2017 Volume 43 Issue 4 Pages 231-237
With a view to establishing a methodology for using the heat from aerobic fermentation of woody biomass as a heat source for greenhouses, the influence of temperature, water content and C/N ratio on the fermentation rate of larch shavings was investigated using a laboratory-scale fermentation apparatus. Larch shavings were mixed with fermented chicken manure, which was utilized to alter a C/N ratio of the mixture, and further mixed with a microorganism source. A 2-L aluminum fermenter loaded with the mixture was maintained at a constant temperature with forced aeration. Oxygen concentration was continuously monitored at the inlet and outlet of the fermenter, and the fermentation rate was evaluated as the oxygen consumption rate estimated from the difference in the measured oxygen concentrations. The results showed the highest oxygen consumption rate was obtained at 40°C and 60% of water content (wet mass basis) at a C/N ratio of 70. Experiments at C/N ratios of 13, 20 and 70 showed that the oxygen consumption rate per unit mass of the mixture did not always increase with decreasing C/N ratio, while the oxygen consumption rate per unit mass of larch increased. This was because the nitrogen content of the fermented chicken manure was small, and a large amount of the chicken manure needed to be added to reduce the C/N ratio. Analysis of the gas discharged from the fermenter showed that almost all the oxygen consumed in the fermenter was converted to carbon dioxide, which indicated that fermentation took place under aerobic conditions. Finally, the mass and volume of the fermentation materials required for heating were estimated.