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Biodiesel From Sewage Sludge
MTorrice writes "Scientists have developed a way to convert lipids from sewage sludge into biodiesel. The low cost and high yield of the sludge process may make it economically feasible as a source of biofuel, the researchers say. Today, biofuel producers use lipids in vegetable oils to derive biodiesel, a mixture of fatty-acid-like molecules. Biodiesel is compatible with existing diesel engines, burns with less pollution than petroleum-derived diesel does, and comes from renewable resources. But current biodiesel feedstocks are expensive, limiting the fuel's widespread use. The researchers from South Korea found that sewage sludge, the semisolid material left over from wastewater treatment, can yield 2,200 times more lipids than soybeans and costs 96% less to process. To turn the sludge lipids into biodiesel, the researchers heated them with methanol."
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Biodiesel Production from Sewage Sludge: New Paradigm for Mining Energy from Municipal Hazardous Material
† Bio-Energy Research Team, Research Institute of Industrial Science and Technology (RIST), 813-1 Keumho-Dong, Kwang-Yang-City Cholla-Nam-Do, South Korea, 545-090
‡ Department of Environment Systems Engineering,Korea University, Chung-Nam, South Korea
Environ. Sci. Technol., Article ASAP
DOI: 10.1021/es3019435
Publication Date (Web): August 20, 2012
Copyright © 2012 American Chemical Society
Abstract
This work demonstrates that the production of biodiesel using the lipids extracted from sewage sludge (SS) could be economically feasible because of the remarkably high yield of oil and low cost of this feedstock, as compared to conventional biodiesel feedstocks. The yield of oil from SS, 980 000 L ha–1 year–1, is superior to those from microalgal and soybean oils, 446 and 2200 L ha–1 year–1, respectively. According to the case study of South Korea, the price of the lipids extracted from SS was approximately $0.03 L–1 (USD), which is lower than those of all current biodiesel feedstocks. This work also highlights the insight of a novel methodology for transforming lipids containing high amounts of free fatty acids (FFAs) to biodiesel using a thermochemical process under ambient pressure in a continuous flow system. This allowed the combination of esterification of FFAs and transesterification of triglycerides into a single noncatalytic process, which led to a 98.5% ± 0.5% conversion efficiency to FAME (fatty acid methyl ester) within 1 min in a temperature range of 350–500 °C. The new process for converting the lipids extracted from SS shows high potential to achieve a major breakthrough in minimizing the cost of biodiesel production owing to its simplicity and technical advantages, as well as environmental benefits.
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