Extra CO2 sequestration following reutilization of biomass ash

Abstract

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.

Keywords: Black carbon; Fertilizer; Olive cake; Potassium; Soil carbonates.