Alt Carbon collects crushed basalt from the Rajmahal mine and spreads it on their tea estates. Photo: Special arrangement
The last thing you would think of is that dust from mining is climate-friendly. But moving the right type of dust to the right place is the core business of Darjeeling-based Alt Carbon, which has secured $500,000 in investment for Carbon Credits. Central to the company’s approach is a geochemical process called rock weathering.
All rocks naturally break down into minerals over thousands of years. The main reason this happens is exposure to rain and high temperatures, a process that results in atmospheric carbon reacting with these minerals (mainly calcium and magnesium) and turning into bicarbonate.
Eventually, they enter the ocean through aquifers or underground streams and rivers, where the carbon is locked for eons.
As a result, the ocean is a major carbon sink, capturing approximately 30% of the carbon dioxide produced by human activities. If left unchecked, this process would take hundreds of millions of years. However, as the amount of carbon dioxide in the air increases, and as agreed by the Intergovernmental Panel on Climate Change, some of the carbon dioxide already in the air will need to be removed by 2050 to keep temperatures above 2 degrees Celsius. Governments and businesses are experimenting with and investing in programs to speed up natural carbon removal processes. This is the effect of “enhanced” rock weathering.
Basalt is a type of volcanic rock that is rich in minerals such as calcium and magnesium. Many areas of Maharashtra and Gujarat, where the volcanic Deccan Traps are located, are rich in basalt, such as parts of Jharkhand and West Bengal, where the Rajmahal Traps are located. The latter is often mined for construction.
“Once this basalt is crushed into a fine powder, its effective surface area is greatly increased. This speeds up the formation of bicarbonate by ten to a hundred times, and can wash into the ocean within a month (depending on the soil, temperature and rivers),” said Dr. Sambuddha Misra, associate professor and expert in chemical oceanography at the Indian Institute of Science, Bangalore. He is also the chief scientist of Alt Carbon.
The company, which grew out of the family-owned tea estate industry, collects tons of crushed basalt from the Rajmahal mine, transports it to Darjeeling, about 200 kilometers away, and spreads it on tea estates in the area.
As an organic fertilizer, basalt dust enriches soil and accelerates carbon sequestration. So far, the company has used about 500 tons of dust. Although it’s still early days, it would take about 3-4 tons of basalt dust to sequester or capture one ton of atmospheric carbon over two to four years. “Normally, it would take 1,000 years for natural basalt to capture this much carbon,” said Shrey Agrawal, CEO and co-founder of Alt Carbon.
Every ton of carbon sequestered in this way counts as a carbon credit. In September this year, the company reached an agreement with Frontier (a consortium composed of McKinsey Sustainability, Alphabet, Meta, Shopify and Stripe) to purchase a batch of carbon sequestered in this way for US$500,000 in advance. Last week, the company signed another agreement with NextGen, a company that aggregates carbon capture from projects around the world, to buy an unspecified amount of such credits at $200 per ton of locked carbon. Carbon credits generated in this way are purchased by companies, which they can use to offset carbon emissions as required by national law. But for now, such purchases are largely voluntary.
While the basic principles of enhanced rock weathering are well established, questions remain about whether the processes used by different companies can accurately measure the claimed carbon sequestration. Analysis by the Carbon Plan research team, which synthesized the existing published literature on the results of weathering experiments, said the differences between 116 such studies spanned “four orders of magnitude”, meaning some projects claimed to have trapped 100 tonnes , while other projects claim 1 million tons are trapped. Factors such as rock, farmland type, and climate have a significant impact on weathering. There are also year-to-year differences, with faster weathering in the initial stages and slower weathering later on. There are also differences in how projects measure sequestration rates.
“We hope to sequester about 50,000 tons in the next few years. The laboratory facility that Dr. Misra has set up is designed to measure these aspects of weathering. We have a protocol called FELUDA with other companies interested in using our method This protocol can be used.
Published – October 20, 2024 at 04:30 AM (US Standard Time)
