ANALYSIS: ERW has large potential to scale, but logistics key, say developers
Quantum Commodity Intelligence – Terrestrial enhanced rock weathering, the process of spreading basalt and other types of crushed rocks on farming land to capture carbon dioxide (CO2), has the largest potential to scale among CO2 removal (CDR) technologies, argue its proponents.
However, the process involves complex logistics that have yet to be fully ironed out and is dependent on a few suppliers and uncertain monitoring and reporting, which has curbed funding to the space, they also said.
The technology, known among its practitioners simply as 'ERW', has become associated in the past year with large fundraises from the likes of Eion ($12 million) and Undo (also $12 million), currently the two largest companies in the space, and a host of other startups.
Several ERW companies have also signed deals with tech-enabled fund Frontier (Alkali Earth, EDAC Labs, Carbon To Stone, Mati, Inplanet, Lithos, Travertine) to get their projects off the ground.
Meanwhile, US NGO CarbonPlan has identified ERW as the CDR technology with the largest potential to scale, the best "social license" because of associated
co-benefits, such better soil fertility, and one that is at least as permanent as direct air capture and bioenergy with carbon capture and storage, at 1,000 years or more.
Rock weathering occurs naturally and is estimated to remove at least 1.1 gigatonnes of CO2 equivalent a year, but scientists say they can "compress" the process from millions of years to one to four years by selecting the best material, applying the material to optimal soils and increasing the surface area covered.
Relatively new CDR
"When people talk about carbon removal, they usually start their list with direct air capture, then maybe biochar and forestry, maybe soil carbon and bioenergy with carbon capture and storage come next," said Eion's Tim Preisenhammer during a recent forum organised by registry Puro.earth. "ERW is still relatively new to the field as a carbon removal method, but I actually think that ERW deserves much more attention," he said.
"Our process mineralises carbon, leading to high permanence, but unlike other means of carbon removal, it also scales very quickly. So to put it simply, with ERW, you get the all-important permanence of a tech-based carbon removal approach with the scalability of a nature-based approach," he added.
Eion uses a mineral called olivine mined in Norway, ships it to the US state of Mississippi, then spreads it on farm land thanks to partnerships with local agricultural product suppliers and farmers – giving it access to 1 million acres of land – and then measures the removal of CO2e.
The company received a big boost earlier in the year when its Norwegian olivine supplier Sibelco re-commissioned a mothballed rock crusher, enabling it to scale up "immediately" the supply of rock.
"The beauty of enhanced rock weathering is its simplicity. We do not need any first-of-a-kind machinery all we do is source the rock, pulverise it using existing technology, transport it, put it on fields, and measure the carbon removal," said Preisenhammer.
The logistics are complex enough, but the monitoring, reporting and verification (MRV) is still subject to some debate and firms in the space have all invested heavily in their own research and development as well as their own protocols, they said. This was recognised in the first methodology for the sector, developed by Puro.earth, which was published last year.
The Finnish registry has said it hopes that, over time, uncertainties will be ironed out as capacity increases. "Quantification of how much carbon is removed through ERW at a point in time is challenging. This is due to a small change in the measurable weathering result (signal) relative to the underlying background result and the slow nature of the process in soil under natural environmental conditions," said Puro.earth.
More data
"Over time, ERW projects will collectively develop large data sets that will allow for the refinement and validation of quantification approaches to calculate the removed volumes, along with many other of the core aspects of this methodology."
ERW companies said Puro.earth has chosen a conservative approach, where the amount of carbon credits (CORCs) issued at a given time are based on the amount of CO2 sequestration that has already happened.
While this was done for understandable reasons, "this makes it particularly hard to finance projects," said a source at one of the ERW companies.
The source also noted some limitations on spreading crushed rock on land in certain geographies, such as Western Europe, due to existing regulations, while the largest CO2 capture potential is currently thought to be in the southern hemisphere.
Meanwhile, UK-based standard Isometric confirmed to Quantum it is working on its own ERW methodology to be released soon.
ERW carbon credit prices
The cost of the carbon credits marketed by the sector's companies has been high, at between $120 and $530/tCO2e for advanced market commitments, which has put off many carbon credit buyers.
"We have all the pieces together. We have rock, we have fields, we have a way of crushing it, and we have our measurement process. What we're looking for now is offtake agreements to help us put all the pieces together," said Eion's Preisenhammer.