Sorghum, sorghum/alpha-cellulose mixture, and corn were anaerobically digested at 55°C at effluent solids contents of 8-12% total solids (TS), using trace nutrient supplementation. Volatile solids (VS) loading rates at much higher levels than conventional maxima were maintained without volatile fatty acid (VFA) accumulation. Semi-continuously fed digesters with organic loading rates (OLR) up to 12 gVS kg-1d-1produced methane at rates up to 3.3 L kg-1d-1. Continuous feeding of corn at an OLR of 18 gVS kg-1d-1resulted in a methane production rate of 5.4 L kg-1d-1. VS removal efficiencies at maximum OLRs were 60% (sorghum) and 67% (corn). At an OLR of 4 gVS kg-1d-1sorghum alone as a feedstock led to excess ammonia-N accumulation. Excess ammonia did not accumulate at sorghum loading rates of 8 and 12 gVS kg-1d-1nor with a sorghum/alpha-cellulose mix loaded at 8 gVS kg-1d-1. Instantaneous gas production rates were directly related to feedstock cell soluble content, with peak instantaneous biogas production rates from corn (OLR of 8 gVS kg-1d-1approaching 25 L kg-1d-1following a three-day feeding. © 1992.
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