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A Waste of Energy? Two CSU Professors Study the Feasibility of Anaerobic Digestion

October 1, 2009
An influent/effluent mechanism. Bubbling indicates that microbes are chemically ballanced and that the anerobic digestion system is  functioning properly.

An influent/effluent mechanism. Bubbling indicates that microbes are chemically ballanced and that the anerobic digestion system is functioning properly.

By Catherine Keske

Converting animal waste into energy through anaerobic digestion (a bacterial process that breaks down organic materials within waste in the absence of oxygen) is an attractive idea because it prevents nutrients from entering the water and the air, reduces odors, and creates a source of on-farm energy.

In anaerobic digestion of organic materials, microbes consume organic materials as a food source in a moist, oxygen-free (anaerobic) environment. This biodegradation serves to release nutrients (nitrogen and phosphorus) bound in organic materials, freeing them to be recycled by plants into new growth. The microbes produce biogas as a byproduct of this process. This biogas is of particular interest because it contains a high concentration of methane, giving it the potential to generate clean energy.

Colorado (and the Intermountain West, in general) presents challenges for anaerobic digestion, due, at least in part, to low humidity and high solids content waste (low moisture), which make it difficult to obtain the “right” balance of “bugs” to conduct the anaerobic digestion process. This summer, Dr. Sybil Sharvelle and Dr. Catherine Keske each conducted research funded by the Colorado Governor’s Energy Office exploring how to further anaerobic digestion in the Intermountain West.

Dr. Sharvelle’s pilot technical feasibility study of dry digestion showed that there is promise for technology to be developed in the near future that will handle high solids content waste. The proposed solution is to separate the anaerobic digestion process into distinct portions, mirroring the biological process. In this system, high solids wastes are placed in an anaerobic bay where water passes through the waste, effectively leaching out valuable organics which are later converted into methane.

Dr. Keske’s research focused on the economic feasibility of anaerobic digestion in the region. She reports that when the conditions are right, “co-digestion” with multiple sources of waste (not just animal waste) has the potential to be profitable. The economic challenge lies in finding a consistent source of feedstocks and keeping digester maintenance costs under control. While the economics do not show that anaerobic digesters are a good investment for most agricultural operations at this time, her research shows that operations facing potential lawsuits may save legal fees by installing anaerobic digesters. This is particularly the case for swine operations, which have a disproportionately higher incidence of nuisance lawsuits.

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3 Comments leave one →
  1. October 15, 2009 4:45 pm

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