Methane—Cow Power

ADVERTISEMENT

Cattle, meaning dairy cows and beef animals, belong to a diverse group of animals called ruminant animals, or simply ruminants. Ruminants possess a four-part digestive system composed of a stomach similar to a human stomach and three additional chambers that carry out a different digestion than found in the stomach. Ruminants exist on a diet of fibrous plants that require a good deal of chewing to digest. These animals do this by swallowing partially chewed food, regurgitating it, chewing it again to further break up the pieces (called chewing the cud), and then re-swallowing the material. The smaller, chewed pieces move into the other compartments that contain enormous numbers of anaerobic bacteria and protozoa, especially the biggest compartment called the rumen. Rumen microbes degrade fibers into organic acids that the animal relies on for energy. As the microbes work they release methane, which the animal must constantly eliminate by belching or passing along to the large intestines. The methane drifts upward into the atmosphere and mixes with other greenhouse gases.

CO2 receives most of the blame for the crisis of greenhouse gases and global warming, but, in fact, other gases cause much more harm to the environment. Methane contributes about 20 times more to global warming than CO2. The EarthSave environmental organization has calculated that animal agriculture produces 100 million tons (91 million metric tons) of methane a year. Cattle produce about 20 percent of the methane emissions in the United States, and, unlike new methane-reducing technologies for factories and wastewater treatment plants, these cattle must keep producing methane as long as they live.

Environmental scientists have considered two divergent solutions to cattle methane: capturing the methane for energy or altering normal ruminant digestion to produce less methane. Capturing the methane from belching cows presents an understandably difficult task, so engineers have turned their attention to the large amounts of methane that come from cattle manure. Pacific Gas and Electric Company has embarked on a program to capture this “cow power.” Roy Kuga, its vice president of energy supply said, “With nearly 2 million dairy cows in California, there is great potential for the state’s agriculture and power sectors to work together to address the challenges of climate change.” Cattle have become a hot topic among environmental scientists due to their enormous production levels of a renewable energy source.

Cow power farms work by conveying the manure to covered tanks or lagoons. Gas collecting devices receive the methane as it rises out of the waste load and, with a small amount of processing, pipe the natural gas to an energy utility company’s distribution system. On the other side of the country, Central Vermont Public Service, an electric utility company, uses manure methane to fuel an energy generator and converts the output to electricity for its customers. A Vermont environmental planner Jason Bregman has predicted, “The next generation of renewable energy systems will seek out organic matter in municipal, commercial and agricultural waste streams as a relatively easy source of fuel to obtain and process energy.” Other states and many other countries have begun their own methane waste-to-energy programs.

Reducing the methane a cow produces requires adjustments to the cow’s diet. Grasses that cattle graze contain a stringy fiber called lignin that can only be digested with cud chewing and the action of the rumen’s anaerobes. Laboratories have begun to develop new grasses that contain less lignin so that grass-fed beef and dairy cows emit less methane. The Carnegie Mellon University engineer Christopher Weber explained to Discovery magazine in 2008, “Genetically modified grass could be an appealing solution. It could be more acceptable to the carnivores among us than meat grown in test tubes or giving up meat altogether.” The promise of adjusting cattle’s diets offers some promise, but it is still a long way from helping solve climate change. A more daunting obstacle comes from the fact that cattle are not the world’s only methane producers. The following ruminant animals all produce methane: alpacas, antelopes, bison, camels, deer, giraffes, goats, llamas, oxen, pronghorns, sheep, water buffalos, wildebeests, and yaks.

Methane use and methane reduction are two rapidly emerging technologies. If environmental engineers can design successful means of capturing methane for energy use, they will certainly help in advancing sustainable energy sources. Overall, methane will continue to be a problem in global warming.