It’s been a while since the last big to-do about adding limestone to the planet’s oceanic waters, but researchers sponsored by oil company Shell are saying that they’ve found the ultimate solution this time.
Adding limestone extracts to the surface of the planet’s oceans could dramatically lower the levels of CO2 into the atmosphere. This is because adding lime to seawater creates an increase in alkalinity, which in turn improves the water’s ability to scrub the air clean of carbon.
As early as the 1990s scientists were working on similar plans. But most projects ran into trouble because the logistics of getting masses of limestone to certain locations was calculated to generate even more CO2. Various other problems were also cited, including the costs of actually extracting lime from limestone.
But the Shell sponsored feasibility study, recently reported in Chemistry & Industry magazine is promising. The project’s coordinator, Gilles Bertherin, cites potentially massive ecological benefits from adding limestone to the waters. “Adding calcium hydroxide to seawater will also mitigate the effects of ocean acidification, so it should have a positive impact on the marine environment,” according to Bertherin. Corven, as a management consultant, calculated that by using local means wherever possible, the plan is going to be feasible.
Kruger’s approach is new and bafflingly simple. He says that there are many spots around the globe where limestone can be found which also contain their own energy resources. Especially regions with ‘stranded’ energy which are normally considered too remote to be economically viable to exploit are ideal for calcination on site, Kruger argues. Nullarbor Plain in Australia is one such site that contains a vast expanse (10,000km3) of limestone. It also ‘soaks up’ roughly 20MJ/m2 of solar irradiation daily, Kruger
explained in Chemistry & Industry magazine.
An academic, Professor Klaus Lackner, also interviewed in the magazine, confirmed this. Lackner, a researcher at Columbia University, said ‚ÄòThe theoretical CO2 balance is roughly right…it is certainly worth thinking through carefully.’
Researchers have wildly disagreed about the exact role of the oceans in the world’s CO2 generation, but one school holds that they act as the largest carbon sink. Some put a figure of 2 billion tons absorbed anually. Increasing the uptake of carbon by the world’s oceans could have a drastic effect. Just a few percentages would make a huge difference.
The last major project researching the possibilities of adding lime to oceanic waters was sponsored by Shell competitor Exxon. The project, headed by Haroon Kheshgi of the Exxon Research and Engineering Company came to the conclusion in the early 1990s that increasing the alkalinity of the ocean surface was possible if limestone was extracted on site.
But one should not underestimate the remainder of the logistics involved if such a project would actually take off; Ben Matthews at Choose Climate commented, saying that Kheshgi’s method involved a series of difficulties; “To get this lime, you have to heat limestone (CaCO3) with coal in kilns, driving off CO2. This produces almost as much CO2 as the seawater would take up (80%), except that you have it conveniently in one place, and perhaps it might be possible to store it compressed out of the way. The whole process seems extremely inefficient. Soda ash (Na2CO3) could be used instead, but there isn’t enough of it available”, Matthews lamented.
The same commentator also calculated that the amount of limestone needed annually to soak up the CO2 we add to the atmosphere each year comes to around 30 billion tonnes. He also projected that it’s about ten times the rate that was mined in 1996. “Imagine the scale of superquarries that would need to be dug for this purpose, they would dwarf those for roadbuilding, which already face intense opposition. Furthermore, once fully mixed into the ocean, the long term change would be almost negligible”, Matthews asserted.
Apart from Shell and Exxon, the US Bush administration has also expressed an interest in the solution. The Climate Change Technology Program (CCTP) Strategic Plan, which is run since 2001 by the Energy and Commerce Departments includes it as one of a few major league possibilities to combat climate change.