Calling on All Fleet Operators to be Negative – Carbon Net Negative That Is!

Drivers for Reducing Greenhouse Gas Emissions

It can be easy to think of harmful pollutants as just the cost of doing business, an unfortunate necessity of our need to move people, food, and products from place to place. The emissions that are harmful to human health are concentrated more greatly in urban areas and almost all the US research on the relationship between exposure and socioeconomic status shows that disadvantaged communities are the most affected.[1] This leads to an increase of health problems such as asthma, respiratory issues, heart and lung disease, and cancer in those areas.[2] There is a growing movement around the country and around the world to reduce the amount of carbon emissions that we put into our environment. One of the drivers for this is legislative. The Low Carbon Fuel Standard (LCFS) developed and implemented in California, adopted by Oregon, and currently being considered by New York, provides a thorough accounting of carbon emissions for easy integration into the marketplace and monetization.[3] New York has pledged to cut its greenhouse gas emissions and to achieve net carbon neutrality as a state by 2050.[4] The individual choices that consumers are making are also having a large impact. A 2017 study found that a third of consumers are now buying from brands based on their social and environmental impact, and a collection of four 2016 case studies found that more than 88% of consumers are willing and seeking to pay more for eco-friendly and carbon-neutral products.[5]

Greenhouse Gas Emissions in the Transportation Sector

The largest source of greenhouse gas emissions is the transportation sector, but it doesn’t have to be. There are solutions to bring the entire transportation sector to a carbon net negative status. Oftentimes, when people think of emission-free transportation, they think of electric cars, plugged in at home to a solar panel system, and they hope that a similar solution for the large trucks in the transportation sector will come soon. The solution is here, it’s already being implemented, and it’s even better than home-generated electric power. To explain why, it helps to understand how overall emissions are measured. Arguably, the most comprehensive metric in wide use is the carbon intensity (CI) as defined by the LCFS. The CI is a measurement of the grams of carbon dioxide equivalent (CO2e) emissions per megajoule (MJ) of energy over the entire lifecycle of a fuel, often called cradle to grave (or well to wheels for petroleum or soil to oil for biofuels). For every unit of available energy within a fuel pathway, the CO2e emissions are tallied for sourcing the raw fuel material, transporting it to a refinery, refining the fuel, distributing it, and burning it in an engine. The CO2e emissions for any process materials are factored in as well.

How Renewable Natural Gas Achieves Net Negative Carbon Emissions

The CI for electric cars is zero since no emissions are generated anywhere in the cycle. This is called carbon net neutrality. Vehicles running on renewable natural gas (RNG) can go even further though and can be carbon net negative. The lifecycle emissions of a fuel include mitigation of emissions that would otherwise be released into the atmosphere. At dairy farms all over the world, the manure releases methane as it degrades, a greenhouse gas 25 times as potent as CO2.[6] By processing the manure in a closed system called an anaerobic digester, the methane can be captured and processed into RNG, effectively stripping it out of the global pollution stream. This same concept is utilized at other sites such as landfills and wastewater treatment plants. The resulting RNG is the only type of carbon net negative fuel of any in the LCFS, with the lowest fuel pathway essentially removing 276 g CO2e per MJ burned from the atmosphere.[7] In 2018, Cummins Westport began manufacturing dedicated natural gas engines that have near-zero carbon emissions and that have NOx emissions 90% below the thresholds set by the EPA and the California Air Resources Board (the B6.7N, L9N, and ISX12N engines).[8] The combination of RNG with Cummins Westport’s Near Zero Compressed Natural Gas Engine technology achieves an actual reversal of carbon emissions in a way that no other fuel does and, since there are no other fuel sources that actively divert emissions in this way currently under consideration by the LCFS, RNG is the only net carbon-negative fuel for the foreseeable future.

Why RNG Makes Sense

With RNG, everyone can do well by doing good. Some quick math can illustrate this. The g CO2e/MJ values for RNG and California ULSD are -276.24 and 102.01 respectively, giving a difference of -378.25 g CO2e/MJ. There are 144.77 MJ in a diesel gallon equivalent (DGE), giving a difference of -54,760.8 g CO2e per DGE between RNG and ULSD.[9] In the first week of September 2019, the average market value of LCFS credits was $194.65, giving a value of $10.66 in LCFS credits between using a gallon of ULSD and using the equivalent 3.78 cubic meters of RNG.[10] These cost savings can be shared between everyone on the supply chain: the RNG producers, the distributors, the fueling stations, and the consumers. RNG is a more stable alternative to traditional petroleum as well. It is sustainably produced in the US, making it far less vulnerable to geopolitical events and relationships. It is also an immediately ready solution for fleets to take advantage of right now. If, in the future, other fuel sources emerge that can achieve net negative carbon intensity, the process of getting a LCFS pathway approved can take years to accomplish. On top of this, the practicalities of establishing a fuel infrastructure with the breadth needed to sustain an active fleet are substantial. Over the course of decades, CNG fueling infrastructure that is ready-made to support RNG, including ANG’s 53 stations in 21 states, has made it increasingly easy for fleet managers to make the switch to RNG. ANG is on target to source 100% of our natural gas from renewable resources by 2020, and we enjoy working with fleet managers as we move toward a brighter future.


About the Author Trey Teal has over 15 years of experience in the renewable energy industry working on commercial and grant-funded renewable energy R&D and production. He has experience working with renewable natural gas, anaerobic digestion, biodiesel, and gasification for projects with the private, public, academic, and military sectors. In addition to working with ANG, Trey also serves as the Chief Technology Officer for Biodico. Trey holds a B.S. in Economics from Duke University and has an E.I.T. in mechanical engineering with the State of California















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