Co-pyrolysis for the valorization of food waste and oriental herbal medicine byproduct

Abstract

The pyrolysis of biowaste has become an appealing approach for energy conversion, and a popular research topic for the biomass and bioenergy communities. In this research, the co-pyrolysis of food waste (FW) and herbal medicine byproduct (HMB) (i.e., the byproduct generated from the decoction processing of herbal medicines) was studied as a strategy to valorize and dispose of the biowaste. The effects of flow rate of inert gas (N2), pyrolysis temperature, and blending ratio of FW/HMB on the pyrolytic product compositions and yields were examined. Pyrolysis temperature and the blending ratio of FW/HMB affected the compositions and yields of pyrolytic products, while the N2 flow rate did not. At higher temperatures, more non-condensable gases and less char were produced. The highest yield of hydrogen (H2) (0.4 wt.%) was achieved with the mixture of FW and HMB with a weight ratio of 1:3 at 700 °C. At the same co-pyrolysis conditions, the yield of pollutants (e.g., phenolic and polycyclic aromatic hydrocarbon compounds) was at maximum 70 % less than the yields achieved at the other co-pyrolysis conditions. The results reveal that the synergetic effect existing between FW and HMB during co-pyrolysis can be exploited to increase the H2 yield with minimal formation of phenolic compounds and PAH derivatives. The chars made from the mixture of FW and HMB had higher heating values of 22.2–23.7 MJ kg−1 that are comparable with those of coal. This study should help prove the effectiveness of the co-pyrolysis process to simultaneously valorize and dispose of biowaste.