Search

The number of reforestation projects worldwide is increasing. In many cases funding is obtained through the claimed carbon capture of the trees, presented as immediate and durable, whereas reforested plots need time and maintenance to realise their carbon capture potential. Further, claims usually overlook the environmental costs of natural or anthropogenic disturbances during the forest’s lifetime, and greenhouse gas (GHG) emissions associated with the reforestation are not allowed for. This study uses life cycle assessment to quantify the carbon footprint of setting up a reforestation plot in the Peruvian Amazon. In parallel, we combine a soil carbon model with an above- and below-ground plant carbon model to predict the increase in carbon stocks after planting. We compare our results with the carbon capture claims made by a reforestation platform. Our results show major errors in carbon accounting in reforestation projects if they (1) ignore the time needed for trees to reach their carbon capture potential; (2) ignore the GHG emissions involved in setting up a plot; (3) report the carbon capture potential per tree planted, thereby ignoring limitations at the forest ecosystem level; or (4) under-estimate tree losses due to inevitable human and climatic disturbances. Further, we show that applications of biochar during reforestation can partially compensate for project emissions.

Agriculture is a major contributor to global greenhouse gas (GHG) emissions and must feature in efforts to reduce emissions. Organic farming might contribute to this through decreased use of farm inputs and increased soil carbon sequestration, but it might also exacerbate emissions through greater food production elsewhere to make up for lower organic yields. To date there has been no rigorous assessment of this potential at national scales. Here we assess the consequences for net GHG emissions of a 100% shift to organic food production in England and Wales using life-cycle assessment. We predict major shortfalls in production of most agricultural products against a conventional baseline. Direct GHG emissions are reduced with organic farming, but when increased overseas land use to compensate for shortfalls in domestic supply are factored in, net emissions are greater. Enhanced soil carbon sequestration could offset only a small part of the higher overseas emissions., The greenhouse gas (GHG) mitigation potential of organic methods is poorly understood. Here, the authors assess the GHG impact of a 100% shift to organic food production in England and Wales and find that direct GHG emissions are reduced with organic farming, but when increased land use abroad to allow for production shortfalls is factored in, GHG emissions are elevated well-above the baseline.

Introduction: According to the United Nations (UN, 2017), the world population increased by approximately 1 billion inhabitants during the last 12 years, reaching nearly 7.6 billion in 2017. Although this growth is slower than 10 years ago (1.24% vs. 1.10% per year), with an average increase of 83 million people annually, global population will reach about 8.6 billion in 2030 and 9.8 billion in 2050. Population growth, urbanization, and income rise in developing countries are the main driver of the increased demand for livestock products (UN, 2017). The livestock sector requires a significant amount of natural resources and is responsible for about 14.5% of total anthropogenic greenhouse gas emissions (7.1 Gigatonnes of carbon dioxide equivalents for the year 2005; Gerber et al., 2013). Mitigation strategies aimed at reducing emissions of this sector are needed to limit the environmental burden from food production while ensuring a sufficient supply of food for a growing world population. The objectives of this manuscript are to 1) discuss the main greenhouse gas emissions sources from the livestock sector and 2) summarize the best mitigation strategies.

The COVID‐19 pandemic is a major shock to society in terms of health and economy that is affecting both UK and global food and nutrition security. It is adding to the ‘perfect storm’ of threats to society from climate change, biodiversity loss and ecosystem degradation, at a time of considerable change, rising nationalism and breakdown in international collaboration. In the UK, the situation is further complicated due to Brexit. The UK COVID‐19 F ood and N utrition S ecurity project, lasting one year, is funded by the Economic and Social Research Council and is assessing the ongoing impact of COVID‐19 on the four pillars of food and nutrition security: access, availability, utilisation and stability. It examines the food system, how it is responding, and potential knock on effects on the UK’s food and nutrition security, both in terms of the cascading risks from the pandemic and other threats. The study provides an opportunity to place the initial lessons being learnt from the on‐going responses to the pandemic in respect of food and nutrition security in the context of other long‐term challenges such as climate change and biodiversity loss.

Greenhouse gas removal technologies are needed to reach the targets of the UNFCCC Paris Agreement. Among existing technologies, the use of biochar is considered promising, particularly biochar derived from the large quantities of sugarcane residues available in South America and elsewhere. However, the net greenhouse gas removal potential of sugarcane biochar has not been assessed hitherto. We use a scenario-based anticipatory life cycle assessment to investigate the emissions associated with a change from the combustion of sugarcane residues in a combined heat and power plant to the pyrolysis of these residues for biochar production and field application in Sao Paulo State, Brazil. We define scenarios based on different mean marginal electricity production and biochar production share. The results indicate that emissions from covering the electricity deficit generated by partial combustion of biomass during biochar production is the main emitting process. Overall, the processes associated with biochar production lower the net greenhouse gas benefits of the biochar by around 25%. Our analysis suggests that allocating 100% of the available sugarcane residues to biochar production could sequester 6.3 ± 0.5 t CO2eq ha−1 yr−1 of sugarcane in Sao Paulo State. Scaled up to the entire State, the practice could lead to the removal of 23% of the total amount of GHGs emitted by the State in 2016.

Harvesting sugarcane (Saccharum officinarum) produces large quantities of biomass residues. We investigated the potential for converting these residues into biochar (recalcitrant carbon rich material) for soil carbon (C) sequestration. We modified a version of the RothC soil carbon model to follow changes in soil C stocks considering different amounts of fresh sugarcane residues and biochar (including recalcitrant and labile biochar fractions). We used Sao Paulo State (Brazil) as a case study due to its large sugarcane production and associated soil C sequestration potential.Mechanical harvesting of sugarcane fields leaves behind > 10 t dry matter of trash (leaves) ha-1 year-1. Although trash blanketing increases soil fertility, an excessive amount is detrimental and reduces the subsequent crop yield. After the optimal trash blanketing amount, sugarcane cultivation still produces 5.9 t C ha-1 year-1 of excess trash and bagasse (processing residues) which are available for subsequent use.The available residues could produce 2.5 t of slow-pyrolysis (550°C) biochar C ha-1 year-1. The model predicts this could increase sugarcane field soil C stock on average by 2.4 ± 0.4 t C ha‑1 year‑1, after accounting for the climate and soil type variability across the State. Comparing different scenarios, we found that applying fresh residues into the field results in a smaller increase in soil C stock compared to the biochar because the soil C approaches a new equilibrium. For instance, adding 1.2 t of biochar C ha‑1 year‑1 along with 3.2 t of fresh residue C ha‑1 year‑1 increased the soil C stock by 1.8 t C ha‑1 year‑1 after 10 years of repeated applications. In contrast, adding 0.62 t of biochar C ha‑1 year‑1 with 4.5 t of fresh sugarcane residues C ha‑1 year‑1 increased the soil carbon soil stock by 1.4 t C ha‑1 year‑1 after 10 years of application. These are reductions 25% and 40% of the potential soil C accumulation rates compared with applying available residues as biochar. We also tested the sensitivity of the model to biochar-induced positive priming (i.e. increased mineralization of soil organic C) using published values. This showed that the C sequestration balance remains positive over the long term, even considering an extremely high positive-priming factor. Upscaling our results to the total 5 Mha of sugarcane in Sao Paulo State, biochar application could sequester up to 50 Mt of CO2 equivalent per year, representing 31% of the emissions attributed to the State in 2016.This study provides first insights into the sequestration potential of biochar application on sugarcane fields. Measurements of changes in soil C stocks in sugarcane field experiments are needed to further validate the model, and the emissions to implement the practice at large scale need to be taken into account. As the climate crisis grows, the need for greenhouse gas removal technologies becomes crucial. Assessing the net effectiveness of readily available technologies is essential to guide policy makers.

