CROPGEN - Renewable Energy from Crops and Agro-wastes

Objectives

The overall objective is to produce from biomass a sustainable fuel source that can be integrated into the existing energy infrastructure in the medium term, and in the longer term will also provide a safe and economic means of supplying the needs of a developing hydrogen fuel economy. The project is based on the use of anaerobic digestion (AD) as a means of producing methane from biomass, including energy crops and agricultural residues. The technology of biochemical methane generation is well established: the breakthrough to a cost-effective and competitive energy supply will come from engineering and technical improvements to increase conversion efficiencies, and from reductions in the cost of biomass by the introduction of integrated systems making use of novel and multi-use crops and agro-wastes. The research will determine how the technology can best be applied to provide a versatile, low-cost, carbon-neutral biofuel in an environmentally sound and sustainable agricultural framework.

Key issues

Annual growth plant tissue with its high water content is inherently unsuitable for combustion or other thermal treatments: the ideal route for such materials is through biochemical conversion. The concept of an energy-only farm, where annual crops are grown solely for biomethanisation, is still speculative and depends on two key factors: the development of digesters with higher conversion efficiencies than current conventional reactors; and the optimisation of other costs and benefits. These problems could be solved in the medium term. The concept of energy self-sufficient farming units can be realised in the short term by introduction of integrated systems making effective use of bio-residues in energy production. This, coupled with selection of crop species with multipurpose use as soil improvers and fodder crops, could yield a positive energy balance allowing export of energy off the farm.

Technical approach

The work will identify crops and agro-wastes best fitted to energy production in an integrated farming environment, consider energy losses in production and processing, and use these to set net energy production targets. The role of storage and pre-treatments will be considered. Co-digestion will be evaluated for improving energy yields. Some agricultural residues will be investigated as potential high-yield substrates. Innovative bioreactor designs and operating modes will be tested. A database of bio-kinetics for use in design and operation will be established. True life-cycle costs for biogas production will be determined in large-scale trials for verification of laboratory data and predictive models. The work will consider the need for continuity of energy supply in a farm environment. Issues of sustainability, environmental impact and socio-economic factors will also be addressed.