(519f) Update to Biodiesel Production From Activated Sludge and Economic Analysis

Biodiesel is a renewable fuel that can supplement petroleum fuel supply. One of the reasons why biodiesel is not yet cost-competitive with petroleum fuels is due to the high cost of feedstock - up to 70 -95% of biodiesel production cost. A feedstock with high potential for less expensive biodiesel production is activated sludge obtained from wastewater treatment plants. However, drying of sludge prior to oil extraction and reaction is a major operating cost of this process since it is so high in water content. Previous studies by this group have shown that the lipids present in sludge can be converted to biodiesel. In this case, supercritical methanol was used as a reactant and catalyst for biodiesel production.

A study was conducted to determine the optimum and cost-efficient yield of biodiesel produced from reacting wet sludge using only supercritical methanol. The goal of this investigation is to address the challenge of reducing sludge moisture content by investigating the feasibility of using activated sludge for cost-efficient biodiesel production with little or no drying of the feedstock. A model system of oleaginous yeast, Rhodotorula glutinis, was used to evaluate the production of biodiesel in a system similar to sludge. The combination of a fluidized sand bath and 46ml tubular stainless steel reactors were used for the supercritical methanol reactions. Two methods of this non-catalytic process, 1-step and 2-step processes, that could produce high FAME yields were studied and compared in terms of FAME yields and kinetic rate constants. With these results, plant schematics were proposed and economic analyses were conducted to investigate the cost efficiency of both non-catalytic methods. One was recommended with great potential for producing biodiesel from activated sludge at a cost-efficient price.