Programme of Work 2013-2015IndexA. Feedstocks and the AD Process 1. ObjectivesThe general objectives of Task 37 are:The main objective of the Task 37 work programme is to address the challenges related to the economic and environmental sustainability of biogas production and utilisation. While there are many biogas plants in OECD countries, operation in the vast majority of cases can only be sustained with the help of subsidies to be able to compete with the fossil energy industrial sector. There is a clear need to enhance many of the process steps in the biogas production chain in order to reduce both investment and operating costs. Task 37 started the process optimisation work in the 2010-2012 work programme and will intensify this focus in 2013-2015. Until recently the environmental performance of biogas production and utilisation was not assessed in a detailed manner and studies have started to highlight concerns about emissions of greenhouse gases at various stages of the biogas production chain. Task 37 started to address emissions in the 2010-2012 work programme and will focus special attention on environmental sustainability of biogas production and utilisation and establish best practices for emissions reduction. In combination, process optimisation studies in Task 37 will attempt to significantly improve both economic and environmental performance of the biogas value chain where the end product is heat or electricity or biomethane for pipeline injection and use as a vehicle fuel and will include utilisation of the digestate.
2. RationaleBased on many favourable reports over a number of years AD is a favoured treatment processes for organic residues and wastes; particularly for feedstocks with high water content. AD has been adopted by a range of sectors to tackle ground water pollution in agriculture, treatment of municipal sewage and treatment of green municipal waste and is used in a range of industrial processes to recover energy from residues while substantially reducing the overall impact of a primary process on the environment. However, AD is also a useful process for dedicated energy production and the production of renewable fuel in the form of biomethane from both purpose-grown crops as well as residues. The AD process has the added benefit of preserving nutrients found in the feedstock and allowing these nutrients to be recycled back to the soil, thereby reducing the amount of fossil-derived fertilisers needed for subsequent crop production. AD provides additional income and jobs in distributed installations, often in rural communities. The AD treatment of agricultural residues helps to reduce greenhouse gas emissions of both methane (CH4) and nitrous oxide (N2O). It also promotes better hygiene in relation to safe treatment of animal by-products and provides better recycling of nutrients back to the soil. Life cycle studies show that biogas from residues saves considerably more greenhouse gas emissions than first generation liquid biofuels for transport, bioethanol and biodiesel. A greater energy yield per hectare is achievable with biomethane than with first generation liquid biofuels. The treatment of green wastes or biowastes, likewise, enables the production of renewable energy, saving CO2 emissions, while providing an effective alternative to landfilling of waste that leads to higher CH4 emissions. However, more recent studies have highlighted potential high methane emissions from various steps in the biogas value chain. The sources of these emissions need to be identified, quantified and eventually reduced to an acceptable level. By the end of the 2010-2012 triennium there were more than 8000 biogas installations in the Member Countries of Task 37. IEA has played a significant role in the definition and promotion of best available biogas technologies that are in use on farms, in organic waste treatment facilities and on waste water treatment sites. However, while there is substantial further potential for expansion of the AD sector, based on availability of potential feedstocks, challenges to maximise the potential benefits in terms of energy yield and to reduce both investment and operating costs remain. There is a well understood need to reduce the reliance of biogas plants on subsidies such as investment grants, feed-in tariffs and green certificates. 3. Work programmeThe work programme has been developed on the basis of three actions: 1. Information collated on the specific interests and on-going programmes in the IEA Bioenergy Member Countries through Task Members. 2. The status of trends in substrate availability, gas utilisation and biofertiliser utilisation. 3. Discussion and adoption of the Work Programme with the Task 37 members after their feedback from the national ExCo members. A. Feedstocks and the AD ProcessDemonstration of new developments and lessons learned (Success Stories). AD Process optimisation. b) Study of the kinetics of the AD process, specifically focussing on bacteria selection, process accelerators, inhibition and trace elements, all as a function of feedstock used in wet and dry processes, for the increase of methane yield and rate of production that will allow reduced reactor volumes and reduced costs. (If appropriate, parts a) and b) might be combined). AD of source segregated biodegradable waste and biodegradable fractions of residual MSW. AD of sewage sludge/waste water treatment Biogas from Algae B. AD Products UtilisationUp-grading Biomethane as a transport fuel Digestate up-grading techniques C. Sustainability
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