Governments are exploring ways to suck the carbon out of the atmosphere to help keep global warming in check.

As the U.S. state of California tries to slash its climate-changing emissions by 40 percent by 2030 – and 80 percent by 2050 – it is looking at some unusual new technologies, beyond simply cutting its use of fossil fuels.

A California company called Blue Planet is capturing carbon dioxide from a fossil fuel power plant and binding it to small rock particles, to produce the aggregate needed for concrete.

If such material was used in every bit of concrete created in the state, it “would potentially offset all of California’s (power plant) emissions,” said Ken Alex, of the California governor’s office of planning and research.

The state is also looking at storing carbon in soil, through more composting of waste or burying biochar, a form of charcoal, and at technologies such as pumping carbon dioxide underground in an effort to turn it into limestone.

“California recognises we’re not going to get below 1.5 degrees or 2 degrees (of climate change), probably, without carbon sinks or sequestration in some form,” Alex said on the sidelines of the U.N. climate talks in Bonn this week.

As the world continues to battle to cut the use of fossil fuels fast enough to hold global warming to relatively safe levels, governments are exploring not just ways to ratchet up carbon-cutting ambitions but also ways to suck the carbon that is already there back out of the atmosphere.

Some “negative emissions” technologies – such as replanting deforested areas with more trees, which absorb carbon to grow – are relatively uncontroversial.

But other efforts – including a proposal to plant huge areas of the world’s land to forests, which could be harvested and burned for energy, with the carbon them pumped into permanent underground storage – raise worries about risks to everything from land rights to food security.

“Humans are very good – and California’s a great example – at inventing things and then going, eeeww, it has consequences,” Alex noted.

“The perspective of the state is there are a lot of issues around ethics and governance”, particularly with things like pumping carbon underground, he said. “It’s a more complicated question than you may at first think.”


With the expected global rise in temperature still headed toward 3 degrees Celsius above pre-industrial levels – and the most climate-vulnerable countries saying the increase needs to be at most half of that – scientists, businesses and governments are looking for innovative ways to close the gap.

Some of those include potential “geoengineering” technological fixes aimed at making global-scale changes to earth systems, such as spraying reflective sulfate particles into the upper atmosphere to mimic the cooling effect of volcanic eruptions – a still untested technology that may pose little-understood risks to world rainfall patterns.

Other proposals include dumping iron oxide into the world’s oceans to spur the growth of carbon-absorbing plankton, creating genetically modified crops with leaves that reflect more sunlight back into the atmosphere, or vaporising seawater to create more sun-reflecting clouds.

The problem with many of the technologies, critics say – beyond the inherent risks in tinkering with the earth’s systems – is that their potential availability could slow efforts to reduce climate-changing emissions.

In Britain, for example, the government is now banking on capturing carbon from power plants and pushing it into storage underground to meet some of its carbon-cutting goals, a move that is slowing efforts to actually cut emissions, said Kevin Anderson, deputy director of the UK-based Tyndall Centre for Climate Change Research.

And the United States, now led by an administration that promotes the use of climate-change-spurring coal, held a first congressional subcommittee meeting last week looking at geoengineering technologies.

Such a meeting happening in Washington, under a government unconcerned about cutting fossil fuel use, is “worrying”, said Hugh Hunt, a Cambridge University engineer who is among those looking at geoengineering options.

“Does that mean someone who has quite a lot of power might write a check and say, ‘Let’s do this engineering’?” he asked.

The Intergovernmental Panel on Climate Change, an independent international body of climate scientists, will issue a report next year looking at how the Paris Agreement aim of holding global warming to 1.5 degrees Celsius might be achieved.

That report is widely expected to suggest that some kind of “negative emissions” will be needed, at least temporarily, to pull back from an expected overshoot of the goal, scientists say.

But achieving the goal is still possible without such risky technologies, if governments have the political will to push ahead with much faster emissions cuts, said Harjeet Singh, a climate policy advisor for aid agency ActionAid International.

“These are unproven technologies and we don’t know the implications,” he said. “Should we try an unproven technology just because we don’t want to make any shift in our lifestyle? Easier options are on the table,” he said.


Advocates for “negative emissions”, however – some of them engineers and scientists who hold patents on some of the new technologies – say that trying out possibilities, in a growing range of small-scale experiments taking place around the world, is simply common sense preparation for action if emissions-cutting efforts fail.

“We need to take more shots. We need to try more stuff,” said Julio Friedmann, a senior advisor for energy innovation at Lawrence Livermore National Laboratory in the United States, and an associate of the U.S.-based Energy Futures Initiative, a non-profit energy innovation group.

“Industrial and engineered solutions to this challenge are part of what’s required,” he said at an event on the sidelines of the U.N. climate talks.

California is open to exploring new technologies, said Alex, of the state governor’s office.

It is, for instance, looking at whether Caltrans – the California Department of Transportation – might be able to create a standard for using Blue Planet’s carbon-trapping concrete aggregate in highway construction, a move that could dramatically increase its use.

But he worries about some of the other technologies.

“What happens if a country or a jurisdiction or an individual or a corporation decides they want to … send mylar (reflective balloons) into space or do some of these other geoengineering possibilities? How do we govern that? Who should have a voice in that?” he asked.

By Laurie Goering @lauriegoering; editing by Alex Whiting.