How Extracting Hydrogen from Biomethane Can Be Carbon-Negative

Written by Paul Wiseman for Industrial Info Resources (Sugar Land, Texas)--Achieving Net Zero 2050 goals will require more than just reducing carbon dioxide (CO2) emissions, said Dan Lashof, director of the World Resources Institute's (WRI) U.S. office, in a recent webinar. Some carbon emissions are going to be unavoidable, he said, so making other processes carbon-negative will help to make up the difference. There is a way to put hydrogen processing in the carbon-negative category, he said.

Lashof was among the speakers at a webinar entitled "Hydrogen from Biomethane: A Carbon-Negative Fuel?" hosted by ATA Insights for RENMAD H2 U.S.

One way to achieve carbon-negative status in the processing of hydrogen is to start with biomethane, or renewable natural gas (RNG) as it's known in the U.S. Hydrogen emits no CO2 when used for electric vehicles (EVs) or to replace fossil fuels in internal combustion engines (ICEs). The difference in its carbon footprint comes about in the production phase.

Currently, Lashof pointed out, about 96% of hydrogen in the U.S. is produced by the steam reforming of natural gas, a process that releases about 10 kilograms (kg) of carbon for every 1 kg of hydrogen it produces. A few facilities mitigate the resulting emissions with onsite CCS to turn "brown" hydrogen into "blue," but they currently are in the minority.

RNG, on the other hand, can come from a variety of sources, all of which involve CO2 that was absorbed from the atmosphere by photosynthesis. Landfill methane is currently the main source of RNG, Lashof said, but other options include wastewater treatment plants; agricultural products such as manure; dry biomass (including corn stover, debris from forest-thinning activities performed to reduce forest fire dangers); and others.

All those options normally emit methane, so capturing it in RNG for use as a hydrogen feedstock could be the first step in reducing or at least redirecting and making use of methane that would otherwise pollute the air. Any CO2 released in steam reforming is going back where it came from, so at that point it's carbon neutral.

To take it a step further to carbon negative would involve adding the CCS option, Lashof pointed out. The extracted carbon could be stored underground or reused again in another process that still requires carbon.

Using biomass as feedstock adds another benefit besides just being carbon-negative. Lashof said capturing methane from RNG could create more ESG value. He cited a paper to that effect released by Lawrence Livermore Labs, in which his own WRI organization participated. The paper, entitled "Roads to Removal," stated that other methods of carbon capture may be more immediately cost-effective, "but as a carbon-removal mechanism, using bio resources could be one of the most cost effective."

The Demand
Meeting climate standards will require much more on the clean fuels side, and RNG/biomethane presents an opportunity to help meet that demand. RNG production currently accounts for about 2% to 4% of U.S. natural gas consumption, a very small amount, with limited potential for expansion. But if methane were converted to hydrogen through steam reformation, it would produce about 5 million to 9 million tons of hydrogen per year. Lashof said U.S. green hydrogen production stands at about 12 million tons annually.

Much more green hydrogen is needed, with exact amounts depending on a particular predictor's scenario, but Lashof said numbers range from 50 million to 130 million tons per year by 2050. He admitted, "We're not going to be able to produce all that from biomethane."

Most of the green hydrogen will come from electrolysis using some form of renewable power, he noted, but those methods do not lend themselves to carbon-negative production in the way biomethane does. And since methane from landfills and wastewater treatment plant cannot be ramped up, another source must be found that creates biomethane as a primary process.

"Using dry biomass through a gasification pathway, in many scenarios, is viewed as one of the bigger potential sources of methane that has the potential to achieve negative emissions," Lashof said. In what he called the best-case scenario, dry biomass could produce 700 million tons of biomethane per year. If the steam reforming process for all of that included CCS, the potential for carbon negativity could make up the difference for many hard-to-decarbonize processes.

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