..Two papers published last week debunk the idea of planting large volumes of trees to pull carbon dioxide out of the air — saying there just isn’t enough land available to pull it off — and also various other strategies for “carbon dioxide removal,” some of which also include massive tree plantings combined with burning their biomass and storing it below the ground….
…Boysen and her colleagues find the land space that would be required for the amount of trees necessary to keep temperatures within a 2-degree threshold under our current climate trajectory could have “dire consequences for food production or the biosphere.” And even under more optimistic scenarios, where future carbon emissions are lower and fewer trees would be necessary, they conclude that “high inputs of managed water and fertilizers would be needed in order to avoid fierce competition for land — with potentially negative side-effects for climate and society.”
…The solution that’s been proposed in numerous reports and climate models… is a technology known as bioenergy and carbon capture and storage, or BECCS. This strategy involves establishing large plantations of fast-growing trees, capable of storing large quantities of carbon, which can then be harvested and used for fuel. Biomass burning facilities would need to be outfitted with a special carbon-capturing technology, which would capture the carbon dioxide produced and store it safely away, potentially in geological formations deep underground. It’s an ambitious proposal, and one that many scientists have pointed out is nowhere near the point of becoming feasible, even from a technological perspective….
Lena Boyson et al The limits to global-warming mitigation by terrestrial carbon removal Earth’s Future (AGU) May 17 2017
- Plain Language Summary: In 2015, parties agreed to limit global warming to “well below” 2°C above pre-industrial levels. However, this requires not only massive near-term greenhouse gas emissions reductions but also the application of “negative emission” techniques that extract already emitted carbon dioxide from the atmosphere. Specifically, this could refer to the establishment of extensive plantations of fast-growing tree and grass species in combination with biomass conversion to carbon-saving products. Although such deployment is seen as promising, its carbon sequestration potentials and possible side-effects still remain to be studied in depth. In this study, we analyzed two feasibility aspects of such a negative emissions approach using biomass plantations and carbon utilization pathways. First, we show that biomass plantations with subsequent carbon immobilization are likely unable to “repair” insufficient emission reduction policies without compromising food production and biosphere functioning due to its space-consuming properties. Second, the requirements for a strong mitigation scenario staying below the 2°C target would require a combination of high irrigation water input and development of highly effective carbon process chains. Although we find that this strategy of sequestering carbon is not a viable alternative to aggressive emission reductions, it could still support mitigation efforts if sustainably managed.