Anaerobic digestion can turn waste into a valuable resource
Billions of tons of organic waste are generated every day by households, industries, and municipalities. It’s discarded into landfills or discharged as effluent, or both, at a huge cost to the environment. But what if that waste could be turned into energy? The good news is that it can, through anaerobic digestion.
In anaerobic digestion, organic waste is broken down by specialized bacteria in an oxygen-free environment. This process occurs naturally under the layers of buried waste in a landfill, producing methane and carbon dioxide, both greenhouse gases. The process can be mimicked in the controlled environment of a biodigester, and instead of emitting methane and carbon dioxide into the atmosphere, biogas is captured and used as energy.
While anaerobic digesters are commonly used in landfills and on farms to process manure, they are less common in residential areas. Here are some examples of how anaerobic digestion can be beneficial in different settings and at different scales.
Yaphank Anaerobic Digester, New York
The Yaphank anaerobic digester, one of the world’s largest, is expected to open in Long Island, New York, in 2024. The facility will be able to process 210,000 tons of organic waste, fats, and oils every year. This would reduce the organic waste that Long Island produces by nearly half, while also generating 500,000 million British thermal units (MMBtu) of biogas. Biogas can provide power to thousands of households. The process will also produce 45,000 tons of compost and 260,000 gallons of nutrient-rich liquid fertilizer that can be used to enrich soils and enhance plant growth. By harnessing the methane-rich biogas, the facility prevents the emission of 85,000 tons of greenhouse gases a year.
BC Organics Biodigester, Wisconsin
BC Organics in Greenleaf, Wisconsin, offers dairy farmers a more sustainable solution for managing their livestock manure, reducing phosphorus runoff, and processing manure from farms into natural gas. The facility, which is expected to process more than 360 million gallons of manure annually, will not only reduce the negative impact of runoff on the environment but also produce 1,630 MMBtu of renewable natural gas and enough compressed natural gas to replace 11,000 gallons of diesel fuel each day.
In addition to that, it will produce more than 400,000 gallons (about 1514164 L) of clean water and 135 tons of fiber bedding every day. This is a classic example of how a waste product can be turned into products that offer value while also protecting the environment.
Bar-Way Farm, Deerfield, Massachusetts
Bar-Way Farm, a small family-owned dairy farm, uses a combination of food waste and manure in its digester, a process known as co-digestion. It makes anaerobic digestion feasible on small dairy farms like Bar-Way, which has about 300 cows on its 600 acres of cropland. The cows produce about 2,000 gallons (about 7570.82 L) of milk daily, as well as lots of manure. The manure and organic food and beverage waste are processed with anaerobic bacteria, which produce methane-rich biogas inside the digester.
The 660,000-gallon anaerobic digester processes more than 9,000 tons of manure and 36,500 tons of food waste annually, converting it into renewable energy and low-carbon fertilizer. Fueling a 1-mW electrical generator, the facility produces enough energy to provide power to 1,600 homes while offsetting more than 2 million pounds (about 907184 kg) of carbon dioxide emissions annually. The process generates about 1.62 MMBtu per hour of heat used by the facility and the farm.
The digester not only provides the farm with a manure management solution, but it also provides a nutrient-rich liquid fertilizer that is spread on the fields to enhance crop growth. The fibrous solids that remain are used for cow bedding. The farm receives rental income for hosting the digester on the farm, as well as hot water, heat, and discounted electricity.
From Waste to Energy
These examples show just how valuable anaerobic digestion can be for municipalities, farms, and businesses. As we look to the future, it makes sense for increased enterprises to adopt the process, unleashing the carbon-neutral power and valuable byproducts that lie waiting within what was once waste.
ROI and Operating Costs
Anaerobic digester projects usually yield a two- to five-year ROI, influenced by organic load and capital costs, which can be offset in the United States via the Investment Tax Credit (ITC). In contrast to aerobic methods costing $0.01-$0.05 per gallon ($5.67 per thousand gallons) for treatment, anaerobic digestion often generates income, about $0.39 per thousand gallons treated.
Fluence was named a 2023 Top Waste-to-Energy Solutions Provider by Energy Tech Review and offers waste-to-energy solutions designed for specific industries. Contact Fluence to learn more about these technologies and how they can turn your waste into a valuable resource.