To limit warming to well below 2°C, most scenario projections rely on greenhouse gas removal technologies (GGRTs); one such GGRT uses soil carbon sequestration (SCS) in agricultural land. In addition to their role in mitigating climate change, SCS practices play a role in delivering agroecosystem resilience, climate change adaptability and food security. Environmental heterogeneity and differences in agricultural practices challenge the practical implementation of SCS, and our analysis addresses the associated knowledge gap. Previous assessments have focused on global potentials, but there is a need among policymakers to operationalise SCS. Here, we assess a range of practices already proposed to deliver SCS, and distil these into a subset of specific measures. We provide a multidisciplinary summary of the barriers and potential incentives towards practical implementation of these measures. First, we identify specific practices with potential for both a positive impact on SCS at farm level and an uptake rate compatible with global impact. These focus on: (a) optimising crop primary productivity (e.g. nutrient optimisation, pH management, irrigation); (b) reducing soil disturbance and managing soil physical properties (e.g. improved rotations, minimum till); (c) minimising deliberate removal of C or lateral transport via erosion processes (e.g. support measures, bare fallow reduction); (d) addition of C produced outside the system (e.g. organic manure amendments, biochar addition); (e) provision of additional C inputs within the cropping system (e.g. agroforestry, cover cropping). We then consider economic and non‐cost barriers and incentives for land managers implementing these measures, along with the potential externalised impacts of implementation. This offers a framework and reference point for holistic assessment of the impacts of SCS. Finally, we summarise and discuss the ability of extant scientific approaches to quantify the technical potential and externalities of SCS measures, and the barriers and incentives to their implementation in global agricultural systems., To limit warming to well below 2°C, many scenario projections rely on greenhouse gas removal by soil carbon sequestration (SCS) in agricultural land. Here, we provide a multidisciplinary summary of the barriers and potential incentives towards practical implementation SCS. First, we identify specific practices with potential for both a positive impact on SCS and an uptake rate compatible with global impact. Then, we then consider economic and non‐cost barriers and incentives for implementing SCS, and potential externalised impacts of implementation. Finally, we discuss the ability of existing methods to model the potential of SCS in global agricultural systems.

Several greenhouse gas removal technologies (GGRTs), also called negative emissions technologies (NET) have been proposed to help meet the Paris Climate Agreement targets. However, there are many uncertainties in the estimation of their effective greenhouse gas (GHG) removal potentials, caused by their different levels of technological development. Life Cycle Assessment (LCA) has been proposed as one effective methodology to holistically assess the potential of different GGRT removal approaches but no common framework is currently available for benchmarking and policy development. In this article, challenges for LCA are reviewed and discussed together with some alternative approaches for assessment of GGRTs. In particular, GGRTs pose challenges with regards to the functional unit, the system boundary of the LCA assessment, and the timing of emissions. The need to account within LCA of GGRTs for broader implications which involve environmental impacts, economic, social and political drivers is highlighted. A set of recommendations for LCA of GGRTs are proposed for a better assessment of the GGRTs and better accounting of their carbon removal potentials to meet the targets established within the Paris Agreement.

Sugarcane (Saccharum officinarum L.) cultivation leaves behind around 20 t ha−1 of biomass residue after harvest and processing. We investigated the potential for sequestering carbon (C) in soil with these residues by partially converting them into biochar (recalcitrant carbon-rich material). First, we modified the RothC model to allow changes in soil C arising from additions of sugarcane-derived biochar. Second, we evaluated the modified model against published field data, and found satisfactory agreement between observed and predicted soil C accumulation. Third, we used the model to explore the potential for soil C sequestration with sugarcane biochar in São Paulo State, Brazil. The results show a potential increase in soil C stocks by 2.35 ± 0.4 t C ha−1 year−1 in sugarcane fields across the State at application rates of 4.2 t biochar ha−1 year−1. Scaling to the total sugarcane area of the State, this would be 50 Mt of CO2 equivalent year−1, which is 31% of the CO2 equivalent emissions attributed to the State in 2016. Future research should (a) further validate the model with field experiments; (b) make a full life cycle assessment of the potential for greenhouse gas mitigation, including additional effects of biochar applications on greenhouse gas balances.

Carbon dioxide and nitrous oxide are two important greenhouse gases (GHG) released from cropping systems. Their emissions can vary substantially with climate, soil, and crop management. While different methods are available to account for GHG emissions in life cycle assessments (LCA) of crop production, there are no standard procedures. In this study, the objectives were: (i) to compare several methods of estimating CO 2 and N 2 O emissions for a LCA of cropping systems and (ii) to estimate the relative contribution of soil GHG emissions to the overall global warming potential (GWP) using results from a field experiment located in Manitoba, Canada. The methods were: (A) measurements; (B) Tier I and (C) Tier II IPCC (Intergovernmental panel on Climate Change) methodology, (D) a simple carbon model combined with Intergovernmental Panel for Climate Change (IPCC) Tier II methodology for soil N 2 O emissions, and (E) the DNDC (DeNitrification DeComposition) agroecosystem model. The estimated GWPs (−7.2–17 Mg CO 2 eq ha −1 y −1 ; −80 to 600 kg CO 2 eq GJ −1 y −1 ) were similar to previous results in North America and no statistical difference was found between GWP based on methods D and E and GWP based on observations. The five methods gave estimates of soil CO 2 emissions that were not statistically different from each other, whereas for N 2 O emissions only DNDC estimates were similar to observations. Across crop types, all methods gave comparable CO 2 and N 2 O emission estimates for perennial and legume crops, but only DNDC gave similar results with respect to observations for both annual and cereal crops. Whilst the results should be confirmed for other locations, the agroecosystem model and method D can be used, at certainly one selected site, in place of observations for estimating GHGs in agricultural LCA.

