Anaerobic Digestion of Solid Agricultural Biomass in Leach-Bed Reactors

• Published in: Bioengineering (Basel) Vol. 10; no. 4; p. 433
• Main Authors: Pyykkönen, Ville, Winquist, Erika, Seppänen, Ari-Matti, Vainio, Markku, Virkkunen, Elina, Koppelmäki, Kari, Rasi, Saija
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 29-03-2023; MDPI
• Subjects: agricultural biomass; Alternative energy sources; Anaerobic digestion; Beans; Bioengineering; Biogas; Biomass; Broad beans; Clover; Emissions; Energy consumption; Experiments; Farms; Feasibility studies; Greenhouse gases; Horses; leach-bed reactor; Manures; Methane; Mixtures; Nitrogen; nutrient recycling; Properties; Reactors; Refuse as fuel; Substrates; Finland; nutrient recycling; agricultural biomass; leach-bed reactor; biogas
• ISSN: 2306-5354; 2306-5354
• DOI: 10.3390/bioengineering10040433

This study focuses on the feasibility of the dry anaerobic digestion of solid agricultural biomass for efficient renewable-energy production and nutrient recycling. Methane production and the amount of nitrogen in the digestates were measured in pilot- and farm-scale leach-bed reactors. In the pilot scale, with a digestion time of 133 days, the methane production of a mixture of whole crop fava bean and horse manure corresponded to 94% and 116%, respectively, of the methane potentials of the solid substrates. The mono-digestion of fava beans resulted in relatively low methane production (production/potential ratios of 59% and 57%). In two full-scale experiments, the methane production of mixtures of clover-grass silage, chicken manure, and horse manure corresponded to 108% and 100% of their respective methane potentials with digestion times of 117 and 185 days. In co-digestion, the production/potential ratios were similar in the pilot and farm experiments. High nitrogen loss was observed in the farm scale when the digestate was stored in a stack covered with a tarpaulin during summertime. Thus, although the technology seems promising, attention needs to be paid to management practices to minimise nitrogen losses and greenhouse gas emissions.