Atmospheric carbon dioxide is still rising and looks set to continue rising for decades to come. This makes a limit of a two degrees Celsius temperature increase, compared with pre-industrial times, rather difficult to achieve. Accordingly, we need to urgently implement ways of sucking carbon dioxide out of the atmosphere. This is not the same as carbon capture and storage, which captures carbon dioxide from the chimneys of coal-fired power stations and stores it underground.
There are at least three ways to achieve carbon dioxide removal from ambient air.
One method, described in New Scientist on 21 July 2012, is ocean fertilisation. This involves tipping iron into the ocean. Phytoplankton, floating algae, absorb carbon dioxide out of the atmosphere. When they die, they sink to the seabed taking the carbon with them. Ocean regions which are iron deficient are not providing the nutrients which plankton need to grow. In these regions, carbon dioxide is not being absorbed. Silicon is also needed by the plankton.
A trial reported in the New Scientist article showed that ocean fertilisation can work. At best, however, a global program could absorb about one gigatonne of carbon per year, about one-tenth of current emissions resulting from human activity. According to modelling by Ken Caldera, this is “too little to be the solution, but it’s too much to ignore”.
Another method involves channelling air by fans onto a honeycombed plastic slab, where carbon dioxide, which is acidic, reacts with aqueous potassium hydroxide, which is alkaline. Then the resulting solution of potassium carbonate is filtered before reacting with calcium hydroxide, producing potassium hydroxide along with pellets of calcium carbonate. Heating this to 900 degrees Celsius releases pure carbon dioxide gas which is captured. The principles were first established by Klaus S. Lackner 20 years ago but now Carbon Engineering, founded by David Keith with backers including Bill Gates, has established a pilot plant which extracts a tonne of carbon dioxide from the air per day. (The Economist, 9 June 2018).
But what would we do with the captured carbon dioxide and how much would this all cost? The plan is to turn it back into fuel – which would mean that zero, rather than negative, emissions would be the outcome. This may be worthwhile if the fuel is produced at a competitive price. But with a transition to renewable energy, would the fuel produced be actually needed? And would it be cheap enough to supplant coal, oil, and gas? If the future of the automobile is electric, does this idea have a long-term benefit? If not, what would we do with the carbon dioxide sucked out of the air? The cost of building enough machines to be effective would cost trillions of dollars.
The third way is proven technology and could achieve a significant reduction in atmospheric carbon dioxide, plus it would have many other benefits.
Trees! We have deforested much of the land and now we need to reforest it.
The Economist article dismissively says that achieving the desired reduction would mean foresting an area the size of India and Canada. So what? We don’t have to plant them all in one place! Trees not only soak up carbon dioxide, they provide cooling shade. In addition, they provide habitat for animals and insects and food.
The area of Canada is 10 million square km and the area of India is 3.3 million. The total land area of the world is 149 million. No doubt some of that would not be suitable for tree planting.
Many countries have large land areas and trees can be planted beneficially in cities, on borders of farming areas as well as large areas of land.
China, the US, Brazil, and Australia all have areas comparable with Canada and Russia has even more (16.4 million).
My priority is to contribute t tree planting and it is easy to do. Countries that I have contributed to include Brazil, China, Indonesia, and Australia.
It would be good if Bill Gates contributes too – he has much more money that I and could make a huge difference.