Muddled Environmental Meddling

limestone-lifesaverThe idea of using carbon sequestration to reduce atmospheric CO2 levels has been bandied about for years, I vaguely recall writing about it when I first freelanced for New Scientist in 1990. It struck me then as a ludicrous approach to tackling climate change akin to sweeping the problem under the carpet. Now, a press release from another journal for which I once wrote on a regular basis, Chemistry & Industry (published for the UK’s Society of Chemical Industry) is suggesting yet another madcap approach to climate.

The “open source” concept being put forward by and reported in C&I suggests that we could reduce atmospheric CO2 levels and so ameliorate anthropogenic global warming by heating millions of tonnes of limestone in the world’s deserts to release its locked in CO2, ship the resulting lime to the seaside and dump the rock into the oceans where it will apparently absorb twice as much dissolved CO2. It’s backed by multinational petrochemical giant Shell.

Now forgive me for being uber skeptical but isn’t there something just a little hypocritical about an oil company looking to macro scale chemical engineering to manipulate the environment. The C&I article quotes Tim Kruger, formerly of Shell, and now consulting on the project for Corven as mentioning Australia’s Nullarbor Plain as being a prime location for the process. Lots of energy from sunlight to heat the abundant limestone to calcify it. And, presumably excess energy to sequester the huge volumes of CO2 released at source.

The mention of Australia reminds me of another particularly crass attempt by humanity to control the environment that went badly wrong – the cane toad. The cane toad was introduced into Queensland, Australia, en masse, in the 1930s in an effort to control the cane beetle that was ravaging the sugar cane industry. Of course, cane toads are now one of the most widespread and biggest pests in the region, with no obvious way of controlling their numbers, other than introducing an exogenous, but unidentified predator species.

I suspect that, overall, dumping lime into the oceans will be as successful as dumping cane toads into sugar cane plantations. There will be unknown after shocks that will cause more harm to the environment and global ecosystems overall than anyone could predict.

First, off, there’s the problem of what to do with the CO2 released from the limestone mined in the deserts that serves as the raw material for the process. Secondly, the huge tonnages involved are going to be so big that this project really will never work, especially as shipping all that lime from the desert to the oceans will require energy and release its own huge quantities of CO2 before dumping even begins. But, more than that there will be enormous, unforeseen environmental effects of dumping this material into the oceans on such a scale.

The idea of using even “stranded” energy to release CO2 from limestone, ship the limestone to the oceans, where it will apparently absorb dissolved CO2, has to be fundamentally flawed. There are issues of pH, absorbancy, equilibria, and marine ecosystems to consider. Surely, it would be simpler and more efficient to find a way to tap the stranded energy and supply it to population centres directly, thus cutting our dependency on fossil fuels without attempting to tamper with the oceans. Several macroscale engineering ideas have been bandied about and some, such as iron seeding and nitrogen control, have even been trialled, with little success and evidence of detrimental environmental impact. Let’s not add lime to the list.

I interviewed Kruger for the August issue of Intute Spotlight in which I will cover this topic in more detail. You might also be interested in checking out the Sciencebase page.