Carbon capture, ocean fertilisation and offsets trading (part 2)

A few days ago I published the first installment of a report of a scientific seminar on carbon capture hosted by the Royal Society. In that post I referred to Environment Secretary Hilary Benn’s opening words, and précised a presentation given by geophysicist Peter Styles of Keele University.

Today I discuss a presentation made by microbial ecologist Dr Carol Turley of the Plymouth Marine Laboratory. Turley is a specialist in ocean acidification and ocean/atmosphere climate feedback.

The oceans’ role in the global carbon cycle is second to that of rocks, and around half of the carbon dioxide from fossil fuel burning has already been taken up by the oceans. Turley’s scientific interest is in the enhanced ocean uptake hypothesis, which suggests that seeding the seas with iron particles will lead to an increased uptake of atmospheric carbon dioxide.

Phytoplankton bloom observed in 1999 during the Southern Ocean Iron RElease Experiment (SOIREE)

At the end of November I wrote about recently published work by oceanographer Michael Lutz, who with his co-workers has shown that the iron-seeding plan will not work as advertised. Lutz says that the process – which leads to the formation of large carbon-consuming algal blooms – ignores important natural processes, and could play havoc with ocean ecosystems.

Turley referred to field trials carried out in 1999 by an international team of scientists. In the Southern Ocean Iron RElease Experiment (SOIREE), a 50 square kilometre patch of water was seeded with iron to test the enhanced uptake hypothesis. Following the release, the researchers found increased amounts of algal biomass, and that the level of carbon dioxide had decreased from initial levels.

The core hypothesis was validated by the SOIREE experiment, but the key question is what happens to the carbon, and in particular whether it is removed from the atmosphere for the long term. This is the subject of ongoing work, including measurements with the satellite-borne Sea-viewing Wide Field-of-view Sensor (SeaWiFS). This device is designed to monitor ocean colour, which is influenced by such things as levels of phytoplankton and chlorophyll.

Remote sensing techniques such as this can tell us a lot, but in-situ measurements are needed to provide necessary detail. And what we need to know is this: does the carbon sink to the ocean depths, what effect does iron seeding have on ocean ecosystems, for how long is the carbon locked up, and are there any negative consequences?

Turley was very matter of fact in her delivery, but my overall impression was of someone who is sceptical about the claims made for enhanced carbon uptake by ocean fertilisation. For example, we were told about the activities of a private firm – CLIMOS – and its large scale ocean experiment. Turley believes that the company’s activities are ethical, but she referred to the need for a strict code of conduct on the carrying out of such trials. She also spoke of gaps in our knowledge of ocean biological pumps, and of direct ocean sequestration of carbon dioxide.

Potential problems identified by opponents of ocean seeding include increasing acidification of the world’s oceans, and the consequences of carbon dioxide leaking out of the system.

Ocean seeding is not the only area in which algae could be used to mitigate global warming. Turley talks positively about using genetically-engineered algae to produce biofuels. There is a lot money and political capital already invested in biofuels, but many scientists and environmental experts are opposed to using arable land – which is needed to feed an ever-increasing world population – to produce fuels for internal combustion engines. Could algae be the answer?

In her talk, Turley noted that producing biomass with algae is six times more efficient than with arable crops, and her own research group in Plymouth is working on photo-bioreactors for this very purpose. So far, these are only experimental setups, but Turley appears confident that the process can be scaled up to industrial levels.

Of the three scientific presentations at the Royal Society seminar, Turley’s I found the most interesting. However, we are still talking about novel technologies that are years away from real-world implementation, and will therefore not help us deal with the more immediate problem.

To be continued… (see part 1; part 3)