The use of land for intensive arable production in Europe is associated with a range of externalities that typically impose costs on third parties. The introduction of trees in arable systems can potentially be used to reduce these costs. This paper assesses the profitability and environmental externalities of a silvoarable agroforestry system, and compares this with the profitability and environmental externalities from an arable system and a forestry system. A silvoarable experimental plot of poplar trees planted in 1992 in Bedfordshire, Eastern England, was used as a case study. The Yield-SAFE model was used to simulate the growth and yields of the silvoarable, arable, and forestry land uses along with the associated environmental externalities, including carbon sequestration, greenhouse gas emissions, nitrogen and phosphorus surplus, and soil erosion losses by water. The Farm-SAFE model was then used to quantify the monetary value of these effects. The study assesses both the financial profitability from a farmer perspective and the economic benefit from a societal perspective. The arable option was the most financially profitable system followed by the silvoarable system and forestry. However, when the environmental externalities were included, silvoarable agroforestry provided the greatest benefit. This suggests that the appropriate integration of trees in arable land can provide greater well-being benefits to society overall, than arable farming without trees, or forestry systems on their own.

PurposeThe focus of the life-cycle assessment (LCA) of an agricultural plant product is typically on one crop. However, isolating one crop from the cropping system that it belongs to is often challenging because the crops are often interlinked with the other crops in the cropping system. The main objectives of this discussion article are as follows: (i) to discuss the characteristics of cropping systems which might affect the LCA methodology, (ii) to discuss the advantages and the disadvantages of the current available methods for the life-cycle assessment of cropping systems, and (iii) to offer a framework to carry out LCA of crops and cropping systems.MethodsThe definition of cropping systems is provided together with a description of two types of LCA: product LCA and system LCA. The LCA issues related to cropping system characteristics have been classified as (1) crop interrelationship, (2) crop management and emissions, and (3) functional unit issues. The LCA approaches presented are as follows: cropping system, allocation approaches, crop-by-crop approach, and combined approaches. The various approaches are described together with their advantages and disadvantages, applicability, comprehensiveness, and accuracy.Results and discussionThe cropping system approach is best suited for system LCA. For product LCA, none of the methods is fully exhaustive and accurate. The crop sequence approach takes into consideration the cropping system issues, if they happen within the year or season, and cannot be applied for intercropping and agroforestry systems. The allocation approaches take into account the cropping system effects by establishing a mathematical relationship between crops present in the cropping systems. The model for integrative life-cycle assessment in agriculture (MiLA) approach considers cropping system issues if they are related to multiproduct and nutrient cycling, while the crop-by-crop approach is highly affected by assumptions and considers cropping system issues only if they are related to the analyzed crop.ConclusionsEach LCA approach presents advantages and disadvantages. For system LCA, the cropping system approach is recommended. For product LCA, environmental burdens should be attributed applying the following hierarchy: (1) attributed to the crop if based on a clear causality, (2) attributed with combined approaches and specific criteria, and (3) attributed with allocation approaches and generic criteria. These approaches should be combined with the cropping system approach..

Scientists generally agree that, by 2100, the annual extraction of an average of 3.3 Gt of carbon equivalent from the atmosphere will be necessary to limit the increase in global average temperatur...

Enhanced silicate rock weathering for long-term carbon dioxide sequestration has considerable potential, but depends on the availability of suitable rocks coupled with proximity to suitable locations for field application. In this paper, we investigate the established mining industry that extracts basaltic rocks for construction from the Paraná Basin, Sao Paulo State, Brazil. Through a Life Cycle Assessment, we determine the balance of carbon dioxide emissions involved in the use of this material, the relative contribution of soil carbonation and enhanced weathering, and the potential carbon dioxide removal of Sao Paulo agricultural land through enhanced weathering of basalt rock. Our results show that enhanced weathering and carbonation respectively emit around 75 and 135 kg carbon dioxide equivalent per tonne of carbon dioxide equivalent removed (considering a quarry to field distance of 65 km). We underline transportation as the principal process negatively affecting the practice and uncover a limiting road travel distance from the quarry to the field of 540 ± 65 km for carbonation and 990 ± 116 km for enhanced weathering, above which the emissions offset the potential capture. Regarding Sao Paulo State, the application of crushed basalt at 1 t/ha to all of the State's 12 million hectares of agricultural land could capture around 1.3 to 2.4 Mt carbon dioxide equivalent through carbonation and enhanced weathering, respectively. This study suggests a lower sequestration estimate than previous studies and emphasizes the need to consider all process stages through a Life Cycle Assessment methodology, to provide more reliable estimates of the sequestration potential of greenhouse gas removal technologies.

This study assesses the greenhouse gas (GHG) emissions and sequestration of a silvoarable system with poplar trees and a crop rotation of wheat, barley, and oilseed rape and compares this with a rotation of the same arable crops and a poplar plantation. The Farm-SAFE model, a financial model of arable, forestry, and silvoarable systems, was modified to account for life-cycle greenhouse gas emissions. Greenhouse gas emissions from tree and crop management were determined from life-cycle inventories and carbon storage benefits from the Yield-SAFE model, which predicts crop and tree yields in arable, forestry, and silvoarable systems. An experimental site in Silsoe in southern England served as a case study. The results showed that the arable system was the most financially profitable system, followed by the silvoarable and then the forestry systems, with equivalent annual values of EUR 560, 450 and 140 ha−1, respectively. When the positive and negative externalities of GHG sequestration and emissions were converted into carbon equivalents and given an economic value, the profitability of the arable systems was altered relative to the forestry and silvoarable systems, although in the analysis, the exact impact depended on the value given to GHG emissions. Market values for carbon resulted in the arable system remaining the most profitable system, albeit at a reduced level. Time series values for carbon proposed by the UK government resulted in forestry being the most profitable system. Hence, the relative benefit of the three systems was highly sensitive to the value that carbon was given in the analysis. This in turn is dependent on the perspective that is given to the analysis.

There is an increased interest in the use of poultry litter as fuel by the relevant industries. Hence the environmental impacts of using turkey litter as fuel to generate electricity instead of using litter as fertilizer were systematically analysed for the first time. For this purpose, a systems modelling-based life cycle assessment approach was used, with data obtained directly from the UK turkey industry. Impacts were calculated per 1000 kg turkey live weight produced at the farm gate (functional unit). The avoided burdens method was used to quantify the effects of the alternative litter use. Differences in the environmental impacts between the two litter use scenarios resulted from the combined effect of the following sub-processes: the loss of nitrogen as a crop fertiliser, the transport for collecting litter and distributing the ash as a phosphorus and potassium fertiliser, displacement of electricity generation by a combined cycle gas turbine, specific trace gas emissions from combustion and the loss of soil carbon from the reduced organic matter supply to arable soils. The results showed that there are substantial environmental benefits from using turkey litter as a fuel to generate electricity rather than using it directly as a fertiliser with reductions in burdens of cumulative primary energy demand (14%), eutrophication potential (55%) and acidification potential (70%). The reduction in acidification and eutrophication potentials were mainly associated with reduced ammonia emissions from the storage and land spreading of the litter. Reductions in greenhouse gas emissions were small (3%) because losses of soil carbon as a result of not applying litter to land partially counteracted the benefits of reduced fossil energy use. Small increases in nitrogen oxides, volatile organic carbon, particulate matter below 10 μm aerodynamic diameter and dioxin emissions were found, although only nitrogen oxides were especially linked to combustion. Despite its potential benefits, stringent management, monitoring and regulation of biomass fuelled power production is still needed, given the potential hazards of local high emissions. Although turkey litter was analysed in this study, similar results can be expected for broiler litter use as a fuel, as long as geographical conditions are similar.

