Meeting the Paris agreement goals of reducing carbon emissions to zero by 2050 will not stop climate change. Solving the problem of climate change will require centuries of effort. Unless the carbon that we have already emitted into the atmosphere is removed, then the world will continue to warm, ice will continue to melt, sea levels rise and species will continue to be driven to extinction.
Stopping or reversing the warming of the planet will require removal of very large amounts of CO2 from the atmosphere. But how could this be achieved? We know plants absorb carbon dioxide as they grow. What if we plant more trees? Unfortunately this will not work. There is not enough land on the planet to grow the plants necessary to absorb the carbon dioxide necessary. Fortunately, the earth is not all land. Roughly 70% of the earths surface is ocean and the ocean too contains plant life.
There is one natural carbon sink which if understood and managed better could potentially stop climate change in its tracks: Seaweed.
Ocean plant life has saved the earth death once before. During the Permo Triassic extinction event almost 75% of life on the earths surface died out and 95% of life in the ocean died out and went extinct. The exact causes of this extinction event are still debated but the most widely accepted explanation is massive and sustained volcanic eruptions filled the air with CO2, leading to warming, acidic oceans and a polluted atmosphere. Its thought that the ocean became devoid of oxygen and the skies become thick with CO2 and difficult to breathe.
It was the oceans which were hardest hit, but not everything found conditions tough. for small single celled algae conditions were ideal and the grew and spread across the worlds oceans.
As these algal blooms spread across the oceans and as, the algae grew it produced oxygen. When the individual algae died they sank to the bottom of the ocean and in doing so they took with them carbon from the atmosphere and buried it in the sediments at the bottom of the sea. The biggest concentrations of algae at the time occurred in the shallow Tethys Ocean in what is now Saudi Arabia. These carbon rich sediments over time evolved into the oil deposits that Saudi Arabia enjoys today. There is a concern however, that in burning these deposits and others like them around the world the fossil fuel industry may be recreating the hellish conditions which gave rise to that mass extinction 250 million years ago..
Today the algae is beginning to bloom again. As algae grows it sucks the oxygen out of the ocean forming “dead zones” where other living organisms find it impossible to live. These Dead zones are spreading across the earths oceans. But not all parts of the sea are dying. In one part of the ocean things are growing a little too well. The Sargasso sea is the home to extensive growth of macro algae or seaweed. Unlike most seaweed, the seaweed of the Sargasso is free floating and lives and grows whilst drifting around at the surface of the ocean, unattached to the seabed. It forms extensive matts of growing algae (known as “Sargassum” which provides habitats for a wide range of species including turtles, crabs and fish.
This algae appears to be spreading. The reasons for this are not yet fully understood but the two main culprits are fertilizer runoff and climate change. Increased nutrients, warmer waters and more Carbon dioxide m the oceans could be feeding the growth of Sargassum. This is causing problems for the beaches of Mexico and the Caribbean as huge amounts of dead seaweed wash ashore, blanketing beaches in a rotting stinking mess. The seaweed can reproduce by fragmetation as small pieces break off and grow into more seaweed. One benefit of Sargassum is that it appears to absorb large amounts of Carbon and as some of it dies to takes this carbon to the ocean depths locking it away.
Perhaps this could be used to help us fight climate change? Farming sargassum on a massive scale could make a considerable dent in the carbon problem. The idea would be just to increase the amount of carbon falling to the sea floor but to use the sargassum to abate fossil fuel usage and produce products which result in carbon being locked away from the atmosphere. So what can we do with all this algae? Well quite a lot it turns out. Rotting algae will produce the equivalent of natural gas, which can be burned and used as a fuel. Whilst this might not appear to help reduce carbon emissions remember that in growing the Sargassum has absorbed carbon from the atmosphere so the nett contribution to atmospheric CO2 is zero, its carbon neutral (unlike the natural gas it replaces).
Sargassum has also been used a feedstock to produce liquid fuels such as biodiesel and bioethanol. Again these fuels can be produced in a carbon neutral way and without using any valuable farmland.
But this is not all that can be done with sargassum. I can be used to make animal feed. I turns out that feeding cattle seaweed can not only help feed and fatten them up but it also reduces the amount of methane (a greenhouse gas with nearly 20 times the warming potential of CO2) that they produce.
Sargassum can also be used to produce plastics, but unlike plastics produced from fossil fuels these plastics can be biodegradable allowing them to be composted to produce soil. It is even possible to produce lightweight materials from algae with similar characteristics to paper, cardboard and timber without using any forests.
Farming Sargasso would not require a lot of complexity. large floating barriers, perhaps made from recycled ocean plastic, could be used to corral the material and prevent it being washed ashore. Boats and ships could scoop and harvest the material and transfer it to tankers where it could be stored and processed. Since dead seaweed is just another form of hydrocarbon, it would make sense to utilise as much of the current fossil fuel infrastructure as possible. Following the maxim Reuse, reduce and recycle, oil tankers, refineries and distribution networks could all be converted to handle the vast volumes of sargassum and sargassum products which could be produced from this resource.
Harvesting sargassum, when done at scale, would very likely be cheaper than exploring, drilling and extracting fossil fuels. The greatest advantage of sargassum farming is that it may encourage the fossile fuel industry to switch from fossil to bio fuels and become part of the climate solution rather than just the source of the problem. This might enable the political skirmishes over climate change to become more tractable as interests align.