Negative net-zero carbon. The phrase sounds redundant or oxymoronic. But it is a real thing. You can have less than net-zero carbon emissions if you capture and use emissions that otherwise would be released as greenhouse gas into the atmosphere.
Traditional natural gas moved through pipelines comes from deep underground wells. It is often part of making petroleum.Therefore, even though natural gas burns cleaner and produces fewer emissions than oil, it is a fossil fuel.
Renewable natural gas (RNG), or biogas, is derived from organic waste material found in food and farm animal waste, garden and lawn clippings, and plant-based material. The most common source of biogas is the naturally occurring biological breakdown of organic waste at facilities such as wastewater treatment plants and landfills.
In their decomposed state, these materials create methane gas. RNG also can be made from degradable carbon sources like paper, cardboard and wood.
Feedstocks for biogas are practically everywhere. In California, the most climate conscious of states, so much waste is available that more than 20% of the state’s residential gas needs could be met with RNG, according to a University of California Davis study.
California Air Resources Board (CARB) data shows that the average “carbon intensity” of all renewable natural gas vehicle fuel in the state’s Low Carbon Fuel Standard (LCFS) program was negative for the first time in program history.
Dairy and swine gas, which has a negative 300 carbon intensity (CI), captures methane emitted by cow and hog manure and diverts it into fuel “actually reducing global warming,” according to Cliff Gladstein, president of Gladstein, Neandross & Associates, a clean transportation consulting firm.
RNG made up nearly 90% of all natural gas vehicle fuel in the low carbon fuel program and consumed in California in the first half of 2020, up from around 77% in 2019, according to CARB data.
Calculating the negative
“Renewable natural gas is basically taking what would have been emissions coming out of landfills and dairy farms, like methane just spewing off,” Thomas Healy, CEO of startup hybrid driveline maker Hyliion Holdings, told FreightWaves.
Even as evidence shows the benefits of biogas, which Hyliion plans to use to create electricity to power its Class 8 Hypertruck ERX, California is focused on battery-electric trucks to combat the transportation part of its pollution problem. The electric grid source of power for zero-emission trucks can be dirtier than RNG.
“As opposed to letting it just go off into the atmosphere, you capture it and then you put it in the truck to drive the truck off of it,” Healy said.
“The pollution that would have come in off of that landfill or dairy farm was way worse than the emissions that’s going to come out of our tailpipe.So, from that standpoint, it actually can be below zero in terms of carbon emissions”
Biogas typically consists of methane and carbon dioxide with traces of other elements. Biogas is cleaned and conditioned to remove or reduce non-methane elements to produce RNG. It is processed so it’s interchangeable with traditional pipeline-quality natural gas and can be delivered via the nation’s pipeline infrastructure.
“The EPA actually did a really interesting study where they found that if you captured all that methane coming off of those RNG capture potential areas, you could run about 200,000 trucks on purely renewable natural gas every year,” Healy said.
There are about 175,000 natural gas-powered trucks and buses on U.S. roads today. Most are commercial vehicles in the refuse, transit, and medium- and heavy-duty truck markets.