High-solids semi-continuous anaerobic digestion of corn silage in bag-type digester

Abstract

The aim of this paper is to discuss the usability of a newly designed partially stirred horizontal anaerobic bioreactor made from triple layer bag material Sioen B6070 and heated by circulating hot air. For verification of the possibility of processing typical agricultural fibrous substrate at relatively high solids content in this type of reactor, the semi-continuous mesophilic (40±3°C) anaerobic digestion of corn silage of KWS Atletico cultivar was conducted. The reactor with a total volume of 0.7 m3 provided 0.5 m3 working volume. Liquid slurry from the 1st stage of the agricultural biogas station Pustejov II was used as inoculum. The silage dosage was performed so that the reactor reached high methane production intensity at low volumetric production of the digestate for 120 days. The average organic loading reached 4.27 kgVS m−3 d−1 while the average hydraulic retention time decreased to 85 days. The dry biogas production intensity was 3.42 mN3 m−3 d−1 with an average methane content of 52.5 vol%. The specific methane production from corn silage was 0.419 mN3 kgVS−1. At the end of the test, the digestate contained 13–14 wt% of total solids (TS) and 82–85 wt% of volatile solids in TS. The bag-type digester with hot air heating can be used by small farmers where there is no viable biogas cogeneration.

Keywords

• biogas
• bioreactor
• corn silage
• high-solids anaerobic digestion
• horizontal bag-type digester