Texas manure as fuel

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The livestock industry is creating economic opportunity for agribusiness in Texas. Beef, dairy cattle, hogs and poultry manure, also known as feedlot biomass, can be put to practical use as a renewable energy source, with dry manure and liquid manure producing different types of energy. Manure can be used for gas, electricity and fuel for a boiler, or it can be burned directly for cooking or lighting.

The best approach to using animal wastes for power depends on the amount of moisture and non-biodegradable solid materials that are contained in the manure. Both methods solve a manure disposal problem while mitigating odors and negative environmental effects.

Dry Manure for Fuel

Dry manure has long provided heating and cooking fuel for rural societies. If the water content of manure is low enough (less than 20%), dry manure can be burnt directly. Solid, dry manure includes manure from beef feedlots and dairy drylots. Burning dry manure can also release energy for the production of biogas. While supplying its own energy needs, a cattle feedlot operation could also solve its manure disposal problem, reduce odors, provide jobs, and increase the local tax base - all by installing a manure-to-energy generator on site.

The environmental benefits to processing manure into fuel include cleaner air and water. Some dairies get rid of manure by sluicing it off to lagoons, which produce methane that escapes into the air. Methane has a global warming effect that is 21 times that of carbon dioxide, so using the methane for energy production significantly reduces greenhouse gas emissions. And because manure that is used in the biogas plant is not washed off land surfaces by rain and irrigation into local rivers and streams, the local watershed also benefits.


Source: Texas A&M University

Texas A&M Dry Manure Research
The Texas Agricultural Experiment Station's test results focus on using pulverized manure samples as reburn fuel in a secondary combustion chamber to lower the nitrogen oxides and specific metal emissions from coal-firing in the primary combustion chamber.

Because solid feedlot waste must be processed differently from the liquid waste of dairy operations, Texas A&M researchers are trying to determine what process and what mix of the product will create the most useable heat and, as a result, energy.


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Manure Fuels Texas Ethanol Plant

Texas is the nation's leading cattle state, with an abundance of animal waste that can be used to create energy. Because transporting dry manure far distances to power plants is impractical, it is most often used as a fuel regionally. Hereford, located in the Texas Panhandle, is known as the cattle capitol of the world with more than one million head of cattle and 100,000 dairy cows located within a 100-mile radius of the town. Hereford has added another name to their city - the ethanol capitol of Texas (see video). The area is supplying a new ethanol plant with fuel in the form of manure from cattle feedyards, eliminating the need to burn expensive natural gas.

In 2005, Panda Ethanol began construction on a $120 million ethanol plant on a 380-acre site in Hereford which is expected to be in full production in 2008. The Hereford plant is a fine example of what can be achieved when the ethanol and livestock industries work together for the benefit of both the industries and the community. Projected energy savings are equivalent to 1,000 barrels of oil per day and transportation costs are greatly reduced as well. To take advantage of another waste resource, Panda is using gray water from the city wastewater facility.

The Panhandle area was selected because of the close proximity to the facility's source of fuel (manure) as well as the feedstocks (corn and milo) that will be used. The plant utilizes a technology involving a bubbling bed fluidized gasifier that converts cattle manure and cotton gin waste into clean-burning biogas to power the plant. Corn is readily available, as this area already ships in most of their corn from the Midwest by unit train to supply the local feedyards. At harvest time, local corn will be used. Milo (a small drought-resistant grain sorghum), produced in the Panhandle, will also be used.

Local farmers have contracted with Panda to supply the manure free of charge just to get rid of the mounds of waste rather than paying to have it carted away. The Hereford ethanol plant will bring new jobs and an increased tax base to the community. About 500 to 600 workers are needed during construction of the plant and after it is fully operational, it will employ about 60 people on a permanent basis. The plant is expected to produce 100 million gallons of ethanol fuel each year.

For information on other ethanol plants in Texas, see Texas Ethanol Plants.

