenges, we consider how they might be addressed for four PBs: climate change, freshwater use, biosphere integrity and chemical pollution and other novel entities. Four key opportunities are identified: (1) development of a common system of metrics that can be applied consistently at and across different scales; (2) setting ‘distance from boundary’ measures that can be applied at different scales; (3) development of global, preferably open-source, databases and models; and (4) advancing understanding of the interactions between the different PBs. Addressing the scientific and technical challenges in operationalizing the planetary boundaries needs be complemented with progress in addressing the equity and ethical issues in allocating the safe operating space between companies and sectors.
The contemporary interest in urban cultivation in the global North as a component of sustainable food production warrants assessment of both its quantitative and qualitative roles. This exploratory study weighs the nutritional, ecological, and social sustainability contributions of urban agriculture by examining three cases—a community garden in the core of New York, a community farm on the edge of London, and an agricultural park on the periphery of San Francisco. Our field analysis of these sites, confirmed by generic estimates, shows very low food outputs relative to the populations of their catchment areas; the great share of urban food will continue to come from multiple foodsheds beyond urban peripheries, often far beyond. Cultivation is a more appropriate designation than agriculture for urban food growing because its sustainability benefits are more social than agronomic or ecological. A major potential benefit lies in enhancing the ecological knowledge of urbanites, including an appreciation of the role that organic food may play in promoting both sustainability and health. This study illustrates how benefits differ according to local conditions, including population density and demographics, operational scale, soil quality, and access to labor and consumers. Recognizing the real benefits, including the promotion of sustainable diets, could enable urban food growing to be developed as a component of regional foodsheds to improve the sustainability and resilience of food supply, and to further the process of public co-production of new forms of urban conviviality and wellbeing.
This review concentrates of the fundamental processes occurring in fluidized filters especially when concerned with the removal of gases by filtration. (from paper)
The behaviour of cracking catalyst with mean size 60 mu m fluidized by air at pressure from 1 to 7 bars was observed by cinephotography in a two-dimensional column. A series of runs was performed with constant gas superficial velocity. The size and number of bubbles passing through the bed decreased markedly as the pressure was increased, the change being most marked around 4 bars. The decrease in bubble flow rate was accompanied by an increase in the void fraction of the particulate phase. The dominant mechanism of bubble splitting at all pressures was by division from the roof, and the maximum stable bubble size decreased with increasing pressure.
Taking a life cycle approach to addressing economic, environmental and social issues, the book presents a series of new practical case studies drawn from a range of sectors, including mining, energy, food, buildings, transport, waste, and ...
The following review concentrates on the fundamental processes occurring in fluidised filters. Section II gives a brief summary of filtration in fixed granular beds, to define terms and concepts used in analysis of fluidised filtration. Attention is restricted to 'stationary' filtration, in which the collection medium is the granular material itself, without discussing 'non-stationary' effects caused by structural changes resulting from dust accumulation within the filter. Section III sets out an analysis of filtration in a fluidised bed, derived from conventional models of filtration in fixed beds and reaction in fluidised beds. The interpretation of available experimental results in terms of this model is summarised in Section IV. Section V reviews two variations which have been proposed on a simple configuration of: electrofluidised filters, and rotating fluidised beds. Actual and potential applications of the technique are discussed very briefly in Section VI. (from paper)
The aim of this book is to link demand and supply ofenvironmental information in the field of Life Cycle Management.
LCA has been developed primarily for industrial production systems. Application to agricultural systems requires systematic application of existing methodology and new methodological developments. Conventional approaches can obscure potential options for improving the environmental performance of systems involving agricultural production due to use of restricted system boundaries, incomplete assessment of impacts, and exclusion of ancillaries from the analysis. For use of nutrients such as phosphorus, it is proposed that Impact Assessment should be based on the quantity dispersed after use rather than on the input to the productive system. Eventually, the impacts associated with depletion should be based on technological or thermodynamic assessment of concentration for reuse, but this approach requires further theoretical development.
This paper uses an industrial case study of a boron system producing five co-products to examine different allocation methods recommended by ISO 14041 and compare them with the allocation methods most commonly used by LCA practitioners. In particular, allocation by physical causality is discussed. The paper illustrates how the use of whole system modelling can help to identify the correct type of causality for allocation. The case examined here concerns marginal changes of product-related parameters in the system, in this case represented by the output of boron co-products. The analysis shows that in some cases it can be correct to allocate the burdens on the basis of a simple physical quantity, such as mass, as long as the allocation parameter is based on physical causation and is not chosen arbitrarily. In whole system modelling, the correct causality is identified by the model itself, so that the possibility of allocation by an arbitrary parameter is avoided. However, as for system disaggregation and expansion, allocation through mathematical modelling may only be possible if detailed data for the system are available.
New method of production from TiO//2 and graphite in various reactor types is described in equation form.
Linear Programming (LP) is a powerful mathematical technique that can be used as a tool in Life Cycle Assessment (LCA). In the Inventory and Impact Assessment phases, in addition to calculating the environmental impacts and burdens, it can be used for solving the problem of allocation in multiple- output systems. In the Improvement Assessment phase, it provides a systematic approach to identifying possibilities for system improvements by optimising the system on different environmental objective functions, defined as burdens or impacts. Ultimately, if the environmental impacts are aggregated to a single environmental impact function in the Valuation phase, LP optimisation can identify the overall environmental optimum of the system. However, the aggregation of impacts is not necessary: the system can be optimised on different environmental burdens or impacts simultaneously by using Multiobjective LP. As a result, a range of environmental optima is found offering a number of alternative options for system improvements and enabling the choice of the Best Practicable Environmental Option (BPEO). If, in addition, economic and social criteria are introduced in the model, LP can be used to identify the best compromise solution in a system with conflicting objectives. This approach is illustrated by a real case study of the borate products system.
Purpose Liquefied natural gas (LNG) is expected to become an important component of the UK’s energy supply because the national hydrocarbon reserves on the continental shelf have started diminishing. However, use of any carbon-based fuel runs counter to mitigation of greenhouse gas emissions (GHGs). Hence, a broad environmental assessment to analyse the import of LNG to the UK is required. Methods A cradle to gate life cycle assessment has been carried out of a specific but representative case: LNG imported to the UK fromQatar. The analysis covers the supply chain, from gas extraction through to distribution to the end-user, assuming state-of-the-art facilities and ships. A sensitivity analysis was also conducted on key parameters including the energy requirements of the liquefaction and vaporisation processes, fuel for propulsion, shipping distance, tanker volume and composition of raw gas. Results and discussion All environmental indicators of the CML methodology were analysed. The processes of liquefaction, LNG transport and evaporation determine more than 50% of the cradle to gate global warming potential (GWP). When 1% of the total gas delivered is vented as methane emissions leakage throughout the supply chain, the GWP increases by 15% compared to the GWP of the base scenario. The variation of the GWP increases to 78% compared to the base scenario when 5% of the delivered gas is considered to be lost as vented emissions. For all the scenarios analysed, more than 75% of the total acidification potential (AP) is due to the sweetening of the natural gas before liquefaction. Direct emissions from transport always determine between 25 and 49%of the total eutrophication potential (EP) whereas the operation and maintenance of the sending ports strongly influences the fresh water aquatic ecotoxicity potential (FAETP). Conclusions The study highlights long-distance transport of LNG and natural gas processing, including sweetening, liquefaction and vaporisation, as the key operations that strongly affect the life cycle impacts. Those cannot be considered negligible when the environmental burdens of the LNG supply chain are considered. Furthermore, the effect of possible fugitive methane emissions along the supply chain are critical for the impact of operations such as extraction, liquefaction, storage before transport, transport itself and evaporation.
Geoffrey Hunt first developed an interest in nanotechnology in late 2002 when planning a visit to Japan to discuss the ethical implications of technological futures, and he put forward a tentative overview of nanotechnological possibilities in a ...
