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Who is Evaluating CT’s? • Alameda, CA • County of Santa Barbara, CA • City of Los Angeles, CA • County of Los Angeles, CA • CIWMB & SCAG, CA • Toronto, Ontario, CN • New York City, NY • St Croix, U.S. Virgin Islands • Collier County, FL • Lake City, FL • County of Hawaii, HI • Catoosa County, GA
Why Are CommunitiesConsidering CT’s? • Increase diversion from landfills (as per Europe and Japan) • Produce needed electric power • Generate “green power” under a Renewable Performance Standard
What Technologies are Typically Evaluated? • Pyrolysis • Gasification • Plasma Gasification • Anaerobic Digestion
Pyrolysis The thermal degradation of organic materials, through the use of an indirect, external source of heat, typically at temperatures greater than 925° F, in the absence or near absence of oxygen, to produce pyrolysis char, pyrolysis oil, and a syngas composed primarily of H2, CO, CO2, CH4 and complex hydrocarbons, with inorganic materials converted to ash.
Gasification The thermal conversion of organic materials in the presence of heat at temperatures typically above 1,400° F, and in a limited supply of oxygen (less than stoichiometric), to produce a syngas composed primarily of H2 and CO, with inorganic materials converted to a solid, vitreous slag.
Plasma Gasification The use of AC and/or DC electricity passed through graphite or carbon electrodes, with steam and/or oxygen/air injection (less than stoichiometric), to produce an electrically conducting gas (a plasma) typically at greater than 7,000° F, that converts organic materials, including tars, oils and char, to a syngas composed primarily of H2 and CO, with inorganic materials converted to a solid, vitreous slag.
Anaerobic Digestion The biological conversion of biodegradable organic materials in the absence of oxygen at temperatures under 200 F. The process is carried out by anaerobic microorganisms that convert carbon-containing compounds to a biogas (primarily methane and carbon dioxide). The residue is a stabilized organic material that can be used as a soil amendment.
Potential Benefits of CT’s • Residues can be low (5-10%) and inert • Increases landfill life, eliminates impacts (air and water) • The syngas/biogas is a fuel for producing electric power • Attain “sustainable waste management”?
Technical Challenges • Little experience with MSW as a feedstock • Significant up-scaling of conversion units needed to meet city/county waste flows • Vendors lack experience integrating pre- processing, conversion & power production • Little data on air emissions, especially for MSW feedstocks