Attacking Short-Lived Climate Pollutants (SLCPs)

When it comes to attacking climate change, focusing on reducing Short-Lived Climate Pollutants (SLCPs) should be on the top of the list of emission reduction strategies. In a December 28 opinion in the LA Times, scientists Veerahbhadran Ramanathan and Daniel Press of UC San Diego and UC Santa Cruz, respectively, make the case for attacking SLCPs right away.

According to Ramanathan and Press, we need to add to our list of emission sources: methane, carbon soot, ozone and hydrofluorocarbon coolants. These pollutants are “About 25 to 4,000 times more potent warmers than carbon dioxide.” They are called “short-lived climate pollutants” because unlike C02 that remains in the atmosphere for a century or more, they remain in the atmosphere from mere days in the case of carbon soot and methane, to 15 years in the case of HFCs.

“Curbing the emissions of SLCPs, unlike curbing carbon emissions will have an immediate effect and can dramatically slow global warming within a few decades. To put real numbers on it the scientists suggest that reducing emissions of methane by 50%, black carbon 90% and fully replacing HFCs by 2030 would cut in half projected global warming over the next 35 years. Achieving these reductions, they suggest, “will delay environmental disaster and give us time we desperately need to radically change our energy diet.”

Municipal organic waste produces harmful methane gas–emissions that have long been considered 25 times more potent that carbon dioxide. For the past ten years, CR&R and its development team have been working to develop a comprehensive approach to managing municipal organic waste now going into landfills. The results of this effort are now bearing fruit as completion of what will be among the largest anaerobic digestion (AD) plants in the world is near at hand. Located in Perris, California near the city of Riverside, is a 320,000 ton per year AD facility that will process organic waste from Southern California cities and turn it into soil products and a biologically-produced methane called “biomethane.”

Biomethane is a natural gas produced from the decomposition of food and green waste in an oxygen negative environment called “anaerobic digestion” or AD. The process is essentially an artificial stomach that accelerates the decomposition of organics producing biogas. The biogas produced by the artificial stomach is about half methane and half C02. In order to make the biogas fuel grade, the C02 content of the raw biogas must be removed through a process called gas upgrading. Once the C02 is removed, the biomethane is suitable for fueling trucks and buses. Substituting biomethane fuel for natural gas results in a negative carbon intensity rating of -22, according to the California Air Resources, compared to natural gas that has a carbon intensity of +80. Burning biomethane fuel in a truck employing the newly developed ultra low NOX engines by Cummins Westport results in the cleanest heavy duty engines in today’s world, comparable to all-electric motors or fuel cells.

AD development as a strategy for reducing SLCPs has many other benefits as well for the environment.

Using AD as a means of managing municipal organic waste makes it possible for communities to achieve recycling rates of 75% or more, in line with California’s ambitious recycling goals. Also, AD is a pathway for building soils. The bi-product of digestion is a “digestate,” a nutrient rich organic substrate suitable for producing composts and organic fertilizers. These products can help us sequester carbon in our soils,  further reducing GHG emissions.

Unlike the electric and fuel cell technologies suitable for heavy duty transportation, AD is a technology that is here and now. The CR&R project will be full scale application of the technology that points the way for a mature AD industry capable of making a major contribution to the reduction of SLCPs. Its development demonstrates, as the authors suggest, that, “it’s possible to make real progress on climate change now, above and beyond what the Paris agreement calls for. We have the levers; we just need to pull them.”