Recent trends on sewage sludge transesterification: review

Abstract

The need for non-existent or low-cost sources to be a feedstock for the biodiesel industry as a source of lipids has led to the trend of sewage sludge (containing high fat content) and thinking about it and finding ways to benefit from it. On the other hand, he use of sludge is an environmental treatment, as it rids the environment of tons of sludge produced daily and a solution to a problem for treatment plants that were looking for ways and solutions to get rid of it and save the cost of getting rid of it and converting it into clean and promising energy. It was found that the sewage sludge in all its primary and secondary types is a feedstock rich in free fatty acids (FFA), which is the raw material for the production of biodiesel, while treating it with one of the types of catalyst alcohols. According to a review of previous studies, it was found that acidic catalysts are most suitable for biodiesel production from sewage sludge, because sewage sludge has a free fatty acid content of 65-70%, which is a high percentage. It is a severely high percentage of free fatty acids found in pure vegetable oils that do not exceed 5%. The heterogeneous acid catalysts were preferred over the homogeneous ones because of the satisfactory results they provided and the high productivity of biodiesel compared to the homogeneous ones, and they are more economical as they can be reused more than once, but also many times. Reacting sewage sludge lipids with a type of catalyst alcohol and forming biodiesel called transesterification or esterification, and it may be traditional or in-site, and in-site is more important and economical than conventional. It was found from previous references that heterogeneous catalysts in general and zeolite types in particular are the most suitable for oil extracted from sewage sludge. Where The yield reached 100% using a type of zeolite.