Anaerobic Digesters Turn Animal Waste into Renewable Energy
Animal waste, once commonly used as a fuel source in regions where firewood was scarce, is now being transformed into renewable energy with the help of anaerobic digestion technology.
Christine Costello, associate professor of agricultural and biological engineering at Penn State’s College of Agricultural Sciences, said anaerobic digesters offer farmers an effective way to improve manure management while creating additional revenue streams.
The technology works by breaking down organic materials, including livestock manure, in an oxygen-free environment. This process produces biogas, which contains methane that can be captured and used to generate electricity or renewable natural gas. By converting methane into usable energy, digesters help reduce greenhouse gas emissions and decrease dependence on fossil fuels.
In addition to renewable energy, the digestion process produces nutrient-rich digestate that can be applied as an organic fertilizer. On dairy farms, the solid portion of the digestate can also be reused as bedding for livestock, providing another practical benefit.
According to the U.S. Department of Agriculture, nearly 400 anaerobic digesters are currently operating on large livestock farms across the country, with the majority located on dairy operations.
However, the U.S. Environmental Protection Agency estimates that more than 8,000 large dairy and hog farms have the potential to support biogas recovery systems.
Costello’s research also focuses on co-digestion, which combines manure with materials such as food waste, perennial grasses, and winter cover crops. This approach can increase renewable energy production, improve nutrient recycling, reduce emissions, and generate extra farm income through food waste processing fees.
To help producers evaluate the technology, Costello’s team developed a decision-support tool that estimates energy output, environmental benefits, project costs, and potential financial returns, making it easier for farmers to assess whether anaerobic digestion is a worthwhile investment.
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