Unheated anaerobic digestion of crop residues in greenhouses in temperate regions

Abstract

The aim of this study was to investigate the effects of temperature and input condition on methane yield from the unheated anaerobic digestion of crop residues in temperate regions. We conducted two tests: batch tests at three different temperatures (17, 25, and 37 °C) and a pilot-scale continuous unheated AD test in Fukushima, Japan. In unheated AD, the material input management based on the organic loading rate (OLR) was more important than hydraulic retention time. The highest methane gas yield in continuous test was 453 L kg-VS−1 d−1 when the OLR was 0.42 g-VS L−1 d−1 at a digestion temperature of approximately 27 °C and that was 83.9 % of the total methane yield obtained in the batch test.