Taking a life cycle approach to addressing economic, environmental and social issues, the book presents a series of new practical case studies drawn from a range of sectors, including mining, energy, food, buildings, transport, waste, and ...
This book presents six visionary essays on the past, present and future of the chemical and process industries, together with a critical commentary.
This research compares and contrasts the physical and chemical characteristics of incinerator sewage sludge ash (ISSA) and pyrolysis sewage sludge char (PSSC) for the purposes of recovering phosphorus as a P-rich fertiliser. Interest in P recovery from PSSC is likely to increase as pyrolysis is becoming viewed as a more economical method of sewage sludge thermal treatment compared to incineration. The P contents of ISSA and PSSC are 7.2–7.5% and 5.6%, respectively. Relative to the sludge, P concentrations are increased about 8-fold in ISSA, compared to roughly 3-fold in PSSC. Both PSSC and ISSA contain whitlockite, an unusual form of calcium phosphate, with PSSC containing more whitlockite than ISSA. Acid leaching experiments indicate that a liquid/solid ratio of 10 with 30 min contact time is optimal to release PO4-P into leachate for both ISSA and PSSC. The proportion of P extracted from PSSC is higher due to its higher whitlockite content. Heavy metals are less soluble from PSSC because they are more strongly incorporated in the particles. The results suggest there is potential for the development of a process to recover P from PSSC.
This paper presents a detailed account of the supply chain for iron and steel in the UK, using material flow analysis. Due to the lack of a universally agreed methodology of material flow analysis, we include an explanation of the accounting methodology employed in the study. Data for the supply chain has been collected reaching back three decades, enabling analysis of trends in production and consumption of iron and steel over the years. This first part of a series of two papers quantifies the iron and steel flows through the UK economy including the annual amount of iron and steel embodied in all final goods that enter the use phase in the UK. The second part explores the more elusive flows of scrap generation and recycling. In this first paper we show that the UK no longer has the capacity to recycle the scrap it collects and is increasingly relying on foreign economies to do so. We also observe that trade in iron and steel products and ferrous metal containing final goods has increased dramatically over the years, but remained relatively balanced. Today, one-half of UK's iron and steel production is exported, whereas one-half of the iron and steel entering the UK use phase comes from imported final goods. The efficiency with which the UK iron and steel industry transforms iron ore and scrap into iron and steel products has increased substantially. However, there is no significant downward trend in the absolute level of iron and steel use in the UK. Between 1970 and 1981 the annual amount of steel put to use dropped from 16.4 to 10.7 million metric tonnes but climbed back up to 15 million metric tonnes twice since then 2006 Elsevier B.V. All rights reserved.
Allocation of environmental burdens is a recognised methodological problem in Life Cycle Assessment (LCA). It is the process of assigning to each of the functions of a multiple-function system only those environmental burdens and impacts that each function generates. It is argued in this paper that allocation is an artifact of applying LCA to individual products rather than to the whole productive system. To solve this problem, a new "marginal allocation" approach is proposed, based on whole system modelling. Marginal allocation is applicable when marginal changes about some defined state of the product system are to be considered and when the functional outputs can be varied independently. The specific approach developed here is based on representing the system by a model in the Linear Programming (LP) format. The allocation coefficients are equivalent to the marginal values calculated at the solution of the LP model. Marginal values represent a realistic description of the causal relationships between burdens and functional outputs and thus reflect the behaviour of the system. Changes in the system behaviour can also be modelled by LP. The approach is illustrated on three simple examples of multiple-function systems: combined waste treatment, co-production and recycling. © 1999 Elsevier Science Ltd. All rights reserved.
One of the main shortcomings of Life Cycle Assessment (LCA) when applied to the Nuclear Fuel Cycle, is that there is currently no recognised procedure to deal with radionuclide emissions in the Impact Assessment stage. A framework which considers both human and environmental impacts is required and a methodology which is compatible with the other impact assessment approaches in LCA must be developed. It is important that the discussion is not only restricted to concepts, but that a working methodology is developed which can be readily applied by LCA practitioners. A provisional method is available for assessing radiological impacts on human health, but no consideration has been given to potential effects on the environment. A methodology is proposed in this paper which assesses irradiation of the environment using Environmental Increments (EI) as the quality standard. This approach is based on the same principles as for the Ecotoxicity classification group, and it represents a working methodology which can be continuously improved as knowledge in the area increases.
Twelve of the main European LCA software packages currently available are examined with the aim of establishing which are the most appropriate for LCAs on industrial processes. The packages performances are assessed in terms of Volume of Data Windows™ environment Network Capabilities Impact Assessment Graphical representation of the inventory results Sensitivity analysis Units Cost User Support Flow Diagrams Burdens allocation Transparency of data Input & output parameters Demo version Quality of data The review concludes with a Specification Table which summarises the facilities available on each software package. The general conclusion from this study is that for industrially based LCAs, there are four packages which may offer advantages over the rest. These are The Boustead Model, The Ecobilan Group's TEAM™, PEMS 3.0 and SimaPro 3.1.
Phosphorus is an abundant resource, even though the most economically attractive reserves are geographically concentrated, so that whether and when production will peak are highly uncertain. However, analysis of the global use of phosphorus primarily in agriculture (including animal husbandry), reveals an exceptionally “leaky” supply chain: losses, including leaching from soils and animal excreta, amount to some 90% of the inputs. The potential for innovation to improve the efficiency of phosphorus use is therefore enormous, going beyond recovery of phosphorus from waste water to reducing the losses from the whole use system. Drivers to improve the system efficacy include the concerns over distribution and possibly security of supply and also the environmental impacts of phosphorus emissions. Future production, use and price of phosphorus therefore depend as much on changes in food consumption and agricultural practices as on changes in mining and processing.
The Imperial Chemical Industries (ICI) group has developed a method, called the "environmental burden system," to rank the potential environmental impacts of its emissions and wastes. The method uses potency factors to characterize the potential environmental impacts of wastes and emissions in ten major impact categories. When compared to the more traditional approach of reporting the total mass of emissions and wastes, the environmental burden approach provides a more meaningful picture of the potential impact of emissions; it helps identify the most harmful wastes and emissions; it provides the public with a better understanding of the potential impact of company operations; and it helps communicate the effectiveness of waste and emission reduction programs.
This book has been written to meet their needs.
The difficulties in predicting the frictional energy gradient for pipeline flow of settling slurries are well known. Whenever possible, it is desirable to carry out tests on a representative sample of the material to be conveyed, and scale the results to other pipe sizes. This paper presents a mechanistic approach to scaling tests results, based on the physical processes of solid trnapsort identified in the work of Newitt, Shook and Wilson. A basic distinction is drawn between solids conveyed in pseudo-homogeneous suspension, and solids stratified at higher concentration in the lower part of the pipe. The suspended and non-suspended solids are assumed to contribute independently to the friction gradient, in a fashion characterised by material constants which depend on the slurry under consideration. The proportion of solids conveyed as stratified load is taken to vary with mixture velocity in the general manner proposed by Wilson. The tests were designed to determine the material constants which describe the variation of pressure drop with mixture velocity in heterogeneous flow. The approach is illustrated by results obtained for three settling slurries of foundry sand, masonry sand and crusted granite, in horizontal pipes of diameter 0.20 m and 0.44 m (8 inch and 18 inch nominal). In each case, the validity of the scaling method is demonstrated. (A)
Correlations for the efficiency of removal of dust from a gas by Brownian diffusion, inertial deposition, gravitational settling, and direct interception in a fixed bed of spherical granular collector particles are applied to predicting the performance of a packed bed filter. The results clarify the difference between filtration of sub-micron particles and particles larger than 1 mu m. Filter efficiency is shown to be dependent on operating temperature, with pressure exerting a much weaker effect.
