Effect of Chemical Composition on Thermal Decomposition Behavior of Herbaceous Plants for Production of Plant-based Biochar for Storing Carbon in Soils

Abstract

In order to use plant biomass as biochar for storing carbon in soils, the relationship between the chemical composition of plants and biochar yield obtained by thermogravimetric (TG) analysis was studied. The extractive content of herbaceous plants such as dokudami (Houttuynia cordata), halcyon (Erigeron philadelphicus), and mugwort (Artemisia Spp.) was higher than that of Japanese cypress (Chamaecyparis obtusa), and the yields at 250 and 300 °C tended to decrease with increasing extractive content of plants. This indicated the possibility that thermal decomposition of herbaceous plants can be conducted at low temperatures (below 350 °C). In addition, the content of crystalline carbohydrates (remaining upon treatment with 5% sulfuric acid) of herbaceous plants was lower than that of Japanese cypress, and the yield at 400 °C tended to decrease with increasing crystalline carbohydrate content of plants. This indicated the possibility that herbaceous plants can be used to obtain biochar with higher yield at 400 °C than woody plants. Therefore, herbaceous plants are considered to be feasible resources as raw materials for biochar production for storing carbon in soils.