Dr Zoe M Harris

The effect of a transition from grassland to second-generation (2G) bioenergy on soil carbon and greenhouse gas (GHG) balance is uncertain, with limited empirical data on which to validate landscape-scale models, sustainability criteria and energy policies. Here, we quantified soil carbon, soil GHG emissions and whole ecosystem carbon balance for short rotation coppice (SRC) bioenergy willow and a paired grassland site, both planted at commercial scale. We quantified the carbon balance for a 2-year period and captured the effects of a commercial harvest in the SRC willow at the end of the first cycle. Soil fluxes of nitrous oxide (N2O) and methane (CH4) did not contribute significantly to the GHG balance of these land uses. Soil respiration was lower in SRC willow (912 +/- 42gCm(-2)yr(-1)) than in grassland (1522 +/- 39gCm(-2)yr(-1)). Net ecosystem exchange (NEE) reflected this with the grassland a net source of carbon with mean NEE of 119 +/- 10gCm(-2)yr(-1) and SRC willow a net sink, -620 +/- 18gCm(-2)yr(-1). When carbon removed from the ecosystem in harvested products was considered (Net Biome Productivity), SRC willow remained a net sink (221 +/- 66gCm(-2)yr(-1)). Despite the SRC willow site being a net sink for carbon, soil carbon stocks (0-30cm) were higher under the grassland. There was a larger NEE and increase in ecosystem respiration in the SRC willow after harvest; however, the site still remained a carbon sink. Our results indicate that once established, significant carbon savings are likely in SRC willow compared with the minimally managed grassland at this site. Although these observed impacts may be site and management dependent, they provide evidence that land-use transition to 2G bioenergy has potential to provide a significant improvement on the ecosystem service of climate regulation relative to grassland systems.

This article evaluates the suitability of the ECOSSE model to estimate soil greenhouse gas (GHG) fluxes from short rotation coppice willow (SRC-Willow), short rotation forestry (SRF-Scots Pine) and Miscanthus after land-use change from conventional systems (grassland and arable). We simulate heterotrophic respiration (R h), nitrous oxide (N 2 O) and methane (CH 4) fluxes at four paired sites in the UK and compare them to estimates of R h derived from the ecosystem respiration estimated from eddy covariance (EC) and R h estimated from chamber (IRGA) measurements, as well as direct measurements of N 2 O and CH 4 fluxes. Significant association between modelled and EC-derived R h was found under Miscanthus, with correlation coefficient (r) ranging between 0.54 and 0.70. Association between IRGA-derived R h and modelled outputs was statistically significant at the Aberys-twyth site (r = 0.64), but not significant at the Lincolnshire site (r = 0.29). At all SRC-Willow sites, significant association was found between modelled and measurement-derived R h (0.44 ≤ r ≤ 0.77); significant error was found only for the EC-derived R h at the Lincolnshire site. Significant association and no significant error were also found for SRF-Scots Pine and perennial grass. For the arable fields, the modelled CO 2 correlated well just with the IRGA-derived R h at one site (r = 0.75). No bias in the model was found at any site, regardless of the measurement type used for the model evaluation. Across all land uses, fluxes of CH 4 and N 2 O were shown to represent a small proportion of the total GHG balance; these fluxes have been modelled adequately on a monthly time-step. This study provides confidence in using ECOSSE for predicting the impacts of future land use on GHG balance, at site level as well as at national level.

The Intergovernmental Panel on Climate Change (IPCC) report that to limit warming to 1.5 °C, Bioenergy with Carbon Capture and Storage (BECCS) is required. Integrated assessment models (IAMS) predict that a land area between the size of Argentina and Australia is required for bioenergy crops, a 3–7 time increase in the current bioenergy planting area globally. The authors pose the question of whether vertical farming (VF) technology can enable BECCS deployment, either via land sparing or supply. VF involves indoor controlled environment cultivation, and can increase productivity per unit land area by 5–10 times. VF is predominantly being used to grow small, high value leafy greens with rapid growth cycles. Capital expenditure, operational expenditure, and sustainability are challenges in current VF industries, and will affect the ability to utilise this technology for other crops. The authors argue that, whilst challenging, VF could help reach wider climate goals. Application of VF for bioenergy crops could be a game changer in delivering BECCS technologies and may reduce the land footprint required as well as the subsequent associated negative environmental impacts. VF bioenergy could allow us to cultivate the future demand for bioenergy for BECCS on the same, or less, land area than is currently used globally.

