Removal of inorganics from sludge and digestate: the BiAR process

This conference contribution will present a novel technology for renewable ash-free fuel production from low-value ash-containing feedstocks such as sludge digestate, wood bark or rice husks that cannot be utilized directly as a heating fuel, because of the high (low melting point) ash content. Biomass Ash Removal (BiAR) process introduces the low-temperature solvolysis in cheap solvents to transform the organic matter into a liquid state, allowing its separation from the solid ash by a simple filtration or sedimentation. After the BiAR process, all tested feedstocks reduced their ash content below threshold admitted for heating biomass set by UNI EN ISO 17225:2014 standard. As anaerobic digestion is capable to recover about 50% of the carbon in form of methane (according with COD balance), BiAR could be used to ‘retrofit’ those installation to recovery the remaining 50% organic carbon leading to a potential 100% carbon, thus energy, recovery. A potential complete compensation of costs associated to dehydration and disposal of digestate could be achieved. The PCT application has been recently filed for the BiAR process (PCT/IT2016/000140).