Science

CO2-capturing rock dust boosts crop yields by up to 16%

CO2-capturing rock dust boosts crop yields by up to 16%
The application of dust produced via "enhanced rock weathering" has been found to significantly increase soybean and maize yields
The application of dust produced via "enhanced rock weathering" has been found to significantly increase soybean and maize yields
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The application of dust produced via "enhanced rock weathering" has been found to significantly increase soybean and maize yields
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The application of dust produced via "enhanced rock weathering" has been found to significantly increase soybean and maize yields
Dr. Dimitar Epihov inspects soybeans in one of the test plots
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Dr. Dimitar Epihov inspects soybeans in one of the test plots

The application of crushed rock to farmers' fields may not only reduce greenhouse gases, it could also boost crop yields by up to 16%. These are the findings of a new study conducted by scientists from the University of Sheffield’s Leverhulme Centre for Climate Change Mitigation.

The research actually builds on a previous U Sheffield study that we heard about back in 2020. At that time, scientists were analyzing the effectiveness of a technique known as enhanced rock weathering.

In their natural state, rocks naturally absorb atmospheric carbon dioxide as they break down in the environment. The greater the number of pieces they break down into, the greater the total surface area available for carbon sequestration, and thus the greater the amount of CO2 that can be absorbed.

Most rocks take a long time to fall into small pieces on their own, however. Additionally, in order for all those pieces to absorb CO2, they have to be laid out across a large area where they're all exposed to the atmosphere. That's where enhanced rock weathering comes in.

The process involves mechanically pulverizing rocks down to the consistency of dust, then spreading that material across agricultural fields. Farmers wouldn't necessarily have to spend any extra time doing so, as the dust could be spread alongside fertilizers or other additives that were already being applied to the fields anyway.

In the 2020 study it was determined that if practiced on a global basis, enhanced rock weathering could draw up to 2 billion tonnes (about 2.2 billion tons) of carbon dioxide from the atmosphere every year. For a bit of context, that's significantly more than the amount of CO2 emitted annually through global aviation and shipping combined.

The rocks could be obtained from sources such as mining operations, and farmers could be financially incentivized to use the dust on their fields. And if the money isn't enough on its own, then the promise of higher yields may help.

Dr. Dimitar Epihov inspects soybeans in one of the test plots
Dr. Dimitar Epihov inspects soybeans in one of the test plots

The new study was conducted over a four-year period at the University of Illinois Energy Farm, on fields in which maize and soybeans were grown on a rotating basis. Some plots in those fields were left untreated to serve as controls, while others had the basalt dust applied at a rate of 50 tons (45 tonnes) per hectare every year.

It was ultimately found that yields of the treated plots were 12-to-16% higher than those of the controls.

This outcome was due mainly to the fact that the basalt raised the soil's pH, which in turn boosted the plants' ability to take up nutrients already present in the soil. Additionally, as the basalt disintegrated in the soil, it released nutrients of its own such as phosphorus, potassium and calcium.

As an added benefit, plants from the basalt-treated plots were higher in micro- and macronutrients, increasing their nutritional value for both humans and livestock. The carbon sequestration effect was also confirmed – it's now believed that application of crushed rock dust can remove about three to four tonnes of atmospheric carbon dioxide per hectare per year.

"We have shown with hard-won data, the carbon removal potential of enhanced weathering practices in the real world," said the lead scientist, U Sheffield's Prof. David Beerling. "It’s a big step forward in understanding the enormous potential of this technology to mitigate climate change while simultaneously improving yields and soil health."

A paper on the research was recently published in the journal Proceedings of the National Academy of Sciences.

Source: University of Sheffield

10 comments
10 comments
Robt
Serious science at its best
Captain Danger
Some questions come to mind.
1) how much CO2 is required to crush , transport and apply the rock
2) what are the projected long term effects on the soil
3) are the effects the same on all soils or in some cases with ll the effect be neutral or detrimental?
ArdisLille
Does this mean all our frivolous backyard lawns might have potential to be actually helpful?
TechGazer
Captain Danger beat me to it. It seems a lot of companies want money for their CO2 reduction or sequestration process ... without mentioning how much CO2 the process releases. Crushing rock into powder seems pretty energy-intensive, plus the energy needed to produce the crushing equipment and replace the worn parts. The rock or dust also has to be transported, which is more energy consumption. How many of these processes or techniques are really just passing the buck on to someone else?
Doug Lough
“Enhanced Rock Weathering” Aka pulverized stone. Why the fancy name?
SamH
Rock dust can be quite hazardous (eg silicosis). One would hope that hasn't been overlooked in the quest for carbon rebates.
Ripper
It costs about $1200,- AUD to spread 50 ton/ha of any dry granular material. Add to that all the transport, processing and storage of a huge amount of rock. 50ton/ha means a single B-double combination full of crushed rock for every hectare. Input cost per hectare is likely well above $3000,- AUD, far to high to receive a reasonable return on investment time frame. Not to mention the cost of wear and tear on machinery to process and transport these large amounts. Nice idea, not practical nor economically viable.
Expanded Viewpoint
WHY would anyone want to introduce something into our crops that steals CO2 away from them? The crop yield increases are due to the re-mineralization of the soils the crops are being grown in, NOT from some fancied idea that CO2 is bad for plants and thus must be kept away from them! When plants take in CO2, they use it as part of their food source! Plants give off Oxygen, which all animal life depends upon!
How much CO2 is generated and released into the atmosphere in the process of smashing big rocks into little ones? Then you have the CO2 that is released into the air by the trains and trucks that are used for getting it to the farm lots, where Carbon fueled machines spread it around. This is just some more claptrap ginned up by mis-informed climate alarmists.

Randy
Treon Verdery
an alternative technology to heighten crop yield with mineral microdust is to have a thing like a piezoelectric, ultrasound emitting ceramic element on the plow blade or discing blades. Just like 90 watt ultrasonic cleaners can disintegrate things, the piezo element disintegrates the gravel and mineral chunks already at the soil. That makes pH adjusting mineral dust right on-site. Noting that making the mineral microdust out of the mineral chunks pre-existing at the field saves all the energy of transporting minerals from mines.
Rabbit
It’s called “Enhanced Rock Weathering” because we are imitating a process that happens naturally. Basalt rocks are formed when lava cools quickly and at a certain temperature range, it is very common all over the world. We have many Basalt rocks quarry’s all over the world and machinery used to pulverize the stone I would not be overly worried about not being able to produce smaller stone and rock dust using to much fossil fuels the amount of carbon that can be sequestered is huge. Basalt is rich in minerals like calcium and magnesium. When these minerals are exposed to water they react with CO2 in the air. With the chemical reaction the carbon is stable. Just doing my best to answer some of the folks with concerns. I think this Is a cool idea because anyone spread rock dust and as soon as it gets rain the process starts. This does raise the Ph of the soil but in time it should be lowered as rain also over times make the soil acidic again.