Wet Manure for Biogas

Anaerobic Digestion and Methane Recovery

Wet manure that is produced from dairy cattle and hogs confined in enclosed areas produces biogas, which contains about 60% methane, which is a greenhouse gas and contributor to smog that remains in the atmosphere trapping heat for 9-15 years.

Methane is also a primary component of natural gas and an important source of energy. Biogas from manure can be captured and purified to yield pipeline grade methane that is chemically the same as natural gas. It can be used on the premises for electricity or to fuel boilers or other thermal applications. Pipeline grade methane can be transported by pipeline for sale to the local power grid to run electric generators. Manure deposited on fields and pastures, or otherwise handled in a dry form, produces insignificant amounts of methane.

Liquid manure usually occurs when flushing livestock pens with water. In the anaerobic digestion process this manure is collected and broken down by bacteria in a low-oxygen environment which generates methane emissions (biogas). Anaerobic digesters (or methane digesters) such as airtight digester tanks or covered anaerobic lagoons are used for this process.

Methane digesters particularly appeal to dairy farmers because it provides a safe means of disposing of manure and avoiding odors while creating a usable energy source. Using methane in this way also prevents animal waste from polluting the ground water, and methane from seeping into the atmosphere, thereby rising levels of greenhouse gases and smog.

Anaerobic digesters are available at competitive rates and are currently in use on farms across the country, although on a small scale. For a description and photos of a covered anaerobic lagoon, see this PowerPoint presentation by the California Polytechnic State University: Construction and Operation of a Covered Lagoon Methane Recovery. At the beginning of 2008, there were 111 anaerobic digesters operating across the U.S. that produce electricity or gas to fuel boilers.

The U.S. Environmental Protection Agency (EPA) has established a voluntary program to reduce methane emissions in the livestock industry. This program, known as the AgSTAR Program, encourages adoption of anaerobic digestion technologies that recover and combust biogas (methane) for odor control or as an on-farm energy resource.


Creating energy through anaerobic digestion.

Copyright© The Pembina Institute 2006
Illustrator: David Mussell
Cowpower Video

Many livestock operations store the manure they produce in waste lagoons, or ponds. A growing number of these operations are placing floating covers on their lagoons to capture the biogas. They use it to run an engine/generator to produce electricity.

Cow Power
It takes 2.4 kilowatt-hours (kwh) of electricity to burn a 100-watt light bulb for a day. The electrical energy available in one cow's daily manure contribution can produce 3.0 kwh of "cow power."


Photo courtesy of DOE
Anaerobic Digester Tank
The air-tight anaerobic digester tank converts biomass waste to methane. Capping and channeling the methane into a productive use, instead of releasing it into the atmosphere, helps to mitigate global warming while producing a renewable energy that can be used for heating, electricity, or operation of an internal combustion engine.

The material drawn from the anaerobic digester is called sludge, or effluent. It is rich in nutrients (ammonia, phosphorus, potassium, and more than a dozen trace elements) and is an excellent soil conditioner. It can also be used as a livestock feed additive when dried.


Methane digesters add significantly to cattle feedlot operations, as they:

•add revenue to dairy operations;
•cut waste management costs;
•provide electricity and power needs;
•reduce manure odor by as much as 95%;
•reduce pesticide costs;
•reduce surface and groundwater contamination;
•help minimize run-off and other water quality issues;
•capture methane, sulfur compounds and other gases, which would otherwise have been released into the atmosphere; and,
•create nutrient-rich fertilizer, compost, livestock feed additive, and cow bedding out of the left-over byproducts.
Animal Waste Management and Water Quality

The management of animal waste is a serious concern for farm operators across the country. Large dairy and cattle operations produce enormous quantities of manure and thus methane, one of the most potent greenhouse gases. In addition to creating unpleasant odors, pathogens in manure can make water unsafe to drink or to use for recreation. Dairy farms, livestock holding areas and feedlots are areas of concentrated animal waste which can be washed off of land surfaces by rain and irrigation into local rivers and streams, and end up contaminating the local groundwater (water beneath the earth's surface in underground streams and aquifers).

