Simply ramping up the deployment of bio-energy with carbon capture and storage (BECCS) may not be enough to guarantee an acceleration in meeting climate targets. Analysis based on a complex set of Earth system models shows that achieving net negative carbon dioxide emissions is also strongly linked to the geographical location of bio-energy feedstock.
The study draws attention to the importance of maintaining tropical forests and their vital role as carbon sinks. Allowing deforestation in the tropics to facilitate large-scale BECCS appears to tip the balance towards higher atmospheric concentrations of carbon dioxide near the end of the century.
Run using high-performance computing facilities in Norway, the analysis illustrates that the trade-offs and side effects of growing bio-crops must be evaluated on a global scale to provide the full story.
“We need to assess this technology from all angles,” said Helene Muri, who started the project when at the University of Oslo and is now based at NTNU. “The findings of my study show how tricky it could be to apply BECCS in the ‘right’ way.”
Muri points out that of the 400 Intergovernmental Panel on Climate Change scenarios that have a 50% or better chance of less than 2°C warming, 344 assume the successful and large-scale uptake of negative emission technologies such as BECCS. Guidance on where to place bio-crops will be a key input.
Muri’s study focuses on the climate response of two different large-scale BECCS deployment scenarios. The first involves increased harvesting for BECCS predominantly through re-planting on abandoned agricultural sites. In the second scenario, bio-crops grow in cleared woodland – largely in tropical and extra-tropical areas, including Africa, east Australia and South America. In the simulation runs, the projects are estimated to cover between four and five percent of the non-glaciated land surface by 2100.
“About half a million CPU hours were used to generate the data for this study using the Norwegian Earth system model, which took several weeks to complete on multiple processors,” said Muri. The fully coupled simulations feature an interactive carbon cycle and include the effects of climate on crop yields.
But the opportunities don’t stop there. “There is also a need to assess the more regional details of BECCS, and how different feedstocks can be best used in different areas,” Muri said.
Muri reported her results in Environmental Research Letters.