A “technical fix” that could stop global warming by taking billions of tons of carbon dioxide out of the atmosphere and save the coral reefs from being destroyed by acidification has been developed by scientists.
The process could be used on an industrial scale to remove excess carbon dioxide caused by the burning of fossil fuels from the atmosphere in “a matter of decades rather than millennia,” according to researchers from Harvard and Penn State universities.
The process relies on speeding up a process that happens naturally, whereby carbon dioxide dissolved in sea water breaks down volcanic rock and soils to make alkaline carbonic salts.
The water flows into the ocean and increases its alkalinity. Sea water containing more alkali can absorb more carbon, so more carbon from the atmosphere is “locked up” and becomes harmless bottom sediments, according to the journal Environmental Science and Technology.
Researchers estimate that it would take a cube of volcanic rock 10 kilometres across to return the concentration of carbon dioxide in the Earth’s atmosphere to pre-industrial levels.
Unlike other proposed “technical fixes” that “sequester” carbon dioxide from the atmosphere, this one makes the sea more alkaline and therefore counteracts the other side effect of more carbon dioxide entering the atmosphere - the acidification of the sea.
The alkalinity of the sea has remained the same for 60 million years but the burning of fossil fuels has caused it to decrease.
It is feared that the drop in alkalinity will slow down the oceans’ take up of carbon dioxide - which accounts for half the Earth’s natural capacity for “scrubbing” carbon from the atmosphere.
It will also threaten animals whose bodies are made from calcium, which is alkaline, such as corals, shellfish and phytoplankton.
Scientists say the technique is adaptable to operation in remote areas, run on natural gas or geothermal energy.
“The technology involves selectively removing acid from the ocean in a way that might enable us to turn back the clock on global warming,” said Kurt House, a graduate student at Harvard University.
However, Prof Andrew Watson of the University of East Anglia, who was one of the authors of a Royal Society paper on the acidification of the sea, said the “fundamental problem” with dissolving rock into the sea was “the immense scale on which you need to do it to make any impact.”
He added: “We are producing 8 billion tons of CO2 a year and that takes the combined efforts of all coal mining, oil and gas production. If you want to make an impact on that you need a process of the same order of magnitude to make a difference.
“The local effect would be alkali pollution of the sea - but we are polluting the sea globally by putting carbon dioxide into the ocean. This method is expensive and therefore it’s not the first line of attack for the global warming problem.
“The first is energy conservation, the second the substitution of fossil fuels with solar energy or biofuels, and the third - and above dissolving rock into the sea - comes carbon capture and storage from power plants. We know what technology is needed for that and engineering companies can do it.”
Prof Watson, an expert on the carbon cycle and the oceans, said that dissolving rock was “worth considering” if the world got into a situation in which the oceans were dying because of acidity and we needed to alleviate the problem. “If you did it the right way you might be able to save the coral reefs from the worst effects. I would see it being done in areas where there may be another reason for doing it as well, such as this.
“There is no single ’silver bullet’ for global warming.”
Other “technical fixes” for global warming have concentrated on seeding the oceans with iron filings or nitrogen to stimulate algal growth in the hope that this would then die and take the carbon the plankton contained to the sea bed.