Can seaweed combat climate change?

The United Nations Intergovernmental Panel on Climate Change (IPCC) has just released a report on the current state and predictions of anthropogenic climate change as a followup to the Paris Agreement. The Paris Agreement was an international treaty, pending ratification, with the goal of preventing the average global temperature from reaching 1.5 C above pre-industrial levels. The IPCC laid out the global consequences if the 1.5 C threshold is exceeded. The results were not good: sea level rise, ocean acidification, species extinctions, increasing storm frequency and intensity (as we watch hurricane Michael make landfall less than 1 month after hurricane Florence). The IPCC stated that if we can’t develop technology to remove CO2 from the atmosphere these scenarios will come to fruition sooner than previous studies indicated.

The oceans act like a giant CO2 sponge and over 1/3 of anthropogenic CO2 is absorbed into the sea. Increasing CO2 in the ocean causes the water to become more acidic. Ocean acidification has strong negative effects on a number of organisms, especially calcifying or shell building animals. The IPCC is focused on removing CO2 from the atmosphere, but perhaps taking CO2 out of the oceans would also be a key strategy in reducing anthropogenic climate change.

Could seaweeds be used to take CO2 out of the ocean? Like terrestrial plants, algae uses the process of photosynthesis to take up CO2 and release oxygen, locking carbon away in it’s tissues. This idea of decarbonization by algae has been tested by a group in Korea, and they found that they could use natural or constructed kelp beds to take up and store 10 tons of carbon per hectare every year. Another research team made a rough calculation that global macroalgae could pull down up to 268 million tons of carbon per year.

The problem with using macroalgae for carbon storage is that algal tissues will eventually break down and through bacterial decomposition CO2 will be re-released. There have been a few ideas of what to do with all the carbon sequestered in seaweed: some suggest sinking it to the bottom of the ocean while others say to use it as a bio fuel to reduce the use of fossil fuels.

Reducing emissions will go a long way in avoiding many of the doomsday scenarios, but doesn’t address the current and near future ocean acidification issues. While seaweed can’t solve climate change, it will undoubtedly play a major role in curtailing CO2 within the oceans.