The key idea of the FlexSNG concept is to switch between maximized syngas production and co-production of biochar. Biochar is a storable and valuable gasification by-product with some different end-use application options. One is its use as high-quality fuel, as intended in the FlexSNG concept to improve low-quality feedstock by mixing with biochar. Biochar has many uses, including soil amendment, as stand-alone mixed fertilizer, for co-composting with green wastes, as construction material, as fodder additive, for wastewater treatment or remediation of contaminated soils. Not least, biochar is considered as a permanent natural carbon sequestration sink and so as one important Carbon Dioxide Removal solution in the future.
The end-use for biochar depends on its properties, which vary from the feedstock and the severity of the biochar preparation process (temperature and time). Therefore, the physicochemical and surface characteristics of the biochar from the first two gasification campaigns at VTT are determined by EIFER.
Biochar from FlexSNG gasification is a dry, porous black powder containing around 75-85% carbon and only minor amounts of oxygen and hydrogen. Its fuel properties are promising due to the low volatile content <15% and the high HHV > 30 MJ/kg. The amount of ash is considerably increased compared to the feedstock bark, the ash composition reflects a slight contamination with the bed materials used. All concentrations of heavy metals as well as polyaromatic hydrocarbons are below the thresholds of the European fertilizing regulation. The surface structures of the biochar confirm a high sorption capacity due to the increased surface area and a high porosity. All results confirm the good quality of the biochar so far; no restrictions for the common end-use application for biochar are found.
In the next steps, biochar will be evaluated regarding its material use and its long-term stability for carbon sequestration in soils. Pellets from biochar will be manufactured and shipped backed to VTT for further gasification tests.