Innovative method for biogas upgrading and CO2 storage: preliminary economic evaluations

A previously investigated innovative carbon dioxide removal process from biogas, characterized by the capture of the removed carbon dioxide, was preliminarily designed and economically evaluated. The studied process uses industrial residues for carbon dioxide capture and storage, through an accelerated carbonation process. The considered industrial residues are air pollution control residues (APC) from Waste-to-Energy plants, which are characterized by a high content of alkaline earth metals, calcium in particular, in the form of hydroxides, oxides or silicates. The carbon dioxide is removed from the biogas by alkali solution absorption. The load solution, containing carbonate and bicarbonate ions is regenerated through reaction with calcium contained in the APC residues, forming calcium carbonate (APC carbonation) and reproducing – at least in part – the original alkali compound. A technical feasibility assessment of the method was carried out, based on pilot plant operation results, highlighting some constraints on the possibility of operating at very large scale, due to the high amount of required residues. Then a preliminary economic assessment of the method was carried out, with the aim of estimating the specific cost of treatment on appropriate industrial scale and compare it with the costs of commercial methods.