The purpose of this study was to evaluate the anticipated environmental benefits from integrating a dairy farm and a greenhouse; the integration is based on anaerobic digestion of manures to produce biogas energy, biogenic CO2, and digested slurry. A full Life Cycle Assessment (LCA) has been conducted on six modeled cases applicable in British Columbia, to evaluate non-renewable energy consumption, climate change, acidification, eutrophication, respiratory effects and human toxicity. Compared to conventional practice, an integrated system has the potential to nearly halve eutrophication and respiratory effects caused by inorganic emissions and to reduce non-renewable energy consumption, climate change, and acidification by 65-90%, while respiratory effects caused by organic emissions become negative as co-products substitute for other materials. Co-digestion of other livestock manures, greenhouse plant waste, or food and food processing waste with dairy manure can further improve the performance of the integrated system.
The book has been widely adopted for teaching purposes at the undergraduate and postgraduate level.
The filtration efficiency of a shallow fluidized bed of silica sand has been measured at 800DEGREESC and 1000DEGREESC for redispersed fly ash from a fluidized combustor and char fines from the NCB fluidized gasifier. Efficiency is much higher for fly ash, because of better retention due to stronger adhesion forces, but the filtration of both dusts is limited by retention on the surface of the collector. Retention can be enhanced by addition of a liquid retention aid to the collector, or by operating under conditions where the dust is sufficiently soft to experience better adhesion. For fly ash complete retention is achieved by operating the filter at 1000DEGREESC, near the sintering point of the ash. For gasifier fines retention is improved substantially by using heavy fuel oil as a retention aid, but further development is needed to improve efficiency towards the theoretical limit of collection.
To model the behaviour of a fabric filter it is essential to be able to predict the amount of cake removed as a result of the force applied to the filter medium by a cleaning pulse. Experimental measurements have been made of the fraction of cake removed as a function of the force exerted by an impulse tester designed to simulate the conditions experienced in a pulse jet filter. These experiments have shown that the force required to remove a given quantity of cake depends upon the areal cake density. The nature of this dependence has been predicted from theoretical consideration of the role of adhesion and cohesion forces, assuming that the cake breaks away in spalls of a regular shape and uniform size.
In order to analyze the motion of interacting bubbles in a fluidized bed, it is postulated that the velocity of a bubble may be approximated by adding to its rise velocity in isolation the velocity which the continuous phase would have at the position of the nose if the bubble were absent. This principle is applied to the coalescence of two bubbles on a common vertical line and found to agree quantitatively with experimental measurements obtained both by the authors and by other workers.
The approach developed by Nguyen et al. (1975) for predicting bubble behaviour in beds of Geldart's (1973) Group B particles has been modified to enable application to beds of larger scale. The model predicts that the size and spatial distribution of bubbles at any level above the distibutor is dependent on the bed depth above that level. Davidson and Harrison's (1963) expression for bubble rise velocity in freely-bubbling beds fortuitously gives a good estimate for the overall mean velocity of interacting and coalescing bubbles.
This is the first compilation of methods, tools and models that can be used to design products and manufacturing processes that prevent pollution from occurring in the first place, rather than treating the wastes after they are formed.
Purpose Screening social life cycle assessment (S-LCA) can be applied to identify the social hotspots associated with a production activity or supply chain. The objective of this paper is to explore how the quality of the results of a screening S-LCA can be improved, illustrated by a case study of sugarcane production in Brazil, an activity which has been criticized for its records on social sustainability due to issues such as poor working conditions for field workers and treatment of migrant workers. Methods Cradle-to-gate production of sugarcane in Brazil has been modeled using input-output analysis. The associated social impacts have been modeled using the framework of the Social Hotspots Database (SHDB), which is one of the first databases providing information on social risks along supply chains. The results from the SHDB were complemented with results from a systematic analysis of relevant literature. Content analysis was applied to 38 publications in English relevant to the social impacts of sugarcane production in Brazil, including peer-reviewed articles, “gray literature,” non-governmental organization reports, and conference presentations. Qualitative data analysis software NVivo 8 was used to facilitate the analysis of the publications. A deductive category system was established based on the subcategories recommended in the UNEP/SETAC social life cycle assessment guidelines. Social impacts were further aggregated and analyzed by social themes and impact categories. Results and discussion The social impacts of the sugarcane life cycle in Brazil arise almost exclusively within the Brazilian sugarcane sector itself. Fifteen social themes are identified as hotspots in the SHDB, and nine of them are also identified by content analysis. Health and safety and labor rights and decent work are the impact categories with the highest risks. Besides negative impacts, content analysis is capable of identifying several positive impacts related to sugarcane production. Due to the use of aggregated country-level data, social impacts of manual and mechanical harvesting of sugarcane cannot be differentiated in SHDB; however, this can be achieved by content analysis. Conclusions SHDB is effective for identifying social impacts at the country level, but the data are inevitably aggregated and only show averages across different technologies and geographical areas; therefore, the database is of limited value in distinguishing between alternative operations and locations. Content analysis can facilitate foreground data collection by differentiating operations and identifying both negative and positive impacts at the level of individual activities. We recommend that S-LCA databases can be integrated with results of content analysis to improve the richness—representativity and specificity—of results from a screening S-LCA, to differentiate between alternative production routes and processes.
Some fundamental problems, arising in the filtration of gases by fixed beds of granular collector, are reviewed. Capture of gas-borne particles by the collector normally occurs mainly by the processes of Brownian diffusion, inertial impaction and electrophoretic migration. Diffusional and electrophoretic capture are controlled by processes occurring close to the surface of the collector, and theoretical models are reasonably successful in predicting capture rates. Theoretical estimates for inertial impaction are much less reliable, and reasons for this are discussed. Retention of a particle by the collector is governed by a balance between particle kinetic energy and adhesion energy; trajectory calculations can be used to estimate conditions under which a captured particle is retained by the collector.
The Construction sector is characterised by complex supply networks delivering unique end products over short time scales. Sustainability has increased in importance but continues to be difficult to implement in this sector; thus, new approaches and practices are needed. This paper reports an empirical investigation into the value of the UN Sustainable Development Goals (SDGs), especially Sustainable Consumption and Production (SDG12), when used as a framework for action by organisations to drive change towards sustainability in global supply networks. Through inductive research, two different and contrasting approaches to improving the sustainability of supply networks have been revealed. One approach focuses on the “bottom up” ethical approach typified by the Forest Stewardship Council (FSC) certification of timber products, and the other on “top-down” regulations exemplified by the UK Modern Slavery Act. In an industry noted for complex supply networks and characterised by adversarial relationships, the findings suggest that, in the long term, promoting shared values aligned with transparent, third-party monitoring will be more effective than imposing standards through legislation and regulation in supporting sustainable consumption and production.
ISO 14041 requires that allocation by physical causality must reflect the quantitative changes in product outputs or functions and will not necessarily be in proportion to simple physical measure such as mass. This paper examines the instances where physical causality can be represented by mass. However, it also goes further than ISO to demonstrate that the type of causality in the system is not necessarily always the same and can change depending on the way the system is operated. Whole system modelling and the marginal allocation approach are used to identify the correct type of causality for different operating states of the system and the corresponding changes in the environmental burdens. This is generally not possible with the other allocation methods, also examined in this paper. Both process- and product-related burdens are considered and the approach is illustrated by a reference to an existing system producing five boron co-products.
Water model experiments are described in which spheres of various diameters and specific gravities were dropped from typical industrial heights into water. Maximum penetration distances, trajectories and retention times were measured and compared with theoretical predictions based on transient fluid flow. The relative importance of steady drag, added mass and history forces were demonstrated. Results indicate that immersion times are extremely short ( similar 1 second) for aluminum additions and low density ferro-alloys. High density ferro-alloys remain immersed considerably longer and penetrate much deeper.
