Animal Wastes: An Energy Resource That Is Win-Win

I first became aware of the animal waste issue in 1995 when a lagoon of liquid pig wastes in Iowa overflowed its banks and contaminated a nearby waterway. It made the national news, including the Washington Post, and resulted in one of my DOE colleagues asking me if we had a program to generate fuels/energy from such wastes. This was a logical question as I then headed DOE’s renewable electricity programs and biomass issues were under my purview. I answered honestly, no, but immediately headed to the offices of my biomass program and directed that such a program be started. I designated one of the senior biomass staff to head it up, it started the next day, and the new program head, a Ph.D, was unofficially given the title “Dr. Poop”.

Not having such a program earlier was clearly an oversight on my part, and I began to educate myself on the realities of animal wastes and their possibilities for productive application. One step was tracking down people in the DOE national laboratory system that knew about such things, and I found an expert at Oak Ridge. He directed me to useful information, of which there was quite a bit, and helped me organize an all-day meeting at the University of Tennessee with animal waste experts that explored these issues in detail. It was illuminating to say the least, especially for this boy from the Bronx who didn’t see his first bull until he was 16 and his first pig until he was in graduate school. I’ve never been the same since.

A few facts and numbers will put the issue in context. The U.S. produces lots of livestock (cows, chickens, turkeys, etc.) and therefore lots of animal wastes. Until recently the U.S. was the leading global meat producer but is now #2 behind China (42 million metric tons/MMT vs. 83 MMT), with Brazil coming in third at 25 MMT. EPA, which plays an important role in animal waste management in the U.S., estimates that this waste is produced on 1.3 million farms across the nation. The numbers of animals raised each year in the U.S. is staggering – more than 9 billion chickens, 250 million turkeys, 100 million beef and dairy cattle, 65 million pigs, and other animals (sheep, goats, ..) that are raised as part of our food economy. The net result of all this is about one billion annual tons of animal wastes – about ten times the amount of municipal sewage – that have to be dealt with in a way that does not jeopardize human, fish, or ecosystem health.


Why are animal wastes a threat? Agriculture, including livestock, is a major source of nitrates that pollute water supplies. Animal wastes also contain disease-causing pathogens such as E coli, Salmonella, and Cryptosporidium that can be many times more concentrated than in human waste. “More than 40 diseases can be transferred to humans through manure.” Antibiotics added to animal feed to project against infection and speed up llivestock growth (about 30 million pounds annually, or 80% of antibiotic use in the U.S.) gets into human foods and contributes to the evolution of anti-biotic resistant bacteria. In addition, wastes at pig farms emit hydrogen sulfide, a corrosive gas that if inhaled at high concentrations can lead to brain damage and death.

Can’t we just contain this stuff so it doesn’t get into our water supplies? The facts are that some waste lagoons are as big as several football fields and are prone to leaks and spills.


To quote the Natural Resources Defense Council:
“In 1995 an eight-acre hog-waste lagoon in North Carolina iburst, spilling 25 million gallons of manure into the New River. The spill killed about 10 million fish and closed 364,000 acres of coastal wetlands to shellfishing.

In 2011, an Illinois hog farm spilled 200,000 gallons of manure into a creek, killing over 110,000 fish.

In 2012, a California dairy left over 50 manure covered cow carcasses rotting around its property and polluting nearby waters.

When Hurricane Floyd hit North Carolina in 1999, at least five manure lagoons burst and approximately 47 lagoons were completely flooded.

Runoff of chicken and hog waste from factory farms in Maryland and North Carolina is believed to have contributed to outbreaks of Pfiesteria piscicida, killing millions of fish and causing skin irritation, short-term memory loss and other cognitive problems in local people.

Nutrients in animal waste cause algal blooms, which use up oxygen in the water, contributing to a “dead zone” in the Gulf of Mexico where there’s not enough oxygen to support aquatic life. The dead zone fluctuates in size each year, extending a record 8,500 square miles during the summer of 2002 and stretching over 7,700 square miles during the summer of 2010.

Ammonia, a toxic form of nitrogen released in gas form during waste disposal, can be carried more than 300 miles through the air before being dumped back onto the ground or into the water, where it causes algal blooms and fish kills.”

Complicating all this is the reality of ‘intensification’, the fact that “..smaller family farms have been replaced by corporate operations hounding thousands of animals in assembly-line conditions.” For example, the number of pig farms in the U.S. in 2011 was one tenth the number in 1980 but the number of pigs sold was about the same. Ten companies today produce more than 90% of the nation’s poultry and 70% of U.S. beef cattle come from farms with at least 5,000 head of cattle.

This concentration of livestock growing in factory farms, called concentrated animal feeding operations (CAFOs) is driven by economic imperatives. It leads to a buildup of animal wastes in small land areas, which if properly stored and used, can be a valuable resource. If not properly managed the waste produced by CAFOs can pollute the environment, especially water sources. Waste is often pumped into open-air lagoons from which liquid manure is sprayed onto fields as fertilizer. The amount of waste applied often exceeds what the crops can absorb, leaving the rest to escape into the air or as runoff into surface waters.

There are many productive uses of manure, including fuel and energy production. These include recovery of undigested anti-biotics, recovery of solid materials for use in building materials, and production of dry plant and crop fertilizer that is the byproduct of biodigestion. It is this latter activity that offers a ubiquitous and large energy resource.

As reported by the Agriculture Extension Division of Colorado State University: “The demand for clean energy, coupled with concern for management of livestock wastes, has revived an interest in generating methane from livestock manures. The most widely accepted technology currently available for converting organic wastes present in livestock manure is anaerobic digestion (AD). AD is a biological process by which microorganisms convert organic material into biogas, containing methane and carbon dioxide. Biogas produced by this process can be utilized to generate electricity or can be cleaned up and supplied to natural gas lines. Collection and utilization of methane generated from livestock manure offers the potential to reduce global emissions of methane (a greenhouse gas), reduce CO2 released from fossil fuels, diminish odor from agricultural facilities, and improve water quality. In many cases, anaerobic digestion either decreases on-farm energy costs or increases revenues from energy resale.” An interesting number is that, on average, “..a single dairy cow produces approximately 120 pounds of wet manure per day” which has an energy value of about 14,000 BTU. Thus, “It would take manure from approximately 50 cows to produce enough biogas for heating a typical home.”


Proper management and use of animal wastes is clearly a ‘win-win’ if we can prevent water and air pollution and tap into a potentially large energy resource. For example, China is actively pursuing biodigestion of human and animal wastes, particularly in rural areas that lack grid connections, for producing biogas for lighting and cooking. The International Energy Agency’s CADDETT Reneable Energy Program ( “..gathers information on full-scale commercial projects which are operating in the member countries..”. Its Renewable Energy Register, a database of demonstrated renewable energy projects, contains many biodigestion entities – e.g., ‘Poultry Litter as a Fuel for Electricity Production’, ‘Electricity and Heat from the Aanaerobic Digestion of Farm Wastes’, and ‘Centralized Manure Digestion Plant’. Information is readily available; what is now needed is widespread implementation.