Transition into Net-Zero Carbon Community from Fossil Fuels: Life Cycle Assessment of Light-Driven CO₂ Conversion to Methanol Using Graphitic Carbon Nitride

Abstract

Direct conversion of waste CO2 into CH3OH by solar irradiation has emerged as the most enthralling alternative to conventional steam methane reforming, which reduced the concentration of greenhouse gases and the consumption of fossil resources. A cradle-to-gate life cycle assessment was carried out to assess the environmental feasibility of implementing the current g-C3N4-based photocatalytic CO2 reduction system based on 1 kg CH3OH production. It was observed that the emerging photocatalytic CH3OH system induced 68 and 53% less carbon footprint and fossil usage, respectively, in producing the same amount of CH3OH as compared to the conventional approach. The CO2 reduction reaction step was identified as the main contributor in photocatalytic system, which accounted for more than 50% of the total environmental impact scores. In the conventional system, the score points of global warming and fossil depletion contributed the most by the product purification and desulfurization step, respectively. In addition, sensitivity analysis manifested that the lowest environmental burden of 46.50 kg of CO2 equiv carbon emission and 15.27 kg oil equiv fossil consumption was obtained in the photocatalytic CH3OH system upon replacing fossil-based energy with hydro-powered electricity. These results suggest a potent replacement of the incumbent industry system for the amelioration of climate benefits and resource conservation with the advanced development of the photocatalytic system.

Prospective Life Cycle Assessment Bridging Biochemical, Thermochemical, and Electrochemical CO2 Reduction toward Sustainable Ethanol Synthesis

“…Additionally, carbon footprint unveils that the electrochemical process will be competitive among all three processes when coupled with electricity with a CI of 0.25 kg CO 2 eq/kWh or lower and is estimated to achieve carbon neutrality when powered by electricity with a CI of 0.12 kg CO 2 eq/kWh. As such, to achieve future commercialization of electrochemical ethanol production technology, more research efforts are urgently required to develop low-carbon electricity sources, particularly those derived from renewable energy, to eliminate the intrinsic great carbon footprint attributed to the conventional electricity mix …”

Recent advances in CO2 reduction with renewable reductants under hydrothermal conditions: towards efficient and net carbon benefit CO2 conversion

“…The summarized research demonstrated that multiple value-added chemicals or fuels can be produced from CO 2 hydrothermal conversion, as depicted in Figure 17a REVIEW Figure 17 (a) Main products that can be obtained by hydrothermal CO 2 conversion 33-35, 39, 40, 48, 50, 79, 81, 87, 88, 90, 91, 96, 98, 105, 109-112 , (b) Comparison of formic acid production efficiency by different CO 2 catalytic methods 48,51,79,88,90,96,107,[113][114][115][116][117][118][119][120][121][122][123][124][125][126] , (c) comparison of greenhouse gas emissions by different CO 2 catalytic methods 89,[127][128][129][130][131][132][133][134][135][136] (yellow balls represent photocatalysis, brown balls represent electrocatalysis, blue balls represent catalytic hydrogenation, green balls represent biomass and regenerable metals).…”

Turning CO2 into sustainable graphene: a comprehensive review of recent synthesis techniques and developments

“…For instance, Ling et al achieved a reduction in greenhouse gas concentration and fossil resource consumption through the direct conversion of waste CO 2 into methanol by solar irradiation, with a LCA indicating that the emerging photocatalytic system induces 68% less carbon Figure 10. Comprehensive life cycle assessment of photocatalytic CO2 reduction system compared to conventional steam methane reforming [196]. Reprinted with permission from [196].…”