Biochar utilization in thermochemical biodiesel production from perilla seed

Abstract

Transportation sector faces environmental challenges due to carbon dioxide emissions from the heavy use of fossil fuels in internal combustion engines. Biodiesel (BD) has emerged as a carbon-neutral fuel option due to its seamless compatibility with petroleum-derived diesel. However, BD production suffers from inefficient carbon utilization, as the selective use of lipids in biomass remains unused waste. To address this issue, this study proposes a thermochemical platform for zero-waste BD production using perilla seed as a model feedstock. In this approach, defatted perilla seed, remaining after lipid extraction, is converted into biochar, which is then utilized as a catalyst to expedite the kinetics of transesterification. Production of defatted seed biochar (DSB) was conducted under four different pyrolysis temperatures of 400, 500, 600, and 700 °C. Characterizations of the produced biochars revealed that DSB produced at 600 °C (DSB600) exhibited the highest surface porosity with concentrated base metals, making it ideal for catalytic applications. When applied to thermally-induced transesterification, DSB600 demonstrated superior catalytic performance with a BD yield of 98.27 wt% at 250 °C, surpassing the results from biochars produced at other temperatures. To evaluate the practical applicability, the properties of perilla-derived BD was theoretically estimated against standardized specifications for pure BD. However, perilla BD failed to meet the required standards due to a high content of unsaturated components. In response to this limitation, its blending with saturated BD from other feedstocks, such as palm, was explored. This optimal blending composition of perilla BD to palm BD was estimated to be 20–50 wt%. This strategic approach helps effectively complement the shortcomings of both BDs while enhancing the viability of perilla BD for practical applications.