*3.6. Technical and Economic Feasibility of the Biochar-Concrete System*

The possible emissions of GHGs to the environment because of the decay/decomposition of the biomass are avoided by the process of valorising the biomass to produce biochar. Reducing GHG emissions of CO2-eq./kg in the biochar life cycle using different biomass was estimated. In addition to reducing the net emission of GHG, the use of biochar in concrete has played a vital role in improving its chemical and mechanical properties. Most studies in the past showed significant improvements in concrete's compressive and flexural strength [3,64–68]. Other mechanical properties of concrete, such as toughness, flexibility, elongation, permeability, thermal stability, and thermal conductivity, were also observed [19,64,69,70]. Despite a relatively high cost of production of biochar [71], compared to natural filler materials such as sand, it is still considered a better construction

material due to its associated environmental benefits of reduced CO2-eq./kg as well as the generation of other value-added products such as syngas, bio-oil production in pyrolysis.

Apart from the environmental and other technical benefits of using biochar in concrete, its economic viability is crucial in deploying it in the construction industry. Kung et al. [72] reported a higher and more feasible feedstock value of 10.98 \$/t for biochar production by slow pyrolysis compared to a correspondingly lower value of 2.85 \$/t pyrolysis. A lesser value of biochar production in fast pyrolysis is due to higher net losses of feedstock and is considered unviable both in economic and environmental profits. A more excellent feedstock value in slow pyrolysis is a viable solution for biochar production. As reported by several researchers, [73] biochar production from forest residue using a portable system, the cost of biochar production can be further reduced, equaling 470 \$/t of oven-dried by technologically improving the portable system.
