Massive digester project taps mother lode of biogas in California
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| The City of Los Angeles' Hyperion Wastewater Treatment Plant uses a series of 20 egg-shaped digesters similar in design to those GEI is building to process agricultural biowaste in the Imperial Valley. (Photo courtesy of Guepard.) |
Imperial Irrigation District provides water and power to hundreds of agriculture operations; and now, with the help of Guépard Energy Inc.'s unprecedented digester-powered system, some of the 450,000 animals in IID's service area are going to return the favor.
The 740-MW, southeastern California utility recently finalized the purchase of up to 18 MW of renewable power from four planned GEI agricultural biowaste management facilities. Each facility will process 400,000 pounds per day of agricultural biowaste from confined animal operations and cattle feedlots using what is considered in the United States to be municipal waste treatment technology.
Biogas power promises a variety of benefits
Guépard Energy Inc. CEO, William Harrison, elaborated. "Basically, we are building a wastewater treatment plant for the agriculture industry. This type of technology has been in use in this country since the 1980s, but this is the first time it has been applied to animal and green waste. It's very common in Europe, where there are 23 such systems operating in Denmark alone," he added.
IID General Manager Jesse Silva sees the project as an opportunity to diversify the utility's supply base while supporting the region's cattle industry and the area farmers who supply their feed. "Guépard's process also has the added environmental benefits for our region's air and water quality," he observed.
The biogas power represents IID's first purchase of this form of renewable energy and will be mixed into its general portfolio. The utility has also recently signed a contract with CalEnergy to receive 170 MW of power from a geothermal powerplant that the energy developer and producer is constructing at the Salton Sea in the Imperial Valley.
"Diversifying our power mix is a big priority with our board of directors because it keeps energy costs down and ensures supply," Silva explained, "but until recently, renewable energy was relatively expensive. When an innovative project like Guépard's digester system or CalEnergy's geothermal plant makes it more affordable, the other advantages of renewable resources are value added."
The first 5-MW system is slated to go online in the second quarter of 2004. The next system will roll out in the third quarter and the last two will follow at the end of 2004.
The sites—two feedlots, a grain milling operation and a beef processing plant—are interconnected with IID's grid. Although an assessment has not yet been completed, Silva expects that the system will require few if any upgrades to handle the increased transmission.
System's by-products find market in rural economy
Each site will consist of five 1.25-MW power units that will run off a combination of animal and green waste. The state-of-the-art, high-efficiency digesters will each use about 500 kW to generate 5 MW of green electricity and 500 horsepower of steam, in addition to 80 tons of 100-percent organic solid and liquid fertilizer. In contrast, the typical agricultural biowaste plant usually produces from 500 kW to 1 MW.
The San Diego-based renewable energy company selected the sites based not only on their waste stream, but on their steam use as well. An average size feedlot of 45,000 head uses about 200 horsepower of steam to roll and process grains for animal feed, at an annual cost of about $100,000. The steam generated by the GEI anaerobic digester system will more than meet this need, allowing the lot owners to take natural gas and diesel burners off line. GEI plans to sell the excess steam to local users. "Steam can be exported up to six miles by pipeline," noted Harrison. "In an area with so many confined animal operations, we won't have to go looking for a market."
Guépard sees more biogas opportunities in western states
GEI plans to roll out similar plants in the western states over the next five years and has identified viable sites in California, Utah and Idaho. San Diego Gas & Electric Company, Southern California Edison, Pacific Gas & Electric Company and several municipal groups are among the potential customers for renewable power from large-scale digester systems.
Harrison believes the Imperial Valley project will serve as a showcase for rural communities throughout the west facing the growing pressure of agricultural waste disposal. "Our process offers a constructive way for dairies, feedlots, chicken ranches and hog farms to reduce their environmental impact," he declared. "This technology is good for the community, the economy, and good for American independence from foreign energy sources."
