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Anaerobic Digestion

Anaerobic Digestion Resources

If 50 percent of the food waste generated each year in the U.S. was anaerobically digested, enough electricity would be generated to power 2.5 million homes for a year. By anaerobically digesting food waste, two valuable products, renewable energy and soil amendment, can be generated.

What is Anaerobic Digestion?

Anaerobic digestion is a process where microorganisms break down organic materials, such as food scraps, manure, and sewage sludge, in the absence of oxygen. Recycling food waste through anaerobic digestion produces biogas and a soil amendment, two valuable products.

Biogas, made primarily of methane and carbon dioxide, can be used as a source of energy similar to natural gas. The solid residual should be land applied or composted and used as a soil amendment.

Food can either be digested at facilities specifically designed for the organic portion of municipal solid waste, or co-digested at wastewater treatment plants and manure digesters. Co-digestion is a process whereby additional, energy-rich organic materials (e.g. food scraps or fats, oils, and grease) are added to dairy or wastewater digesters with excess capacity. Co-digestion uses existing infrastructure to divert food scraps and fats, oil, and grease. Some haulers charge less if the food waste is separated from the trash and sent for anaerobic digestion rather than landfilling.

The two main types of anaerobic digesters are low-solids and high-solids (dry fermentation) and are based on the percent solids of the material being digested. Low-solids digesters generally process materials with less than 15 percent solids and are common at wastewater treatment plants and manure digesters. High-solids digesters are common in Europe and becoming more common in the United States.

Anaerobic Digestion Success Stories

Disclaimer of Endorsement: Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government, and shall not be used for advertising or product endorsement purposes.


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