Scientists devise method to combat climate change using common NZ rock
New Zealand academics have figured out a way to sequester massive amounts of carbon dioxide using a common rock. Sequestering is a method of capturing a material, in this case the climate change gas carbon dioxide, with another material from which it cannot escape. So far, theyve sequestered only a few grams of CO2 in a proof of concept exercise, but it looks theoretically possible to sequester an entire year of manmade CO2 emissions (about 40 billion tonnes in 2020) using a small percentage of the worlds supply of the rock, which is called olivine. Thats a long way off because the scale needed to achieve anything is massive, say the academics leading this research, Allan Scott from the University of Canterbury and Christopher Oze from Occidental College, California. Importantly, the process emits considerably less CO2 than it sequesters and is therefore net positive for the environment, they say. This is true even if coal is burned to produce the necessary energy. READ MORE: * China, the world's top emitter, aims to go carbon-neutral by 2060 * Auckland, Wellington have lowest greenhouse gas emissions per capita * Coal production is sneaking up. How can we kick the habit? This paper represents a major advance in the ability to reduce global CO2 emissions using mineral sequestration, Scott said in an email. The key is a substance called magnesium hydroxide. Scientists have long known that it effectively sequesters CO2. The problem has been finding a large supply. The breakthrough achieved by Scott, Oze and colleagues is identifying a process to extract magnesium hydroxide from olivine. Olivine is a greenish rock thats produced in the Earths crust and pushed to surface by faults or other processes. In New Zealand, theres thought to be a 871 billion tonne deposit in the Red Hills near Nelson. The Semail ophiolite deposit in Oman is many orders of magnitude larger, and olivine is found on every continent. In simplified terms, Scott and Oze ground olivine into a powder, combined it with hydrochloric acid and subjected it to an electrical current. The result was magnesium hydroxide and some byproducts that did not raise concerns or may have economic value. The hydrochloric acid was entirely recoverable, for example, and could be reused. When carbon dioxide and magnesium hydroxide are combined, they produce magnesium carbonates, an inorganic salt that has a variety of economic uses. Scott imagined that magnesium hydroxide would be shipped to a site producing CO2, a coal-burning plant for example. The CO2 would be stripped from the exhaust and exposed to the magnesium hydroxide. The resulting material could be landfilled, injected underground or otherwise disposed of. But the CO2 no longer exists and cant leach out or escape. And now for the scale: Using magnesium hydroxide to remove and sequester anthropogenic CO2 estimated for 2020 (40B tonnes) would require about 105B tonnes of olivine. Reducing global atmospheric CO2 levels by an additional 10B tonnes would necessitate a further 26B tonnes of olivine. Thats about 0.1 per cent of the Oman deposit or 16 per cent of Red Hills deposit. Theres probably enough olivine in Oman to last more than 1000 years. The next step is to scale up to a few kilograms, Scott said in an interview. Theyve applied to protect the intellectual property, published a short paper on the process and now hope experts in other fields will contribute. The simplest solution to global warming would be to reduce CO2 emissions, Oze told an Occidental College publication. But heres a scalable process thats readily available, so that if were collectively willing to operate at the level of magnitude needed, we are ready to sequester and use people-made CO2 at a scale once thought impossible.