Adsorption of CO2 by solid sorbents has been proposed as a pathway to decrease the emissions associated with combustion of fuels. However, if employing the waste residues of the combustion process (e.g. biomass combustion bottom ash), a pathway towards a green circular zero-waste and zero-emissions economy may be achieved. As such, a carbonaceous adsorbent has been produced (via chemical activation) using biomass combustion bottom ash as a precursor. This process entailed an intelligently designed experimental campaign based on a randomised Taguchi L9 orthogonal array, which revealed moderate activation temperatures (∼625 °C) and times (30 min) coupled with high ramp rates (10 – 15 °C/min) to be preferable. Following this method, a highly microporous (∼93 %) material was produced possessing a surface area of 643.6 m2/g. This, in turn, facilitated a substantial increase in CO2 uptake, namely, 1.29 mmol/g at 50 °C (quadruple that of the parent carbon and double that of the physically activated counterpart). Additionally, the working capacity as well as the heat of adsorption were measured. The latter properties are often overlooked with main focus drawn towards purely the adsorption capacity; however, they are imperative for industrial deployment of CO2 adsorbents.