Tag Archives: Biogas

Sewage Treatment Facilities to Turn Food Waste into a Resource

new energy

Months ago, waste trucks in Los Angeles County, California started collecting food scraps from restaurants, grocery stores, hotels, and food processing plants, grinding them into a slurry and dropping off the liquid to a wastewater treatment plant, where it is mixed in with sewage and processed in an anaerobic digester.

What was the end result? Biogas, that can be burned as fuel.

This plant is hardly the first sewage treatment plant to take in food waste, and it certainly won’t be the last. Efforts to recycle food waste are growing nationwide, and many are doing it the traditional way, by collecting and composting food scraps. But there is increasing interest in sending food waste, particularly from commercial sources, to facilities that use anaerobic digesters to convert the food into biogas in place of composting.

About 15 wastewater treatment facilities in the U.S. have started taking in food waste to co-digest with sewage in tanks or large digester eggs — a small number, but that’s up from one or two about a decade ago, according to the American Biogas Council. Following the lead of Europe, more U.S. cities are trying new ways to harvest energy from food that otherwise would have rotted in landfills and emitted methane, a powerful greenhouse gas.

New York City, as part of an ongoing pilot program, sent tons of food waste from Brooklyn and Staten Island to the Newtown Creek wastewater treatment plant in Brooklyn and processed it in an anaerobic digester to produce biogas for the facility. They are hopeful the project will continue in order to keep the material as close to NYC as possible because their only other alternative is to turn it into traditional compost at their facility, more than 216 miles away round trip. Turns out, renewable energy provides more value than composting for the city.

Hopefully, NYC will be  successful in turning the pilot program into an expansion project because Newton Creek couldn’t possibly handle the volume of food waste New Yorkers produce in a day, especially with the commercial food waste ban to being in early 2015.

According to the American Biogas Council, about 860 sewage treatment plants in the U.S. already produce biogas using anaerobic digestion, in which bacteria break down matter in an oxygen-free environment and produce biogas that powers the facilities.  Adding food waste to the mix is the tricky part.

Experts agree that anaerobic digestion is growing quickly, but the cost of building an anaerobic digestion system ranges widely, depending on the size of the plant, the feedstock, types of end products produced, and other variables. It’s not cheap. The anaerobic digesting process is also complex as the food waste brought in must be processed to remove contaminants then converted into a pumpable slurry for injection into the digesters.

On-site aerobic digesters, like the Eco-Safe Digester, that could tank the pre-sorted, pre-digested food waste as a means of generating ready-to-use AD feedstock for the 860 sewage treatment plants would certainly help to transform something complex into something quite simple.

The wave of innovation in food waste recycling is picking up speed globally. Food waste is something we should all try to manage as a resource.

Putting Food Waste to Work


Kroger Supermarkets is now the first company to utilize the process of anaerobic digestion as a way of powering its facilities.  But what exactly does this mean and how are they achieving that goal?  The answer is simple: BIOGAS.

We all know that food gives us energy, but how could our food generate enough energy to power an entire supermarket? Many different forms of organic waste can be used to run anaerobic digestion; however, food waste holds the most stored energy of all these ‘ingredients.’ Carbohydrates, proteins and lipids are all readily converted to biogas as is the wastewater that contains food waste by means of anaerobic digestion.  Therefore, food waste alone has the potential to sustain entire businesses.

When anaerobic digestion occurs, a mixture of methane, carbon dioxide and other trace gases combine to form biogas. Because biogas is renewable it offsets non-renewable resources, such as coal, oil, and fossil fuel-derived natural gas. Producing biogas creates U.S. jobs and benefits local economies. Biogas can be used to replace natural gas in many applications including: cooking, heating, steam production, electrical generation, vehicular fuel, and as a pipeline gas.

In nature, biogas comes from locations such as landfills, covered lagoons, livestock operations, etc. anywhere there exists organic decomposition. In controlled environments, like at Kroger’s Compton Facility, the food waste is fed into the anaerobic digester, where it will be shredded, mixed, processed, exposed to heat, and stripped of pathogens while promoting the growth of microbes all to aid in the breakdown of the waste producing biogas.

Eventually, the usable biogas is stored in gas holders until it is needed for its energy. This biogas contains so much thermal energy that it can very easily be converted into a source of electricity.

Instead of land-filling spoiled apples, Kroger decided to capitalize on their energy potential by means of anaerobic digestion. As a result, Kroger is not only being eco-friendly by reducing methane emissions, but it is also being smart economically, as the company is now saving enormous amounts of money on energy.

Great Potential


Insinkerator is to residential sustainability  as the Eco-Safe Digester is to commercial sustainability. 

How last week’s pasta is on track to become the next big thing in environmental sustainability.

HIDING IN YOUR KITCHEN, disguised as the most mundane appliance imaginable, might be the next great tool for urban sustainability. We’re talking about your garbage disposal unit, the thing that sits beneath your sink and chomps your food scraps into oblivion. Maybe you use it daily and never give it a second thought. Or perhaps you’re an eco-conscious sort, and each time you flick the switch you wonder, “Is this thing bad for the environment?”

The answer to that question, it turns out, is no. In fact, as more cities try to cut their carbon footprints, slash their trash heaps and produce more energy, this humble domestic convenience could prove an intriguing ally. Here’s why: When you throw your food leftovers into the garbage can, they eventually end up in a landfill. There, as they decompose, they release methane, a greenhouse gas that contributes powerfully to global warming. Organic waste also takes up valuable space, costs money to process and lives up to its name—leaving this stuff to rot in a landfill wastes the chance to tap its energy.

Send your food scraps through your disposal and into the sewer system, though, and they’ll likely end up as biogas, a mix of mostly carbon dioxide and methane produced by microbes as they digest the organic material. Unlike most landfills, many wastewater treatment plants actually use the methane they generate. Sewage treatment is an energy-intensive business; by encouraging microbes to gobble up your waste inside special tanks, these facilities are able to capture the gas to power their operations. In the past, when sewage plants made more methane than they needed, they simply flared it off. But now they’re looking for ways to expand usage of the biogas, like delivering it into natural gas pipelines or the electricity grid.

This makes your banana peels and last week’s pasta a potential source of locally made energy, like your own tiny barrel of oil. Or perhaps an entire oil well: The average supermarket generates 1500 pounds of food waste every day. Nationally, food scraps make up roughly 14 percent of food waste, most of which ends up as landfill trash, according to the Environmental Protection Agency.

Having caught on to the value of organic waste, a number of cities are looking for ways to increase the amount that flows to their sewage plants. Across the U.S., nearly 850 wastewater treatment plants use biogas as a source of energy. The race to make biogas is altering the image of the sewage treatment industry, which is rebranding itself from “wastewater management” to “water resource recovery.”

If you happen to be a company that manufactures garbage disposals or garbage digesters, all of this amounts to an interesting business opportunity. Disposers can effectively divert food waste away from landfills and turn it into both an economically and an environmentally productive resource.

The biogas movement is spreading slowly, and it may still be a while before Americans feel empowered and proactive every time they dump leftover soup down the drain. But as far as appliances go, there’s nothing in your kitchen with quite as much revolutionary potential.

This article was posted in the June Issue of United Airlines Hemispheres Magazine written by Hillary Rosner.