Codigestion of manure and organic waste at centralized biogas plants: process imbalances and limitations

Summary

The present study focuses on process inhibitions in Danish centralized biogas plants. Collection of data from the plants and a number of interviews showed that inhibitions occur frequently. High concentrations of ammonia, long chain fatty acids or other inhibitory compounds, and foaming in prestorage tanks are well known causes of inhibition. These problems mainly occurs due to: 1) inadequate knowledge about the waste composition and 2) its degradation characteristics, 3) inadequate process surveillance especially with regard to volatile fatty acids and 4) insufficient pre-storage capacity causing inexpedient mixing of the different waste products in the pre-storage tanks.