The Importance of Carbon-negative Bioenergy
Representatives from every country on Earth met in Paris in 2015 to re-affirm the goal of limiting climate change to 1.5 – 2 C, as part of the United Nations Framework Convention on Climate Change process. Despite the commitments achieved at that meeting, the challenge is a daunting one. Global greenhouse gas emissions have typically followed worst-case-scenario projections (though recent reductions in the US and China offer some room for optimism). The math of 2 C is still staggering, and any climate stabilization will involve technology improvements across all sectors of the economy. Most projections now assume that we will exceed cumulative emissions thresholds, and will have to take carbon dioxide out of the atmosphere in the future to compensate
Various concepts for such ‘carbon dioxide removal’ or ‘negative emissions’ technologies have been proposed, but the most promising involve bioenergy – the production of fuels, electricity, or heat from biomass. How does this work? Plants absorb CO2 from the atmosphere as they grow, and that carbon is then cycled back to the atmosphere once those plants die and decay, or are consumed by herbivores. Carbon negative bioenergy involves harvesting biomass, extracting usable energy from it, and then preventing some of that carbon from returning to the atmosphere by either pumping CO2 into geological storage underground (Bioenergy with Carbon Capture and Storage, or BECCS), or by storing the solid by-products of bioenergy conversion in soils (e.g., biochar).
Most climate stabilization scenarios suggest that we’ll need to widely deploy such technologies over the next decades to reach the 2 C goal, to the point where on the order of 20% of all human energy use is coming from a carbon-negative bioenergy system. There is great controversy on whether this is possible within the scientific community – it has been called the “World’s Biggest Gamble”, and researchers have questioned the viability and sustainability of such technologies, and whether they might be a distraction from the hard work of reducing emissions. However, interest in the topic is growing in both academic and industrial circles. The world’s first commercial-scale BECCS operation was recently inaugurated at a corn ethanol biorefinery in Illinois that had previously sequestered one million tons of CO2 in a successful technology demonstration, and biochar production companies are proliferating in both the US and Europe.
Other Links & Resources:
- Vox: Can we build power plants that actually take carbon dioxide out of the air?
- CarbonBrief: 10 ways ‘negative emissions’ could slow climate change
- University of Michigan Energy Institute Beyond Carbon Neutral initiative
- Arizona State University Center for Negative Carbon Emissions
- Center for Carbon Removal