Solid-state anaerobic digestion of spent wheat straw from horse stall.

This research investigates the anaerobic digestion of spent wheat straw from horse stalls for biogas production, comparing it to the use of raw wheat straw. The results show that the spent wheat straw produces greater biogas yield and results in higher cellulose and hemicellulose degradation than raw wheat straw.

Research Content and Methodology

• The study focused on the solid-state anaerobic digestion (SS-AD) of spent wheat straw from horse stall bedding, comparing it to the digestion of raw wheat straw. It noted that spent wheat straw had lower amounts of cellulose and hemicellulose but a higher volatile fatty acid content than the raw material.
• The SS-AD experiments were carried out at a total solids (TS) content of 22%, with the inoculum sourced from a liquid AD system. The researchers varied the feedstock-to-inoculum (F/I) ratio at levels of 2.0, 4.0, and 6.0 to investigate its effect on biogas production.

Findings of the Research

• The research found that spent wheat straw yielded methane more rapidly than raw wheat straw at F/I ratios of 2.0 and 4.0. Methane yield from spent wheat straw peaked 8 and 3 days earlier than those from raw wheat straw at the respective ratios. This indicates that spent wheat straw might be a more preferable material for biogas production due to shorter peak time than raw wheat straw.
• The maximum methane yield recorded was 150.0 L/kg of volatile solids from the spent wheat straw at an F/I ratio of 4.0. This was significantly higher (56.2%) than the yield from raw wheat straw, suggesting improved biogas production with spent wheat straw.
• In terms of biomass degradation, spent wheat straw performed much better than raw wheat straw. The degradation rates of cellulose and hemicellulose from spent wheat straw exceeded those from raw wheat straw by 24.1% and 49.4%, respectively. This means spent wheat straw is more easily digestible and contributes to higher biogas yield than raw wheat straw.

Implication of the Study

• This research points to the potential of spent wheat straw as a more optimal feedstock for biogas production methods such as SS-AD. The high volatile fatty acid content, quick methane yield, and improved cellulose and hemicellulose degradation make it a promising raw material for sustainable energy production.