Anaerobic co-digestion of forage radish and dairy manure in complete mix digesters.

Pilot-scale digesters (850 L) were used to quantify CH 4 and H 2 S production when using forage radish cover crops as a co-digestion feedstock in dairy manure-based digesters. During two trials, triplicate mixed digesters were operated in batch mode with manure-only or radish + manure (27% and 13% radish by wet weight in Trial 1 and 2, respectively). Co-digestion increased CH 4 production by 11% and 39% in Trial 1 and 2, respectively. As H 2 S production rapidly declined in the radish + manure digesters, CH 4 production increased reaching high levels of CH 4 (⩾67%) in the biogas. Over time, radish co-digestion lowered the H 2 S concentration in the biogas (0.20%) beyond that of manure-only digestion (0.34–0.40%), although cumulative H 2 S production in the radish + manure digesters was higher than manure-only. Extrapolated to a farm-scale (200 cows) continuous mixed digester, co-digesting with radish could generate 3150 m 3 CH 4 /month, providing a farmer additional revenue up to $3125/month in electricity sales. [ABSTRACT FROM AUTHOR]