BBSRC NIBB Anaerobic Digestion (AD) Network
terrestrial grown materials such as reed canary grass (ref ERA-net bioenergy), and for understanding how changes resulting from altering the germplasm and chemical composition of the feedstock through breeding programmes could affect digestability and importantly the intermediate carboxylic acid pool. The Network has synergies with the proposed network in ‘Integrated technologies from plants to products’ led by Prof Leek. There is also much interest in using both micro and macro-algae as digestion feedstocks, but with only moderate success to date. Although much research effort has gone into increasing algal lipid content by strain selection and manipulation of growth conditions, there has been relatively little work on how the whole or residual algal biomass might be modified to improve its conversion potential through anaerobic processing.

Feedstock enhancements, novel feedstocks

& new markets working group

Anaerobic digestion is currently the only technology at market place with the capability of converting high moisture content mixed-waste biomass to a fuel product that can be used with minimal refining. The conversion efficiency is substrate dependent, however, and ranges from < 40% for sewage biosolids and microalgae to > 90% for food waste. Pre-treatments that have been used to improve biodegradability include thermal, mechanical, chemical and physical processes. Synergies between different feedstocks leading to improve overall conversion are also sometimes reported, but the mechanisms underlying such interactions are understood poorly if at all. More recently, the use of enzymes has been considered as a pre-treatment, as well as improvements to the enzymic hydrolysis phase through process manipulations. To move towards the full realisation of anaerobic digestion as a more efficient bioenergy production process and/or as the foundation of a biorefinery, feedstock selection is an important factor. Current energy crop feedstocks are those that compete directly with human and animal feed production because of their ‘high digestability’ in either context: yet there is potential for developing less competitive