Patricia Thornley

Importance of non-CO2 emissions in carbon management

Background: GHG budgets highlight a need for urgency, yet analyses are often CO2-focused, with less attention paid to non-CO2. Results: In this paper, scenarios are used to explore non-CO2 drivers and barriers to their mitigation, drawing out implications for CO2 management. Results suggest that even optimistic technological and consumption-related developments lead to on-going increases in global N2O, largely to improve food security within a changing climate. This contrasts with existing analysis, where lower levels of N2O by 2050 are projected. Conclusions: As avoiding ‘2ｰC’ limits the emissions budget, constraints on reducing non-CO2 add pressure to energy system decarbonization. Overlooking how a changing climate and rising consumption restricts efforts to curb non-CO2 will result in policies aiming to avoid 2ｰC falling short of the mark.

Biofuels: balancing risks and rewards

This paper describes a framework that can be used to evaluate the environmental risks and benefits associated with biofuel production. It uses the example of biodiesel produced from Argentinean soy to show how such a framework can be used to conceptualize trade-offs between different environmental, social and economic impacts of biofuel production. Results showing the greenhouse-gas savings and overall life-cycle impact of different ‘soy-biodiesel’ production methods are presented. These impacts and the significance of uncertainty in overall assessments of key parameters, such as greenhouse-gas savings, are discussed. It is shown that, even where sufficient knowledge exists to be able to quantify these impacts, the sustainability of supply of a particular biofuel is inextricably linked to values and ethical judgements. However, tailoring certification efforts to the issues that are most likely to make a significant difference to the overall sustainability could improve the effectiveness of certification efforts. The potential for a framework to guide and focus certification efforts is discussed and future research and policy priorities suggested.

Cost effective greenhouse gas reductions in the steel industry from an Organic Rankine Cycle

Large quantities of low grade heat (LGH) are genera ted within many process industries, and the recovery of LGH is a potentially significan t means of improving process efficiency, but it is often difficult to find an ap propriate internal heat load. One alternative is to use appropriate technologies to c onvert the low grade heat to electricity for use on site. This paper describes the environme ntal and techno-economic evaluation of a case study examining the potential application of an Organic Rankine Cycle (ORC) to generate electricity from LGH from the stacks of a coke oven used in steel production. 21 MW of LGH was available for recovery at the plant and resource accounting and lifecycle analysis methods were used to evaluate the environmental and economic benefits of the operation of an ORC. The r esults showed that between 1 and 3% of the CO 2 emitted directly through the production of coke wo uld be offset by installation of an ORC, with lifecycle environmenta l impacts of coke production reduced by less than 1%, although this was sufficie nt to offset over 10,000 t CO 2 annually. However, the amount of electricity gener ated was sufficient to replace all currently imported electricity and economic analysi s indicated a relatively attractive discounted payback period of between 3 and 6 years, suggesting this may be a commercially viable option, which could present a r elatively cost effective method of achieving greenhouse gas savings in the process ind ustries.

Consensus, uncertainties and challenges for perennial bioenergy crops and land use

Perennial bioenergy crops have significant potential to reduce greenhouse gas (GHG) emissions and contribute to climate change mitigation by substituting for fossil fuels; yet delivering significant GHG savings will require substantial land‐use change, globally. Over the last decade, research has delivered improved understanding of the environmental benefits and risks of this transition to perennial bioenergy crops, addressing concerns that the impacts of land conversion to perennial bioenergy crops could result in increased rather than decreased GHG emissions. For policymakers to assess the most cost‐effective and sustainable options for deployment and climate change mitigation, synthesis of these studies is needed to support evidence‐based decision making. In 2015, a workshop was convened with researchers, policymakers and industry/business representatives from the UK, EU and internationally. Outcomes from global research on bioenergy land‐use change were compared to identify areas of consensus, key uncertainties, and research priorities. Here, we discuss the strength of evidence for and against six consensus statements summarising the effects of land‐use change to perennial bioenergy crops on the cycling of carbon, nitrogen and water, in the context of the whole life‐cycle of bioenergy production. Our analysis suggests that the direct impacts of dedicated perennial bioenergy crops on soil carbon and nitrous oxide are increasingly well understood and are often consistent with significant life cycle GHG mitigation from bioenergy relative to conventional energy sources. We conclude that the GHG balance of perennial bioenergy crop cultivation will often be favourable, with maximum GHG savings achieved where crops are grown on soils with low carbon stocks and conservative nutrient application, accruing additional environmental benefits such as improved water quality. The analysis reported here demonstrates there is a mature and increasingly comprehensive evidence base on the environmental benefits and risks of bioenergy cultivation which can support the development of a sustainable bioenergy industry.

Scope of System for Analysis

Abstract This chapter recaps the purpose of life cycle assessment as a tool to assess bioenergy system greenhouse gas balances. It emphasises the importance of goal and scope consideration and definition in any LCA study and shows how that may translate to application of different system scopes and methods. Key issues to consider for bioenergy LCAs are introduced, e.g. whether or not to include land-use change, and there is a general introduction to where the reader can find relevant information and data in the rest of the book.

