New biogas plant in Marin County turns local trash into energy

Step 5 : The gas is piped to engines, which turn a generator that creates electricity.

Step 4: The gas is cooled and filtered in the plant.

Step 3: The gas is collected by wells at the landfill. About 2,100 cubic feet per minute of gas is collected per day and is delivered via pipeline to the Redwood Landfill Gas to Energy plant.

Step 1: Trash from Marin homes and businesses is collected and goes to the Redwood Landfill in Novato.

The next time you flip on a light switch, you might think about that trash you took out last week.

A Novato biogas plant is taking locally collected garbage and turning it into electricity for local consumption. Biogas is a renewable fuel, primarily a mixture of methane and carbon, and producing it is much more efficient than solar power. It would take between 64–84 acres of solar arrays to produce the 3.9 megawatts of power the biogas plant is capable of, said Karen Stern, communications manager, Waste Management, Northern California.

The plant, which began service in September, was built by Waste Management, a nationwide company based in Houston. It owns and manages the landfill.

MCE, formerly known as Marin Clean Energy, has entered into a 20-year agreement with Waste Management to purchase the electricity.

The plant is estimated to provide enough renewable electricity to serve more than 5,000 MCE customers in Marin and Napa counties and the cities of Benicia, El Cerrito, Lafayette, Richmond, San Pablo and Walnut Creek.

How the biogas plant works: The organic trash, like food and paper, is collected from homes and businesses and buried. As it decomposes, it begins to emit gas, which is captured by a network of 106 wells scattered around the landfill. The gas is contained, carbon filters capture the moisture, and a treatment system of compressors cool and filter the gas to remove toxic particles.

The processed gas is then piped to two reciprocating engines that turn a generator that creates electricity. The electricity is then exported to MCE customers.

Exhaust from the engines is also treated to remove carbon monoxide and nitrogen oxide making it one of the lowest emission facilities of its kind, said Ramin Khany, district manager of the Redwood Landfill and Recycling Center.

Collecting the gas emitted from a landfill isn’t new. But what’s unique about the Redwood plant is that the methane gas generated by the decomposition of organic materials in the landfill will power the plant. Previously, 100 percent of the collected gas was flared off.

Waste Management estimates the plant will eliminate 8,900 metric tons of greenhouse gas emissions each year.

Waste Management has about 80 biogas plants around the U.S., the next closest one to the Novato plant is located in Livermore.

At $14.5 million, this facility is expensive compared to other biogas plants the company has built, due to having to meet stricter environmental regulations in California, Khany said. Elsewhere, the plants have cost about $11 million to build.

“The margin of profit is not high, but the good its doing is deeply satisfying for the company,” he said.

Biogas is in a good position to overtake solar power as a source of energy, said Patrick Serfass, executive director at the American Biogas Council.

“The growth potential for renewable natural gas is outpacing solar. Factors behind the potential include 66.5 million tons of food waste in the U.S. each year, manure from 8 trillion cows, chickens, turkeys and pigs, and the petroleum industry’s fracking surge has unleashed abundant, low-cost natural gas,” he told Capitol politicians earlier this year.

Waste Management would like to build more plants like the Redwood facility, but sites need to meet certain criteria. The Novato site fit the profile as it’s close to a power source (PG&E) close to city infrastructure, and a distribution partner like MCE.