WHEN THE BILL FOR THE GRIFT COMES DUE: Clean Fuel Startups Were Supposed to Be the Next Big Thing. Now They Are Collapsing: Hydrogen and biofuel projects have become money pits, threatening climate progress.

Startups promising to power planes, ships and trucks with clean fuel are sputtering before they get off the ground, showing how hard it will be to wean many industries off oil and gas.

A company backed by United Airlines that raised hundreds of millions of dollars to turn trash into jet fuel appears to have shut down. Another, backed by Airbus, JetBlue and GE Aerospace, that was working on using hydrogen to power planes went bust. Chevron, BP and Shell, meanwhile, are scaling back projects to make biofuels from cooking fats, oils, greases and plant material.

“The excitement of the early days has not lived up to the hype,” said Andy Marsh, chief executive of Plug Power, a startup that recently opened one of the country’s first plants making green hydrogen, a potential replacement for fossil fuels in industries such as steel making and chemical production.

Shares of Plug Power have tumbled more than 90% since the passage of the U.S. climate law two years ago. Shares of biofuels startup Gevo, where Marsh is a board member, are down about 80% in that span.

The failures and delays are all but extinguishing the early optimism after the climate law passed. Rising costs have pushed out project timelines and made it more difficult for companies to raise money. The government’s delays in completing tax credits are adding to the challenges.

Without clean fuels, emissions at many companies are expected to keep climbing, threatening U.S. and global climate targets. Industries including aviation and shipping are counting on the new fuels because wind and solar power and batteries can’t meet their huge energy needs.

Emissions are the least. If the greens had practiced sound science and replaced coal with nuclear plants 40 years ago, we’d have plenty of cheap power and a cleaner environment.