Could part of the answer to saving the Earth from global warming lie in the
earth beneath our feet?
A team from Newcastle University aims to design soils that can remove carbon
from the atmosphere, permanently and cost-effectively. This has never previously
been attempted anywhere in the world. The research is being funded by the Engineering
and Physical Sciences Research Council.
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
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.
The scientists are investigating whether this process occurs as it may encourage
the growing of more plants, crops etc in places where calcium-rich soils already
exist. It would also open up the prospect that bespoke soils can be designed
(i.e. with added calcium silicates, or specific plants) which optimise the carbon-capture
process. Such soils could play a valuable role in carbon abatement all over
The team will first try to detect calcium carbonate in natural soils that have
developed on top of calcium-rich rocks or been exposed to concrete dust (which
contains man-made calcium silicates). They will then study artificial soils
made at the University from a mixture of compost and calcium-rich rock. Finally,
they will grow plants in purpose-made soils containing a high level of calcium
silicates and monitor accumulation of calcium carbonate there.
The multi-disciplinary research team, including civil engineers, geologists,
biologists and soil scientists, is led by David Manning, Professor of Soil Science
at Newcastle University. “Scientists have known about the possibility
of using soil as a carbon ‘sink’* for some time,” says Professor
Manning. ”But no-one else has tried to design soils expressly for the
purpose of removing and permanently locking up carbon. Once we’ve confirmed
the feasibility of this method of carbon sequestration, we can develop a computer
model that predicts how much calcium carbonate will form in specific types of
soil, and how quickly. That will help us engineer soils with optimum qualities
from a carbon abatement perspective. A key benefit is that combating climate
change in this way promises to be cheap compared with other processes.”
Significant scope could exist to incorporate calcium-rich, carbon-locking soils
in land restoration, land remediation and other development projects. Growing
bioenergy crops on these soils could be one attractive option.
“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.”
The 18-month research project “Engineering the Soil Carbon Sink: A Novel
Approach to Carbon Emission Abatement” began in September 2007. It is
receiving total EPSRC funding of just under £240,000.
Tarmac is providing the research team with access to a number of sites in order
to carry out soil assessments. Renew Tees Valley is helping to link the team’s
work to bioenergy crop production. The team will also work with Defra (the Department
for Environment, Food and Rural Affairs) and a number of farmers/landowners
to identify sites for study.
Calcium carbonate is a common, naturally occurring, completely stable mineral
that would not be eroded by rain filtering through the soil. In many soils calcium
carbonate occurs as coatings on pebbles and grains, and as grains associated
Calcium silicates are minerals that occur naturally in many different rocks
and also in artificial materials such as concrete.
*A carbon ‘sink’ is any natural or human activity or mechanism
that absorbs carbon dioxide and removes it from the atmosphere. Soils are the
most significant sink for terrestrial carbon, containing twice as much as in
the atmosphere and three times as much as is held in land plants. Soils can
act as ‘sinks’ for carbon in more than one way – carbon is
held as organic matter derived from plants, and held as inorganic carbonate
minerals whose carbon is derived from what are called plant root exudates. These
exudates are the juices that plants ooze from their roots to corrode minerals
and mobilise the nutrients they need – and it is this process which the
current project aims to exploit.
The potential use of soil to remove atmospheric carbon is analogous in many
ways to the use of reed beds to clean up contaminated water.
CO2 is the main greenhouse gas generally believed to be contributing to manmade