The chill-on-demand system is a new technology designed to provide cooled products on demand, thereby avoiding chilled storage. It uses the cooling effect provided by endothermic desorption of carbon dioxide previously adsorbed onto a bed of activated carbon and has the potential to be applied to any type of product that needs to be cold at the point of consumption. The principles of life cycle engineering have been utilized to evaluate the overall environmental performance of one possible application of this technology: a self-chilling beverage can, with a steel outer can to contain the beverage and an inner aluminium can to contain the adsorbent. An attributional life cycle assessment has been undertaken considering all the life cycle stages of a self-chilling can: manufacture of each part of the beverage container, its utilization, collection of the used can, and management of the waste by reuse, recycling and landfilling. Activated carbon production is included in detail, to assess its contribution to the overall life cycle. The results are compared with those for conventional aluminium and steel beverage cans stored in two types of retail chiller: a single door refrigerator and a large open-front cooler. A sensitivity analysis explores alternative scenarios for activated carbon production and for recovery of the can components post-use for reuse or recycling. The results highlight the importance of using activated carbon produced from biomass by a process with efficient use of low-carbon electrical energy, energy recovery from waste streams and appropriate air pollution control, and of achieving high rates of recovery, re-use and recycling of the cans after use. The results suggest limited markets into which the product might be introduced, particularly where it would displace inefficient chilled storage in an electricity system with a high proportion of coal-fired generation.
Bioenergy has an important role to play in helping the UK meet its carbon target in 2050 and the European Renewable Energy Directive objectives for 2030. There are however uncertainties associated with the use of bioenergy, and whether or how much it contributes to green-house gas emission reductions. In order to help identifying environmental benefits and burdens associated with biomass use for energy production, an attributional life cycle assessment has been carried out of a biomass-fired CHP plant: the Heathrow Airport energy centre. This facility burns woodchips sourced from nearby forests providing 2 MWe of electricity and 8 MWth of thermal energy which delivers heat and cooling to Heathrow Terminal 2 and low temperature hot water to Terminal 5. A hot spot analysis is conducted to identify the process steps with the largest environmental impact, starting from the harvesting of the forest residue to the disposal of the boiler ash. A scenario analysis is performed to compare the impacts of the biomass plant against fossil alternatives and to identify which renewable energy sources, between biomass and MSW, should be prioritised for development and investment. The results show a reduction in GHG emissions from using biomass, with further benefits if the bottom ash is collected and re-used as a soil conditioner for land-farming or forestry. The paper also discusses the treatment of biogenic carbon in the assessment.
In reverse-flow cleaning of cakes deposited on porous filters, the pressure drop induced across the cake at the point of its detachment is the cleaning stress, ie the tensile stress which must be applied to overcome adhesion of the cake to the medium or the cohesion of the cake itself. A thicker cake requires a smaller pressure gradient for removal and therefore less cleaning gas flow and less pressure drop through the medium itself. Provided that true surface filtration occurs, the cleaning stress should be independent of cake areal mass. J. Sievert and F. Loeffler's data for a singed polyester needlefelt suggests that this is indeed so, and that the cleaning stresses induced by reverse-flow cleaning are close to those required if the filter is cleaned by mechanically-induced acceleration.
Purpose Following the boom of shale gas production in the USA and the decrease in the US gas prices, increasing interest in shale gas is developing in many countries holding shale reserves and exploration is already taking place in some EU countries, including the UK. Any commercial development of shale gas in Europe requires a broad environmental assessment, recognizing the different European conditions and legislations. Methods This study focuses on the UK situation and estimates the environmental impacts of shale gas using lifecycle assessment (LCA); the burdens of shale gas production in the UK are compared with the burdens of the current UK natural gas mix. The main focus is on the analysis of water impacts, but a broad range of other impact categories are also considered. A sensitivity analysis is performed on the most environmentally criticized operations in shale gas production, including flowback disposal and emission control, by considering a range of possible process options. Results and discussion Improper waste water management and direct disposal or spills of waste water to river can lead to high water and human ecotoxicity. Mining of the sand and withdrawal of the water used in fracking fluids determine the main impacts on water use and degradation. However, the water degradation of the conventional natural gas supply to the UK is shown to be even higher than that of shale gas. For the global warming potential (GWP), the handling methods of the emissions associated with the hydraulic fracturing influence the results only when emissions are vented. Finally, the estimated ultimate recovery of the well has the greatest impact on the results as well as the flowback ratio and flowback disposal method. Conclusions This paper provides insights to better understand the future development of shale gas in the UK. Adequate waste water management and emission handling significantly reduce the environmental impacts of shale gas production. Policy makers should consider that shale gas at the same time increases the water consumption and decreases the water degradation when compared with the gas mix supply. Furthermore, the environmental impacts of shale gas should be considered according to the low productivity that force the drilling and exploitation of a high number of wells.
A new generation of gas filter media is becoming available, based on rigidly bonded ceramic granules or fibres, and suitable for high-temperature duty. This paper outlines the main considerations in selecting and applying such a medium. Pressure drop through a 'virgin' medium is readily predictable from simple tests at ambient conditions. Behaviour on 'conditioning' over many cycles of filtration and cleaning can be determined by a simple 'coupon test', which shows the range of filter velocities which can be used and the cleaning action needed. Low-density media have some advantages, and this paper concentrates on one such medium which has been found to have good performance: Cerafil 12H10, formed as a bonded mat of synthetic ceramic fibres. It is currently supplied as cylindrical candles, but other geometries are under development. Experience in using Cerafil to filter gases generated by a pyrolytic incinerator treating contaminated soil is outlined.
Results obtained previously by other research workers are used to show that the stress which must be imposed on a dust cake in order to detach it is independent of cake loading and that this stress level is consistent with the stress required to detach the cake by mechanically-induced acceleration. See also abstract 1988/559.
To achieve sustainability in the global economy requires all organisations to operate in ways which are equitable and socially acceptable, technological viable, economically affordable and with minimum impact to the environment. Worldwide, and in particular in the UK, the sustainability of the oil refining industry has come under increasing scrutiny in an environment with high energy demand and stringent regulations. The oil refining sector processes large amounts of raw materials and produces substantial quantities of waste which need to be treated, mostly at facilities away from the refinery site. Waste management represents a challenge to the industry not only because of the impacts to the environment but also due to high treatment costs. This thesis describes research carried out to investigate and address some of the problems related to sustainability, in particular the management of raw materials and waste, based on the Valero Refinery, Pembroke, Wales as a specific example. The starting point of this research was a review of general theory, legislation and practice for measuring, monitoring and managing raw materials consumption and waste production. This was followed by an analysis of specific waste management practices at the Valero Refinery which showed that individual process units can do much to improve their performance by increased monitoring and control. Following the identification, classification and quantification of refinery waste over 2007-2013, it was observed that although variable, the annual amount of total waste produced has shown an increasing trend from about 21 kt to 24 kt with a peak of 29 kt in 2011. Similarly, the total annual costs of waste treatment have increased from about £2.0 M to £5.0 M. From this trend it was identified that hazardous waste was the largest (about 75 % w/w) and costliest (about 70 % of total) waste to treat, composed mainly of fluoridic caustic (about 85 %) but with significant contributions from phenolic caustic and oily sludge. Finally, a novel application of material flow analysis (MFA) methodology was developed to detect points where value could be recovered and waste reduced during a refinery-wide turnaround for maintenance and project purposes. The MFA revealed that waste management practices, in particular collection, segregation and temporary storage of some wastes, can be improved to avoid environmental contamination, landfilling and transportation within and outside the Refinery boundaries. It also evidenced opportunities to investigate alternative treatment methods, especially for used catalysts.
Gas-fluidized beds are commonly operated in a regime in which the rising particle-lean regions are dispersed in a 'continuous phase' of fluidized particles. The continuous phase is variously termed the dense, particulate, or emulsion phase, while the rising voids are termed bubbles if their diameter is less than that of the bed itself and slugs if their dimensions approach the diameter D or width of the containing column. Bubbling and slugging have been subjected to more research effort, experimental and theoretical, than any of the other regimes which have been recognized. The more important and useful findings are summarized. Refs.
