Raphael Slade

New improvements for lignocellulosic ethanol

The use of lignocellulosic biomass for the production of biofuels will be unavoidable if liquid fossil fuels are to be replaced by renewable and sustainable alternatives. Ethanol accounts for the majority of biofuel use worldwide, and the prospect of its biological production from abundant lignocellulosic feedstocks is attractive. The recalcitrance of these raw materials still renders proposed processes complex and costly, but there are grounds for optimism. The application of new, engineered enzyme systems for cellulose hydrolysis, the construction of inhibitor-tolerant pentose-fermenting industrial yeast strains, combined with optimized process integration promise significant improvements. The opportunity to test these advances in pilot plants paves the way for large-scale units. This review summarizes recent progress in this field, including the validation at pilot scale, and the economic and environmental impacts of this production pathway.

Battery electric vehicles, hydrogen fuel cells and biofuels. Which will be the winner?

Addressing the economic and environmental sustainability problems of todays road transport requires, inter alia, the rapid introduction of alternative, low-carbon fuels and highly efficient, low-emission powertrains. It is unlikely that the transition from oil-based fuels and conventional internal combustion engines will occur organically at the necessary rate and following an optimum path, hence policy intervention is required. However, in order to design effective policies it is essential that the potential role of the alternative technologies is understood as best as current knowledge allows. Several high-profile studies have compared the potential of alternative road transport technologies, such as hybrids, plug-in hybrids, battery electric vehicles, hydrogen fuel cells and biofuels. The studies, critically reviewed in this paper, have generated a tremendous amount of knowledge. However, we have identified limitations that should be addressed in future comparative studies. These are: a) the complexity of the passenger car market, consisting of many segments characterised by different requirements and use patterns, is not adequately represented; b) future changes in driving behaviour brought about by new policy and technology are generally not considered; c) different studies use different performance indicators for alternative fuels and powertrains, making results difficult to compare and their interpretation difficult for the non-expert. We test the effect of these limitations on the Total Cost of Ownership of each of the alternative technologies mentioned above. We demonstrate that building market segments and behavioural change into a comparative analysis significantly affects its results and we recommend that this is done in future studies.

The greenhouse gas emissions performance of cellulosic ethanol supply chains in Europe.

BackgroundCalculating the greenhouse gas savings that may be attributed to biofuels is problematic because production systems are inherently complex and methods used to quantify savings are subjective. Differing approaches and interpretations have fuelled a debate about the environmental merit of biofuels, and consequently about the level of policy support that can be justified. This paper estimates and compares emissions from plausible supply chains for lignocellulosic ethanol production, exemplified using data specific to the UK and Sweden. The common elements that give rise to the greatest greenhouse gas emissions are identified and the sensitivity of total emissions to variations in these elements is estimated. The implications of including consequential impacts including indirect land-use change, and the effects of selecting alternative allocation methods on the interpretation of results are discussed.ResultsWe find that the most important factors affecting supply chain emissions are the emissions embodied in biomass production, the use of electricity in the conversion process and potentially consequential impacts: indirect land-use change and fertiliser replacement. The large quantity of electricity consumed during enzyme manufacture suggests that enzymatic conversion processes may give rise to greater greenhouse gas emissions than the dilute acid conversion process, even though the dilute acid process has a somewhat lower ethanol yield.ConclusionThe lignocellulosic ethanol supply chains considered here all lead to greenhouse gas savings relative to gasoline An important caveat to this is that if lignocellulosic ethanol production uses feedstocks that lead to indirect land-use change, or other significant consequential impacts, the benefit may be greatly reduced.Co-locating ethanol, electricity generation and enzyme production in a single facility may improve performance, particularly if this allows the number of energy intensive steps in enzyme production to be reduced, or if other process synergies are available. If biofuels policy in the EU remains contingent on favourable environmental performance then the multi-scale nature of bioenergy supply chains presents a genuine challenge. Lignocellulosic ethanol holds promise for emission reductions, but maximising greenhouse gas savings will not only require efficient supply chain design but also a better understanding of the spatial and temporal factors which affect overall performance.

