Turning Cow Manure into Energy

Michelle Xiao
December 17, 2017

Submitted as coursework for PH240, Stanford University, Fall 2017


Fig. 1: A cow on a dairy farm thats waste can be used for energy generation. (Source: Wikimedia Commons)

Cleaner energy sources are being sought after to replace traditional gas and coal power because they do not pollute the environment. Some common sources of clean energy include solar, wind, water, and geothermal power. However, another potentially strong candidate for clean energy is cow manure, which is a biofuel. Biofuels are derived from plants and animals and have a wide range of applications. For example, ethanol, a biofuel that is produced from corn, is commonly added to gasoline as a secondary source of fuel. Using these biofuels could save about 1.8 billion barrels of oil. [1] While the primary focus of those biofuels like ethanol is alternative fuel, cow manure can be used for both electricity and fuel. In both applications, the concept behind energy production is the collection of methane gas that is a product of manure. [2] Because methane is the primary gas that is turned into energy when burning natural gas, there is a huge potential for collecting methane gas from cow manure.

Manure for Power

Some dairy farms with cows, like the one shown in Fig. 1, are going above and beyond just producing milk as profit. [2] The farms have invested in a machine called a digester that collects the cow manure into a pile. Waste vegetables from the local grocery store, like lettuce, are added to the digester, and the contents are mixed. This mixture serves as a good place for microorganisms to brew, and the process produces methane gas. [3] The methane gas is collected into an engine and converted into power. This power can then be used to heat homes and produce electricity. [3] While this method is used relatively scarcely with dairy farms around the country, those that have invested in the digester can become self sufficient with energy, removing the need to pay electricity bills. Some farms even produce excess energy and are able to sell the energy and make a profit. [2] In a farm with around 1000 cows, manure has the potential to produce 250-300 kW of electricity every day, which is enough to power 300 homes. [2]

Manure for Fuel

Cow manure as energy not only interests dairy farms, but the idea has also interested car company Toyota. [4] The company has plans to build a power plant that turns the methane from cow manure into hydrogen and power for electricity. The hydrogen in particular could be used to fuel Toyota's fuel cell hydrogen cars. [4] The plant will also produce enough power to sustain over 2000 homes and fuel for 1500 cars. [4] Using methane gas from cow manure is a cleaner alternative to gasoline powered cars and natural gas to heat homes. While untraditional, this method of energy production has lots of potential.

© Michelle Xiao. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] T. Gura, "Driving Biofuels from Field to Fuel Tank," Cell 138, 9 (2009).

[2] K. Zezima, "Electricity From What Cows Leave Behind," New York Times, 23 Sep 08.

[3] A. Yu, "Waste Not, Want Not: Why Aren't More Farms Putting Poop To Good Use?," NPR, 23 Apr 17.

[4] P. W. Howard, "Toyota to Build Power Plant to Convert Cattle Manure into Electricity, Hydrogen," USA Today, 30 Nov 17.