George Plester's letter on the problem of intermittency in electrical supply from wind has been overstated. The generation and distribution system is designed to cope with rapid unpredictable changes in demand, so it can cope with slower and predictable changes in supply from one particular source. With regards to geographical averaging, the variations in output are damped on a UK-wide scale. It is a mistake to see any energy source in isolation from others in the system. For example, CHP plant can provide a spinning reserve with the power output variable to back-up variable souces like wind. The overall conclusion should look at the whole ssytem and how individual components fit into it.
In recent years society as a whole has become more aware and concerned about environmental issues. In light of increasingly stringent legislation and the more critical eyes of external stakeholders, companies have come to realise the heightened need for their actions to be seen as environmentally responsible. The innovation process provides companies with an excellent opportunity to influence the environmental impacts associated with their products. However, merely providing product developers with new processes and a toolbox of available ecodesign tools is rarely sufficient to facilitate more environmentally conscious decision-making in innovation. This paper proposes that employee participation within the development of new initiatives will aid the implementation of those initiatives. It highlights the first results from a study undertaken at Unilever seeking to initiate employee participation within initiatives for environmentally conscious innovation by ascertaining the attitudes of employees involved in the product innovation process regarding environmental responsibility and its integration into innovation.
The heart of the book is a detailing of the analytical methods-with special, but not exclusive emphasis on DEA methods-for evaluating and ranking the most promising R & D and technical innovation being developed.
This book examines the multitude of ways in which we value the environment from a social science perspective.
A new approach is proposed for direct measurement of the aerodynamic diameter of particles entrained in a gas. A probe, which can be a pitot static tube, is inserted into the flow. The velocity of each particle approaching the stagnation point is measured, for example by laser Doppler anemometry using a single optical fibre within the probe. The particle size distribution and concentration can be built up from a succession of single particle measurements. The instrument could be used to measure the efficiency of gas cleaning equipment, or to detect surges in particle size or concentration.
Topics covered in 'Slurry Transport using Centrifugal Pumps' include a review of fluid and particle mechanics, the principles of slurry flow, force-balance analysis of particle motion and deposition, heterogeneous slurry flow in horizontal pipes, vertical and inclined slurry flow, non-Newtonian slurry flow, the performance and testing of centrifual pumps, the effects of solids on pump performance, wear in pumps and pipelines, components of slurry systems, system design and operability and practical experience with slurry systems. (A.P.)
Social and Environmental Life Cycle Assessment (SELCA) is an analytical tool for profiling and evaluating the interaction between the social and technological systems within the life cycle of given service. Environmental Life Cycle Assessment (ELCA) and Social Life Cycle Assessment (SLCA) are undertaken with their own objectives using independent methodologies. Integrating the outcomes of the two assessments provides more comprehensive and insightful descriptions of the potential impacts of a life cycle, including the key social factors through which the life cycle is sustained and modified. The SELCA approach is outlined using the examples of two fuel cycles of coal and waste in energy-generation. There are some methodological issues in combining ELCA and SLCA which we highlight in order to encourage further work on the integration of environmental and social processes in LCA.
Geoffrey Hunt first developed an interest in nanotechnology in late 2002 when planning a visit to Japan to discuss the ethical implications of technological futures, and he put forward a tentative overview of nanotechnological possibilities in a ...
While participation in environmental decision-making is widely recognised and valued in democratic countries as beneficial, its format and scope have not always been the source of agreement. The use of environmental systems assessment (ESA) offers the opportunity for structuring knowledge and decision-making systematically and appropriately to decision makers' concerns, to enable lay publics to participate in development of policy and implementation in public sector initiatives. In order to perform participatory ESA, effective means of involving lay people are required. This paper describes the development and testing of an innovative interactive multimedia package (WOMBLE), written for non-experts to enable them to use the expert tool WISARD, a quantitative life cycle assessment package, to enable involvement in developing and assessing options for management of Municipal Solid Waste (MSW). It was shown that this combination of tools can reduce the time needed to achieve effective communication, learning and active engagement. © Imperial College Press.
Activated carbons have excellent performance in a number of process applications. In particular, they appear to have the most favourable characteristics for adsorption processes, thanks to their high porosity and large surface area. However, a comprehensive assessment of the environmental impacts of their manufacturing chain is still lacking. This study evaluates these impacts taking the specific case of activated carbon produced from coconut shells in Indonesia, which is the major coconut producer county. Coconut shells as raw materials are utilized for activated carbon production due to their abundant supply, high density and purity, and because they seem to have a clear environmental advantage over coal-based carbons, particularly in terms of acidification potential, non-renewable energy demand and carbon footprint. Life Cycle Assessment and process analysis are used to quantify all the environmental interactions over the stages of the life cycle of an activated carbon manufacturing chain, in terms of inputs of energy and natural resources and of outputs of emissions to the different environmental compartments. Estimates for the environmental burdens over the life cycle have been obtained by developing mass and energy balances for each of the process units in the production chain. The results indicate the operations with the greatest effects on the environmental performance of activated carbon production and hence where improvements are necessary. In particular, using electrical energy produced from renewable sources, such as biomass, would reduce the contributions to human toxicity (by up to 60%) and global warming (by up to 80%). Moreover, when the material is transported for processing in a country with a low-carbon electricity system, the potential human toxicity and global warming impacts can be reduced by as much as 90% and 60% respectively.
Complex decision contexts involving multiple (and often competing) policy objectives are common in both strategic and operational decisions encountered in engineering projects or programmes. The need to consider multiple objectives and to address the concerns of diverse stakeholders raises particular difficulties in applying sustainable development principles to defining and choosing an optimum project, process, product, policy or solution. This paper derives some fundamental characteristics of appropriate support for sustainable development decisions. Using these characteristics, three methodologies, which have been proposed as support tools for making strategic decisions and assessing policy choices for their contributions towards sustainable development, are reviewed critically with reference to their theoretical basis and informed by case studies of engineering applications. Recommendations are made to support best practice and to develop more effective support for such decisions in future.
Under some circumstances, electric vehicles (EVs) can reduce overall environmental impacts by displacing internal combustion engine vehicles (ICEVs) and by enabling more intermittent renewable energy sources (RES) by charging with surplus power in periods of low demand. However, the net effects on greenhouse gas (GHG) emissions of adding EVs into a national or regional electricity system are complex and, for a system with significant RES, are affected by the presence of storage capacity, such as pumped hydro storage (PHS). This article takes the Portuguese electricity system as a specific example, characterized by relatively high capacities of wind generation and PHS. The interactions between EVs and PHS are explored, using life cycle assessment to compare changes in GHG emissions for different scenarios with a fleet replacement model to describe the introduction of EVs. Where there is sufficient storage capacity to ensure that RES capacity is exploited without curtailment, as in Portugal, any additional demand, such as introduction of EVs, must be met by the next marginal technology. Whether this represents an average increase or decrease in GHG emissions depends on the carbon intensity of the marginal generating technology and on the fuel efficiency of the ICEVs displaced by the EVs, so that detailed analysis is needed for any specific energy system, allowing for future technological improvements. A simple way to represent these trade-offs is proposed as a basis for supporting strategic policies on introduction of EVs.
Particularly in the UK, there is potential for use of large-scale anaerobic digestion (AD) plants to treat food waste, possibly along with other organic wastes, to produce biogas. This paper presents the results of a life cycle assessment to compare the environmental impacts of AD with energy and organic fertiliser production against two alternative approaches: incineration with energy production by CHP and landfill with electricity production. In particular the paper investigates the dependency of the results on some specific assumptions and key process parameters. The input Life Cycle Inventory data are specific to the Greater London area, UK. Anaerobic digestion emerges as the best treatment option in terms of total CO2 and total SO2 saved, when energy and organic fertiliser substitute non-renewable electricity, heat and inorganic fertiliser. For photochemical ozone and nutrient enrichment potentials, AD is the second option while incineration is shown to be the most environmentally friendly solution. The robustness of the model is investigated with a sensitivity analysis. The most critical assumption concerns the quantity and quality of the energy substituted by the biogas production. Two key issues affect the development and deployment of future anaerobic digestion plants: maximising the electricity produced by the CHP unit fuelled by biogas and to defining the future energy scenario in which the plant will be embedded.
