Anaerobic digestion is an important technology across a wide range of industries. Meat producers in particular are increasingly adopting it because it helps operations both dispose of waste and become more energy-efficient.
Anaerobic digestion is used to extract biogas — a mixture of methane and carbon dioxide — from organic wastes. Digestate, a byproduct of the anaerobic digestion process, is a stable, fermented waste that can be reused as a fertilizer.
Organic wastes from food and beverage processing are especially suitable for waste-to-energy treatment. Waste streams may include process wastewater, whey, primary sludge from wastewater pretreatment, and manure, as well as slaughterhouse wastes and many other biosolids.
Growing Use of Anaerobic Digestion
With improved and new anaerobic digestion technologies available, greater numbers of poultry and beef producers are adopting them to treat manure and other effluents, according to ProFood World.
As of May 2016, there were 242 anaerobic digesters operating on livestock farms in the United States, according to the most recent data available from AgSTAR, the biogas recovery division of the U.S. Environmental Protection Agency. Of that number, 196 of the operations were dairy farms; 39 were hog farms; seven each were poultry, beef, and mixed food-processing plants. The agency notes the sum of these is more than 242 because some projects accept manure from more than one animal type. In 2015, these farms generated the equivalent of 981 million kWh of energy.
This is just a fraction of the potential for anaerobic digestion. AgSTAR estimates that biogas recovery systems are technically feasible at more than 8,000 large dairy and hog operations, which could generate more than 13 million MWh per year, displacing roughly 1,670 MW of fossil fuel-fired generation. The greatest potential exists for hog farmers, about 86 percent of the total electricity generation potential.
Waste-to-energy anaerobic digestion systems treat wastewater while also generating both electricity and thermal energy that can be used on site for operations or for powering the facility.
Wastewater Treatment Standards
Effective wastewater treatment is particularly important for agricultural operations that must meet local water quality standards, which vary by jurisdiction in the U.S., but ultimately are drafted to ensure compliance with the Federal Clean Water Act.
Jason VerHoef is the industrial wastewater sales manager for RWL Water, which provides water treatment, wastewater treatment and waste-to-energy solutions to a range of industries, including agriculture and food processing. He explained to ProFood World:
Allowing states to enforce water quality standards independently allows each state to ensure surface and ground water quality based on the most appropriate methods for their region. What may be appropriate for a beef processing plant in a dry region in Texas may not be applicable to a duck farm in Long Island, N.Y.
Incentives for Biogas Adoption
Technologies such as anaerobic digestion may get a boost in adoption from the Agriculture Environmental Stewardship Act (H.R.5489), introduced by Representatives Tom Reed (R-N.Y.) and Ron Kind (D-Wis.) in June 2016.
The goal of the legislation is to create incentives for farms to adopt technologies to generate renewable energy and fertilizer by recycling farm wastes such as manure. It promotes the adoption of nutrient recovery and biogas systems through a 30 percent investment tax credit for qualifying systems. Its Senate counterpart, S-3248, was introduced in July by Senators Sherrod Brown (D-Ohio) and Pat Robert (R-Kansas).
Anaerobic digestion is an important technology for effective, efficient food production. With it, users can reduce water consumption, reduce wastes, and generate energy. There is also the potential for saving money and, in some cases, creating new revenue streams. When combined with other technologies, anaerobic digestion, waste-to-energy treatment, and biogas production can be very cost-effective and environmentally friendly solutions even for the most difficult-to-treat waste streams.
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