From sugar plantations in Brazil to tea plantations in India, gravel rocks are sprinkled on large tracts of farmland around the world to combat climate change.
Called Enhanced Rock Weathering (ERW), the technology is designed to accelerate the natural capture and storage of carbon dioxide – a warm greenhouse gas.
It could be that large enterprises, technology giants, airlines and fast fashion companies line up to buy carbon credits from ERW projects to “offset” or cancel their own emissions.
– What is ERW? –
ERW is designed to turbocharge natural geological processes called weathering.
Weathering is the collapse of carbonic acid on rocks, which forms when carbon dioxide in the air or soil dissolves in water.
When rainwater falls on the rock, weathering occurs naturally, and the process can lock carbon dioxide into bicarbonate from the air or soil, ultimately limestone.
ERW increases the speed of the process by using fast rocks like basalt (basalt), which are ground to increase their surface area.
– How effective does ERW have? –
ERW is still a fairly new technology and there are questions about how much carbon it can remove.
An American study found that applying 50 tons of basalt on one hectare per year may have up to 10.5 tons of carbon dioxide per hectare over four years.
However, scientists have much lower removal rates of basalt applied to oil palm fields in Malaysia and sugar cane fields in Australia.
“Field trials show that the number and interest rates of capture have been overestimated,” said Paul Nelson, a soil scientist at James Cook University.
Rates depend on variables including rock type and size, moisture and heat of the climate, soil type and land management.
Measuring captured carbon is difficult.
The most popular technology measures “cations”, which release positive and negative ions from the rocks during weathering.
But these cations are produced no matter what acid the rock reacts to.
“If there are acids that are stronger than carbon, it will react with those acids,” Nelson said. So, even if carbon dioxide is not captured, measurable cations will be produced.
Wolfram Buss, a researcher at the Australian National University of CO2 removal, said that this does not mean that ERW is meaningless, it just requires careful calibration and measurement.
“There is no doubt that this technology works,” he said.
“But, to make sure we actually remove how much carbon dioxide, it takes more money to do basic research.”
– Are there any other benefits? –
The increased rock increases soil alkalinity, which can enhance crop growth, soil nutrients and soil formation.
Basalt is both natural and abundant and is often a by-product of quarrying, thus reducing the cost of the process.
Experts point out that even if the rock reacts with other acids in the soil, it fails to lock down carbon dioxide at that stage, it can still have planetary benefits.
This is because otherwise, the acid in the soil will eventually wash away rivers and oceans, causing carbon dioxide release during acidification.
If rocks neutralize this acid in the soil, “you have prevented carbon dioxide from being released from the water into the atmosphere downstream,” Nelson said.
However, the size of the people who may “block” emissions is unclear.
– What are the risks? –
ERW is widely considered safe because it speeds up only existing natural processes. However, some fast rocks have high levels of potentially toxic heavy metals.
Scattered ground rocks also require appropriate protective equipment.
But the main risk is that false measurements overestimate the captured carbon.
Some projects have sold carbon credits from ERW. If a company purchases ERW credit to “offset” its emissions, but the process captures less than expected, it can lead to higher net carbon dioxide.
– Where to complete ERW? –
Projects are in most parts of the world, including Europe, North America, Latin America and Asia.
Earlier this year, a project in Brazil announced that it has provided the first ever proven carbon-driven credit from the ERW project.
The process is being used or tried in tea gardens in Indian soybean and soybean and corn fields.
– What are the investors’ interests? –
An ERW startup – Mati Carbon, who works in India – received a $50 million carbon removal project award earlier this year.
In December, Google announced the world’s largest ERW deal at the time, removing credit lines at 200,000 tons of carbon and was provided by Startup Terradot in the early 2030s.
The cost of the transaction was not disclosed, but Terradot had a separate agreement with companies representing H&M to sell 90,000 tons for $27 million.
SAH/CWL/PST
