Some dairy farmers might be tempted to apply “been-there-done-that” thinking to on-farm anaerobic digesters. After all, digesters have been around for decades, with wide adoption in Europe. But few U.S. farmers have made the investment required of anaerobic digestion (AD). In 2002, there was an estimated 40 digesters operating on U.S. livestock farms, according to the Environmental Protection Agency (EPA) AgStar program. By 2006, the number had grown to 97 with 80 more digesters in the planning stages. Germany, on the other hand, has more than 25,000 biogas plants.
With today's emphasis on "being green", moe U.S. livestock operations may give AD a serious look. "A number of factors make the production of renewable energy from livestock waste particularly appealing," writes Cornell professor Brent Gloy in "Creating Renewable Energy from Livestock Waste: Overcoming Barriers to Adoption."

Among them are:

• In a world of rising energy prices, AD can save dairies money. By generating their own electricity through AD, dairies can replace traditional energy sources with what they produce from manure.
• Higher fertilizer prices make it critical for dairies to make the most of their manure’s nutrients for crop production. AD can help.
• There are more incentives today for renewable energy production.
• Though the AD process doesn’t eliminate odors, it can reduce them, Gloy writes. This helps to mitigate negative public attitudes toward livestock waste.
• AD can help reduce concentrated animal feeding operations’ (CAFO) environmental impact, an important goal as CAFOs face more regulations.
• “The production of energy from manure results in the destruction of methane which is a potent greenhouse gas,” Gloy writes. “Likewise, the energy created by the process off-sets energy produced by fossil fuels.”

Challenges to AD

Gloy points out barriers to adopting on-farm biogas production:

1. It’s site-specific. Economics favor biogas production at the farm, he writes. But the value of energy in a ton of as-excreted manure is relatively small. “As a result it’s difficult to economically transport large amounts of waste materials to centralized digestion sites,” Gloy writes. (Table 1) And the best “sites for biogas production – large livestock operations – may not be located in areas with favorable markets for the energy produced from the system.”
2. Because each farm has different characteristics – types of housing, manure handling systems and bedding – different technologies are required. This makes a one-style fits all solution unlikely, Gloy writes.
3. “There is little coherent policy associated with biogas production,” Gloy writes. There needs to be a national policy directed toward developing markets for energy produced by biogas systems and also quality standards for biogas inserted into gas pipelines, he says.
4. The process to sell electricity generated by AD must be streamlined. Working with individual utilities to market electricity generated from AD can be difficult. “National, rather than regional-, state- or utility-level requirements of incentives for this type of energy are more likely to be effective in stimulating the industry,” Gloy says.
5. Currently, on-farm use and electrical generation are the most common markets for biogas. Additional markets would make production more appealing.

Will on-farm anaerobic digesters be for everyone? Certainly not at the present time. Might anaerobic digesters present some dairies with new opportunities? Yes, even those that might have examined digesters previously might see opportunities now where digesters did not make sense in the past.

To learn more…

Brent Gloy is a professor in Cornell’s Department of Applied Economics and Management. His work on anaerobic digestion and bioenergy, as well as tools for analysis and other material on the topic, can be found at http://agfinance.aem.cornell.edu/AD%20systems.html>
At the site, find Gloy’s paper “Creating Renewable Energy from Livestock Waste: Overcoming Barriers to Adoption.” Extension Bulletin 2, 2008.
John Hanchar is farm business management specialist. Contact in the Livingston County office at 585-658-3250. Ext. 112. Email: jjh6@cornell.edu

Anaerobic digestion is a biological process where bacteria convert organic materials to biogas. Biogas consists primarily of methane and carbon dioxide. The methane content of biogas produced from livestock waste is typically in the range of 55 to 65%. The gas also contains other compounds such as hydrogen sulfide, which is corrosive. Source: Brent Gloy.

Table 1
Energy content and value of potential AD feedstocks

*Values derived from various sources including: Krich, et.al., Martin and Roos.
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