Fermentation Products of Cellulose

IN WORKING on the products resulting from the anaerobic decomposition of biologic waste material, the writers, with others (1), have observed that the reactions, which are brought about by bacteria, cause the formation of considerable amounts of gas. This gas is principally methane and carbon dioxide, with small amounts (3-5 per cent) of hydrogen and nitrogen, the latter probably from solution in the liquor. The ratio between CO2 and CH4 varies from about 1:10 to 1:1 when air is excluded and sugars are absent. In attempting to explain this variation in gas composition we have carried out experiments using various selected materials of known composition. Our preliminary work on the digestion of cellulose, summarized in Table I, showed that the material decomposed or digested was converted practically quantitatively into gas and that the ratio between CO2 and CH4 was about 1:1.5, except in the blank where it was 1:8.3. The simplest equation for the decomposition of cellulose would be C6H10O5 + H2O 3CO2 + 3CH4 According to this equation, the CO2:CH4 ratio should be 1:1. When the organic matter in inoculating material is reduced to a relatively small value, this ratio becomes practically the theoretical for the equation given (Table II). As a gas containing 50 per cent methane has a calculated heat value of 500 British thermal units per cubic foot (coal gas runs 525-550), it seemed worth while to see whether or not crude plant material could be converted into gas in sufficient quantities to be of practical importance. Naturally, being in the heart of the Corn Belt, the material selected was cornstalks. The results were favorable (Table III) .