Valorisation of agricultural biomass-ash with CO(2)

This work is part of a study of different types of plant-based biomass to elucidate their capacity for valorisation via a managed carbonation step involving gaseous carbon dioxide (CO(2)). The perspectives for broader biomass waste valorisation was reviewed, followed by a proposed closed-loop process for the valorisation of wood in earlier works. The present work newly focusses on combining agricultural biomass with mineralised CO(2). Here, the reactivity of selected agricultural biomass ashes with CO(2) and their ability to be bound by mineralised carbonate in a hardened product is examined. Three categories of agricultural biomass residues, including shell, fibre and soft peel, were incinerated at 900 ± 25 °C. The biomass ashes were moistened (10% w/w) and moulded into cylindrical samples and exposed to 100% CO(2) gas at 50% RH for 24 h, during which they cemented into hardened monolithic products. The calcia in ashes formed a negative relationship with ash yield and the microstructure of the carbonate-cementing phase was distinct and related to the particular biomass feedstock. This work shows that in common with woody biomass residues, carbonated agricultural biomass ash-based monoliths have potential as novel low-carbon construction products.