The last thing you would expect is that dust from mining would be climate- friendly. But the right kind of dust moved to the right place is the core business of a Darjeeling-based company, Alt Carbon, and has already garnered $5,00,000 in investments for carbon-credit companies. At the heart of the company’s approach is the geo-chemical process called rock weathering.
All rocks naturally break down into minerals over thousands of years. The consequence of this process is that atmospheric carbon reacts with these minerals (calcium and magnesium largely) and becomes bicarbonates. Eventually through aquifers, or underground streams and rivers, they make their way into the oceans where the carbon is locked in for aeons.
The oceans, thus, are the major carbon sinks and capture about 30% of the CO2 from human activities. Left to nature, this process takes aeons. However, with the levels of carbon dioxide building up in the air and a consensus by the tergovernmental Panel on Climate Change that some amount of carbon dioxide already present in the air needs to be removed by 2050, for keeping temperatures from exceeding 2 degree Celsius by the end of the century, governments as well as businesses are experimenting and investing in schemes to accelerate natural carbon removal processes. This is where ‘enhanced rock weathering comes in.
Basaltic rock, a kind of volcanic rock, is rich in minerals such as calcium and magnesium. Many parts of Maharashtra and Gujarat, where the volcanic Deccan Traps are located, are rich in such basaltic rock as parts of Jharkhand and West Bengal where the Rajmahal Traps are situated.
“Once such basaltic rock is crushed into a fine powder, its effective surface area is greatly increased. This accelerates the formation of bicarbonate anywhere from tenfold to a hundredfold and can be flushed into the ocean depending on the soil, temperature and rivers within a month,” said Sambuddha Misra, Associate Professor and expert in chemical oceanography, at the Indian Institute of Science, Bengaluru. He is also the chief scientist at Alt Carbon. The company, which derives from a family-owned teagarden industry, collectstonnes of crushed basalt from the Rajmahal mines, transports it about 200 kilometres to Darjeeling and has them sprinkled on tea estates in the region.
Being an organic fertiliser, the basaltic dust enriches the soil as well as accelerates carbon sequestration. So far, the company has used about 500 tonnes of dust. Though still early years, it takes about 3-4 tonnes of basalt dust to sequester, or trap, a tonne of atmospheric carbon over two to four years. “Normally it would have taken 1,000 years for natural basaltic rock to capture that much car- bon,” said Shrey Agrawal, CEO and co-founder, Alt Carbon. This September, the company entered into an agreement with Frontier, a consortium of McKinsey Sustainability, Alphabet, Meta, Shopify and Stripe, to buy a tranche of carbon sequestered this way in advance for $5,00,000. Carbon credits generated this way are bought by companies and they can use it to offset their carbon emissions, required under their nation- al laws. Currently though, such purchases are largely voluntary.