Quantification and valorisation of agricultural bioresource residues in England

Abstract

This research investigates the current utilization of livestock waste arising from manures, slurries and crop-based feedstocks via Anaerobic Digestion (AD) in England with a focus on the quantification of the technical biomass resource potential and the economics. The technical potential refers to slurries and manures that are stored and not immediately spread to land, hence available to use in AD systems. A GIS tool has been developed that evaluates the availability of livestock waste and compares it with the actual utilisation of manures by operational biogas plants to quantify the latent biogas potential from unused livestock. The GIS tool has been applied to a region in the South West of England in order to analyse the impact of policies setting out minimum targets of 25 % and 50 % utilization of the biomass technical potential in AD plants. An Excel-based biogas calculator has been developed that enables economic assessment of on farm AD projects. Operational and financial data has been gathered via interviews and questionnaire from eight case studies representative of on farm biogas installations utilizing agricultural feedstocks. This dataset has been used to evaluate the predictions of the biogas calculator and estimate the four parameters of the underlying first order kinetic model via non-linear curve fitting in Matlab. Across England there are approximately 29 million tonnes of manures and slurries per annum that could be used to feed anaerobic digestion systems. Only about 5 % of this potential is utilized. An additional 32.7M GJ year-1 of renewable energy could be generated as biogas if the unutilised 95 % of agri-biosolids was used as feedstock in AD systems. In the region examined 40 additional AD plants with capacities ranging between 100 to 198 kWel and 131 additional AD plants with capacities ranging between 61 to 190 kWel are needed if the policy targets of utilizing respectively 25 % and 50 % of total biomass potential from livestock are to be met. This confirms that manures and slurries are underutilised substrates for anaerobic digestion and that there is still considerable potential for further development in England. This study also lays the foundation for the creation of a fully integrated biomass resources management tool.

Date of Award	29 May 2019
Original language	English
Awarding Institution	University of Bath
Supervisor	Tom Arnot (Supervisor) & Marcelle McManus (Supervisor)