Enhanced rock weathering—a nature-based carbon dioxide removal process that accelerates natural weathering—results in significantly higher first year crop yields, improved soil pH, and higher nutrient uptake, according to a paper, published in PLOS ONE on 27 March.
Enhanced rock weathering (ERW) involves spreading finely crushed silicate rock such as basalt on agricultural land. It is a scalable and permanent climate technology with the potential to sequester gigatons of carbon dioxide from the atmosphere.
Co-authored by scientists at UNDO, a leading enhanced rock weathering project developer, and Newcastle University, the article is the latest enhanced rock weathering (ERW) study assessing the impact on crops in a temperate climate.
Professor David Manning, Professor of Soil Science, Newcastle University School of Natural and Environmental Sciences, and co-author of the paper, commented, “The results of this trial give further scientific credibility for enhanced rock weathering and greatly improve its value proposition to farmers. Newcastle University is pleased to partner with UNDO. Our joint research into the co-benefits for farmers of basalt amendment is helping to pave the way for the widespread adoption of enhanced rock weathering in the agricultural community.”
Yit Arn Teh, Professor of Soil Science, Newcastle University, and co-author of the paper, said, “Independent bodies, such as the IPCC and UK Committee for Climate Change, have repeatedly highlighted the urgent need for climate action in the agriculture and land use sector to counter the effects of dangerous climate change. At the same time, the agricultural sector is under increasing pressure to meet key sustainability and environmental targets, against a backdrop of rising farm operating costs, driven by the cost of living crisis.
Scientists have come up with several ideas to make rocks combine with carbon faster.
The simplest is to grind the rocks up, making a fine gravel or dust that reacts more easily with the air or water. Olivine, for instance, is a very common rock below the Earth’s crust, but a rare one on the surface because it weathers so quickly. In theory, olivine dust spread on beaches or in the ocean would break down in a matter of years, locking up carbon as it dissolves. (This might also help address ocean acidification, by taking up some of the excess carbon that is making the seas more acidic.)
Basalt is another candidate for this kind of enhanced weathering. In some experiments, farmland treated with ground basalt not only captured carbon, but also grew more crops as the basalt helped the soil hold onto needed nutrients.2
Other ideas for enhanced weathering try to speed up the chemical reactions involved. This might be done by adding chemical catalysts, or living things like bacteria or lichens—anything that eases the path for carbon to bind with elements in the rock.
Dubbed the mother rock, basalt is a volcanic mineral and one of the most abundant on the planet. This makes it the obvious one to scale, says Beerling, especially as it is so rich in both the elements needed to capture carbon – calcium and magnesium silicates – as well as nutrients such as phosphorus and potassium for crops.
Olivine, a common mineral in the earth’s sub-surface that is mined across the globe, also has its champions, and Eion Carbon, opens new tab is one of several companies looking to harness its sequestering powers. In the U.S. it has been approved as a soil improver since the 1940s, despite the fact, says Beerling, that it can contain both chromium and nickel, and is mined alongside asbestos, none of which would be welcome in the food chain.
For centuries farmers have been amending the soil with rock
minerals to improve fertility. Rock minerals are rich in many of the
nutrients that are needed to support healthy soils and can benefit soil
water availability for crops. Some of the vital nutrients found
naturally in rocks include calcium, magnesium, potassium and
phosphorus, and micronutrients like zinc and iron. Recently, farmers
have been exploring how different rock minerals can be applied to the
soil to improve soil health, boost crop yields, and sequester CO2.
The breakdown of rock, referred to as weathering, naturally consumes
CO2 from the atmosphere through the weathering reactions of
silicate minerals in the rock. When rock is pulverized into a powder,
the reactive surface area increases which effectively speeds up the
natural weathering process, leading to greater CO2 drawdown.
Limited studies show that when some types of pulverized silicate
rocks are applied to agricultural soils as amendments, they can
provide co-benefits to growers in addition to sequestering carbon.
The new model simulated enhanced rock weathering on 1,000 agricultural sites around the world under two emissions scenarios from 2006 to 2080. They found that in the 75-year study period, those agricultural sites would draw down 64 gigatons of carbon dioxide. Extrapolating that to all agricultural fields, representing the world’s total potential application of this strategy, up to 217 gigatons of carbon could be sequestered in that time period.
“The latest IPCC report said we need to remove 100 to 1,000 gigatons of carbon by 2100 in addition to steeply reducing emissions to keep global temperature from rising more than one and a half degrees Celsius,” said Baek. “Scaling up to global croplands, the estimates of carbon removal we found are roughly comparable to the lower end of that range needed to have a fighting chance of meeting those climate goals.”
Because weathering progresses more quickly in hot and wet environments, enhanced rock weathering would work more quickly in tropical regions than higher latitudes, the study highlights. Farmers and companies looking to invest in carbon drawdown solutions make cost- and carbon-efficient choices by targeting basalt application in tropical fields.
The model revealed another promising result: Enhanced rock weathering works just as well, if not a little better, in warmer temperatures. Some other carbon drawdown approaches, such as those that rely on soil organic carbon storage, become less effective with continual warming.
My local organic certified fertiliser company produces, and I use, a fertiliser made of composted fish waste, limestone, trace elements and basalt dust and I’m happy with its performance.
BUT, the fish waste is produced by an unsustainable industry that is strip-mining the sea and I worry a LOT about how must energy is needed to grind to a powder the tonnes of basalt and limestone for the final product. I don’t doubt the science behind enhanced weathering, what I have never seen in any of the paeans to its efficacy, is what kind of CO2 debt it carries onto the ground
Like every other industrial process, we hope any production of mineral dust in the future will be powered by clean energy sources. True for steel, EVs, solar panels and wind turbines.
That’s exactly my problem with it.
What will it take in industrial and energy use, and CO2 production over what timeline, and at what scale, to get to the start of the timeline in the graphic that says, “farmers spread rock on their pasture”? In the past, basalt powder would have been a by-product of other processes such as making graded gravel for macadam roads, but to make it deliberately for this purpose, on a scale big enough to make a difference to atmospheric CO2 is never part of the conversation.
I went through this with biochar, which I also make and use, years ago, it too was going to save the planet according to some people who should have known better
Like precision fermentation, it always seems to start at “so once we have everything organised, this is how it works”, but we don’t have everything organised, we haven’t even started organising most of it.
Getting significant amounts of basalt and olivine powder onto soil would be a huge effort. I can’t help but speculate about separating basalt powder from dark lunar soil and lofting it out to orbiting and fall to the Earth. Using PVs with no atmosphere to inhibit the sunlight reaching them to power magnetic launch of the material. It would have to be cast out in containers because clouds of abrasive dust would grind down every satellite it came in contact with.
Fun to speculate however inaccurately but the effort and energy involved would be far more productive addressing CO2 emissions on Earth.
I don’t think anyone is suggesting moon dust.
Plenty of basalt here.
Yes. My idle speculation is a result of reading all sorts of SF as a kid.