Given its strong dependence on natural gas, it is surprising that California has nearly 540 MW of coal-fired electric generation capacity spread over 15 facilities, all of which are under pressure in the midst of the state's climate change mitigation efforts to stop operations or convert to clean fuels.

Natural gas is not a leading candidate for these potential conversions. Instead, biomass is the preferred option.

"There is a perception that California will continue moving toward more reliance on renewables and less on fossil fuels," said Steve Kelly, an executive with the Sacramento-based California Independent Energy Association, who said the key for biomass is the availability of fuel supplies.

While the conversions to gas-fired power generation are technically feasible, the economics aren't as good as with biomass and other renewable options, according to staff at the California Energy Commission (CEC). The 64 MW Mount Poso facility in Kern County is one whose owners decided to switch to biomass because of the state's greenhouse gas (GHG) emissions limits and strong push for renewables, a CEC spokesperson told NGI.

Regarding the lack of interest in adding to the state's already large natural gas fleet, energy staff speculate that the reason is economics. The bottom line is that utilities, such as Pacific Gas and Electric Co. (PG&E) and Southern California Edison Co. (SCE), in whose service areas all of the coal plants are located, will pay a lot more for renewable-based power than for gas-fired electricity.

"A renewable facility is eligible for a higher priced RPS [renewable portfolio standard] contract," said the CEC spokesperson, citing energy commission staff estimates of the cost of converting a coal plant to biomass at about $1,000/kW, along with the ability to leave the plant mostly intact. That compares to the cost of about $2,000-4,000/kW to built a new biomass facility, the CEC estimates indicate.

The CEC also estimates that the cost of converting a coal plant to run on gas -- changing from a solid to gaseous fuel -- would likely be a lot more than $1,000/kW, even though the cost of building a new natural gas-fired plant is in the range of $700-1,500/kW.

"In many cases it may be more economical to tear down the existing coal plant and build an entirely new natural gas-fired facility in its place," the CEC spokesperson said.

Among the 15 coal plants in the state, 11 of them are located in three counties -- Contra Costa in the East San Francisco Bay Area, Kern in the southern end of the central valley, and San Bernardino, 50 miles east of Los Angeles. They range in size from an 108 MW facility in San Bernardino County to a 17 MW plant in the same country. Most of the plants came online in the 1987-1992 time period when there was a major push for cogeneration, which is involved in nine of the plants.

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