Tuesday, October 16, 2018

Carbon Capture: BECCS

BECCS is an acronym for Bio Energy with Carbon Capture and Storage. It uses plant material in a pyrolysis process to produce electricity. As discussed in the earlier post about biochar, the pyrolysis process produces three outputs:

  • a carbon-rich gas called syngas which is flammable, and contains about half the energy density of natural gas.
  • the solid char, a charcoal which has a much higher concentration of carbon than the original plant material.
  • a thick tar referred to as bio-oil, which is much higher in oxygen than petroleum but otherwise similar.

BECCS is a commercial operation to pyrolyze organic material at scale, usually by growing trees specifically for the purpose.

  • generate electricity by burning the syngas
  • use the char to keep the carbon it holds sequestered for a significant length of time. Though this might involve burial deep underground, char is also useful as a soil additive and takes many years to biodegrade. We could handle a substantial amount of carbon returning to the environment at a long enough cadence.
  • the bio-oil currently has little commercial use but has great potential, as it could displace petroleum in a number of chemical processes.

Because the feedstock for BECCS is newly grown vegetative material, it is strictly carbon neutral. If the char keeps carbon out of the atmosphere for a lengthy period of time, BECCS becomes carbon negative and draws down carbon from the environment while providing revenue via power generation to fund its own operation.

BECCS gets a substantial amount of attention because it is already operating at a substantial scale, removing hundreds of kilotons of carbon dioxide from the atmosphere each year. This is a few orders of magnitude off from where we need to get, but is proof that the process works.

The existing BECCS installations capture byproducts produced in existing agricultural processes, like fermenting corn for ethanol production. An analysis of geo data in 2018 estimated that BECCS could draw down approximately 100 megatons of carbon dioxide per year by 2020 using available land area.