Applying Crushed Rock to Croplands Reduces Atmospheric CO2, Study Finds

Up to two billion tons of CO2 could be absorbed each year by adding crushed rocks to farmlands. The technique could be employed by countries to help them meet their climate targets.
Jul. 29, 2020
Costas Vasilopoulos

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A new study pub­lished in Nature sug­gests that large-scale dis­per­sion of finely crushed rocks on farm­lands can func­tion as a car­bon diox­ide reser­voir and sig­nif­i­cantly reduce the atmos­pheric amount of CO2.

The tech­nique is known as enhanced rock weath­er­ing and researchers cal­cu­late that when prop­erly deployed, it has the capac­ity to sequester up to two bil­lion tons of CO2 from the Earth’s atmos­phere each year.

See more: Climate Change

The amount of CO2 removed coun­ter­bal­ances the annual emis­sions of the global avi­a­tion and ship­ping sec­tors com­bined or almost half of Europe’s annual green­house gas emis­sions.

Rock weath­er­ing can help nations meet the Paris Agreement objec­tives and limit global warm­ing to less than 2 ºC (3.6 ºF) above the pre-indus­trial lev­els, the researchers noted.

The pro­posed method requires finely grind­ing basalt vol­canic rock and other mate­ri­als from the min­ing and con­struc­tion indus­try and spread­ing the crushed rocks on arable and peren­nial crops.

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Due to its min­eral chem­istry, the rock dust oper­ates as a CO2 seques­tra­tor, absorb­ing the gas from the atmos­phere. The stored car­bon diox­ide is then grad­u­ally con­verted to dis­solved inor­ganic car­bon and is removed via drainage waters.

The largest global emit­ters of green­house gases also exhibit the largest abil­ity to reduce the atmos­pheric CO2 by apply­ing the method, the study deter­mined, due to their exten­sive agri­cul­tural land.

Carbon diox­ide draw­down strate­gies that can scale up and are com­pat­i­ble with exist­ing land uses are urgently required to com­bat cli­mate change, along­side deep and sus­tained emis­sions cuts,” David Beerling, a pro­fes­sor at the University of Sheffield in the United Kingdom and the lead author of the study, said.

Spreading rock dust on agri­cul­tural land is a straight­for­ward, prac­ti­cal CO2 draw­down approach with the poten­tial to boost soil health and food pro­duc­tion,” he added. Our analy­ses reveal the big emit­ting nations – China, the United States, India – have the great­est poten­tial to do this, empha­sis­ing their need to step up to the chal­lenge.”

In Europe, rock weath­er­ing would per­form most effec­tively in Spain and France, offer­ing the means to off­set their green­house gas emis­sions by 40 per­cent.

The cost involved to achieve a two-bil­lion ton decrease of atmos­pheric car­bon diox­ide by 2050 varies between $80 and $190 per ton of CO2 for the big emit­ters, depend­ing on the labor, fuel and elec­tric­ity costs of each coun­try.

Farmers look­ing to add agri­cul­tural lime­stone to their fields to reduce soil acid­i­fi­ca­tion are poten­tial appli­ca­tors of rock weath­er­ing and the exist­ing logis­ti­cal infra­struc­ture can accom­mo­date a fast appli­ca­tion of the method.

The prac­tice of spread­ing crushed rock to improve soil pH is com­mon­place in many agri­cul­tural regions world­wide,” researcher Steven Banwart said. The tech­nol­ogy and infra­struc­ture already exist to adapt these prac­tices to uti­lize basalt rock dust. This offers a poten­tially rapid tran­si­tion in agri­cul­tural prac­tices to help cap­ture CO2 at large scale.”

The study also spec­i­fied that the cre­ation of reg­u­la­tory and incen­tive frame­works is nec­es­sary for the method to suc­ceed and urged the gov­ern­ments to cre­ate inven­to­ries of suit­able rock mate­ri­als.





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