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If you drive down State Route 238 between Maricopa and Casa Grande, Arizona, with the wind blowing just right, you may get a whiff of the newest form of renewable energy in APS' energy portfolio.
That's because there are more than 4.6 million tons of manure generated in the region every year. Located in this area are several Concentrated Animal Feeding Operations (CAFOs). On one side of SR238, there are more than 100,000 cattle in feed lot pens. A little further down the road are more than two million chickens at the Hickman’s Egg Farm. Dairies and more feed lots further east and south add another 100,000 to the total number of cows in this regional cluster of CAFOs.
These operations contribute to the dust, truck traffic, noise, flies and, of course, the odors found in the area. And the methane that naturally forms from the manure is a potent source of greenhouse gases. While farmers and ranchers call it the “smell of money,” new environmental and permit operating regulations in 2006 will make it more difficult for CAFO farmers to operate as they have for decades.
To help mitigate some of these new regulatory issues, APS is partnering with the Dairymen of Arizona and the Arizona Cattle Grower’s Association to create an innovative manure-to-energy technology development project. The project consists of capturing farm animal manure in a process that disposes of the manure, reduces the odor and, most importantly to APS, creates or captures the methane or biogas, which can be used as fuel for a generator.
“Our department always is looking for sources of renewable energy, specifically those that have a dual value,” said Peter Johnston, leader, Technology Development. “In this case, the dual value is that we are able to create energy and help Arizona farmers. And the bonus is we do it all with a renewable resource. At the end of the day, this will make the generation of electricity cheaper.”
The project also supports agriculture, one of the prime industries in Pinal County, while helping APS meet the Arizona Corporation Commission-mandated megawatt-hour certificate goals for the Environmental Portfolio Standard (EPS). APS is using EPS funds to pay for the project’s analysis and initial engineering until the CAFO associations and their farmer members are able to take over the project, acquire funding and hire a developer.
This project has the potential to generate about 28 megawatts of power per year using methane gas from manure. APS Engineers estimate that each dairy cow generates enough manure in one year to produce 200 watts of fuel gas. A feed lot cow can produce 140 watts, one pig, 56 watts and each chicken, two watts.
Technology is used to break down the manure through the application of heat and pressure and in the absence of air. The volatile material in the biomass is “cooked off” into a hydrogen rich synthetic fuel gas. The process is called steam pyrolisis gasification and was developed by BioConversion Technologies in Colorado.
The fuel gas can be burned in a boiler or engine or further refined through a methane reformer. The methane-rich synthetic gas has a BTU content of about 50 percent of pipeline natural gas. This snygas can be cleaned to pipeline quality and injected into a compressed natural gas transmission pipeline for delivery to one of the APS combined cycle power plants such as Redhawk Power Plant.
Pinal County was identified as having the largest CAFO project opportunity based on documents received from the Arizona Department of Environmental Quality and produces twice as much manure as is needed for crop fertilization. As regulatory requirements tighten, the disposal of this excess manure becomes a significant expense.
The project consists of three phases: concept development, a feasibility analysis and preliminary engineering. Phase one is 90-percent complete. A final step of phase one has been project briefings with internal, federal, state, county and local stakeholder groups.
As of publication of this report, we are in the middle of phase two. APS and the association partners are working out the detail costs and revenues to determine the project economics. This phase also will resolve a potential roadblock, what to do with the disposal of the ash from the gasifier.
Phase three, the preliminary engineering package, should take about six months. This initial design package is the basis for an engineering construction firm to be selected to finalize the construction engineering required and build the combined CAFO pre-processing infrastructure along with the two proposed centralized manure conversion facilities.
By being involved with the initial stages of this project development, APS is helping Pinal County farmers remain viable while reducing the impact of the CAFO issues attributed to them. If this project is successful in meeting goals and expectations, similar projects may be explored in other Arizona counties.
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