An economic analysis of anaerobic digestate fuel pellet production: can digestate fuel pellets add value to existing operations?
Date
2021-04-16
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Publisher
Elsevier
Abstract
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.
Description
Publication history: Accepted - 9 April 2021; Published online - 16 April 2021.
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Keywords
Anaerobic digestion, Digestate, Fuel pellet, Economic analysis, Phosphorous
Citation
Cathcart, A., Smyth, B. M., Lyons, G., Murray, S. T., Rooney, D. and Johnston, C. R. (2021) ‘An economic analysis of anaerobic digestate fuel pellet production: can digestate fuel pellets add value to existing operations?’, Cleaner Engineering and Technology. Elsevier BV, 3, p. 100098. doi: 10.1016/j.clet.2021.100098.