Various organizations are pursuing and implementing uses for grease waste materials. This is driven largely by rising prices for fuels and electric power, but also from the need to minimize the problems of sewer blockages, sewer overflows, and odor problems caused by such grease when discharged to local sewers. Using grease-source fuels to replace conventional fuels can also reduce greenhouse gas emissions and reduce conventional air pollutant emissions. Information collected by the authors on several recent projects is used in this paper to review the innovations, successes and problems that are occurring. Urban waste grease resources are primarily of two types (yellow grease and brown grease), and this paper discusses both in terms of energy value and energy products.

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The Sacramento Regional Wastewater Treatment Plant (SRWTP) recently evaluated several alternatives to address long-term biosolids dewatering, drying, and handling and disposal issues. SRWTP decided to evaluate air quality emissions and impacts including permitting requirements, criteria pollutants, greenhouse gases, hazardous air pollutants (HAPS), controlled emissions, and air emissions from hauling trucks and secondary sources that are related to biosolids treatment (e.g., boilers or furnaces for heat drying, fugitive emissions from storage tanks, etc.). This paper provides a full picture of total air quality impacts from biosolids treatment and direct insights into any air quality permitting concerns under current Sacramento Metro Air Quality Management District (SMAQMD) and U.S. Environmental Protection Agency (EPA) air quality laws and regulations.Air emission totals for each biosolids treatment alternative included air emissions from secondary sources, controlled sources, and truck hauling. Air emissions from the following biosolids treatment alternatives were evaluated:• Centrifuge dewatering emissions • Plate and frame press dewatering emissions • Indirect drying emissions -including dewatering and secondary emissions • Direct drying emissions -including dewatering and secondary emissions • Controlled emissions -odor control, impingement plate scrubber, regenerative thermal oxidizer (RTO) • Trucking emissions for each alternative All air emissions from the biosolids treatment alternatives and their associated regulatory impacts were insignificant. No problems were predicted in attaining air district permits or significantly impacting the environment. Emissions from dewatering with no drying, were much lower than any of the drying alternatives (with trucking emissions included). The overall emissions for the combined dewatering, drying, and trucking alternatives presented minimal environmental impacts and should therefore readily receive permits. It should be noted, however, that other non-air quality factors such as odors, cost effectiveness, reliability, and ease of operation may have a strong influence on which alternative is selected.

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