‘Digesting’ Food Waste Can Turn Trash Into Money

November 22, 2013

NOTE: Images in this archived article have been removed.

Image RemovedThere’s an almost comical juxtaposition of glamour and grime in New York. The trendiest dessert spot and most expensive new boutique are often barricaded behind a bulging wall of trash bags, spilling onto the sidewalk. Designer perfume and decaying food notes mingle in the air together.

Fortunately for New Yorkers, obsessed with the newest and the best, enormous trucks routinely appear out of nowhere to rescue them from their banana peels, old sneakers and unwanted lamps. Within seconds the putrid black bag barricades are dismantled, stuffed out of sight in the back of the truck and disappear down the street, out of the city and across state lines. The vast majority of the city’s trash — 10,000 tons a day — ends up in Ohio, Delaware, Pennsylvania and North Carolina. Once the trash is properly out of sight and out of mind in a distant landfill, that’s the end of the story as far as most people are concerned. But while it might no longer be an immediate nuisance to a New Yorker, trash ‘lives’ on for decades in landfills and the methane produced from rotting organic matter, which accounts for one third of what gets thrown away, exacerbates climate change, impacting everyone on Earth.

The Fifth Assessment of the Intergovernmental Panel on Climate Change recently increased its estimate of the global warming potential of methane to 34 times more powerful than carbon dioxide. According to the Environmental Protection Agency (EPA), landfills are the third largest source of methane in the nation. In landfills, food waste also adds an enormous amount of water to the decaying mess, which causes toxic chemicals to leach into the soil.

But what if there was a way to not only keep food waste out of landfills but actually create something valuable out of what otherwise produces only methane and contaminated soil? There is, and the technology has been around for decades.

Anaerobic digesters have been used on farms to help process manure for several years. An anaerobic digester is essentially just an airtight tank filled with a special mix of bacteria, similar to what you’d find in the stomach of a cow. In fact, Patrick Serfass, Executive Director at the American Biogass Council, likes to call anaerobic digesters “optimized cow stomachs.”

When organic waste is shoveled into the digester tanks, the bacteria devour the food and other scraps and produce a biogas, which is mostly methane. The biogas can be combusted to generate electricity and heat, or can be processed into natural gas and transportation fuels. Unlike natural gas from shale, the biogas produced through anaerobic digestion is completely renewable. The digestion process also results in separated solids that can be composted, used for dairy bedding, or just spread directly on fields as a fertilizer. Nutrients from the liquid stream can be used as fertilizers as well.

“Just like a cow, you get a solid, a liquid and a gas after digestion,” said Serfass.

Anaerobically digesting just 50 percent of the food waste generated each year in the U.S. would produce enough electricity to power 2.5 million homes for a year, according to the EPA. Cities across America are just beginning to wake up to the potential of anaerobic digesters as a means to manage waste and generate renewable energy. One of the biggest obstacles remains persuading or compelling people to keep their vegetable peelings and apple cores out of their trash cans.

“In the 80s and 90s Americans started to get serious about recycling,” said Eric Goldstein, a senior attorney with the Natural Resources Defense Council (NRDC) in New York. “But that paper, glass, metal and plastic that we so carefully keep out of the trash can only accounts for about one third of the total waste stream. And because we don’t do it perfectly, we only actually keep about one quarter of our trash out of landfills. I don’t think most people realize that when they toss takeout in the trash they are contributing to climate change.”

Europe is far ahead of America in diverting food waste from the dump. The European Landfill Directive mandates that European Union member states reduce “biodegradable municipal waste” sent to landfills to 35 percent of 1995 quantities by 2016. As a result, 40 percent of waste in the EU is now composted or recycled. Norway, Sweden, the Netherlands, Denmark, Switzerland, Belgium, Austria, and Germany now send less than three percent of their waste to landfills. Copenhagen stopped sending organic waste to landfills in 1990.

