In situ transformation of lipid in waste pepper seeds into biodiesel (i.e., fatty acid methyl esters: FAMEs) via thermally-induced transmethylation on silica was mainly investigated in this study. This study reported that waste pepper seeds contained 26.9 wt% of lipid and that 94.1% of the total lipid in waste pepper seeds could be converted into biodiesel without lipid extraction step for only similar to 1 min reaction time. This study also suggested that the optimal temperature for in situ transmethylation was identified as 390 C-omicron. Moreover, comparison of in situ process via the conventional transmethylation catalyzed by H2SO4 showed that the introduced biodiesel conversion in this study had a higher tolerance against impurities, thereby being technically feasible. The in situ biodiesel production from other oil-bearing food wastes can be studied. (C) 2017 Elsevier Ltd. All rights reserved.