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. 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. 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 Hereford ethanol plant brings new jobs and an increased tax base to the community. The plant is expected to produce 100 million gallons of ethanol fuel each year.
Manure for Fuel
The development of large feedlots for livestock has created economic opportunity for agribusiness in Texas. Hogs, beef and dairy cattle and poultry are often fed in close proximity to maximize efficient production and keep costs low. At the same time, however, this practice produces large amounts of animal manure that may emit odors, methane, nitrous oxide, carbon dioxide, antibiotics and ammonia. Manure can also produce water pollution from uncontrolled runoff of phosphorus and nitrates.
Growing environmental concerns coupled with higher energy prices have led to a renewed interest in using animal manure, also known as feedlot biomass, to produce power. This can be accomplished either by burning manure directly for fuel, gasifying it with heat or by turning it into “biogas” through biological decomposition. The best approach to using animal wastes for power depends on the amount of moisture and essentially non-biodegradable solid materials including dirt (generally called ash) mixed with the manure to be used as a feedstock. Each of these methods disposes of large accumulations of manure while mitigating its possible negative environmental effects.
Environmental benefits to processing manure into fuel include cleaner air and water. 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 into local rivers and streams, the local watershed also benefits.
Manure also can be used to reduce emissions from traditional fuels. A recent scientific study by the Texas Engineering Experiment Station and Texas Agricultural Experiment Station found that co-firing coal plants with manure lowers their emissions of nitrous oxide (NOX). The reburning process involves a second combustion process to reduce these air emissions.
Manure-based power plants can boost rural economic development and provide dairy farmers and feedlot operators with another source of revenue, or at least cut their disposal costs. Although Texas is a leading beef and dairy cattle producer, use of manure for energy is just beginning in Texas. There are promising new plants in Central Texas and the Panhandle both under construction and on the drawing board which have the potential to bring jobs and income to rural Texas, although there are no estimates of the current or potential effects available.
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.
Wet Manure for Fuel
Many livestock operations flush animal pens with water and store the manure in waste lagoons, or ponds. Wet manure that is produced from dairy cattle and hogs produces biogas when confined in enclosed areas. This is called Anaerobic Digestion. The biogas produced by anaerobic digestion contains about 60% methane, which is a primary component of natural gas and an important source of energy. To take advantage of this, a growing number of livestock operations are placing floating covers on their lagoons to capture the biogas. The gas is then used to run an engine/generator to produce electricity.
In addition, biogas from manure can be captured and purified to yield pipeline grade methane that is chemically the same as natural gas. Pipeline grade methane can be transported by pipeline for sale to the local power grid to run electric generators.
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.
Anaerobic Digestion and Methane Recovery
In the anaerobic digestion process, 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.
Anaerobic digesters are available at competitive rates and are currently in use on farms across the country. At the beginning of 2008, there were 111 anaerobic digesters operating across the U.S. that produce electricity or gas to fuel boilers.
Success Story: Broumley Dairy Farm
In 2004, the City of Waco brought an environmental lawsuit against 14 dairy farmers located along Bosque River for polluting the watershed. In a proactive move, the Central Texas Broumley Dairy Farm partnered with several Texas state agencies on a demonstration anaerobic digester-phosphorus removal project. The goal is to remove 80 percent of the phosphorus from the farm’s waste stream while producing methane gas to generate electricity for sale to the grid.
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 particularly appeal to dairy farmers because 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.
For an overview of the use of feedlot biomass, see the “Feedlot Biomass Overview” in the Texas Comptroller's 2008 Energy Report.
What is an Anaerobic Digester? (pdf), University of Nebraska article.
The Cowpower Video is a humorous, informative video that discusses the role of manure in the productive channeling of methane gas.
Renewable Electricity Production Tax Credits (pdf), Northeast Regional Biomass Program.
Learn more about the benefits of an on-farm digester as a means of manure processing at the Agricultural Utilization Research Institute web site. The site includes the “Manure Digestion System Check List”, a check list for producers to use to determine if a digester is a viable option for them.
The AgSTAR Program
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. AgSTAR focuses solely on the production of power from the anaerobic digestion of biomass such as livestock manure. Here is a sampling of the material available on the site.
More information on the AgSTAR program is available on the EPA web site.