Bioenergy aims to reduce greenhouse gas (GHG) emissions and contribute to meeting global climate change mitigation targets. Nevertheless, several sustainability concerns are associated with bioenergy, especially related to the impacts of using land for dedicated energy crop production. Cultivating energy crops can result in synergies or trade-offs between GHG emission reductions and other sustainability effects depending on context-specific conditions. Using the United Nations Sustainable Development Goals (SDGs) framework, the main synergies and trade-offs associated with land use for dedicated energy crop production were identified. Furthermore, the context-specific conditions (i.e., biomass feedstock, previous land use, climate, soil type and agricultural management) which affect those synergies and trade-offs were also identified. The most recent literature was reviewed and a pairwise comparison between GHG emission reduction (SDG 13) and other SDGs was carried out. A total of 427 observations were classified as either synergy (170), trade-off (176), or no effect (81). Most synergies with environmentally-related SDGs, such as water quality and biodiversity conservation, were observed when perennial crops were produced on arable land, pasture or marginal land in the ‘cool temperate moist’ climate zone and ‘high activity clay’ soils. Most trade-offs were related to food security and water availability. Previous land use and feedstock type are more impactful in determining synergies and trade-offs than climatic zone and soil type. This study highlights the importance of considering context-specific conditions in evaluating synergies and trade-offs and their relevance for developing appropriate policies and practices to meet worldwide demand for bioenergy in a sustainable manner. •Synergies and trade-offs between SDGs from land use for bioenergy.•Synergies are related to water quality, soil quality and biodiversity conservation.•Trade-offs are related to water availability, food security and revenue.•Previous land use and feedstock are more relevant than other context conditions.

Consumers are becoming increasingly attuned to sustainability issues in the food supply chain and demanding retailers to keep pace with their changing expectations. The visual nature of plastic pollution has strengthened public awareness of the environmental impact of plastic packaging. Against this backdrop, biodegradable plastics have been promoted as an alternative to conventional polymers, offering the potential to tackle hard-to-recycle plastics while being compatible with food waste recycling. Given increased recognition of food waste as an untapped resource worldwide and the incoming policy mandating separate collections for household and commercial food waste across the EU from 2023, anaerobic digestion is a particularly promising strategy and can make an important contribution to the transition to circular waste management practices. However, currently no industrial standard exists for 'digestible' packaging. Our research addresses stakeholder attitudes towards the treatment of biodegradable plastic packaging in food waste anaerobic digestion. We conducted 19 semi-structured interviews with a range of stakeholders, including the biowaste recycling sector, retail, governmental bodies and environmental charities. Qualitative data were categorised into thematic nodes based on inductive and deductive strategies. Content analysis showed significantly divergent views on biodegradable plastics. Though most respondents acknowledged the merits of biodegradable plastics, concerns over their compatibility with the current anaerobic digestion infrastructure (e.g. systematic depackaging, retention times) and their ultimate biodegradability were raised. In light of these issues, potential solutions are discussed and the role that legislation and consumer education can play in ensuring that the anaerobic digestion sector can accommodate these novel materials are highlighted.

Wide-scale application of biochar to soil has been suggested as a mechanism to offset increases in CO 2 emissions through the long-term sequestration of a carbon rich and inert substance to the soil, but the implications of this for soil diversity and function remain to be determined. Biochar is capable of inducing changes in soil bacterial communities, but the exact impacts of its application are poorly understood. Using three European sites [UK SRC, short rotation coppice, French grassland (FR) and Italian SRF, short rotation forestry (IT)] treated with identical biochar applications, we undertook 16S and ITS amplicon DNA sequencing. In addition, we carried out assessments of community change over time and N and P mobilization in the UK. Significant changes in bacterial and community structure occurred due to treatment, although the nature of the changes varied by site. STAMP differential abundance analysis showed enrichment of Gemmatimonadete and Acidobacte-ria in UK biochar plots 1 year after application, whilst control plots exhibited enriched Gemmataceae, Isosphaer-aceae and Koribacteraceae. Increased mobility of ammonium and phosphates was also detected after 1 year, coupled with a shift from acid to alkaline phosphomonoesterase activity, which may suggest an ecological and functional shift towards a more copiotrophic ecology. Italy also exhibited enrichments, in both the Proteobacte-ria (driven by an increase in the order Rhizobiales) and the Gemmatimonadetes. No significant change in the abundance of individual taxa was noted in FR, although a small significant change in unweighted UNIFRAC occurred, indicating variation in the identities of taxa present due to treatment. Fungal β diversity was affected by treatment in IT and FR, but was unaffected in UK samples. The effects of time and site were greater than that of biochar application in UK samples. Overall, this report gives a tantalizing view of the soil microbiome at several sites across Europe and suggests that although application of biochar has significant effects on microbial communities, these may be small compared with the highly variable soil microbiome that is found in different soils and changes with time.

