– At the end of a cul-de-sac called Fresh Way, two bright green structures the size of shipping containers gleam in the warm sunlight, quietly sucking from the air the carbon dioxide that is warming the planet.

One structure houses computer monitors and controls. Atop the other, large fans draw air through slabs made of honeycomb-style ceramic cubes. The cubes hold proprietary chemicals that act like sponges, absorbing carbon dioxide at room temperature. Every 15 minutes, the slabs rotate and the cubes are heated, releasing a stream of 99% pure carbon dioxide into a shiny steel pipe.

This is Global Thermostat, one of just three companies at the leading edge of the hunt for ways of skimming carbon dioxide from the air. It is a tiny step, but a hopeful one, toward ­reducing global warming. Amid a steady drumbeat of grim news about climate change, more and more people are captivated by the idea that a feasible process can help offset decades of damage to the atmosphere.

Some big deep-pocketed corporations — including oil companies — are looking, too. They are lured not so much by the virtues of fighting climate change but by the prospects of making money. Though long a prohibitively expensive technology, carbon capture has become a tantalizing possibility thanks to technological advances — and new generous government incentives.

There’s little time to spare. The Intergovernmental Panel on Climate Change has written that any hope to meet the 2 degree Celsius goal for global warming “will require measures to reduce emissions, including the further deployment of existing and new technologies.”

For a decade, the three companies — Carbon Engineering, Climeworks and Global Thermostat — have experimented with such technologies as the shape and chemical makeup of the spongelike membranes in an effort to reduce the towering cost of capturing carbon dioxide directly from thin air.

Now their work is poised to move beyond the lab tables and prototypes. “Our business plan is to show that cleaning the atmosphere is a profitable activity,” said Graciela Chichilnisky, a Columbia University economics professor and one of the co-founders of Global Thermostat who estimates that CO2 could become a trillion dollar market.

Over the past several years, the firms have vied to make technological progress. The cost of carbon capture has fallen from $600 a ton to as low as $100 a ton — and lower if a cheap or free source of heat or energy is available.

Federal subsidies are just as important. New U.S. federal tax credits provide as much as $50 for every ton of carbon dioxide captured and stored underground in well-sealed geological formations.

Oil companies can use the credits to pay for turning captured carbon dioxide into transportation fuels, essentially recycling the CO2. That would help Big Oil meet California regulations requiring lower amounts of carbon in motor fuels.

And the oil giants can also claim a $35-a-ton credit for enhanced oil recovery — injecting carbon dioxide into the ground to increase well pressure and boost oil production in old fields like the Permian Basin in west Texas. Oil companies currently extract natural carbon dioxide from natural reservoirs before pumping it back into the ground.

The federal tax credits, known as 45Q credits, were slipped into the 2018 federal budget in the wee hours of Feb. 9, 2018, after a nine-hour government shutdown. It attracted both parties’ support, with leading roles played by Sen. John Barrasso, R-Wyo., whose state relies heavily on oil, gas and coal production, and Sen. Sheldon Whitehouse, D-R.I., who has spoken almost weekly on the Senate floor about the urgency of climate change and the danger of burning fossil fuels.

One reason they agree: It’s politically more appealing to give away money through a tax credit than it is to impose a carbon tax that takes money away. A carbon tax is levied on the carbon content of such hydrocarbon fuels as coal, oil or natural gas that emit carbon dioxide and it raises prices for such products as gasoline or electricity.

Environmentalists are divided on the tax credits. Most want to bury captured carbon dioxide in geological formations underground rather than using it to produce more fossil fuels.

“We concluded that it was not possible to square it with our work to end fossil fuel subsidies,” said David Hawkins, director of climate policy at the Natural Resources Defense Council, which stayed neutral on the measure.

Of the 65 million tons of CO2 that is pumped underground in the U.S. every year, about 60 million tons is for enhanced oil recovery, said Sally Benson, co-director of Stanford’s Precourt Institute for Energy, and demand is growing.

Whitehouse said “at this point, the only revenue proposition for carbon capture is enhanced oil recovery.”

“As angry and frustrated I am at the behavior of these companies,” he said, “if that’s what it takes to save the planet, I’m willing to make that investment.”