Phosphorus and nitrogen in surface runoff are the major contributors to the contamination. Increasing, dairy farm owners are looking towards anaerobic digestion as a possible solution for animal waste management. Dairy cattle confined in enclosed areas such as freestall barns, produce wet manure that can be flushed into a covered anaerobic treatment lagoon to prevent pollution and odors while producing energy for livestock production operations.



Anaerobic Digester-Phosphorus Removal Project
In 2004, the City of Waco brought an environmental lawsuit against 14 dairy farmers located along Bosque River for polluting (phosphorous-loading) the watershed (higher land that drains water into the river). In a proactive move, the Central Texas Broumley Dairy Farm partnered with several Texas state agencies on a demonstration anaerobic digester-phosphorus removal project that has two objectives: to improve the water quality, water which was being polluted by dairy run-off near the Bosque River; and to generate enough electricity for the farm's operations to sell back to the grid. The project has been a great success, and is expected to begin full operation in 2008.

Texas Plant Installs Manure-to-Gas Digester Tanks

Microgy has invested $12 million in an anaerobic digester biogas production and gas conditioning facility at Huckabay Ridge in Stephenville, Texas. The facility is the first of its kind in the U.S. It is composed of 8 anaerobic digester tanks that digest manure from up to 10,000 cows. Each tank has a capacity of 916,000 gallons. The Huckabay Ridge facility has the capacity to produce 650 million Btu of natural gas per year, enough to provide all the energy needs for more than 10,000 average Texas homes. Microgy plans to build three more similar facilities.


Huckabay Ridge facility

The digesters produce pipeline-grade methane, which is purified, compressed, and fed into a nearby natural gas pipeline that carries it to Austin, Texas, where it is used by the Lower Colorado River Authority as fuel to produce electricity. In October 2008, the natural gas will also be sold to Pacific Gas and Electric Company under a new 10-year contract. The digesters also produce a nutrient-rich compost that is sent back to Producers Compost Incorporated which is situated adjacent to the Microgy facility and provides it with the cow manure used in the digesters. See this U.S. Department of Energy article.

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Additional Resources

For an overview of the use of feedlot biomass, see the Feedlot Biomass Overview in the Texas Comptroller's 2008 energy report.

Dairy Waste to Energy
This SECO report includes feasibility studies on the economic implications of anaerobic digesters on Texas dairy farms. The study provides the information needed to allow state facilities that utilize and generate revenue from agricultural land use to evaluate renewable energy production as a viable economic tool. The biogas digester capital budget sheet is available upon request.

Managing Manure with Biogas Recovery Systems: Improved Performance at Competitive Costs
This is an U.S. Environmental Protection Agency (EPA) publication.

The AgSTAR Program is a voluntary effort jointly sponsored by the U.S. Environmental Protection Agency, the U.S. Department of Agriculture, and the U.S. Department of Energy to encourage farm methane recovery from anaerobic digestion. AgSTAR focuses solely on the production of power from the anaerobic digestion of biomass such as livestock manure.

AgSTAR FarmWare 3.0 & Handbook
The AgSTAR FarmWare 3.0 software is a computerized decision support program that assesses whether or not a methane production, capture, and utilization system can be integrated into your farm's existing or planned manure management system. FarmWare estimates how much the system will cost and the financial benefits that may be gained by producing energy for on-farm use or sale or both. (scroll to end of page to download the software)

Anaerobic Digesters for Farms and Ranches
A DOE web site.

What is an Anaerobic Digester?
A University of Nebraska article.

Cowpower Video
An humorous, informative video that discusses the role of manure in the productive channeling of methane gas.

Renewable Electricity Production Tax Credits
Produced by the Northeast Regional Biomass Program.

Build Your Own Biogas Generator
This web site includes teacher materials and a student showcase.

Manure Digestion System Check List
Learn more about evaluating the benefits of an on-farm digester as a means of manure processing. A check list for producers to use to determine if a digester is a viable option for them is provided. This is an Agricultural Utilization Research Institute web site.

Methane's Greenhouse Gas Properties
This is an U.S. Environmental Protection Agency (EPA) publication.