MITIGATION DETERRENCE.

On this score, the constraints would indeed be few: ample geological stores wreathe the planet, not least its two largest economies, the US and China. The current consensus in the literature and ‘space’ alike is that storage capacity does not pose a limit to sequestration. There is enough room in the crust to fill it several times over with the stones from the past two centuries. But, again, getting the CO2 into this state would not come without energy expenditure; depending on a number of variables – notably the need to grind or crush or otherwise treat the rock to make it more absorbent – mineralisation could add its own hunger to the general demand.114 DAC plants would be built with steel and cement. They would require minimal land compared to BECCS, but build tens of thousands of them and they will certainly leave an imprint. Count in the land required to generate the required solar or wind energy, and the imprint quickly multiplies.115 Where would all the sorbents come from? Some are currently made with feedstock from fossil fuels; others are derived from renewable materials; none involve rare elements, but much of the minutiae is kept in the dark from science and society, as the start-ups obtain a competitive edge from the sorbents and jealously guard their secrets. How will they be disposed of when no longer recyclable? Heaps of those chemical sieves might be left lying around. When manufactured out of brine, they generate chlorine as a byproduct: how would several gigatons of that poison gas be dealt with? It became infamous as a chemical weapon courtesy of Fritz Haber and I.G. Farben. Ineluctably, an infrastructure on this scale – planetary by design and definition – will produce side effects in the biosphere.