Mt. Poso Cogeneration Plant Goes Green
The Mt. Poso Cogeneration Plant operates on 100 percent woody biomass fuel and produces 44 MW of renewable electricity which is transmitted to Pacific Gas & Electric under a long term contract. The plant, which began operations as a coal-fired cogeneration facility in 1989, was retooled to utilize woody biomass fuel by its new ownership, the Mt. Poso Cogeneration Company LLC (MPCC), a partnership of Macpherson Energy and DTE Energy Services. The conversion was finished in February 2012 and was declared “Best Industrial/Manufacturing Project of the Year” by ENR California. Steam produced by the plant is used in the MPCC owned adjacent oil field. The plant uses water from the oilfield operations for produced steam and cooling. Excess water is used for nearby cattle grazing or reinjected into the oilfield.
Biomass refers to woody material that can be used as fuel. The material is generally comprised of waste wood from sawmills, forest thinnings produced in fire prevention, orchard removals and urban waste wood. It excludes organic material that has been transformed by geological processes into substances such as coal or petroleum. Biomass as used for electrical generation at the Mt. Poso Cogeneration facility comes from local agricultural sources in the form of orchard removals, orchard prunings, shells, and pits; and urban waste wood including tree trimmings, woody construction waste, pallets, and clean demolition wood from county and municipalities’ recycling programs.
The existing commercial biomass power generating industry in the United States provides approximately 1,700 MW to the grid. In California there are about 30 biomass fueled plants delivering nearly 600 MW of renewable energy to homes and businesses.
Benefits of the Conversion
Conversion of the Mt. Poso Cogeneration Plant to renewable biomass fuels resulted in numerous benefits including:
- Improved Air Quality: Biomass that would have been burned in the open is subject to controlled combustion and use of emissions control equipment at the MPCC, resulting in improved air quality.
- Renewable Power Generation: MPCC generates electricity and steam from renewable fuel.
- Local Jobs: New, family wage jobs were created as a direct result of this project. Most of the new jobs will be associated with fuels collection, processing and transport activities.
- Carbon Beneficial: The use of biomass to produce energy is considered “carbon neutral,” because biomass energy production makes use of carbon that is already a part of the carbon cycle. Fossil fuel use releases trapped carbon into the atmosphere, thereby raising the overall level of carbon. Additionally, wood waste that otherwise might end up in landfills or left in place to decay instead is burned as fuel at MPCC, reducing the release of methane gas which is considered to be one of the major contributors to climate change.
- Cogeneration Efficiency: The term cogeneration means that one fuel source — biomass — is utilized to create two forms of energy: in this case, power and steam, thus increasing the efficient use of the biomass. The steam is utilized in thermally enhanced oil recovery operations in the adjacent MPCC oil field.
When biomass is used as a fuel, as a replacement for fossil fuels, it still puts the same amount of CO2 into the atmosphere. However, when biomass is used for energy production it is widely considered carbon neutral, or a net reducer of greenhouse gasses because the carbon is already a part of the carbon stock in the atmosphere.
In addition, biomass used in energy production reduces the amount of methane produced as compared to landfilling as a disposal method.
Biomass absorbs CO2 from the atmosphere during its growing lifetime. After its life, the carbon in biomass recycles to the atmosphere as a mixture of CO2 and methane (CH4), depending on the ultimate fate of the biomass material. CH4 converts to CO2 in the atmosphere, completing the cycle. In contrast to biomass carbon, the carbon in fossil fuels is locked away in geological storage forever, unless extracted. The use of fossil fuels removes carbon from long-term storage, and adds it to the stock of carbon in the atmospheric cycle.
Energy produced from biomass residues displaces the production of an equivalent amount of energy from fossil fuels, leaving the fossil carbon in storage. It also shifts the composition of the recycled carbon emissions associated with the disposal of the biomass residues from a mixture of CO2 and CH4, to almost exclusively CO2. In the absence of energy production applications, biomass residue carbon would be recycled to the atmosphere through some combination of rotting (biodegradation) and open burning. Rotting produces a mixture of up to 50 percent CH4, while open burning produces 5 to 10 percent CH4. Controlled combustion in a power plant converts virtually all of the carbon in the biomass to CO2. Because CH4 is a much stronger greenhouse gas than CO2, shifting CH4 emissions to CO2 by converting biomass residues to energy significantly reduces the greenhouse warming potential of the recycled carbon associated with other fates or disposal of the biomass residues.