FAQs Land Use & Agriculture
While they are growing plants take carbon dioxide out of the air, release the oxygen and store the carbon. When they die and rot or burn the carbon is released back into the air.
It is possible to increase the amount of carbon locked up at any one time by increasing the amount of living biomass in existence- for example by planting forests. While these are growing they are a carbon ‘sink’- removing carbon dioxide from the air. Over time a new equilibrium level will be reached, at which stage they become a carbon reservoir.
It is also possible to increase the amount of carbon locked up by interrupting the cycle half way through and preventing the dead biomass from rotting or burning, for example by turning wood into preserved human artefacts. In this form sequestered carbon can accumulate over time.
A lot of carbon from plants is also stored below ground in soils. It is sometimes possible to increase the amount of carbon stored in soils by changing land management practices, but as with above ground biomass, this cannot continue indefinitely. At some point a new equilibrium level is reached.
However, an exception appears to be if biomass is turned into charcoal by heating it in conditions of limited oxygen before it is returned to the soil. In this form micro-organisms have difficulty breaking it down and turning it back into carbon dioxide, allowing it to build up to a greater degree over much longer time frames. This technology is called “biochar”.
We use all of the techniques described above. New forests are planted, soil sequestration is increased through better management practices, biomass is grown and then used as building materials and also stored in engineered biomass silos, and biochar is created and incorporated into soils.
In the scenario there is a 90% reduction in greenhouse gas emissions relative to today’s levels. This sequestration is required to cancel out the remaining 10%.