A system approach-based Life Cycle Assessment (LCA) framework, combined with a simple mechanistic model of bird energy balance was used to predict the potential effects of 15 y prospective broiler breeding on the environmental impacts of the standard UK broiler production system. The year 2014 Ross 308 genotype was used as a baseline, and a future scenario was specified from rates of genetic improvement predicted by the industry. The scenario included changes in the traits of growth rate (reducing the time to reach a target weight 2.05 kg from 34 d to 27 d), body lipid content, carcass yield, mortality and the number of chicks produced by a breeder hen. Diet composition was adjusted in order to accommodate the future nutrient requirements of the birds following the genetic change. The results showed that predicted changes in biological performance due to selective breeding could lead to reduced environmental impacts of the broiler production chain, most notably in the Eutrophication Potential (by 12%), Acidification Potential (by 10%) and Abiotic Resource Use (by 9%) and Global Warming Potential (by 9%). These reductions were mainly caused by the reduced maintenance energy requirement and thus lower feed intake, resulting from the shorter production cycle, together with the increased carcass yield. However, some environmental benefits were limited by the required changes in feed composition (e.g., increased inclusion of soy meal and vegetable oil) as a result of the changes in bird nutrient requirements. This study is the first one aiming to link the mechanistic animal modeling approach to predicted genetic changes in order to produce quantitative estimates of the future environmental impacts of broiler production. Although a more detailed understanding on the mechanisms of the potential changes in bird performance and their consequences on feeding and husbandry would be still be needed, the modeling framework produced in this study provides a starting point for predictions of the effects of prospective genetic progress.

The aim of this study was to (1) quantify the environmental impact of UK turkey systems and (2) develop a methodology for analytical uncertainty analysis, as currently error propagation methods for such analyses of environmental impacts of agricultural commodities rely on time consuming Monte-Carlo approaches. The turkey systems considered were: 1) Stags (males) with controlled ventilation, 2) Hens (females) with controlled ventilation, 3) Stags with natural ventilation, and 4) Hens with natural ventilation, all being the main UK turkey production systems. An LCA modelling framework, based on a system approach and mechanistic sub-models was applied to assess several environmental impact categories, expressed per unit of live weight, and their associated uncertainties. For the first time, detailed production data and their variations from the industry, including slaughter age and weight, feed composition and consumption, mortality, and farm energy use, were used as input. The statistical significance of the differences between the systems was analysed using an analytical “top–down” method for uncertainty analysis, developed in this study. The results show that there were only small, mainly non-significant differences in impacts between the systems, affected mainly by their feed conversion ratio and slaughter weight, both of which were generally higher in the stag systems than the hen systems. A significant difference (P

Climate change has the potential to impair livestock health, with consequences for animal welfare, productivity, greenhouse gas emissions, and human livelihoods and health. Modelling has an important role in assessing the impacts of climate change on livestock systems and the efficacy of potential adaptation strategies, to support decision making for more efficient, resilient and sustainable production. However, a coherent set of challenges and research priorities for modelling livestock health and pathogens under climate change has not previously been available. To identify such challenges and priorities, researchers from across Europe were engaged in a horizon-scanning study, involving workshop and questionnaire based exercises and focussed literature reviews. Eighteen key challenges were identified and grouped into six categories based on subject-specific and capacity building requirements. Across a number of challenges, the need for inventories relating model types to different applications (e.g. the pathogen species, region, scale of focus and purpose to which they can be applied) was identified, in order to identify gaps in capability in relation to the impacts of climate change on animal health. The need for collaboration and learning across disciplines was highlighted in several challenges, e.g. to better understand and model complex ecological interactions between pathogens, vectors, wildlife hosts and livestock in the context of climate change. Collaboration between socio-economic and biophysical disciplines was seen as important for better engagement with stakeholders and for improved modelling of the costs and benefits of poor livestock health. The need for more comprehensive validation of empirical relationships, for harmonising terminology and measurements, and for building capacity for under-researched nations, systems and health problems indicated the importance of joined up approaches across nations. The challenges and priorities identified can help focus the development of modelling capacity and future research structures in this vital field. Well-funded networks capable of managing the long-term development of shared resources are required in order to create a cohesive modelling community equipped to tackle the complex challenges of climate change.

We assess the production impacts of a 100% conversion to organic agriculture in England and Wales using a large-scale linear programming model. The model includes a range of typical farm structures, scaled up across the available land area, with the objective of maximising food production. The effects of soil and rainfall, nitrogen (N) supply/offtake and livestock feed demand are accounted for. Results reveal major reductions in wheat and barley production, whilst the production of minor cereals such as oats and rye increase. Monogastric livestock and milk production also decreased considerably, whilst beef and sheep numbers increased. Vegetable production was generally comparable to that under conventional farming. Minimising the area of fertility building leys and/or improving rates of N fixation increased the food supply from organic agriculture at the national level. The total food output, in terms of metabolisable energy, was 64% of that under conventional farming. This would necessitate substantial increases in food imports, with corresponding expansion of cultivated agricultural land overseas. Significant changes in diet and reductions in food waste would be required to offset the production impacts of a 100% conversion to organic farming.

The dynamic model Nitrogen Dynamics in Crop rotations in Ecological Agriculture (NDICEA) was used to assess the nitrogen (N), phosphorus (P) and potassium (K) balance of long-term organic cropping trials and typical organic crop rotations on a range of soil types and rainfall zones in the UK. The measurements of soil N taken at each of the organic trial sites were also used to assess the performance of NDICEA. The modeled outputs compared well to recorded soil N levels, with relatively small error margins. NDICEA therefore seems to be a useful tool for UK organic farmers. The modeling of typical organic rotations has shown that positive N balances can be achieved, although negative N balances can occur under high rainfall conditions and on lighter soil types as a result of leaching. The analysis and modeling also showed that some organic cropping systems rely on imported sources of P and K to maintain an adequate balance and large deficits of both nutrients are apparent in stockless systems. Although the K deficits could be addressed through the buffering capacity of minerals, the amount available for crop uptake will depend on the type and amount of minerals present, current cropping and fertilization practices and the climatic environment. A P deficit represents a more fundamental problem for the maintenance of crop yields and the organic sector currently relies on mined sources of P which represents a fundamental conflict with the International Federation of Organic Agriculture Movements organic principles.