Biodiesel from Argentinean Soy

Abstract Soy farming is a large-scale industrial activity in many South American countries, where intensive, no-till agriculture is commonly practised. This chapter evaluates the greenhouse gas implications of producing biodiesel from soy in Argentina. The results show clear greenhouse gas benefits. However, they also highlight the distinction between attributional and consequential LCA, including the importance of allocation, since soy production has two main products: soy oil and soy meal and how the environmental burdens are allocated across these two products significantly impacts the results. The importance of an appropriate choice of time frame for LCA calculations is introduced with respect to long-term soil health/condition and the associated methodological challenges of accounting for changes in stocks or reserves as well as material and energy flows in analysis. Finally, the importance of taking into account other environmental impacts in life cycle assessment is highlighted, since this production typology results in a reduction in global warming potential, but increased impacts in a number of other environmental impact categories.

Outlook–for Low Carbon Bioenergy

Abstract It could be argued that the global response to date has arrested the previous rapid growth of greenhouse gas emissions and there has even been unprecedented sustained economic growth simultaneous with a reduction in GHG emissions. However, the contributions declared by individual countries to date do not reach ideal targets. There is undeniably a huge potential for well-designed bioenergy systems to use sustainable feedstocks to deliver much-needed greenhouse gas reductions. Sustainable feedstocks are the basic starting point for any sustainable bioenergy system. Fortunately, there are many examples of sustainable biomass production that have positive impacts, but this cannot be assured simply by feedstock category or description. In order to reap maximum benefits from bioenergy systems, there is a need to evaluate their effectiveness, which is done in a number of different ways, and a need to value the carbon reductions achieved through some form of reward system, though there seems to be no political will to enforce such a policy at present.

Environmental Lessons—Making Bioenergy System Decisions That Benefit the Environment

Abstract In an increasingly climate-conscious world, decision-makers have to weigh options in terms of their costs, benefits, and detriments in order to adapt to the effects of changing climate, reduce the severity of such impacts, and support ecosystem recovery when climate impacts are experienced. Bioenergy systems can be a means to provide alternative sources of energy and reduce greenhouse gas emissions; though problems associated with bioenergy systems include eutrophication and acidification. Furthermore, this can lead to other issues such as disruption of soil carbon balance, soil nutrient depletion, air quality impacts, and, ironically, greenhouse gas impacts if not managed carefully. Therefore, a holistic approach to bioenergy that recognises and values all of the impacts (ecological, economic, and social) is necessary. That is then compounded by consideration of the different bioenergy stakeholders and their perspectives.

Policy Lessons: The Role of Policy Regimes in Maximising GHG Savings in Bioenergy Systems

Abstract Bioenergy systems are being encouraged by global policy regimes and targets to support the development of renewable energy systems. A key driver for this is the desire to reduce global greenhouse gas emissions to avert the most damaging consequences of climate change. Therefore, any bioenergy systems that are incentivised under policy mechanisms should deliver actual global greenhouse gas reductions. Nonetheless, evaluating the net greenhouse gas reductions achieved by bioenergy systems can be challenging and results are often disputed because of variations in scope of system, data inputs, emission factors, or methodological approaches. This chapter reviews the key issues that must be taken into account in developing effective policy instruments to encourage bioenergy systems that reduce net greenhouse gas emissions. The issues are so diverse that many are not best incentivised through energy generation and consequently an alternative approach that values the ecosystem impacts rather than simply the energy provision is required. Additionally, the scope of system commonly used by many policy instruments (system boundary definition) is shown to be inappropriate to deliver the key objective of maximising actual greenhouse gas savings. An alternative scope of system for policy mechanisms is recommended to ensure that future bioenergy provision achieves real emissions savings while maximising other wider socio-economic and environmental benefits.

Waste wood as bioenergy feedstock. Climate change impacts and related emission uncertainties from waste wood based energy systems in the UK

Considering the urgent need to shift to low carbon energy carriers, waste wood resources could provide an alternative energy feedstock and at the same time reduce emissions from landfill. This research examines the climate change impacts and related emission uncertainties of waste wood based energy. For this, different grades of waste wood and energy application have been investigated using lifecycle assessment. Sensitivity analysis has then been applied for supply chain processes and feedstock properties for the main emission contributing categories: transport, processing, pelletizing, urea resin fraction and related N2O formation. The results show, depending on the waste wood grade, the conversion option, scale and the related reference case, that emission reductions of up to 91% are possible for non-treated wood waste. Compared to this, energy from treated wood waste with low contamination can achieve up to 83% emission savings, similar to untreated waste wood pellets, but in some cases emissions from waste wood based energy can exceed the ones of the fossil fuel reference - in the worst case by 126%. Emission reductions from highly contaminated feedstocks are largest when replacing electricity from large-scale coal and landfill. The highest emission uncertainties are related to the woods resin fraction and N2O formation during combustion and, pelletizing. Comparing wood processing with diesel and electricity powered equipment also generated high variations in the results, while emission variations related to transport are relatively small. Using treated waste wood as a bioenergy feedstock can be a valid option to reduce emissions from energy production but this is only realisable if coal and landfill gas are replaced. To achieve meaningful emission reduction in line with national and international climate change targets, pre-treatment of waste wood would be required to reduce components that form N2O during the energy conversion.