While the U.S. clearly still has a lot of catching up to do, municipal composting programs have been springing up across the country. Neil Seldman, senior staffer for the Waste to Wealth Program at the Institute for Local Self Reliance, estimates that there are about 150 U.S. cities, serving 1.2 million households, that now have local composting programs in place. The food waste disposal system that these composting programs put in place, is often the first step towards transitioning to an anaerobic digestion system. Even New York is getting serious about tackling the problem.

In February, New York City Mayor Michael Bloomberg called food waste the city’s “final recycling frontier” in his annual State of the City Address. The city has begun a two-year pilot program for collecting organic material from the curbsides of several Staten Island neighborhoods, two high-rise apartment buildings in Manhattan, and about 100 schools in three boroughs. Should the two-year pilot succeed — with high participation rates and the diversion of significant tonnages — the program will roll out across the city and no longer be voluntary.

Other cities such as Portland, Seattle, San Antonio, and San Francisco have had city-wide composting programs in place for years.

In San Francisco, composting began with restaurants and grocery stores. Then in 2009, an ordinance made it mandatory for all residents to separate organic material for collection. The city collected its millionth ton of organic waste for composting last fall. Overall, 78 percent of San Francisco’s waste is now diverted from landfills.

While composting programs keeps food waste out of landfills and produces a natural fertilizer that returns nutrients to the soil, it has it’s limitations. Most of New York City’s compost or that of any other city, still has to be hauled across state lines — burning fuel all the way.

“You can’t locate a compost pile in Bryant Park,” said Seldman. “It may not smell as bad as a landfill, but it needs to be open air to work, so it can’t be in a residential neighborhood.”

For example, compost from New York City is often taken to a 20-acre site in Wilmington, Delaware. It’s hardly in a country field, but located between all the super highways, it isn’t right next to someone’s house either.

“Anaerobic digestion is going to just explode in the Northeast and Bay Area in the next few years,” predicted Seldman. “In these crowded urban areas, it costs at least one hundred dollars for every ton of trash you have hauled away. It just makes sense to deal with it locally and get value from your waste.”

Where the trend will be slower catching on is in areas where it is still relatively cheap to send everything to the dump. According to Seldman, in Texas and Georgia, the removal of a ton of trash is priced at just twenty dollars.

Some states, however, are leading the way by requiring all commercial generators of food waste, like grocery stores and restaurants, to send all their food waste to an organics recycling facility — a site for composting and anaerobic digestion. Vermont started the trend, passing legislation in the summer of 2012, and has since been followed by Connecticut last summer, Massachusetts this fall and now, New York State is just beginning to consider a similar move.

“The leadership of these states is a big deal,” explained Serfass. “Although the technology is straightforward, an anaerobic digester isn’t cheap to build. If we want companies to be willing to invest in the infrastructure, it certainly helps them to know that they will have a constant stream of food waste coming their way for years to come.”

Several cities, especially on the West Coast, are also out in front on the anaerobic digester trend. In January, the Sacramento BioDigester officially went online. The site currently converts 25 tons of food waste per day into various forms of renewable energy, including heat, electricity, and renewable natural gas. It also produces fertilizer and soil enhancements for California farms. The Sacramento BioDigestor, which is run by CleanWorld, is planning to add a second facility which will increase the daily food waste intake capacity to 100 tons or 40,000 tons per year.

One of the largest anaerobic digesters for food waste is about to go online in San Jose, California. The digester located near the southern tip of the San Francisco Bay was developed by Zero Waste Energy Development Company and has 16 massive digestion chambers, each with a capacity of 350 tons. The digester site will continue to undergo development to expand in three phases over the next several years, with each phase capable of processing 90,000 tons of organic waste a year. When fully completed, it will be one of the largest plants in the world.

California utilities are required to buy 33 percent of their electricity from renewable sources by 2020 in accordance with the state’s Renewable Portfolio Standard. While wind and solar have generally been considered the primary sources for renewable energy, biogas generated through the anaerobic digestion of food waste would also count towards meeting the standard.

“Anaerobic digesters transform food waste from a climate liability to a tool we can use to fight climate change,” said Seldman. “And even if you’re not interested in climate change, it’s still a way to turn trash into money, which is something I think everyone could support.

Tags: Anaerobic Digestion, Renewable Energy