BACKGROUND The aim of the study was to quantify the effects of the use of a protease Ronozyme® ProAct in broiler feed on the environmental impacts of broiler and broiler feed production chains. This was done by using a Life Cycle Assessment (LCA) modelling approach with data from trials using both standard soya-based broiler diets and reduced-protein diets with added protease. RESULTS The results for the feed production chain showed that there was a reduction in all environmental impact categories when protease was used in the diets. The biggest reduction occurred in the category of Global Warming Potential, mainly as a result of decreased carbon dioxide emissions from land use changes related to soya production. In the results for the broiler production chain, there were relatively bigger reductions in Eutrophication Potential and especially in Acidification Potential, mainly as a result of reduced feed protein content and subsequent nitrogen emissions from housing and manure management. CONCLUSION The use of protease in the broiler diets reduced the environmental impacts of both feed production and broiler production. The latter is mainly through reduced ammonia emissions, which has substantial benefit per se in the poultry industry. © 2015 Society of Chemical Industry

The livestock industry is a significant component of the agricultural and rural sectors in the UK. Grassland for livestock accounts for almost half of the terrestrial surface of the UK and almost two-thirds of its managed agricultural land. It therefore accounts for a major proportion of rural employment and income and provides many landscape and biodiversity benefits. Taking an ecosystems-services-framework approach, an integrated livestock-ecosystems linear programming model was developed to assess economic and environmental impacts of the livestock sector. This combined life cycle assessment systems analysis with economic and valuation data and enabled plausible future scenarios to be assessed in terms of provisioning, regulating and cultural services. Analysis showed the main benefit coming from provisioning services and also the significant role the sector plays in providing cultural services, and the trade-offs between these and the cost of regulating services with respect to emissions to air and water.

Large quantities of water are required to produce the food for a nation, some of which is derived within the country and some associated with imported food commodities. In this study, we consider the spatially explicit potential impact of alternative healthier eating scenarios for the UK on global blue water scarcity using the concept of a water scarcity footprint. The water required to produce the food consumed by the UK was estimated at 52.6 Gm 3 /y of which 93% is from rainfall at the point where it falls and 7% is “blue” water withdrawn from surface and ground water resources. Five alternative healthier diets were considered and the impact on the blue water scarcity footprint was modest (ranging from −3% to +2% compared to baseline). However more significant impacts were projected on the geographical distribution of the blue water scarcity footprint. This study has shown that if current trade patterns continue, policies to promote healthier eating in the UK may contribute to increased blue water scarcity at home and in other parts of the world. The use of virtual water estimates and global datasets of water scarcity can help to understand the potential environmental impacts of alternative diets.

We used a Life Cycle Assessment approach to determine whether the inherent differences in emissions to air among existing livestock production systems could be used to reconfigure the UK livestock sector in order to meet current greenhouse gas (GHG) and ammonia (NH 3 ) targets while maintaining production at current levels. Output, defined as financial value, was optimized across all sub-sectors. Using current management systems the greatest livestock output that could be maintained, while meeting emission reduction targets, was 84% of current. Adopting the most appropriate manure management practices and improved feed conversion ratio enables a further increase in outputs to 86% of current. Dairy production could be maintained at 84.1% of current if all production arises from high-yielding herds with autumn calving, all dairy cow manure is managed as slurry and diets to reduce rumen fermentation are adopted. Increasing the proportion of calves obtained from the dairy herd by 10% could maintain beef production at 85% of current. Raising finishing pigs on slurry systems, raising sows and weaners outdoors, finishing pigs at either 89 or 99 kg and improving dietary nitrogen use efficiency could maintain pig production at 87.5% of current. Manure drying within poultry buildings, immediate incorporation of poultry manures to tillage land and reduced protein feeds would allow 82.2% of current poultry meat production. Eliminating free-range egg systems and drying manure within the building could maintain egg production at 85.5% of current. Replacing lowland sheep herds (other than organic) with upland production could maintain sheep output at 86.4% of current.

There is an increasing demand for sustainable agricultural production as part of the transition towards a globally sustainable economy. To quantify impacts of agricultural systems on the environment, life cycle assessment (LCA) is ideal because of its holistic approach. Many tools have been developed to conduct LCAs in agriculture, but they are not publicly available, not open-source, and have a limited scope. Here, a new adaptable open-source tool (Crop.LCA) for carrying out LCA of cropping systems is presented and tested in an evaluation study with a scenario assessment of 4 cropping systems using an agroecosystem model (DNDC) to predict soil GHG emissions. The functional units used are hectares (ha) of land and gigajoules (GJ) of harvested energy output, and 4 impact categories were evaluated: cumulative energy demand (CED), 100-year global warming potential (GWP), eutrophication and acidification potential. DNDC was used to simulate 28 years of cropping system dynamics, and the results were used as input in Crop.LCA. Data were aggregated for each 4-year rotation and statistically analyzed. Introduction of legumes into the cropping system reduced CED by 6%, GWP by 23%, and acidification by 19% per ha. These results highlight the ability of Crop.LCA to capture cropping system characteristics in LCA, and the tool constitutes a step forward in increasing the accuracy of LCA of cropping systems as required for bio-economy system assessments. Furthermore, the tool is open-source, highly transparent and has the necessary flexibility to assess agricultural systems.

Growing populations and a constrained fossil-manufactured energy supply present a major challenge for society and there is a real need to develop forms of agriculture that are less dependent on finite energy sources. It has been suggested that organic agriculture can provide a more energy efficient approach due to its focus on sustainable production methods. This review has investigated the extent to which this is true for a range of farming systems. Data from about 50 studies were reviewed with results suggesting that organic farming performs better than conventional for nearly all crop types when energy use is expressed on a unit of area basis. Results are more variable per unit of product due to the lower yield for most organic crops. For livestock, ruminant production systems tend to be more energy efficient under organic management due to the production of forage in grass–clover leys. Conversely, organic poultry tend to perform worse in terms of energy use as a result of higher feed conversion ratios and mortality rates compared to conventional fully housed or free-range systems. With regard to energy sources, there is some evidence that organic farms use more renewable energy and have less of an impact on natural ecosystems. Human energy requirements on organic farms are also higher as a result of greater system diversity and manual weed control. Overall this review has found that most organic farming systems are more energy efficient than their conventional counterparts, although there are some notable exceptions.

