Part of the business of raising hogs involves managing the manure byproduct, but that can become an environmental expense that is not easily resolved. One key to the solution in the future may be methane digesters. For now, the economics are probably not on your side, but you might bone up on the details, should potential revenue exceed current expense.
Trying to manage a manure lagoon goes beyond preventing spills, and includes converting the product into something useful, that may have value. One of the alternatives involves the carbon credit exchanges, in which companies that have to pump greenhouse gases into the atmosphere can pay others who will offset that action. No-till crop production is one alternative, but the installation of a methane digester on a livestock manure pit is another. By capturing the methane, which is 24 times the problem of carbon dioxide, a livestock operator has a service to sell to the carbon credit exchange patrons. Now, only if methane trapping and burning were economical.
USDA economists Nigel Key and Stacy Sneeringer, writing in the March 2011 issue of Amber Waves, says the adoption of methane digesters have not be adopted widely because of the construction and maintenance costs. Only 24 are operating on hog operations. There are two ways of increasing the use: one is a policy that would encourage use such as gaining revenue from the carbon credit exchange; and the other is a penalty for those who do not employ methane digesters.
The digester uses a cover over a heated manure pit to collect the gas which in turn is burned for heat or to generate electricity. The economists say farm size has an impact over the cost of the installation and whether enough revenue could be generated from the capture and burning of the methane. Swine manure pits are responsible for 43% of the methane from livestock, and other livestock in open manure facilities produce about 13% of the emissions.
The profitability of the equipment depends on the value of the electricity generated, and the economists say, “Electricity generators generally decline on a per head basis with the size of the operation, which makes digesters more cost effective for larger scale operations. In addition, there can be substantial transactions costs associated with selling electricity or certifying and marketing carbon offsets. Larger operations can spread these costs over a larger revenue base.”
But as the market for carbon credits increases, the economics change to benefit smaller operations, “if the offset price increases to $13 per ton, 15 percent of farms with 250-499 head and 45 percent of farms with 500-999 head would earn profits. If the price increases to $26 per ton, 3 percent of farms with fewer than 250 head and 39 percent of farms with 250-499 head would find it profitable to adopt a digester.” Since the amount of manure determines the amount of methane produced, and small farmers do not produce enough manure to be of great value at current prices, the economists suggest acquiring more product to pump into the lagoon, “supplementing manure with food waste from nearby crop or meat processing facilities, breweries, bakeries, and restaurants. When mixed with manure, food waste can provide an efficient feedstock for biogas production, and as an added incentive, livestock operators could collect waste disposal fees from the food facilities. However, the availability and suitability of food waste for use in methane digesters may restrict the feasibility of such mixtures to certain locations.” Another alternative for small farms is a centralized digester.
Current values of carbon on carbon exchanges are not high enough to allow small livestock operations to install methane digesters that would generate electricity to be sold and still gain carbon offset revenue from the methane capture. That is because small farms have less manure than large hog farms. However, any rise in price of carbon credits or the option of a centralized digester to accommodate several farms, may allow the technology to help livestock producers more economically address their environmental issue with manure disposal.