An integrated environmental and economic assessment of land use for food, energy and timber in the UK has been performed using environmental Life Cycle Assessment (LCA) and economic Life Cycle Costing (LCC), to explore complementary sustainability aspects of alternative land uses. The environmental assessment includes impacts on climate change, ecosystem services and biodiversity, all of which include soil carbon emissions. The systems explored include all processes from cradle to farm ‘gate’. The crops assessed were wheat and oilseed rape (under both organic and conventional farming systems), Scots Pine, and willow and Miscanthus. Food crops, particularly conventional food crops, are shown to have the highest climate-changing emissions per ha, whereas energy and forestry crops show negative net emissions. To a lesser extent, the same situation applies to impacts on ecosystems and biodiversity, with carbon storage in biomass playing a larger role than carbon in soils. The energy and forestry crops in this study show an overall beneficial environmental impact, in particular due to soil carbon sequestration, making these land uses the lowest contributors to climate change. Combining this with the non-renewable CO2 emissions displaced will mean that energy crops have an even lower impact. Economically, conventional food crops present the highest costs per ha, followed by organic food crops, energy and forestry crops. Integrating the results from LCA and LCC shows that the climate impacts per monetary unit of all land uses are dominated by soil management and, in the case of food production, also by fertilisation. Taxes or incentives such as “carbon charging” will encourage changes in practice in these areas to improve the sustainability of land management, mainly by building up Soil Organic Carbon (SOC).
The EC Directive on Integrated Pollution Prevention and Control (IPPC), now to be implemented in the UK under the Pollution Prevention and Control Act (1999), will widen the range of issues to be considered by enforcing authorities when determining the Best Available Techniques (BAT) for an installation. IPPC requires integrated control of emissions to air, water and land, the efficient use of energy and raw materials and the avoidance or reduction of impacts caused by disposal of wastes. This paper demonstrates that adopting a life cycle approach for the assessment of candidate techniques can fulfil these new requirements when choosing BAT. The glass manufacturing industry is used as a case study to show that the methodology can be used to assess both primary (in-process) and secondary (end-of-pipe) techniques for pollution prevention and control. General conclusions are drawn regarding the use of life cycle approaches to support the assessment of BAT, limitations in the current methodology and the requirements for future research. © Institution of Chemical Engineers.
The authors present a mechanistic approach in which the motion and coalescence of all bubbles in the bed are calculated to give full information on the temporal and spatial distributions of bubbles. (from paper)
This paper explores the use of LCA as a tool for process environmental management, thereby moving the focus from product to process oriented analysis. The emphasis is on Improvement Assessment in which the 'hot spots' in the system are targeted for maximum environmental improvements. In this context, it is useful to use multiobjective optimisation which renders valuation unnecessary. The approach is illustrated by the case study of the system processing boron ores to make five different products. The results of Inventory Analysis and Impact Assessment are presented and discussed. In Improvement Assessment, a number of improvement options are identified and evaluated, using system optimisation. It is shown that the site environmental performance can be improved over current operation by an average of 20% over the whole life cycle. Thus the study demonstrates that the optimisation approach to environmental process management may assist in identifying optimal ways to operate a process or plant from 'cradle to grave'. This may help the process industries not only to comply with legislation but also provide a framework for taking a more proactive approach to environmental management leading to more sustainable industrial operations and practices.
Ecolabelling is intended to provide a mechanism for conveying information to consumers on products within broad classes of goods which meet tight standards for environmental impact, and to manufacturers or retailers on targets for reducing environmental impact. Therefore life cycle assessment (LCA) is used to identify the most significant environmental impacts, as a basis for defining a minimum number of simple criteria for award of an ecolabel. This process introduces a number of problems which do not always aruse in other applications of LCA. This paper identifies some of the practical difficulties in carrying LCA through to ecolabel criteria, and summarizes some of the solutions being adopted. Specific areas of concern are definition of the functional unit, definition of 'cradle' and 'grave' in the context of different disposal and recycling practices throughout the European community, sourcing of raw materials, and validation, especially of imported goods. © 1993.
Sievert and Loeffler have recently presented data on the cleaning behaviour of a range of non-woven fabrics when subjected both to reverse gas flow and to mechanically induced acceleration. In common with other workers in the field they suggest that, for reverse flow, cleaning is easier if the deposited cake mass is greater; i.e. the pressure drop required across the filter in order to release the cake, and the reverse gas flowrate through it, are both reduced for thicker cakes. In this short paper Sievert and Loeffler's results show that the stress which must be imposed on the cake in order to detach it, is independent of cake loading and that this level is consistent with the stress required to detach the cake by mechanically induced acceleration.
A new generation of gas filter media is becoming available, based on rigidly bonded ceramic granules or fibres, and suitable for high temperature duty. This papers outlines the main considerations in selecting and applying such a medium. Pressure drop through a 'virgin' medium is readily predictable from simple tests at ambient conditions. Behaviour on 'conditioning' over many cycles of filtration and cleaning can be determined by a simple 'coupon test', which shows the range of filter velocities which can be used and the cleaning action needed. Low density media have some advantages, and this paper concentrates on one such medium which has been found to have good performance: Cerafil 12H10, formed as a bonded mat of synthetic ceramic fibres. It is currently supplied as cylindrical candles, but other geometries are under development. Experience in using Cerafil to filter gases generated by a pyrolytic incinerator treating contaminated soil is outlined.
The objective of the book is to critically evaluate current scientific work on defining the issue of sustainability and on measuring progress towards a sustainable state.
How can we design more sustainable industrial and urban systems that reduce environmental impacts while supporting a high quality of life for everyone? What progress has been made towards reducing resource use and waste, and what are the prospects for more resilient, material-efficient economies? What are the environmental and social impacts of global supply chains and how can they be measured and improved?
The industrial energy efficiency in the UK is improved through a government backed closed-loop economy model, which focuses on reducing flows of materials through the economy. In this direction, it is shown that elementary material balances can yield reductions in energy use, outweighing potential savings from improving the energy efficiency of industrial processes. Extending product life represents a reversal of current trends, it requires behavioral change even more than changes in technology or product design. The current approach, in the UK and various other places, is to tax labor rather than use of non-renewable resources, representing economic pressure in diametrically the wrong direction. Closed-loop material use along with industrial symbiosis - co-locating or connecting industries so that a waste or co-product from one becomes an input to another.
P recovery from wastewater treatment plants (WWTPs) as struvite fertiliser is a recognised method of improving P use efficiency and reducing P losses into the environment. The main driver for P recovery from the water industry viewpoint is the reduction in the nuisance of struvite clogging inside pumps and pipes. Struvite recovery leads to an average P recovery rate of 72 ± 7% from centrifuge centrate, with 8.8 ± 0.7% total P and 20.5 ± 3.2% PO4-P removed from the WWTP influent as struvite. This reduces the potential for struvite precipitation, moderates P loads on biological nutrient removal processes and lowers P concentration in the final effluent. Totalling revenue from sale of struvite and operational site savings, P recovery becomes an attractive option for water companies. The implementation of P recovery technologies to produce struvite fertiliser in all UK WWTPs could produce a national P fertiliser source of 7.05 ± 2.01 kt P/year. In addition, sludge produced at WWTPs could be diverted to advanced energy recovery (AER) processes and P recovered from AER residues; up to 21.71 ± 0.95 kt P/year could be recovered in this way in the UK. Combining the two methods of P recovery, UK imports of P fertiliser could be reduced by 36.2 ± 1.1%. P recovery on a large scale has the further benefit of protecting against eutrophication by reducing P emissions to water bodies by 21.7 ± 1.9%. The protection of the environment and reduction in reliance on imported P are major national motivations to legislate P recovery from waste.
