This research is concerned with the efficacy of various heat treatment procedures in converting refractory organic materials to biodegradable substances so they will be convertible to methane gas. Cellulose bound with lignin is not biodegradable. Heat treatment at temperatures near 200/sup 0/C and at pH 13 solubilizes the lignin, freeing the cellulose for methane fermentation. Higher temperatures resulted in extensive cellulose solubilization and reduced biodegradability. Semi-continuous studies indicated that heat treatment can increase methane production by 50 percent and perhaps more if inhibitory concentrations of heat treatment lignin are avoided. Microbiological studies indicated that several aromatic compounds expected from lignin heat treatment were fermentable to methane gas, thus offering promise that greater increase in biodegradability may be anticipated.