How can we get fuel from waste?

Jon Lawson

According to an EDF study, methane is more than 100 times more potent at trapping energy than carbon dioxide, the principal contributor to man-made climate change. 

This is a problem as the colourless gas is given off by rotting organic matter. However there is a solution with an added energy bonus. In the US, Southern California Gas has started rolling out locally-produced renewable natural gas (RNG) at many of its natural gas fuelling stations across the state. The utility recently began purchasing RNG from Pixley-based Calgren Dairy Fuels (Calgren), which captures the greenhouse gas-producing manure from dairy farms and turns it into RNG, a renewable fuel. 

SoCalGas has dispensed 100% RNG from out-of-state sources at its fuelling stations for a year. Calgren's facility is part of a rapidly growing biomethane industry in California and is currently the largest dairy biogas operation in America.

“RNG is an important tool in reducing greenhouse gas emissions, which cause climate change, and we're looking forward to major growth in production of this renewable fuel in California,” said Jawaad Malik, SoCalGas vice president of gas acquisition.  “With the right incentives in place, RNG has significant opportunity to help the state move toward carbon-neutrality in not only the transportation sector but in many areas where traditional natural gas is now used.”

“Calgren is excited to be one of the leading production facilities in the US, which will eventually capture the waste of more than 132,000 cows from at least 18 dairies,” added Lyle Schlyer, president of Calgren. “Using the methane captured from dairy waste for transportation fuel is good for the environment because it not only keeps methane from escaping to the air, it allows us to replace traditional natural gas with a renewable version, and it reduces pollution from diesel truck engines.”

RNG is produced when the methane is captured and upgraded to pipeline standards rather than being released into the air. Organic waste sources such as dairy farms, landfills, sewage, food waste, and dead forest trees create about 80% of all methane emissions in California. Capturing the gas and converting it to RNG rapidly reduces greenhouse gas emissions. In California, a 2016 law requires a 40% reduction of methane emissions from waste sources, with provisions to deliver that energy to customers.

Production of the fuel has accelerated quickly in the state, supported by incentive programs seeking to reduce greenhouse gas emissions from trucking and dairy farms. In just the next three and a half years, at least 160 RNG production facilities will be online in California to serve the transportation fuel sector, producing more than 15.8 million therms of carbon-negative RNG every year and replacing about 119 million gallons of diesel fuel.  That's enough to reduce greenhouse gas emissions by over 3.4 million tons every year, the equivalent of taking more than 730,000 cars off the road.

Renewable natural gas trucks currently displace about 150 million gallons of diesel fuel in California. By increasing RNG trucks by ten times and decreasing diesel trucks by half, California could cut NOx emissions by 200 tons and reduce greenhouse gas emissions by 10 million tons.

In addition, California recently enacted legislation that expands the definition of renewable natural gas to include organic waste such as dead trees, agricultural waste and vegetation removed for wildfire mitigation which is typically converted to RNG by non-combustion thermal conversion. The new legislation has a twin benefit of helping to manage wildfires with reduced debris and also lowering greenhouse gas emissions.

To help expand the growth and use of RNG, SoCalGas has proposed a service that would give its customers the option to purchase a portion of their natural gas from renewable sources, just as millions of people can opt to purchase renewable electricity today. The California Public Utilities Commission (CPUC) has issued a draft ruling authorising such a service, which is expected to be voted on by the end of the year.