Renewable Energy from Hog Manure

By Megan Castle

Public Information Officer

August 1, 2003

Cutting-edge technology using hog manure to produce electricity is happening locally, in Southeast Colorado. The Governor's Office of Energy Management and Conservation (OEMC), working with Colorado Pork LLC, a hog farm near Lamar, Southeast Colorado Power, Tri-State Generation and Technology, Capstone Turbines, Department of Energy, Colorado Department of Public Health and Environment, McNeil Technologies. Southeast Land and Environment and several other partners have been demonstrating the feasibility and cost effectivity of capturing methane gas from an anaerobic digester (AD) to produce electricity.

Colorado Pork LLC is one of only 35-40 farms in the U.S. generating electricity from hog manure. The hog farm's primary generation device is a reciprocating engine. However, more impressive, is this farm is one of the first in the world to generate electricity from a Capstone 30 kW micro turbine, essentially a small jet engine, fueled directly from methane produced from domestic animals' waste.

Manure from any farmed animals produces methane when it decomposes. In small- to medium-sized farms, manure is usually stored in open lagoons in order to avoid runoff, which can contaminate surface and ground water. This manure can be used as an excellent fertilizer once it has broken down. However, as it decomposes, it gives off large amounts of methane, which is about 20-times more potent than C02 in its effects on global warming. Methane, when it is used to create electricity, is not released into the atmosphere.

Methane is a clean burning fuel and can be used for a variety of purposes. For example, in China, thousands of farmers collect methane manually by storing manure in hand-dug pits and using bags made out of animal skins and other materials to collect the methane. The methane is used as fuel to heat homes, cook food and even power automobiles.

Colorado Pork breeds sows and grows piglets to the weaned stage, before selling them to "finishing farms." Even though the farm is considered a small- to medium-sized operation, the hogs produce about 12,500 gallons of waste each day. A typical farm of this size would normally use $10,000 to $11,000 of electricity a month to handle its operations, Colorado Pork, however, uses its hog waste to produce a significant amount of the electricity used by the farm. Colorado Pork, through its generation of electricity and designed-in energy efficiencies, purchases only about $3,500 worth of electricity a month.

Hog manure is gravity fed to an in-ground anaerobic digester. The digester is nothing more than an enclosed pit that uses bacteria (gut bacteria that is already in the manure when it reaches the digester) to help breakdown, i.e., digest, the manure. As the manure is digested, the methane is collected, and since it is basically the same as natural gas, it is connected directly to the reciprocating engine, which is a modified natural gas generator, and the micro turbine; both of which produce electricity.

The reciprocating engine and the micro turbine, operating in tandem or separately, meet about 35 of the electrical needs of Colorado Pork, as well as about half of the peak power (power used at any one time). Any excess electricity produced can be sent back to the grid, but to date none has been sent to the grid. The current situation is that the farm, OEMC, Southeast Power and Tri-State G&T are testing the circuitry before beginning any arrangements to supply any excess power from the farm to the grid. In 2002, the farm, Southeast, and Tri State effected the first "net metering" agreement under the net metering bill passed by the Colorado Legislature and put into effect in 2002.

As a result of this project's electricity generation and the installed energy saving devices, such as using fluorescent lights, Colorado Pork's low monthly electricity bill provides overall savings of about $48,000 per year over comparably sized hog farms with similar product output. Since the whole system cost $375,000, the payback on that investment is roughly eight to ten years.

Additionally, the methane digester produces a very useful benefit for Colorado Pork. The airtight digester cuts down on air pollution and because the digester eliminates much of the manure volume, Colorado Pork only needs a lagoon about one-sixth normal size of comparably sized hog farms, cutting down on potential water pollution and significantly reducing construction costs associated with building a larger lagoon. Additionally, less water is needed to process the hog waste. The anaerobic digester fully meets requirements of Colorado's Amendment 14, which regulates odor emissions, and along with the energy efficiency of the farm the operation provides considerable environmental paybacks.

Prowers County and the Southeast region of Colorado are emerging as a leader in renewable energy, with the hog farm's AD and upcoming wind farm projects. Rural areas have vast potential for creating and sustaining distributed generation, or local power, from renewable fuels, especially those created from waste that may otherwise constitute a public nuisance, or worse.