This volume brings together research and best practice case studies on the topic of environmental accounting for management.
Recent vapour pressure measurements and calculations of thermodynamic equilibrium conditions suggest that, in gases obtained by pressurised coal combustion, only a few percent of the sodium and potassium should remain as vapour phase chlorides. The bulk of the alkalis are predicted to form sulphate, condensed onto entrained fly ash or present as an aerosol. Filtration of the condensed sulphates may suffice to reduce alkalis to levels acceptable to a gas turbine. Alumino-silicate materials appear to be potential filter media, because collected aerosol should be retained by reaction with the filter medium.
This important book describes the concept of `clean technology' as an approach for protecting the environment by preventing the pollution at source, minimising waste and reducing energy use.
Taking a life cycle approach to addressing economic, environmental and social issues, the book presents a series of new practical case studies drawn from a range of sectors, including mining, energy, food, buildings, transport, waste, and ...
The development of the fluidized bed as a continuously renewable gas filter was reviewed with special reference to work in which the performance was enhanced by addition of a liquid retention aid. Preliminary experiments designed to show the potential of the device for hot gas cleaning in combined cycle power generation were briefly described. (A)
Sustainable development requires decision making to incorporate multiple criteria, including environmental impacts based upon life cycle thinking. Within the oil industry, the application of life cycle approaches has tended to focus upon policy and corporate level, strategic decisions with concerns over the resource, and time demands precluding their application at the tactical/refinery level. Following a review of streamlined life cycle approaches, the authors have addressed these concerns by outlining a new approach that is tailored to suit decisions at the tactical level in oil refineries and is accessible to process engineers. Using a real problem at an oil refinery as a case study, this approach has been developed in greater depth and the application of life cycle thinking has been shown to aid the generation of alternatives and to provide the decision maker with valuable insights that can be considered alongside social and economic criteria. It is anticipated that this approach could facilitate the uptake of life cycle thinking at oil refineries, with potential applications at other large industrial facilities.
Every year in Europe refrigerant gases with a greenhouse-warming equivalent of more than 30 Mt CO2 are emitted from retail refrigerators. Furthermore, the effective efficiency of such refrigerators is far below that achievable under ideal (e.g. optimal-load; minimum access) operation. In this work the design of an alternative on-demand cooling unit is presented. The unit is based on the cooling effect provided by desorption of carbon dioxide previously adsorbed onto a bed of graphite-bonded activated carbon: in this paper, a case study of a self-chilling beverage can is used to demonstrate the technology. The high compaction of the activated carbon, and the presence of graphite, enhances the heat transfer properties of the adsorbent, thus enhancing the efficiency of cooling. Furthermore, potential exists for the use of activated carbon and CO2 from waste sources. This paper provides an overview of the design basis and environmental advantages of the unit, and experimental and simulation studies on the thermal dynamics of the cooling process. Particular attention is given to the effective thermal conductivity of the activated carbon bed. The results indicate that adequate on-demand cooling can be achieved within a portable unit. However, scope exists for enhancing the heat transfer within the cooling chamber through design and bed composition alterations. Recommendations for improved unit design are presented.
Paper No. 74-HT-EE.
Changes resulting from economic activities in the quantity and quality of soil in a system under analysis are important considerations in a life cycle assessment (LCA) study because they affect the safeguard subjects of resources and future agricultural productivity. In the approach proposed here, soil is treated as an ancillary which may leave the system in a form different from that at entry. Relevant factors describing possible changes in the soil include: soil mass, nutrients, weeds and weed seeds, pathogens, nutrients, salts, pH, organic matter, and soil texture and structure. Many of the factors can be included by modelling the effects of infrequent activities benefitting the crop(s) under analysis. Three additional factors require separate assessment: changes in the mass of soil, its organic matter content, and soil compaction. Taken together, these approaches provide an integrated assessment method capable of accounting for the overall impacts of agricultural production on soil.
The filtration of coal derived gases at high temperatures and pressures (HTHP) affords the potential for increased efficiency from advanced power systems such as the British Coal gasification based 'Topping Cycle'. Rigid porous silicon carbide filters are amongst the most successful HTHP filters tested to date but questions about their long term durability remain unanswered. An alternative low density, high porosity fibrous ceramic filter medium has been developed and successfully tested on fuel gas at a filtration velocity of 0.1ms-1 and temperature of 950°C. Materials performance appeared adequate for this duty but longer duration tests will be required to confirm long term durability.
Entrainment of solid particles by gas jets discharged downwards through slotted nozzles into bubble-free beds of fluidized particles is considered. The gas flow in the jet is calculated for irrotational flow, using a correlation established previously for slot opening as a function of operating variables. The momentum boundary layer thickness and shear stress at the horizontal interface between jet and particles are then calculated by integral boundary layer analysis. The calculated shear stress distributions are consistent with measurements of the momentum of bed particles caused to saltate by the jet, and explain the dependence of particle movement on the various operating variables. The results provide a direct confirmation of a hypothesis due to Owen on the mechanism of saltation. © 1976.
While the rhetoric of public engagement is increasingly commonplace within industry, there has been little research that examines how lay knowledge is conceptualized and whether it is really used within companies. Using the chemicals sector as an example, this paper explores how companies conceive of publics and "public knowledge," and how this relates to modes of engagement/communication with them. Drawing on qualitative empirical research in four companies, we demonstrate that the public for industry are primarily conceived as "consumers" and "neighbours," having concerns that should be allayed rather than as groups with knowledge meriting engagement. We conclude by highlighting the dissonance between current advocacy of engagement and the discourses and practices prevalent within industry, and highlight the need for more realistic strategies for industry/public engagement.
The aim of this book is to link demand and supply of environmental information in the field of Life Cycle Management.
A LINEARIZED STABILITY ANALYSIS OF THE UPPER SURFACE OF A BUBBLE IN A FLUIDIZED BED LEADS TO PREDICTIONS OF INITIAL GROWTH RATES AND MOST SENSITIVE WAVELENGTHS FOR DISTURBANCES OF THE INTERFACE.IT IS SHOWN THAT THE DEGREE OF INSTABILITY IS PRIMARILY A FUNCTION OF THE EFFECTIVE KINEMATIC VISCOSITY OF THE DENSE PHASE, WHILE THE INTERSTITIAL FLUID VELOCITY HAS A COMPARATIVELY MINOR INFLUENCE.THE RESULTS ARE CONSISTENT WITH AVAILABLE EVIDENCE ON THE INCIDENCE OF BUBBLE SPLITTING IN FLUIDIZED SYSTEMS.(A)
How can we design more sustainable industrial and urban systems that reduce environmental impacts while supporting a high quality of life for everyone? What progress has been made towards reducing resource use and waste, and what are the prospects for more resilient, material-efficient economies? What are the environmental and social impacts of global supply chains and how can they be measured and improved?Such questions are at the heart of the emerging discipline of industrial ecology, covered in Taking Stock of Industrial Ecology.
