2. Biochar Production
2.1. Experimental Methodology
2.1.1. Waste biomass
The feedstocks used for biochar production in this study focused on three kinds of waste biomass: agricultural residues such as corn cobs and corn stover; yard wastes including walnut shells and wood chips; and by-products from bioenergy such as defatted dried distiller grains (DDGs). These waste biomass were collected from a variety of local sources, including crop fields, parks, gardens, yards, and ethanol manufacturers. The collected samples were piled in the green house to air dry and subsequently oven-dried overnight at 80oC. The dry waste was cut into small pieces or ground to less than 3 cm prior to use.