Purpose This study of seven foods assessed whether there are modes or locations of production that require significantly fewer inputs, and hence cause less pollution, than others. For example, would increasing imports of field-grown tomatoes from the Mediterranean reduce greenhouse gas (GHG) emissions by reducing the need for production in heated greenhouses in the UK, taking account of the additional transport emissions? Is meat production in the UK less polluting than the import of red meat from the southern hemisphere?

Data from ten sources comprising 3,851 flocks were modelled to identify variation in levels of mortality in laying hens. The predicted increase with age was curvilinear with significant variation between the seven breed categories. Mortality was higher in loose housing systems than in cages and variable within system, confirming previous reports. Cumulative mortality (CM) was higher in flocks with intact beaks (χ2 = 6.03; df 1; p = 0.014) than in those with trimmed beaks. Most data were available for free-range systems (2,823 flocks), where producer recorded CM at 60-80 weeks of age averaged 10% but with a range from 0% to 69.3%. Life cycle assessment showed that the main effect of increased levels of hen mortality is to increase the relative contribution of breeding overheads, so increasing environmental burdens per unit of production. Reducing CM to levels currently achieved by the 1st quartile could reduce flock greenhouse gas emissions by as much as 25%. Concurrently this would enhance hen welfare and better meet the expectation of egg consumers. More research to understand the genetic x environment interaction and detailed records of the causes of mortality is required so that improved genotypes can be developed for different systems and different breeds can be better managed within systems.

The animal food chain contributes significantly to emission of greenhouse gases (GHGs). We explored studies that addressed options to mitigate GHG emissions in the animal production chain and concluded that most studies focused on production systems in developed countries and on a single GHG. They did not account for the complex interrelated effects on other GHGs or their relation with other aspects of sustainability, such as eutrophication, animal welfare, land use or food security. Current decisions on GHG mitigation in animal production, therefore, are hindered by the complexity and uncertainty of the combined effect of GHG mitigation options on climate change and their relation with other aspects of sustainability. There is an urgent need to integrate simulation models at animal, crop and farm level with a consequential life cycle sustainability assessment to gain insight into the multidimensional and sometimes conflicting consequences of GHG mitigation options. Highlights ¿ Most studies that address options to mitigate greenhouse gas (GHG) emissions in the animal production focus on systems in developed countries and on a single GHG. ¿ Current decisions on GHG mitigation in animal production are hindered by the complexity and uncertainty of the combined effect of GHG mitigation options on climate change and their relation with other aspects of sustainability. ¿ There is an urgent need to integrate simulation models at animal, crop and farm level with a consequential life cycle sustainability assessment to gain insight into the multidimensional and sometimes conflicting consequences of GHG mitigation options.

Pen-y-Bryn senior special school for pupils aged 11 to 19 with severe learning difficulties in Swansea has designed and developed a Social Competence Curriculum for School Leavers. The curriculum is a three year course for pupils in the school aged 16 to 19. The course is pragmatic and community-based and aims to provide a broad, balanced, relevant and differentiated curriculum in order to prepare pupils for life beyond nineteen years in their own community. The article describes and evaluates the key ingredients in the curriculum which was implemented for senior pupils in 1988. The aims of the course, the curriculum areas, teaching objectives, activities and experiences and the pupil's record of personal achievements were carefully designed and developed so that pupils would have the opportunity to leave school at nineteen with confidence and a sense of achievement.

Food production is a major contributor to a country's environmental burden. However, the burdens associated with individual foods vary significantly due to differing agricultural systems and locations, post-harvest storage, manufacturing and transport requirements. Dietary choices can therefore have a significant impact on the overall burdens associated with food consumption. Previous studies have generally considered changes in the proportion of animal-based foods in the diet or changes to a vegetarian, or a vegan diet. Using a life cycle assessment approach and data from published sources supplemented by original analysis, we estimated the blue water scarcity footprint and greenhouse gas emissions associated with the production, manufacture and distribution of three popular starchy carbohydrate foods as consumed in the United Kingdom – British fresh potatoes, Italian dried pasta and Indian dried basmati rice. Although similar to pasta in terms of greenhouse gas emissions per unit carbohydrate, when considered on the basis of typical portion size, potatoes have lower greenhouse gas emissions than pasta or basmati and the blue water scarcity footprint of basmati is two orders of magnitude greater than potatoes or pasta. The increasing preference for pasta and rice and reduction in household purchases of fresh potatoes in the United Kingdom over the period 1981–2010 has resulted in an increase in blue water scarcity footprint and a transfer of burdens from the United Kingdom to Italy and India, however the increased greenhouse gas emissions associated with rice and pasta has been, more or less, compensated by a reduction in emissions associated with purchases of potatoes. This paper has shown that dietary choices within food groups (in this case starchy carbohydrates) have a significant impact on an individual's contribution to greenhouse gas emissions and blue water scarcity footprint. The life cycle assessment approach is useful for understanding where the impacts of dietary choices occur and can inform the supply chain about where efforts should be targeted to reduce those impacts.

A sufficiently high composting temperature should inactivate many common pathogens likely to be present in solid animal waste. Monitoring core temperatures inside compost heaps is not straightforward, which means that heaps are not generally monitored. An alternative is to monitor surface temperatures and use those data to infer core temperatures, and thus whether pathogen inactivation has occurred. This paper describes two methods (thermal imaging and thermocouples) for the measurement of surface temperature, and a modelling approach using time series analysis to predict the temperatures obtained in the core of aerated heaps of composting pig farmyard manure (FYM) from surface temperature data. The model was able to predict core temperatures in the heap quite closely for a period of time for well insulated parts of the heap, although predictions were further from observed values close to the surface of the heap and the aeration pipe.

The rate at which oxygen is consumed during composting is a measure of aerobic microbial activity and is linked to the rate of organic material decomposition. The rate of loss in mass is a function of the mass of the degradable organic fraction and is related to oxygen uptake rate by the reaction rate coefficient, k. The decomposition of a pig manure and straw mix was investigated at temperatures between 10°C and 70°C using respirometric techniques. The oxygen concentrations in the reactor were measured continuously for about 4 days and then converted to hourly oxygen uptake rates for each incubation temperature, T. The specific oxygen uptake rate was used to calculate the reaction rate coefficient at T, kT, for the observed fast and slow stages of decomposition. The effect of the environmental factors was taken into account using a multiplicative approach and a relationship, which expressed kT for each stage as a function of T, was formulated. The maximum measured rate of activity occurred during the fas...

