Governments promote biofuels as renewable, carbon-neutral resources that serve to reduce CO2 emissions. Meanwhile, scientists have determined that biomass burning generates more CO2 emissions per kWh than burning coal does, and the projected rapid growth in biofuel use will only serve to ‘increase atmospheric CO2 for at least a century’.
“[G]overnments around the world are promoting biomass to reduce their greenhouse gas (GHG) emissions. The European Union declared biofuels to be carbon-neutral to help meet its goal of 20% renewable energy by 2020, triggering a surge in use of wood for heat and electricity (European Commission 2003, Leturcq 2014, Stupak et al 2007). … But do biofuels actually reduce GHG emissions?”
“[A]lthough wood has approximately the same carbon intensity as coal (0.027 vs. 0.025 tC GJ−1 of primary energy […]), combustion efficiency of wood and wood pellets is lower (Netherlands Enterprise Agency; IEA 2016). Estimates also suggest higher processing losses in the wood supply chain (Roder et al 2015). Consequently, wood-fired power plants generate more CO2 per kWh than coal. Burning wood instead of coal therefore creates a carbon debt—an immediate increase in atmospheric CO2 compared to fossil energy—that can be repaid over time only as—and if— NPP [net primary production] rises above the flux of carbon from biomass and soils to the atmosphere on the harvested lands.”
“Growth in wood supply causes steady growth in atmospheric CO2 because more CO2 is added to the atmosphere every year in initial carbon debt than is paid back by regrowth, worsening global warming and climate change. The qualitative result that growth in bioenergy raises atmospheric CO2 does not depend on the parameters: as long as bioenergy generates an initial carbon debt, increasing harvests mean more is ‘borrowed’ every year than is paid back. More precisely, atmospheric CO2 rises as long as NPP [net primary production] remains below the initial carbon debt incurred each year plus the fluxes of carbon from biomass and soils to the atmosphere.”
“[P]rojected growth in wood harvest for bioenergy would increase atmospheric CO2 for at least a century because new carbon debt continuously exceeds NPP.”
“[C]ontrary to the policies of the EU and other nations, biomass used to displace fossil fuels injects CO2 into the atmosphere at the point of combustion and during harvest, processing and transport. Reductions in atmospheric CO2 come only later, and only if the harvested land is allowed to regrow.”
May 14, 2018 at 07:41AM