Increasing the Methane Potential of Oat Husks Using a Novel Extrusion Pre-Treatment Technology Prior to Anaerobic Digestion

Oat husks are produced during the milling process of oats. Oat husks are a lignocellulosic material that have the potential for valorization thereby improving the circular economy of agricultural by-products. However, due to the high lignocellulosic content, there are limited valorization pathways for oat husks. To improve the anaerobic digestibility of oat husks, pre-treatment was investigated as a method to aid valorization. A novel extrusion process was used in an attempt to fragment the lignocellulosic structure of oat husks prior to anaerobic digestion. The extrusion pre-treatment was investigated to determine the effect it may have on altering the methane yield and digestibility of oat husks. Biochemical methane potential assays were undertaken using oat husks with no pre-treatment and extruded oat husks. These assays demonstrated that extruded oat husks produced a significantly higher methane yield of 264 ml/gVS fed, which was 27% greater than the methane yield produced from the untreated oat husks. Similarly, the total solids degradation was also significantly higher for extruded oat husks treatment compared to the untreated oat husks. Overall, the extrusion process demonstrated an increased methane yield for oat husks compared to previously published data. The biomethane potential tests suggest that extruded oat husks would be a feedstock suitable for anaerobic digestion.