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III Project Description Tracy Material Recovery Facility and Transfer Station Expansion 30703 S. MacArthur Drive, Tracy, Califomia 95377 Rocklin or Andersen), to be combusted at biomass-to-energy facilities. The electricity is considered renewable power and will assist in achieving the state mandate of utilizing 20% renewable energy by 2010. Current state policy and future laws could increase the 4 amount of renewable energy used in California to 33% by 2020. The applicant proposes to use proven gasification technologies that converts biomass IE into a synthetic natural gas ("syngas") through the process of thermo-chemical r conversion in a biomass gasification unit. This syngas is then used to fuel a specially modified natural gas genset that provides renewable electricity and heat. The biomass gasification process is a thermo-chemical one that 'cooks' biomass in an oxygen starved environment. By depriving the fuel of sufficient oxygen the biomass does not burn, but rather gives off a hydrogen rich syngas. As the biomass gives off the syngas, it is transformed into bio-char and ash of approximately 1-5% of the volume of biomass 4 fuel. The syngas is then captured, cleaned and cooled before being sent as fuel to the Genset. I The Gensets are provided by a variety of nationally known vendors such as Cummins, Caterpillar, or GE. This ensures that there are readily available spare parts and maintenance technicians available locally. The bio-char has demonstrated ability to sequester carbon in solid form for upward of 1,000 years if applied as a soil amendment. A conveyor fed hopper provides the most flexible solution to deliver biomass wood chips into the unit into the fuel hopper. Once in the hopper, the system uses a robust platform and fuel metering sensors to continuously feed the conversion unit in small batches as needed. The biomass conversion chamber as shown in the adjacent figure is essentially a chemical reactor where various complex thermo- chemical processes take place. As it flows through the reactor, the biomass gets dried, heated, converted into gas and reduced into bio-char and ash. Although there is a considerable overlap, each process can be considered to be occupying a separate zone, in which fundamentally different chemical and thermal reactions take place. The fuel must pass through all of these zones to be completely converted. The downdraft conversion unit, employed by the technology, is under vacuum drawn by a high- pressure blower ("negative air"). The essential characteristic of the downdraft design is that the tars given off in the heating zone are drawn through the conversion zone, where they will be broken down or oxidized. When this happens, the energy they contain is usefully recovered and the mixture of gases in the exit stream is relatively clean. Expected total gas contaminant concentration prior to filtration is up to 100 times less than is often seen in updraft and fluid bed systems. Gas Cleaning_ After the syngas has been extracted from the conversion chamber it is cooled and cleaned by a series of scrubbers and filters. First the gas passes through a venturi scrubber, which is Known to remove particulate in the submicrometer range. The gas is then passed through a series of four filters. The first is a coarse filter to coalesce residual liquids. The second is a rejuvenating active sawdust filter, the third ' is a similar passive filter, and the fourth is a fabric bag filter. The filter media are ( sawdust and biomass chips so instead of using expensive synthetic filters that need to 26 170.18.03 CUP Project Description 050710 i