Publication history: Accepted - 9 April 2021; Published online - 16 April 2021.Anaerobic digestion provides renewable energy through waste valorisation, but the digestate by-product is
underutilised and presents a risk to water quality. Mechanical separation partitions phosphorous into the solid
fraction and further processing into a fuel pellet can provide an additional source of energy and revenue. Previous
economic analyses looked only at aspects of the system (e.g. operational costs solely) and the system requires
further investigation to determine viability. In this paper, an economic assessment of digestate fuel pellet production
at farm-scale anaerobic digestion plants was carried out. The significance of this work is to provide a
comprehensive assessment of the energy, phosphorous, and economic balances involved in digestate fuel pellet
production at existing anaerobic digestion plants. The aim of this paper is to determine the financial viability of
digestate fuel pellet production with objectives to compare two mechanical separation technologies: screw press,
and decanting centrifuge. Economies of scale hold true for digestate pellet production and the available digestate
in typical UK farm-based anaerobic digestion plants ( 500 kWe) is insufficient for profitability, with pellet
production costing from £176/t (decanting centrifuge) to £215/t (screw press), compared to a typical wood pellet
sale price of £185/t. Increasing digestate quantity by collaboration of plant operators can reduce the cost of pellet
production to between £95/t and £121/t, improving financial viability and increasing the profit per head of cattle
by 9–20% on a typical dairy farm utilising anaerobic digestion. The system has potential to aid rural development
while also protecting the environment and contributing to the diversification of energy supply.This project was supported by The Bryden Centre. The Bryden Centre
project is supported by the European Union’s INTERREG VA Programme,
managed by the Special EU Programmes Body (SEUPB). The views and
opinions expressed in this paper do not necessarily reflect those of the
European Commission or the Special EU Programmes Body (SEUPB). The
work was also supported by Queen’s University Belfast and the Agri-Food
and Biosciences Institute in Northern Ireland