Supergen - Increasing energy yield from the integration of anaerobic digestion and pyrolysis

This collaborative project is aimed at developing a beneficial synergy between anaerobic digestion (AD) and pyrolysis for the processing of non-source segregated organic fraction of municipal solid waste (MSW).
Biomass-based energy processes are frequently cited as a great opportunity but also a risk because of their competition for productive arable land used for food production. Virgin crop biomass is much easier to use for energy production and for this reason is the basis of first generation biofuel production. Waste and mixed biomass sources are more difficult to process into usable fuel products, and the key research challenges therefore lie in developing technologies to provide second generation biofuels from these waste sources. The vision for the proposed research is to develop a synergy between biological (AD) and thermal (intermediate and fast pyrolysis) conversion processes in which the overall net energy yield from waste biomass can be improved, producing energy carriers that are both storable and transportable. These gains can be achieved as the thermal process allows access to lignin-bound components within the biomass which are otherwise unavailable for anaerobic biological conversion. In return, biological system can process the lower carbon chain molecules in pyrolysis oils and in the aqueous fraction to produce a fuel gas, thus improving the value of the liquid fuel fraction. The solid char also has potential for use as an energy carrier as well as other value-added uses.

The vision includes proving that this hybrid approach can provide a sustainable and societally acceptable means of recovering value from the non-source segregated organic fraction of municipal solid waste (MSW). This waste fraction currently poses the greatest challenge to the UK Government in terms of the requirement for diversion of organic materials generated by society, industry and commerce from landfill: whilst it also offers the potential to contribute significantly to renewable energy targets and to the offset of carbon emissions. This project is therefore closely aligned to the aims of the SUPERGEN call 'Challenges in Bioenergy Technologies' and also to several areas within the RCUK research portfolio on energy, bioenergy and living with environmental change.

The overall aim of the project is to improve the overall net energy yield obtained from residual municipal solid waste, through a combination of thermal pyrolysis and anaerobic digestion. The proposed research will develop understanding of each process individually and will stimulate a new understanding of the processing requirements to develop a synergy between the two technologies (intermediate pyrolysis and anaerobic digestion (AD)). A greater understanding will be achieved for the digestion of oil products, which is currently an area of developing AD research. Advances in the analysis of microbial populations will also be achieved through this project. Collaboratory work packages (WP) will analyse the energy balances of these two processes individually and as a synergy, which will later be used to advise future research and commercial application of the work. These themes will also be reflected in the socio-economics of the project, ensuring potential users of the technology have the opportunity to address their questions regarding the synergy.