A novel spouted bed was developed, suitable for the processing of large light particles subject to substantial cohesion or interparticle attraction. The bed is caused to spin about a vertical axis by the addition of gas through jets at the wall. A torque balance on the bed enables the minimum gas flow rate for rotation to be estimated. (A)
THE MODEL PROPOSED BY CLIFT AND GRACE TO DESCRIBE THE MOTION OF INTERACTING BUBBLES IN A FLUIDIZED BED IS EXTENDED TO APPLY TO FREELY-BUBBLING BEDS.THE MODELR REQUIRES AS A BOUNDARY CONDITION THE SIZE, POSITION AND FREQUENCY OF BUBBLES AT SOME LOW REFERENCE LEVEL IN THE BED.THE MOTION AND COALESCENCE OF BUBBLES IN THE BED IS THEN CALCULATED TO GIVE PREDICTIONS OF BUBBLE FREQUENCY, SIZE AND SPATIAL DISTRIBUTIONS AT ANY HEIGHT ABOVE THE REFERENCE LEVEL.IT IS SHOWN THAT THE PREDICTIONS AGREE CLOSELY WITH MEASUREMENTS OF THESE PARAMETERS IN TWO-DIMENSIONAL BEDS EVEN THOUGH THE MODEL REQUIRES NO FITTED PARAMETERS.(A)
The British Coal Corporation and the University of Surrey, England, are collaborating to develop a model to describe the bubbling behaviour of a fluidised bed combustor. The model is based on the Clift and Grace model of bubble interaction and coalescence, but is being extended to incorporate the effect of heat transfer tubes in the bed. As in any such model, a necessary boundary condition is the size, frequency and sequence of bubbles forming at the distributor. Relatively little data on bubble formation is reported in the literature, especially under conditions such as those obtaining in a combustor where a cold gas stream enters a hot bed. This paper reports an experimental investigation of bubble formation in a 0.3m square atmospheric pressure coal-fired combustor. The distributor comprised nine vertical 'standpipes', ie capped tubes with horizontal radial holes. A 150mm diameter silica window was mounted in the bed wall to enable high-speed video tape recording of the formation of bubbles at one of the standpipes. Transient gas flow and pressure in three of the standpipes were measured and related to bubble formation. The work was undertaken to provide some elucidation of the mechanisms of bubble formation from standpipe distributors and also some of the information necessary for algorithms to simulate the air distributor in the model.
It has long been recognised that plastic objects released into the environment have harmful impacts on wildlife. Public realisation that plastic pollution is a major global environmental problem is more recent and has been sudden, sparked by publication of an analysis of the flows of polluting plastics into the environment and the accumulated stocks of polluting waste, particularly in the oceans.1 This contribution aims first to provide an introduction to the history and uses of plastics in the economy and, secondly, to set out the routes by which plastics leak from the economy into the environment in order to inform development of possible strategies to alleviate the problem of plastic pollution.
Life cycle assessment (LCA) is a method to identify and quantify the environmental performance of a process or a product from "cradle to grave". Its main potential in environmental decision-making lies in providing a quantitative basis for assessing potential improvements in environmental performance of a system throughout the life cycle. This paper introduces the use of multiobjective system optimisation in LCA as a tool for identifying and evaluating the best possible options for environmental management of the product system. A life cycle of a system is optimised on a number of environmental objective functions, defined in terms of the usual LCA burden or impact categories, and a range of environmental optima is found on the Pareto or non-inferior surface. As a result, possibilities for improving the environmental performance of the system are identified. Since system improvements cannot be carried out on the basis of environmental LCA only, it is also shown in this paper that the compromise between environmental and economic performance can be found on the non-inferior surface. The value of multi objective optimisation in system analysis lies in providing a set of alternative options for system improvements rather than a single prescriptive solution, thus enabling the choice of the Best Practicable Environmental Option (BPEO) and Best Available Technique Not Entailing Excessive Cost (BATNEEC). This approach is illustrated by application to a real case study of a system producing five borate products. © 1999 Elsevier Science Ltd. All rights reserved.
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.
Experimental measurements were made of the fraction of cake removed from a polyester needled filter fabric as a function of the force exerted by an impulse tester designed to simulate the conditions experienced in a pulse-jet filter.
Coupons of rigid ceramic filtration media have been conditioned using fine gasifier char and calcium carbonate dusts and both the cake resistance and the stress needed to detach the cake from the medium have been measured. For gasifier char, cake resistance appears to be independent of face velocity and proportional to areas cake loading, while cake removal stress is approximately independent of loading. For calcium carbonate, broadening the size distribution increases the cake resistance but slightly reduces the cake removal stress. Increases in particle size and cake void fraction decrease both cake resistance and cake removal stress. However, since increase in particle size seems often to be accompanied by decrease in cake void fraction, the range of commonly-observed cake resistivities and removal stresses is narrower than might otherwise be expected. © 1992.
Although 'Sustainable Development' is invoked in current political and environmental debates, the concept has eluded precise definition. In general terms, 'sustainability' means working within three sets of constraints: techno-economic, environmental and social. Traditionally, engineering has been concerned with techno-economic issues. Explicit recognition of environmental and social issues has led to the way of thinking called Clean Technology, and to the use of more holistic analytical tools including Life Cycle Assessment. Howeover, it is argued here that a paradigm shift is needed in the way engineering skills and knowledge are used, as inputs to deliberative processes which go beyond techno-economic decisions. The need for this new paradigm is illustrated by the waste management sector, which is increasingly seen as needing the skills of the 'New Model' chemical engineer. © Institution of Chemical Engineers.
To diagnose the processes causing metal wastage from immersed surfaces in fluidized beds, a miniaturized probe was developed for simultaneous measurement of the transient normal and tangential components of particle velocity and stress against a surface. In a two-dimensional bed, high shear stresses are generated by oblique impact of particles in bubble wakes. The associated particle velocities correspond closely with estimates from video records, and are consistent with current understanding of particle motion in fluidized beds. Taken together, the results suggest that metal wastage results from a combination of impact and abrasion. (A)
The influence of dust loading and gas inlet/outlet dimensions on the performance of four industrial scale (0. 45 m diameter) cyclones has been investigated. All experiments were performed under ambient conditions at an inlet velocity of 15 m/s over a loading range of 0. 5 - 130g solid/m**3 air. Measurements of the pressure drop, gravimetric efficiency and grade-efficiency were made. Strong variations in both pressure drop and separation performance with geometry and solid loading were found. These variations are well described by existing predictive relations. The results are analysed to further elucidate the nature of the observed trends.
By means of the life cycle assessment methodology, the purpose of this study is to assess the environmental impact when biomethane from organic waste produced at residential level is used to supply energy to a group of dwellings in the distributed generation paradigm. Three different Combined Heat and Power systems, such as fuel cells, Stirling engine and micro gas turbine, installed at household level are assessed in two different settings: one in Northern Europe (UK) and one in Southern Europe (Italy). Different operating strategies are investigated for each technology. Moreover, marginal electricity production technologies are analysed to assess their influence on the results. This study has demonstrated that the type of bio-methane fed micro-CHP technology employed has a significantly different environmental impact: fuel cells are the most environmentally friendly solution in every category analysed; Stirling engines, although can supply heat to the largest number of dwellings are the least environmentally friendly technology. However, key factors investigated in the model presented in this paper influence the decision making on the type of technology adopted and the operating strategy to be implemented.
Indicators which reflect environmental, economic, health and safety issues, have been categorized as microecometrics and macroecometrics. The former, generally flow based measures, have been developed for local, firm- wide or product based assessments. Microecometrics include materials intensity, energy consumption and emissions data, often from life cycle perspectives. They are, generally, intensive and are scaled with respect to unit of production, GDP or per capita, though other normalization factors have been proposed. In contrast macroecometrics tend to be extensive and represent global conditions such as temperatures and environmental concentrations. Ecometrics are subjective and reflect the dominant value of the individual, family unit, stakeholder group or firm. As such overaggregating or reducing the number of ecometrics for given applications, such as the rating of investments or access to credit, presents potential conflicts. Furthermore, while eco-indicators used for internal corporate reporting should not, necessarily, be validated, those microecometrics which involve external reporting, or multiple stakeholders, are arbitrary if not derived from, or based on, comprehensive life cycle approaches. This paper summarizes ECOMETRICS'98, a workshop held in Lausanne, Switzerland in January 19-20, 1998. It discusses ecometric needs of various users including consumers, designers, private sector decision makers as well as politicians and policy makers. A discussion regarding appropriate microecometrics for industrial sectors including chemical, pharmaceutical, insurance, finance, electronics, manufacturing and consumer products is also summarized.