Pushing the needle back on billowing carbon dioxide emissions may be necessary to avoid catastrophic warming. But for those who are squeamish about drastically engineering the climate by seeding algae blooms or spraying aerosols to form clouds, scientists are exploring the concept of negative emissions.
The physical science section of the Intergovernmental Panel on Climate Change's fifth assessment report, released last September, suggested that bioenergy with carbon capture and sequestration (BECCS) could effectively remove greenhouse gases from the atmosphere. The assessment also notes that bioenergy that produces char could also take a big bite out of greenhouse gases.
Over the course of 100 years, the report said, BECCS could pull 125 billion metric tons of carbon dioxide from the sky, while biochar energy systems could draw down 130 billion metric tons of the gas. For reference, the world churned out just less than 40 billion metric tons of carbon dioxide in 2013, according to the Tyndall Centre for Climate Change Research at the University of East Anglia.
However, "potentials for BECCS and biochar are highly speculative," the report acknowledged. "BECCS technology has not been tested at industrial scale, but is commonly included in Integrated Assessment Models and future scenarios that aim to achieve low CO2 concentrations."
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