An environmental Life Cycle Assessment (LCA) procedure is constructed to compare the total emissions from different techniques for managing livestock wastes. Life Cycle Assessment is a method of holistically and systematically accounting for the environmental benefits and burdens of the production of goods and services including consequential burdens generated elsewhere. As waste emissions are very variable, the methodology is extended to include the uncertainty in the estimates in order to indicate the significance of differences between techniques. The object is to inform policy of whether options are better for the environment by quantifying potential emissions abatement, by highlighting priority environmental impacts and by revealing compromises for further investigation. This paper reports comparative LCAs for several pig waste management options. For example, various slurry application techniques, including: splash plates, band spreaders and injection. If the splash-plate system is taken as a reference, the injector system causes only 64% of the environmental acidification and 71% of the eutrophication of surface waters. The benefits must be offset against the increase in nitrate leaching of 50%. In contrast, the band spreader system offers 28% of the benefits of injection. The environmental impacts have also been expressed as a proportion of the UK national emissions. This gives each impact a weighted-value that enables direct comparisons of disparate impacts. Although band spreader systems showed an aggregated, or total, environmental impact reduction of almost 10%, the reduction is not significant when uncertainty is taken into account. Using an anaerobic digester shows few overall benefits due to the fugitive losses of methane. However, if these can be eliminated the global warming potential from waste management is reduced close to zero.

The options for abating ammonia emissions from livestock buildings and waste stores under UK conditions have been assessed. There is increasing interest in reducing such emissions, which contribute to long-range atmospheric pollution problems, and which, via subsequent deposition, can also harm sensitive ecosystems. A literature review was first carried out, and a “brainstorm” idea-generating session was held, together leading to lists of feasible abatement approaches: one for each of a range of types of livestock buildings and waste stores. A ranking exercise was then conducted. A set of aspects of each application of each feasible abatement approach was drawn up: the aspects considered included not only capital costs and running costs but also such others as animal welfare, stage of development and knock-on effects. Each aspect of each application of each approach was given a ranking of between 1 (very poor) and 5 (very good). When the aspects of “potential abatement” and “achievable abatement now”, as well as either “capital costs” or “animal welfare”, were weighted by a factor of 5, the “best bet” abatement approaches for livestock buildings were identified as (a) dietary manipulation (for all types), (b) raising the C/N ratio by generous use of bedding (for any buildings based on solid manure), (c) exhaust air cleaning, especially by bioscrubbers (for force-ventilated pig and poultry buildings), (d) oil layers or (e) fixing with acid (for slurry-based piggeries) and (f) drying by ventilation of muck (for any poultry building). For waste stores, the “best bet” abatement approaches were identified as (g) replacing storage with industrial scale processing or (h) with land filling (niche solutions only), (i) dietary manipulation, (j) fixing with acid (slurries only), (k) increasing the surface's resistance to ammonia volatilisation (by crusts for cattle slurry, but by floating granules for pig slurry), (l) minimising surface area by heap shape (solid manures), and (m) cover sheets (solid manures). For stored poultry manure, the low moisture content allowed good showings by the additional options of (n) drying, and, in the case of poultry manure with litter in certain parts of the UK, (p) sale for combustion in a Non-Fossil Fuel Obligation (NOFFO) power station, the electricity from which commands a higher price than that from a conventional power station. A closer look at the economic consequences of different abatement approaches was taken by means of a mathematical model: this work is reported in a companion paper.

An experiment is reported in which two bunker silos were filled with about 12 t of ryegrass; one was compacted with a surface pressure of 4·1 kPa and the other was not. Both were instrumented to record temperatures and gas compositions during fermentation and feed-out. Cores of silage (100 mm diameter) were removed from the bunkers and subjected to forced aeration in insulated cylinders. Simple mathematical models were used to simulate CO2 leakage from the silos and the associated loss of dry matter, and temperature changes during the forced aeration of silage cores. The leakage of CO2 from the silos, as shown by the fall in CO2 concentration with time, could be described empirically by an exponential equation and could be simulated with a simple mathematical model. Experimental evidence supported the hypothesis that permeation was the main method of gaseous exchange during fermentation and feed-out, but gas mixing by diffusion and/or convection also occurred within the silos during fermentation. Dry-matter losses by aerobic activity during storage of 120–150 d were conservatively estimated to be about 0·3% and 0·9% for the uncompacted and compacted bunkers respectively. These were considered to be lower than those that could be expected in farm silos, because the sealing was likely to be more thorough. The silages were also more stable, when subject to aeration, than others examined in this laboratory, probably because of high contents of acetic, propionic and butyric acids. Simple mathematical models were of value, but greater sophistication is needed (e.g. multi-compartmental models) to deal comprehensively with the heat and gas flows found in the complex biophysical systems of silage.

The statistical significance of the effects of including different protein sources in poultry diets on the environmental impacts Global Warming Potential (GWP), Eutrophication Potential (EP) and Acidification Potential (AP) of typical UK broiler meat and egg production systems was quantified using the Life Cycle Assessment (LCA) method combined with an uncertainty analysis. The broiler and layer diets compared in the study were either standard soya-based, or alternative diets based on European-grown protein crops, including field beans, field peas, sunflower meal and whole rapeseed. Different methods for accounting for land use change (LUC) in feed crop production were applied, including (1) a weighted average of “new” and “mature” agricultural land used for soya production (“best estimate” scenario), (2) assuming no LUC in the production of soya used in these diets (“sustainable soya” scenario) and (3) including indirect LUC for all arable crop production (“top-down” scenario). Monte Carlo simulations were used to quantify uncertainties in predicted impacts and to perform statistical comparisons between the effects of different diet compositions. The results showed that when included at relatively high levels in the diets (10–30% by mass), peas, beans and rapeseed could slightly reduce the simulated mean value of GWP (up to 12%) of broiler meat and egg production. However, when uncertainties in the data were taken into account, these reductions were not statistically significant. Furthermore, the reduction in GWP strongly depended on the method of LUC accounting applied in the analysis. With the “sustainable soya” and “top-down” scenarios, only small, non-significant differences between the different diets were found. In the case of EP, only small non-significant changes could be achieved with the alternative protein sources. For AP, a significant reduction of more than 20% could be achieved if the crude protein content of the broiler diet was reduced by using peas in combination with pure amino acids. This study demonstrates the importance of a holistic approach, coupled with Monte Carlo uncertainty analysis, to evaluate the environmental impacts of livestock systems. It takes into account the environmental burdens related, for example, to feed production and transport and differences in emissions from housing and the end use of the manure. Furthermore, due to the systematic uncertainty analysis, the statistical significance of the effects of different feeding scenarios can now be evaluated.

A mathematical model of silage consolidation and effluent flow is presented. Silage is modelled as a porous deformable medium containing a fluid. Model predictions for silage settlement heights and effluent production are found to be in good agreement with those found in laboratory-scale experiments (6kg of grass silage) and with findings reported in the literature for full-size silos containing several hundred tonnes of silage. The model can provide a quantitative understanding of the processes involved in effluent production so that scientifically based solutions to problems, such as the effective use of absorbents, can be reached. The model has been used to assess the importance of dry-matter content and silo geometry in determining effluent production. The height/diameter ratio of a silo is predicted to have a significant effect on effluent production. Increasing the height/diameter ratio is predicted to prolong the time from initial drainage to the peak flow of effluent.

