Extraction of biodiesel from vegetable waste hydrolysates and evaluation of its engine performance and emission characteristics

Recently, microbial oil has become one of the promising next-generation feedstocks for producing biodiesel. While microbial oil can be extracted from different sources, there is only limited work on microbial production from fruits and vegetables. In this work, biodiesel was extracted through a two-step process: microbial conversion of vegetable waste into microbial oil using Lipomyces starkeyi, followed by transesterification of microbial oil into biodiesel. The lipid accumulation, composition of microbial oil, and the fuel properties of biodiesel were evaluated. The microbial oil consisted mainly of C16:0, C18:0 and C18:1, which were close to the properties of palm oil. The fuel properties of biodiesel comply with the EN14214:2012 standard. Thus, the vegetable waste can be a good biodiesel feedstock. Three blends (MOB10, MOB20 and MOB30 with 10, 20, and 30% of biodiesel) were tested for engine performance and emission characteristics in a 3.5 kW VCR research engine. At full load, MOB20 reduced the pollutant emissions of CO and HC by 47.8% and 33.2% with the penalty of increased NOx by 3.9%, while BTE reduced by 0.8% with the increased BSFC by 5.2%. Thus, the addition of vegetable waste biodiesel blends reduced the emissions of CO and HC significantly with slight reduction of brake thermal efficiency.