(480c) The Impact of Inorganics on the Production and Use of Biochars Made from Household Biowaste

Biochar can be used as an alternative fuel source or as a soil amendment and potential negative emissions technology for Biomass Carbon Removal and Storage (BiCRS). We have investigated the production and use of biochar from various biowaste sources such as nut shells, coffee grinds and corn cobs. For eight different feedstocks we have studied the impact of ash content on the pyrolysis process and on the reactivity of the subsequent char. Slow pyrolysis was conducted in a tube furnace with flash heating to temperatures between 400-500⁰C and the subsequent chars were measured for CO₂ gasification reactivity using Thermal Gravimetric Analysis at temperature from 700-900⁰C. We have found that ash content in the feedstocks was negatively correlated with char yield and positively correlated with CO₂ gasification reactivity for the feedstocks investigated. The impact of the inorganics on reactivity was further demonstrated by leaching studies on four feedstocks: corncobs, pistachio shells, walnut shells, and pumpkin shells. We found that biochars leached of their inorganics had gasification rates significantly slower than their non-leached counterparts for three of the four feedstocks studied (up to three times slower for walnut shell biochars). As an additional study, we have developed a 2.5 L semi-batch pyrolysis reactor fueled by propane and synthesis gas to produce biochar from household biowaste. We will also present design iterations of this reactor and biochar yields, emissions, residence times, and temperature profiles for various feedstocks.