A mathematical model of the aerobic deterioration of silage is described that includes the physical processes of gas and heat Rows, as well as an established model of microbial growth and the associated chemical changes. Yeasts and acetic acid bacteria are included in the growth model. The version of the model described relates to a cylinder of silage subject to forced aeration, a common experimental configuration. The model was very sensitive to variations in insulation thickness and yeast growth rate, and to initial pH, especially when maize was the forage. Great care is needed when selecting input data for use in the model to be sure that the physical and chemical properties are accurate. The model solution was sensitive to grid size, but with 361 cells, the maximum grid resolution that could be used on a 486 series PC, solutions were achieved with an acceptably small loss of accuracy. The model predicted the results of an experiment on silage deterioration quite accurately. However, the model also predicted that considerable spatial gradients of parameters, such as temperature, pH, and lactic acid, would occur. This indicates the need for care when taking samples or making temperature measurements in deterioration experiments. The model is potentially a useful tool in predicting the optimal time and position to take samples for analysis in a time-course experiment.

Mathematical equations are presented for a model of the processes of air infiltration and oxidation loss occurring when silage is stored in horizontal clamps, driven by a combination of pressure differences and diffusion. The limited information available about parameters of the model is discussed. Results suggest that air enters a clamp owing to pressure differences but distributes itself throughout the clamp by diffusion. These mechanisms account for levels of surface waste and invisible oxidation loss which are typically measured in silage clamps. The model suggests that it should be possible to almost eliminate these types of loss, either by thorough consolidation of the ensiled material, or possibly by improved sealing with plastic sheeting. In practice, consolidation appears to be the most practical approach to the reduction or elimination of losses, since the required density levels are known to be achievable in practice. It is less likely to be possible to improve sealing significantly, particularly between plastic sheet and coated concrete clamp wall.

The aim of this study was to apply the life cycle assessment (LCA) method, from cradle to gate, to quantify the environmental burdens per 1,000 kg of expected edible carcass weight in the 3 main broiler production systems in the United Kingdom: 1) standard indoor, 2) free range, and 3) organic, and to identify the main components of these burdens. The LCA method evaluates production systems logically to account for all inputs and outputs that cross a specified system boundary, and it relates these to the useful outputs. The analysis was based on an approach that applied a structural model for the UK broiler industry and mechanistic submodels for animal performance, crop production, and major nutrient flows. Simplified baseline feeds representative of those used by the UK broiler industry were used. Typical UK figures for performance and mortality of birds and farm energy and material use were applied. Monte Carlo simulations were used to quantify the uncertainties in the outputs. The length of the production cycle was longer for free-range and organic systems compared with that of the standard indoor system, and as a result, the feed consumption and manure production per bird were higher in the free-range and organic systems. These differences had a major effect on the differences in environmental burdens between the systems. Feed production, processing, and transport resulted in greater overall environmental impacts than any other components of broiler production; for example, 65 to 81% of the primary energy use and 71 to 72% of the global warming potential of the system were due to these burdens. Farm gas and oil use had the second highest impact in primary energy use (12-25%) followed by farm electricity use. The direct use of gas, oil, and electricity were generally lower in free-range and organic systems compared with their use in the standard indoor system. Manure was the main component of acidification potential and also had a relatively high eutrophication potential. The LCA method allows for comparisons between systems and for the identification of hotspots of environmental impacts that could be subject to mitigation.

Summary: There is an increasing need for life cycle data for bio-based products, which becomes particularly evident with the recent drive for greenhouse gas reporting and carbon footprinting studies. Meeting this need is challenging given that many bio-products have not yet been studied by life cycle assessment (LCA), and those that have are specific and limited to certain geographic regions. In an attempt to bridge data gaps for bio-based products, LCA practitioners can use either proxy data sets (e.g., use existing environmental data for apples to represent pears) or extrapolated data (e.g., derive new data for pears by modifying data for apples considering pear-specific production characteristics). This article explores the challenges and consequences of using these two approaches. Several case studies are used to illustrate the trade-offs between uncertainty and the ease of application, with carbon footprinting as an example. As shown, the use of proxy data sets is the quickest and easiest solution for bridging data gaps but also has the highest uncertainty. In contrast, data extrapolation methods may require extensive expert knowledge and are thus harder to use but give more robust results in bridging data gaps. They can also provide a sound basis for understanding variability in bio-based product data. If resources (time, budget, and expertise) are limited, the use of averaged proxy data may be an acceptable compromise for initial or screening assessments. Overall, the article highlights the need for further research on the development and validation of different approaches to bridging data gaps for bio-based products. © 2011 by Yale University.

This study estimated the carbon footprint of watching broadcast television using digital terrestrial television and online delivery of video-on-demand. The carbon footprint for digital terrestrial television was found to be 0.088 kg CO 2 e/viewer-hour and for online delivery of video-on-demand ranges from 0.030–0.086 kg CO 2 e/viewer-hour. This was based mainly on the energy consumption in the use phase. Results were sensitive to the number of viewers per display. It was found that the largest environmental impact from watching television is due to the power consumption of the consumer equipment. This amounts to 76% of the total for digital terrestrial television and 78% and 37% for video-on-demand using desktop and laptop computers respectively. The trend for larger television screens which have higher power consumption could increase this. Programme production contributes 12% to 35% and distribution contributes 10–28%. It was found that the audience size of a digital terrestrial channel and whether or not an aerial amplifier was used have a large effect on which distribution method appears to be the most energy efficient.

Modern agriculture is heavily dependent on fossil resources. Both direct energy use for crop management and indirect energy use for fertilizers, pesticides and machinery production have contributed to the major increases in food production seen since the 1960s. However, the relationship between energy inputs and yields is not linear. Low-energy inputs can lead to lower yields and perversely to higher energy demands per tonne of harvested product. At the other extreme, increasing energy inputs can lead to ever-smaller yield gains. Although fossil fuels remain the dominant source of energy for agriculture, the mix of fuels used differs owing to the different fertilization and cultivation requirements of individual crops. Nitrogen fertilizer production uses large amounts of natural gas and some coal, and can account for more than 50 per cent of total energy use in commercial agriculture. Oil accounts for between 30 and 75 per cent of energy inputs of UK agriculture, depending on the cropping system. While agriculture remains dependent on fossil sources of energy, food prices will couple to fossil energy prices and food production will remain a significant contributor to anthropogenic greenhouse gas emissions. Technological developments, changes in crop management, and renewable energy will all play important roles in increasing the energy efficiency of agriculture and reducing its reliance of fossil resources. Keywords: energy in agriculture; fossil energy; agricultural greenhouse gas emissions; land use; agroforestry; policy