Capturing CO 2 from air

Abstract

Schellnhuber (1) proposed some well-known solutions to the climate problem: i) Phasing out of CO2 in the next decades ii) Energy efficiency iii) Emission reduction iv) Systematic decarbonation v) Efficiency and renewables These suggestions are commendable, but their suggested time scheme lacks realism. The emerging economies (China, India, and Brazil) want to develop their economies and raise the standard of living. A prerequisite is access to abundant and cheap energy. They want to realize their objectives by using their large coal reserves. The climate problem can be solved by removing CO2 from the atmosphere. House et al. (2) state that capturing CO2 from the air costs around $1,000 per tonne. They have obviously not looked at enhanced weathering of olivine. We have shown that enhanced weathering of olivine leads to mineral carbonation at $10 per tonne of CO2 [Schuiling and Krijgsman (3)]. This estimate is based on data for the cost of mining and milling of bulk rocks (4). The crushed rock is then left to nature, without costly add-on technologies to speed up its weathering. Our olivine option is one of the remaining 11 contenders of originally more than 2,600 proposals for the Virgin Earth Challenge to remove 1 billion tonnes of CO2 from the atmosphere. If costs were really around $1,000 per tonne of CO2, as claimed by House et al. (2), the proposal would have been kicked out in the first round. All emerging economies possess many large dunite massifs (rocks consisting of >90% of olivine). Emissions can be compensated for by mining and milling them, and spreading the crushed olivine. Emission reduction or emission compensation is equally beneficial against climate change. Wilson et al. (5) show that crushed magnesium silicates weather rapidly, even in adverse climates, and capture large volumes of CO2 without human intervention. Humanity will be forced to change to reduce its carbon footprint, but the rate of change will probably be dictated by the rate at which fossil fuel deposits become exhausted. The Western industrialized nations should work mainly on emission reduction and renewable energy. The emerging economies should compensate for their emissions by enhanced weathering using their own mineral resources, and thus contribute to solve the problems of climate change and ocean acidification at a very moderate cost and in harmony with the environment. Weathering has operated throughout geological history and brought benefits like fertile soils and climate control, without which life would have been impossible.