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S�14T BY:Commerce ;12- 9-91 3:22AM ;# 3 CONDENSATE RETURN-- SOME OBSERVATIONS Prepared by: Stanley W. Zison, Ph.D. , M.P.H. Pacific Energy 5055 E. Washington Bouleyaxd Commerce, California 90040 EXECUTIVE SUMMARY The purpose of landfill gas collection systems is to extract the gas and conduct it to a processing station. The processing station may simply be a flare. Alternatively, it may be an electric power plant which uses internal combustion engines to drive its generators. In either case, the incominggas contains many substances that are toxic to humans and damagng to the environment. For example, landfill gas commonly contains vinyl chloride, a recognised human carcinogen and chronic toxic agent. It also contains benzene, thought to cause leukemia in humans and clearly both chronically and acutely toxic. Other substances include various chlorinated solvents and hydrogen sulfide, an acute and highly lethal poison to humans and other higher life forms . Beyond thepresence of toxic species , landfill as has a bad odor Which can be detected at low concentrations. This is primarily due to the presence of mercapt s and, to a somewhat Iesser. degree, organic acids and .nes. Accordingly, the gas is both toxic d esthetically objectionable. The ¢as processing facility, whether a flare or power generation station, combusts the gas. This greatly reduces the net emission of toxic species such as benzene, hydrogen sulfide and vinyl chloride per unit time . It also reduces the emissions of bad- smelling substances and thereby reduces the nuisance caused by the landfill. Beyond reducing toxic and odorous emissions , the production of electric power from landfill gas correspondingly reduces the use of fossil fuels elsewhere for power generation. During 19880 for example Pacific Energy (PEn) generated 14,570 megawatt- hours of power Irom landfill gas, saving over 120,000 barrels of oil. Recently, the practice of returning condensate to the landfill from which it came has generated some public health concern. The concern stems from the perceived possibility that the condensate may significantly contribute to groundwater contamination. Pacific Energy feels this perception is unjustified and doubts the significance of condensate return to landfills in general. Because, in fact, there appears to be no significant impact, and because not returning condensate poses a very real hardship, it is felt that condensate return should be permitted except i.n cases where adverse impacts are known.* or where anticipated adverse impacts can be scientifically defended. To support its