Recently, 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. Farm-based anaerobic digestion is 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 US.
In 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.
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