Carbon dioxide emissions make up approximately 77% of global greenhouse gas emissions, driving the urgent need for effective carbon capture technologies. Among various approaches, adsorption using porous carbon materials has gained significant attention due to its energy efficiency, cost-effectiveness, and potential for large-scale applications. The effectiveness of these materials depends largely on their surface properties and porosity, which can be improved through functionalization techniques. By introducing nitrogen- and oxygen-containing groups, the adsorption capacity and selectivity of carbon-based adsorbents can be enhanced, making them more suitable for industrial CO₂ capture. However, different functionalization methods used during hydrothermal carbonization (HTC) have varying environmental impacts throughout their life cycle, from raw material processing to disposal. This study conducts a life cycle assessment (LCA) to compare the environmental effects of three functionalization strategies for activated hydrochars derived from loblolly pine: (i) incorporating zeolite, (ii) using CO₂ as a functionalizing agent, and (iii) incorporating noble metals such as Ni, Pd, or Pt during HTC. A structured LCA framework was applied, integrating physical and economic modeling to assess energy consumption, greenhouse gas emissions, and overall environmental sustainability. The results indicate that CO₂-assisted functionalization is the most environmentally friendly option, as it serves both as a reaction medium and a surface modifier, reducing the need for additional chemicals and lowering emissions. Zeolite functionalization has a moderate environmental impact, while noble metal incorporation, despite improving CO₂ adsorption, poses a higher environmental burden due to its energy-intensive synthesis and limited material availability. These findings provide valuable insights into balancing adsorption performance with sustainability, helping to identify scalable and eco-friendly strategies for carbon capture applications.