The commercial performance of cellulosic ethanol supply-chains in Europe

BackgroundThe production of fuel-grade ethanol from lignocellulosic biomass resources has the potential to increase biofuel production capacity whilst minimising the negative environmental impacts. These benefits will only be realised if lignocellulosic ethanol production can compete on price with conventional fossil fuels and if it can be produced commercially at scale. This paper focuses on lignocellulosic ethanol production in Europe. The hypothesis is that the eventual cost of production will be determined not only by the performance of the conversion process but by the performance of the entire supply-chain from feedstock production to consumption. To test this, a model for supply-chain cost comparison is developed, the components of representative ethanol supply-chains are described, the factors that are most important in determining the cost and profitability of ethanol production are identified, and a detailed sensitivity analysis is conducted.ResultsThe most important cost determinants are the cost of feedstocks, primarily determined by location and existing markets, and the value obtained for ethanol, primarily determined by the oil price and policy incentives. Both of these factors are highly uncertain. The best performing chains (ethanol produced from softwood and sold as a low percentage blend with gasoline) could ultimately be cost competitive with gasoline without requiring subsidy, but production from straw would generally be less competitive.ConclusionSupply-chain design will play a critical role in determining commercial viability. The importance of feedstock supply highlights the need for location-specific assessments of feedstock availability and price. Similarly, the role of subsidies and policy incentives in creating and sustaining the ethanol market highlights the importance of political engagement and the need to include political risks in investment appraisal. For the supply-chains described here, and with the cost and market parameters selected, selling ethanol as a low percentage blend with gasoline will maximise ethanol revenues and minimise the need for subsidies. It follows, therefore, that the market for low percentage blends should be saturated before markets for high percentage blends.

Status and prospects for renewable energy using wood pellets from the southeastern United States

The ongoing debate about costs and benefits of wood‐pellet based bioenergy production in the southeastern United States (SE USA) requires an understanding of the science and context influencing market decisions associated with its sustainability. Production of pellets has garnered much attention as US exports have grown from negligible amounts in the early 2000s to 4.6 million metric tonnes in 2015. Currently, 98% of these pellet exports are shipped to Europe to displace coal in power plants. We ask, ‘How is the production of wood pellets in the SE USA affecting forest systems and the ecosystem services they provide?’ To address this question, we review current forest conditions and the status of the wood products industry, how pellet production affects ecosystem services and biodiversity, and what methods are in place to monitor changes and protect vulnerable systems. Scientific studies provide evidence that wood pellets in the SE USA are a fraction of total forestry operations and can be produced while maintaining or improving forest ecosystem services. Ecosystem services are protected by the requirement to utilize loggers trained to apply scientifically based best management practices in planning and implementing harvest for the export market. Bioenergy markets supplement incomes to private rural landholders and provide an incentive for forest management practices that simultaneously benefit water quality and wildlife and reduce risk of fire and insect outbreaks. Bioenergy also increases the value of forest land to landowners, thereby decreasing likelihood of conversion to nonforest uses. Monitoring and evaluation are essential to verify that regulations and good practices are achieving goals and to enable timely responses if problems arise. Conducting rigorous research to understand how conditions change in response to management choices requires baseline data, monitoring, and appropriate reference scenarios. Long‐term monitoring data on forest conditions should be publicly accessible and utilized to inform adaptive management.

How Policy Makers Learned to Start Worrying and Fell Out of Love With Bioenergy

Abstract Bioenergy has come to be given a prominent role in national energy strategies in more than 60 countries around the world. The impetus for these policies draws on a range of motivations: improving energy security, diversifying agricultural production stimulating rural development, job creation, and reducing greenhouse gas (GHG) emissions. Arguably, GHG reductions were never the main driver for bioenergy policy, yet controversy over the extent, timing, and duration of carbon savings threatens to derail policy initiatives to drive up deployment. This paper analyses current controversies around bioenergy in the context of historic developments in the United States, Brazil, or European Union. It addresses two key questions: ‘ how did we end up in this policy mess?’ and, ‘ how do we get out of it ?’ Policy makers have faced three broad challenges to whether policies introduced to support bioenergy can genuinely contribute to GHG mitigation. The first is that carbon accounting frameworks misrepresent the carbon saving benefits of bioenergy, potentially leading policy makers to support policies that have unintended and undesirable consequences. The second is that increasing biomass production on agricultural land can directly, or indirectly, lead to increasing carbon emissions. The third challenge is that increased use of forest biomass does nothing to reduce emissions in the short term, but can only reduce carbon emissions in the distant future. We examine the evidence around each of these challenges and critically evaluate the policy responses. We argue that the greatest risk lies in political loss of confidence and institutional paralysis. Whereas the greatest opportunity lies in the co-evolution of bioenergy production and governance systems, drawing on the collective judgment of stakeholders involved in experiential, interactive, and deliberative decision-making processes.