RIO Tinto and US utilities are urging the US Government to spend $US20 billion ($A20.9 billion) on a technology they say has the best chance for eliminating pollution linked to global warming. The energy companies are lobbying Congress to help create devices that can trap carbon dioxide from coal-fired power plants and bury the gas in underground caverns. Environmental groups, unions and members of Congress from coal states say pilot projects will not begin without US support, which is unlikely to come this year. As the Senate yesterday began debating the first US curbs on greenhouse gases blamed for climate change, coal companies said they would not provide most of the money for capture-and-storage technology. The industry has spent "tens of millions of dollars" on development, and it is too costly for companies alone to finance, said Rio Tinto chief executive for energy Preston Chiaro. "We can't do it without government support for the early projects," Mr Chiaro, who also is chairman of the London-based World Coal Institute, said. "Shareholders simply won't stand for it unless there's a commercial return."

Power plants are the world's biggest source of carbon dioxide, the principal greenhouse gas blamed for global warming, after vehicles, according to the Paris-based International Energy Agency. Rising temperatures driven by human greenhouse-gas emissions are causing Arctic ice to melt and rain to decline in Africa and the Mediterranean, according to United Nations-sponsored researchers. Coal-burning plants supply about half of US power demand. Taxpayer dollars would be better spent on reducing greenhouse gases by expanding solar and wind power, said Arjun Makhijani, president of the Institute for Energy and Environmental Research in Maryland. He suggests linking the wind-rich US Midwest to cities that need more electricity instead of building expensive, gas-producing machinery.

"There's no shortage of energy sources with low carbon dioxide," Mr Makhijani said. "If we're going to invest in something that isn't going to pay off for 15 or 20 years, we're going to dig a much deeper hole and make it much more costly to solve the problem." Fifteen years of tests are needed before capture and storage can be installed at generators, the US Energy Department has said. Worldwide, $US4 billion a year is needed for pilot projects, quadruple the current spending, said Howard Herzog, principal research engineer at the Massachusetts Institute of Technology's energy initiative, who has studied carbon capture since 1989. "I don't think it's a question of the fundamental science," Mr Herzog said. "It's a question of the commercial viability of doing this in an integrated fashion and at a large scale." One method would trap carbon dioxide and pressurise it into a liquid that is injected underground. There the substance would dissolve in brine, form lumps of carbonates or be absorbed in porous rock, according to a report by the Pew Centre on Global Climate Change.

The US, Canada, Australia and Algeria have dabbled in capture-and-storage experiments. The most advanced US project, called FutureGen, in Illinois, was suspended this year after the Government baulked at the project's $US1.8 billion cost. The US coal industry's pitch for public funding is beginning to gain support. Climate change legislation co-sponsored by Connecticut Independent Joseph Lieberman and Virginia Republican John Warner provides $US15.7 billion for research into carbon capture until 2050 and $US307 billion to help coal utilities "transition to the new low-carbon economy". While coal companies already had spent "tens of millions" of dollars on tests so far, they would need $US1 billion of public money a year for 20 years until the technology was proven, Mr Chiaro said. Doubling the annual research budget to $US100 million for wind energy would provide turbines that supplied 20% of the US's power by 2030, said Liz Salerno, manager of policy analysis for the Washington-based American Wind Energy Association. Wind and solar together now supply just 2.4% of electricity demand.

That would require changing priorities in Congress. Tax credits for power produced from coal and natural gas totalled $US13.7 billion from 2002 to 2007, versus $US2.8 billion for renewable generation, according to a study by Congress's investigative arm, the Government Accountability Office. In the same period the US Energy Department spent $US1.4 billion for research on windmills and solar devices, compared with $US3.1 billion on technology to cut emissions from coal. Mandatory cuts in greenhouse gases without new systems to burn coal cleanly would force utilities to use natural gas, a fuel with limited domestic supplies, said Rick Boucher, a Democrat from Virginia, a coal mining state.