Municipalities Moving Toward Anaerobic Digestion

As organic materials make up a greater and greater proportion of municipal waste streams, creative alternatives such as anaerobic digestion are needed.

Although local governments often hesitate to experiment with technologies on the taxpayers’ dime, several cities are venturing forward into using anaerobic digestion for diverting waste and producing energy.

Many of these efforts are the result of creative partnerships driven by a compelling need to find ways to cope with human waste streams as much as by a need to find reliable sources of renewable energy.

Anaerobic digestion may indeed be the next popular source for renewable energy, according to Smithsonian magazine.

• As focus around the world has turned to renewable energy, anaerobic digestion has started to become an economically viable energy source that capitalizes on humans at our most wasteful — and most creative. Local municipalities, including wastewater facilities, as well as private companies and even the [United States] Department of Energy are fine-tuning the tech to make it more efficient and practical.

Diverting Organic Waste

Waste diversion is becoming more and more important worldwide. Most of these programs collect organic matter for composting, which is not always embraced by local residents. As organic materials make up a greater proportion of municipal waste streams — only 5 percent of food waste is composted now — creative alternatives are needed when waste reduction isn’t working. Then the question becomes how to reuse waste effectively.

Many of the local governments using anaerobic digestion successfully began their waste-to-energy programs through wastewater treatment. The East Bay Municipal Utility District is a good example. It now produces 135 percent of its own energy from 11 anaerobic digesters coupled with three turbines. The additional energy is sold.

This type of renewable energy is not intermittent or weather-dependent like wind and solar, noted Jackie Zipkin, manager of wastewater engineering for the East Bay Municipal Utility District. The ability to produce renewable energy around the clock is exciting, she said, and it attracting interest from around the country.

Exploiting Food Waste

In Sacramento, California, a collaboration between the California Energy Commission, the city of Sacramento, and the University of California, Davis, — with help from private businesses — resulted in the siting of a biodigester that converts food waste into biofuel, diverting about 40,000 tons of food waste. The waste-derived fuel is used to fuel the fleet responsible for collecting the organic material for anaerobic digestion. The process eliminates 5,800 tons per year of greenhouse gas emissions.

The Sacramento Municipal Utility District has its own organic waste program, which works with hotels, restaurants, and local dairy farms to divert waste to anaerobic digestion. In the latter case, the utility is working on grant programs to help offset the costs associated with farm-based digestion.

In some other areas, though, projects have met with objections from local residents.

Mandates and Incentives

Many of these projects are in California because the state is financially supporting some of these waste-to-energy projects as well as enacting mandates on waste reduction, explains a mid-2016 report from Renewable Waste Intelligence.

The federal government is working on issues key to biogas distribution and supply chains. This includes examining how to tailor the processes so higher-value products — namely jet fuel and gasoline — can be more easily made.

David Babson, a technology manager at the U.S. Department of Energy’s Bioenergy Technologies Office, told Smithsonian:

• Anaerobic digestion is fascinating because it’s a relatively easy, natural way of turning a broad variety of complex waste into a simple fuel gas. […] Closing waste loops and recovering energy from waste presents a profound opportunity to simultaneously improve waste management and address climate change.