Extra CO2 sequestration following reutilization of biomass ash.

Although combustion ashes are usually used in soils, little attention is paid to the CO2 sequestration potential of this practice. The present study aims to quantify carbon sequestration as carbonate compounds in a tailored synthetic calcareous soil treated with biomass ash from a gasification power plant that uses olive cake. It is estimated that after ash amendment, 14.5g CO2 remained fixed per kg of fly biomass ash, 16.5g CO2 per kg of bottom biomass ash with plant cultivation and 19.7g CO2 per kg of bottom biomass ash without plant cultivation. This inorganic C fixation plus the organic (black) C contained in the ashes made the reutilization of ashes as K fertilizer a relevant practice due to its C resilience and rate, with a yearly C sequestering potential of ca. 8% of 'Soil carbon 4 per mille' goal, an initiative launched at the COP21.