Effect of oxygen on the decomposition of dairy manure at low-temperature carbonization

Abstract.

A thermochemical conversion of biomass such as carbonization and torrefaction has been recognized in producing a carbon-rich solid such as biochar which has been considered as a solid biofuel. However, a large amount of heat energy is required in such technology especially in the drying process and operation at higher temperature. In some cases, higher temperature might inhibit the production of biochar. As a way of producing biochar efficiently, lowering the operating temperature appears to be appropriate to reduce energy consumption. Hence, the objective of the current study is to investigate the effect of oxygen on the decomposition biomass performed at less than 100°C of carbonization. Here, we used dairy manure and carbonized them at 90°C for 7-9 weeks under an inert and oxygen conditions. The results of the inert conditions showed a non-significant decomposition of dairy manure took place and a slight color change has been observed. On the other hands, under the oxygen conditions, we confirmed a significant decomposition had occurred at 90°C of carbonization. This is strongly caused by low-temperature oxidation due to consumption of oxygen during carbon monoxide and carbon dioxide production. In addition, the color of dairy manure turned from brown to dark brown. These results indicate that oxygen is necessary to promote the decomposition of biomass in order to produce biochar at 90°C. The carbonization performed in low-temperature range would have the potential to convert biomass into biochar efficiently, and will contribute to establish the low-carbon society.