UK researchers are amending soils with powdered calcium-silicate (concrete dust) to determine if a carbon fix-boost hypothesis is correct: that crops will be induced to bind extra carbon dioxide, reacting it with calcium taken from the concrete dust (in the soil matrix).
This reaction, whether directed by, or simply mediated by plants and/or soil organisms, would sequester more atmospheric carbon than is possible by production of plant tissue. Good for the climate.
Assuming their work validates plenty of extra sequestration, we think it makes complete sense if the source of calcium-silicate is demolition debris or "rubble". But, it would be idiocy to use commercial concrete that had not gone through a building-product life cycle.
This work conjures up images of abandoned concrete and plastered buildings (as pictured), overgrown by plants busily sequestering C02. Who knew?
Pehaps TreeHugger Lloyd will learn to love concrete in its afterlife...at least a little bit. See: "Sustainable Cement is Like Vegetarian Meatballs"
The concept underlying the initiative exploits the fact that plants, crops and trees naturally absorb atmospheric carbon dioxide (CO2) during photosynthesis and then pump surplus carbon through their roots into the earth around them. In most soils, much of this carbon can escape back to the atmosphere or enters groundwater.
But in soils containing calcium-bearing silicates (natural or man-made), the team believe the carbon that oozes out of a plant's roots may react with the calcium to form the harmless mineral calcium carbonate. The carbon then stays securely locked in the calcium carbonate, which simply remains in the soil, close to the plant's roots, in the form of a coating on pebbles or as grains.
Here's the money quote::
"The process we're exploring might be able to contribute around 5-10% of the UK's carbon reduction targets in the future," says Professor Manning. "We could potentially see applications in 2-3 years, including a number of 'quick wins' in the land restoration sector."
So, who gets the offset credit? The original concrete supplier? Building owner? Farmers?