“The energy security argument for hydrogen doesn’t make much sense anymore,” says Daniel Simmons, the Department of Energy’s Assistant Secretary for Energy Efficiency and Renewable Energy. “But hydrogen has always been a very flexible fuel that can be created from a variety of sources, and that flexibility is looking very attractive these days.”

Almost all the hydrogen produced in the US today is so-called “grey” hydrogen, which means it’s produced from fossil fuels like natural gas. The rest is produced by electrolysis, which uses electricity to break water molecules apart into oxygen and hydrogen. Electrolysis can be carbon neutral if the electricity is produced by renewable sources like wind or solar, but this green hydrogen is still up to five times more expensive to produce than grey hydrogen. “We really need to drive down the cost,” says Simmons. “One of the ways to do that is very large-scale hydrogen projects.”

Earlier this year, the Department of Energy announced $64 million in new funding as part of its H2@Scale program, which is designed to support R&D on scalable green hydrogen projects. The DoE’s call for proposals highlighted six main research areas, including manufacturing techniques for hydrogen storage tanks and fuel cell development for heavy-duty vehicles. But in terms of actual hydrogen production, the DoE is largely focused on improving electrolysis technology.

“Electrolyzers are already being deployed,” says Sunita Satyapal, director of the U.S. Department of Energy’s Hydrogen and Fuel Cell Technologies Office. “To reduce cost we also need to improve their efficiency, because most of the cost of hydrogen is the electricity.”

Satyapal says the efficiency of electrolyzers is currently around 60 percent, but the DoE wants companies to find ways to boost it past 70 percent. At the same time, agency officials want to double the average lifetime of electrolyzers to around 10 years of continuous operation, which is necessary to ensure they’re cost competitive with grey hydrogen and natural gas. DoE officials may see electrolysis as the fast track to scaling hydrogen production, but they’re also investing in other pathways, including waste-to-hydrogen technologies. Last year, the agency awarded $1 million to researchers at Oregon State University to develop a reactor that uses microbes to produce hydrogen from biomass like food scraps and wood chips.

“Waste-to-hydrogen approaches would be regionally-specific, limited by the content and amount of the waste feedstock available,” says Simmons. “This is in contrast to electrolysis, where the major feedstock is water, which is more generally available. Nonetheless, interesting regional opportunities exist for leveraging waste-streams.”

Not everyone is convinced that waste-to-hydrogen solutions can make a significant contribution to scaling green hydrogen production in the US. Thomas Koch Blank, an industry and heavy transport analyst at the Rocky Mountain Institute, a nonprofit clean energy research organization, says issues with waste availability could be a major barrier. He points to Sweden and Norway, two countries that invested heavily in waste-to-energy systems and quickly faced a garbage shortage as the demand for trash outstripped supply. Today, both countries import their trash from elsewhere in Europe to feed their waste-to-energy systems.

“I’m not saying it’s a bad idea,” says Koch. “It’s good to have productive secondary use of our waste streams. But I have a hard time seeing that source for hydrogen scaling to be truly relevant in the big scheme of things.”

Neither Kindler nor Mintzer claim their waste-to-hydrogen systems will be enough to support the growing demand for hydrogen on their own. Instead, they see it as a technology that can work in tandem with other hydrogen production techniques while also helping the US get a grip on its mounting waste problems. “We badly need more hydrogen, and at the same time we need to get rid of the waste that’s piling up,” says Kindler. “Waste-to-hydrogen is a pathway that will complement hydrogen production with electrolysis. Every hydrogen production solution needs to coexist.”

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