Bioenergy has been identified as a key contributor to future energy scenarios consistent with the Paris Agreement targets, and is relied upon in scenarios both with and without bioenergy with carbon capture and storage, owing to the multiple ways in which bioenergy can substitute fossil fuels. Understanding the environmental and societal impacts of land-use change (LUC) to bioenergy crops is important in determining where and how they could be deployed, and the resulting trade-offs and co-benefits. We use systematic review and meta-analysis to assess the existing literature on two poorly understood impacts of this LUC that are likely to have an important effect on public acceptability: cultural ecosystem services and biodiversity. We focus on the impact of LUC to non-food bioenergy crops on agricultural landscapes, where large-scale bioenergy planting may be required. Our meta-analysis finds strong benefits for biodiversity overall (up 75% +/- 13%), with particular benefits for bird abundance (+81% +/- 32%), bird species richness (+100% +/- 31%), arthropod abundance (+52% +/- 36%), microbial biomass (+77% +/- 24%), and plant species richness (+25% +/- 22%), when land moves out of either arable crops or grassland to bioenergy production. Conversions from arable land to energy trees led to particularly strong benefits, providing an insight into how future LUC to non-food bioenergy crops could support biodiversity. There were inadequate data to complete a meta-analysis on the effects of non-food bioenergy crops on cultural ecosystem services, and few generalizable conclusions from a systematic review of the literature, however, findings highlight the importance of landscape context and planting strategies in determining impact. Our findings demonstrate improved farm-scale biodiversity on agricultural land with non-food bioenergy crops, but also limited knowledge concerning public response to this LUC, which could prove crucial to the successful expansion of bioenergy to meet the Paris targets.

There is increasing interest in the use of nonfood second-generation lignocellulosic feedstocks and a move away from food crops for bioenergy applications, but questions still remain on sustainability. Empirical data are needed to quantify the GHG balance of land-use transition to lignocellulosic bioenergy cropping systems, to inform lifecycle analyses and aid model validation. The aim of this project 'Ecosystem Land Use Modeling and Soil Carbon GHG Flux Trial' is to produce a framework for predicting the sustainability of bioenergy deployment across the UK. This GB£4m consortium project is commissioned and funded by the Energy Technologies Institute, UK.

A systematic review and meta-analysis were used to assess the current state of knowledge and quantify the effects of land use change (LUC) to second generation (2G), non-food bioenergy crops on soil organic carbon (SOC) and greenhouse gas (GHG) emissions of relevance to temperate zone agriculture. Following analysis from 138 original studies, transitions from arable to short rotation coppice (SRC, poplar or willow) or perennial grasses (mostly Miscanthus or switchgrass) resulted in increased SOC (+5.0 +/- 7.8% and +25.7 +/- 6.7% respectively). Transitions from grassland to SRC were broadly neutral (+3.7 +/- 14.6%), whilst grassland to perennial grass transitions and forest to SRC both showed a decrease in SOC (-10.9 +/- 4.3% and -11.4 +/- 23.4% respectively). There were insufficient paired data to conduct a strict meta-analysis for GHG emissions but summary figures of general trends in GHGs from 188 original studies revealed increased and decreased soil CO2 emissions following transition from forests and arable to perennial grasses. We demonstrate that significant knowledge gaps exist surrounding the effects of land use change to bioenergy on greenhouse gas balance, particularly for CH4. There is also large uncertainty in quantifying transitions from grasslands and transitions to short rotation forestry. A striking finding of this review is the lack of empirical studies that are available to validate modelled data. Given that models are extensively use in the development of bioenergy LCA and sustainability criteria, this is an area where further longterm data sets are required. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license

The scientific literature contains contrasting findings about the climate effects of forest bioenergy, partly due to the wide diversity of bioenergy systems and associated contexts, but also due to differences in assessment methods. The climate effects of bioenergy must be accurately assessed to inform policy-making, but the complexity of bioenergy systems and associated land, industry and energy systems raises challenges for assessment. We examine misconceptions about climate effects of forest bioenergy and discuss important considerations in assessing these effects and devising measures to incentivize sustainable bioenergy as a component of climate policy. The temporal and spatial system boundary and the reference (counterfactual) scenarios are key methodology choices that strongly influence results. Focussing on carbon balances of individual forest stands and comparing emissions at the point of combustion neglect system-level interactions that influence the climate effects of forest bioenergy. We highlight the need for a systems approach, in assessing options and developing policy for forest bioenergy that: (1) considers the whole life cycle of bioenergy systems, including effects of the associated forest management and harvesting on landscape carbon balances; (2) identifies how forest bioenergy can best be deployed to support energy system transformation required to achieve climate goals; and (3) incentivizes those forest bioenergy systems that augment the mitigation value of the forest sector as a whole. Emphasis on short-term emissions reduction targets can lead to decisions that make medium- to long-term climate goals more difficult to achieve. The most important climate change mitigation measure is the transformation of energy, industry and transport systems so that fossil carbon remains underground. Narrow perspectives obscure the significant role that bioenergy can play by displacing fossil fuels now, and supporting energy system transition. Greater transparency and consistency is needed in greenhouse gas reporting and accounting related to bioenergy.