Land Use and Geo-Engineering - Introduction to Carbon Capture and Sequestration - page 530

the colder climates, or as short as one year in the rainforest of Costa Rica.
The essence of biomass carbon storage is that if a tree dies, a new tree
will grow, and this keeps the CO 2 level constant. If we want to reduce CO 2
levels by growing more trees, the effect is permanent only if one ensures
this forest will fl ourish for many years (see also Question 11.3.1 ).
Question 11.3.1 CO 2 in greenhouses
CO 2 is often used in greenhouses to enhance biomass production. A
farmer has the idea to use the CO 2 from a local natural gas fi red power
plant because the CO 2 will increase the farmer's biomass by 20%. To
fi nance the operation the farmer has the idea of including an annual carbon
credit for the CO 2 he has sequestered. How would you advise him to do
this calculation? Hint: fi nd a country in which carbon credits are issued and
ascertain how the credit regulations defi ne the time scale for carbon
sequestration.
One way to engineer this process is to prevent the decomposition
of biomass. For example, if a tree dies and we then dump it in the deep
ocean, or some other place where we can prevent the natural decom-
position of the tree, we can permanently sequester the carbon. This
sounds like a simple scheme but, as you may have guessed by now,
nothing is simple if we need to carry this out on a scale that impacts the
climate. On such a large scale, one has to carefully analyze the ancillary
impacts. For example, the trees have to be transported and buried; such
processes cost energy and one would like to ensure that the net effect
of the entire process is reduction in the CO 2 levels. The other important
factor is that if trees decompose it is not only CO 2 that is released but
also minerals and nutrients. If these now are buried in the ocean instead
of on land it will create large perturbations of the ecosystems.
An alternative to burying the biomass is to convert it to biochar (see
Box 11.3.1 ). As the carbon atoms in biochar are bound together much
more strongly than in plant matter, biochar is much more resistant to
decomposition by micro-organisms. The fact that biochar has been
found in archeological sites indicates it can be stable for hundreds to
thousands of years. Biochar mixed with soils can improve agricultural
productivity. Converting biomass to biochar can be an alternative to the
burning of biomass in combination with CCS (see Figure 11.3.1 ) [11.8].