(Oil & Gas 360) – While Americans continue to enjoy some of the lowest food costs in the world (as a percentage of income) due to a steady increase in the farming sector’s economic efficiencies, American agriculture is also emerging as a small but growing source of domestic natural gas.
Farm biogas (aka renewable natural gas, or RNG) is gaining momentum as necessity, policies, and financing combine to create the conditions for growth in the sector.
Economically, farm biogenic gas commands a significantly higher price than geologic natural gas in places like California, which has policies to cut greenhouse gas emissions.
Dairy cattle dominate the current farm biogas supply at 85%.
However, a recent report by the American Biogas Council suggests that swine biogas is an unrealized opportunity. Swine accounts for eight percent of farm biogas supply, with poultry and crops comprising the remaining seven. Still, only two percent of hog waste is being used to generate biogas despite having more methane content on a volume basis than dairy cattle.
Hog waste has more logistical issues. It is harder to handle than cattle manure, and the volume per animal is far lower. Unlike dairy farms, hog facilities tend to be localized rather than centralized, so bringing enough volume to justify an anaerobic digester (AD) is difficult. Finally, hog waste is often a readily applicable on-site fertilizer for crops.
Iowa, for example, is home to 23 million hogs, but such high volumes of hog manure can be too much of a good thing. Some state waterways are suffering from high nitrogen from hog manure runoff.
Policymakers have responded with more incentives for anaerobic digestion, which converts decomposable material like manure, crop residues, or food waste into biogas. Biogas is primarily methane but contains contains carbon dioxide and small amounts of other gases. It can be used to generate electricity, which can be used on the farm or added to the electric grid. It is increasingly being upgraded to nearly pure methane and added to natural gas pipelines.
The process also creates digestate as a by-product, which can be processed into non-synthetic fertilizer, reducing the need to purchase synthetic fertilizers. Anaerobic digestion can also enable more effective management of nitrogen compounds. Along with proper application methods, it can reduce the loss of ammonia and nitrogen to air or waterways and thus help protect water supplies. The process can also significantly reduce odor issues.
An anaerobic digester is costly, ranging from $40-60 million for a large-scale state-of-the-art facility. However, it can provide a year-round income stream for a farmer in the event of poor crops or prices.
An AD runs continuously (though it does not require 24/7 staffing. In addition to staffing, an AD requires about five acres of land.
By Jim Felton for oil&gas360.com
