A group of German scientists has now come up with an
environmentally friendly method that they say could do just that. The
technique, dubbed carbon farming, consists in planting trees in arid regions on
a large scale to capture CO2. They publish their study today in Earth System
Dynamics, a journal of the European Geosciences Union (EGU).
“Carbon farming addresses the root source of climate change:
the emission of carbon dioxide by human activities,” says first-author Klaus
Becker of the University of Hohenheim in Stuttgart.
“Nature does it better,” adds Becker’s colleague Volker
Wulfmeyer, “if we understand and can make use of it in a sustainable manner.”
Type of tree
When it comes to sequestering carbon from the atmosphere,
the team shows that Jatropha curcas does it better. This small tree is very
resistant to aridity so it can be planted in hot and dry land in soil
unsuitable for food production. The plant does need water to grow though, so
coastal areas where desalinated seawater can be made available are ideal.
“To our knowledge, this is the first time experts in
irrigation, desalination, carbon sequestration, economics and atmospheric
sciences have come together to analyse the feasibility of a large-scale
plantation to capture carbon dioxide in a comprehensive manner. We did this by
applying a series of computer models and using data from Jatropha curcas
plantations in Egypt, India and Madagascar,” says Wulfmeyer.
The new Earth System Dynamics study shows that one hectare
of Jatropha curcas could capture up to 25 tonnes of atmospheric carbon dioxide
per year, over a 20 year period. A plantation taking up only about 3% of the
Arabian Desert, for example, could absorb in a couple of decades all the CO2
produced by motor vehicles in Germany over the same period.
With about one billion hectares suitable for carbon farming,
the method could sequester a significant portion of the CO2 added to the
atmosphere since the industrial revolution.
But there are more advantages. Carbon farming’s price tag
ranges from 42 to 63 euros per tonne of CO2, making it competitive with other
CO2-reduction techniques such as carbon capture and storage. Further, after a
few years, the plants would produce bioenergy (in the form of tree trimmings)
to support the power production required for the desalination and irrigation
“From our point of view, afforestation as a geoengineering
option for carbon sequestration is the most efficient and environmentally safe
approach for climate change mitigation. Vegetation has played a key role in the
global carbon cycle for millions of years, in contrast to many technical and
very expensive geoengineering techniques,” explains Becker.
The main limitations to implementing this method are lack of
funding and little knowledge of the benefits large-scale plantations could have
in the regional climate, which can include increase of cloud coverage and
rainfall. The new Earth System Dynamics paper presents results of simulations
looking into these aspects, but there is still a lack of experimental data on
the effects of greening arid regions. Also, potential detrimental effects such
as the accumulation of salt in desert soils need to be evaluated carefully.
The team hopes the new research will get enough people
informed about carbon farming to establish a pilot project. “We strongly
recommend more emphasis is put on this technology – at both small and large
scales – and that more research is done to investigate its benefits in
comparison to other geoengineering approaches,” concludes Wulfmeyer.