In-Situ Conversion of the FOG in Trap Grease Into Biodiesel

Biodiesel is a type of alternative fuel made from oil-containing biomass and a variety of fats , oils , and greases (FOG). Biodiesel is a drop-in solution for the diesel engines to reduce the emissions and consequently the US biodiesel industry has been thriving in the recent years under the context of promoting clean fuels. With the production of biodiesel increasing sharply , a variety of feedstocks , especially non-food based oil sources such as algae and municipal sludge , have been introduced. However , one potential feedstock that has hardly been exploited is the trap grease , a mixture of water , solids , and FOG that accumulates in the grease interceptors and sewer pipelines. Trap grease has been a nuisance to the municipal system for years due to its FOG content which is the major cause of CSO and SSO in the US. Current management of trap grease is costly and ineffective. Considering its FOG content , significant yearly generation and low cost , utilizing trap grease as biodiesel feedstock can be a win-win solution for both environmental protection and biodiesel industry , particularly for the latter. Producing biodiesel from trap grease can significantly reduce the cost for the biodiesel producers and more importantly , improve the sustainability of biodiesel production by switching from oil crops (e.g. soybean oil) to waste materials and hence minimizing water and land footprints. However , due to its highly heterogeneous nature , one issue related to the utilization of trap grease is that it takes significant amounts of efforts to extract FOG out of it before the transesterification reaction can be performed , which may not justify the application of trap grease as the feedstock in the industry.  Therefore , direct transesterification , or in-situ conversion , is investigated in this study as an alternative to address this problem. In-situ conversion refers to the process where the reagent and catalyst directly contact the FOG content in the feedstock substrate without the extraction step being performed first. The elimination of the extraction step can benefit the biodiesel production by lowering cost and energy consumption , as well as the reduction in facility footstep. In this study , the in-situ conversion of FOG in the trap grease into biodiesel will be investigated and parameters such as methanol to trap grease ratio (v/m) , catalyst concentration (wt%) , temperature and time will be varied to assess their influences on the in-situ process and to obtain an optimum condition for the process. The yield of biodiesel from the in-situ approach will be compared with that of the conventional extraction-transesterification method to evaluate feasibility of its application in the industry.