Anaerobic Digestion Solves Food Waste and Energy Challenges

May 24, 2016

Lots of talk in Massachusetts and around the country about wind, hydro, and solar being the answer to reducing greenhouse gas (GHG) emissions and dependence on fossil fuels, but what about anaerobic digestion (AD)? With the United States’ first-ever national food waste reduction goal, calling for a 50-percent reduction by 2030, we need to not only focus on clean energy but food waste reduction as well.

Landfill shutterstock_185851901 copyFarm-based anaerobic digestion reduces as much as 85 percent of GHG emissions from farm-based operations, while also solving the challenge of food waste entering landfills and generating renewable energy that is available from energy suppliers such as National Grid via net metering credits. Additionally, with commercial food waste disposal bans in place in many states including Massachusetts, these farm based ADs offer the opportunity to comply, while also contributing to sustaining a farm for the future.

It’s good news that food waste in America continues to gain attention. A National Resources Defense Council 2012 study determined that while eighty percent of freshwater used in the US goes towards growing food, only 60 percent of that food is eaten. The other 40? That ends up in landfills where it decomposes and releases methane, a greenhouse gas 25 times as potent as carbon dioxide. And that’s just part of the food waste story. It may be hard to believe, but nationwide, food leftovers are the single-largest component of the waste stream by weight. Food scraps make up 17 percent (29 million tons/year) of what we send to landfills, or enough to fill the Rose Bowl every three days!

Other recent state and city-level legislation in the United States has made it illegal for some commercial businesses to send organic waste to landfills. Connecticut was the first of these in 2011 and Massachusetts followed suit in 2014 with a commercial food waste disposal ban that prohibits any institution producing more than a ton of organic waste per week from sending it to a landfill. Companies must now dispose of this waste via composting or in alternative ways. One solution is farm-based anaerobic digestion, a cost effective and sustainable solution that benefits food waste generators and the farms involved by converting much of that waste into renewable energy and nutrient-rich fertilizer.

So how does anaerobic digestion work? Methane is created when organic waste decomposes without oxygen, which happens when it’s buried under mountains of non-organic waste. Using anaerobic digestion, this process can be done safely in a closed tank. Though digesters can vary greatly in size and in the way they transform inputs, all utilize an oxygen-free environment to promote the breakdown of organic compounds by microorganisms resulting in methane rich biogas that is captured and converted to electricity.

Municipalities have been taking advantage of these contained systems for decades to break down and eliminate pathogens from wastewater sludge. Methane from the anaerobic digestion that occurs in landfills is also captured at approximately five hundred municipal solid waste facilities in the U.S.

CowDigesterPhotoIn the case of farm-based organics to energy, a closed-loop lifecycle is created where manure from the farm and food scraps and food processing byproducts are combined in a sealed tank where microorganisms digest it and produce biogas. This biogas is biologically scrubbed to clean it of hydrogen sulfide, after which it runs a generator that produces clean energy. This energy supplies the farm with ample electrical power for its operations and provides electricity to the surrounding community. What’s even better is that the byproduct of the process is a nutrient rich, organic, odor-free fertilizer called digestate that the farm can use to replace chemical fertilizers resulting in increased crop yields and lowering dependence on chemicals on the farm.

These AD facilities are not only theoretically carbon neutral but they also produce zero waste and provide more food per acre than was possible before the anaerobic digestion and combined heat and power facilities were installed at each farm.

Jordan Dairy Farm Anaerobic Digester

Anaerobic digester at Jordan Dairy Farm, Rutland, Massachusetts

With farm-located digesters a range of feedstock sources including food processors, universities, hospitals, grocers, and restaurants send their waste to compliment waste from the livestock. At Jordan Dairy Farm in Rutland, Massachusetts, manure from the farm’s three hundred milking cows, each of which produce about 18 gallons of manure each day, is mixed with waste from food waste feedstock suppliers. Inside the 500,000-gallon digester tank, microorganisms turn this soup of organic waste into enough renewable energy to supply electricity to the farm and five hundred homes. According to the Jordan Dairy Farm website, every day enough energy is produced at the farm to offset 5500 lbs of CO2 emissions, the main cause of global warming. And area business such as Polar Beverages located in Worcester, Mass. get a percentage of the power needed to run the company plant via net metering from National Grid.

The Peters Family Farm in Wisconsin runs a similar operation in conjunction with Organic Valley and uses the resulting fertilizer to grow crops that feed their cattle. Smaller scale projects like the Straus Family Farm in Petaluma, California are also popping up where farms and communities are realizing the feel-good benefits of anaerobic digesters and seeing short payback periods for their investments.

iStock_000008131972MediumAccording to the EPA, the 247 anaerobic digesters currently operating on livestock farms are only a small slice of the 8,000 livestock operations that could house similar projects. Companies like Vanguard Renewables, DVO Inc. and Harvest Power have taken note of this opportunity and work to develop, finance, install and operate digesters across the US, with Vanguard Renewables leading the way in farm-based ADs. They call the process they use the Farm Powered Organics to Energy Lifecycle.

So how can the public and companies who are not commercial food producers or users support farm-based AD? Via purchasing Renewable Energy Credits (RECs) where available. Each credit represents one megawatt-hour of energy generated by renewable sources and credits can be purchased from utilities or third parties like 3 Degrees, which buy the credits from the clean energy source. The availability of these RECs is expanding and many states including Massachusetts are developing legislation that will make them a more readily available option for large and small energy purchasers.

Barstow's Longview Farm, Hadley, Mass.

Barstow’s Longview Farm, Hadley, Mass.

In the case of Vanguard Renewables, in addition to Polar Beverages purchasing the electricity generated at Jordan Dairy Farm to run their manufacturing plant in Worcester, Cabot Creamery Cooperative completely powers the butter plant operation W. Springfield, Mass. via RECs from the Vanguard Renewables AD at Barstow’s Longview Farm in Hadley. Barstow’s is a Cabot cooperative member. What’s even better is that Cabot also sends the waste byproduct of that butter production to the farm to help fuel the digester to close the loop. This program just received the 2016 U.S. Dairy Sustainability Award for Outstanding Dairy Processing & Manufacturing Sustainability.Butter_CabotAward_FINAs of now we are still playing a game of catch-up. Germany has over six thousand large-scale digesters and it is estimated that China has nearly eight million small scale community digesters. Here in the U.S. innovative companies, organizations, and state and local government such as Vanguard Renewables, Cabot Creamery Cooperative, Dairy Farmers of America, the EPA’s AgStar program, and Farm Credit East, are working to advance  farm-based AD as a key solution to food waste challenges, GHG emissions reduction, and renewable energy production. What’s an even better by-product of all of this is that this approach to clean energy also supports the legacy of the American farm for generations to come.

-JE Forbes and Aidan Kelly

Photo credits: Photos provided courtesy of Vanguard Renewables

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