CO₂ removal by applying the adsorption process to biochar from waste materials

Area of Science:

• Materials Science
• Environmental Engineering
• Chemical Engineering

Background:

• Lignocellulosic residues are abundant biomass resources.
• Developing cost-effective adsorbents is crucial for carbon capture.
• Spent coffee grounds biochar (SCGB) offers a sustainable alternative to commercial activated carbon.

Purpose of the Study:

• To evaluate lignocellulosic residues, particularly SCGB, as low-cost adsorbents for CO₂ capture in a dynamic column system.
• To compare the CO₂ adsorption performance of various SCGB modifications and other biochar samples against commercial activated carbon.
• To investigate the factors influencing CO₂ capture under dynamic conditions.

Main Methods:

• Pyrolysis of spent coffee grounds to produce biochar (SCGB).
• Modification of SCGB via chemical activation (KOH), magnetization, and calcination.
• CO₂ adsorption testing in a dynamic column system with varying flow rates and concentrations, monitored by infrared sensors.

Main Results:

• Adsorption capacities ranged from 0.43 to 7.17 mmol CO₂/g, varying with adsorbent type and operating conditions.
• Non-activated SCGB exhibited the highest performance (7.17 mmol CO₂/g) under intermediate air flow.
• KOH activation improved textural properties but did not yield the highest dynamic adsorption capacity.

Conclusions:

• SCGB is a promising, low-cost adsorbent for CO₂ capture in dynamic systems.
• Dynamic CO₂ capture efficiency depends on pore accessibility, surface chemistry, and gas residence time, not solely BET surface area.
• Biomass-derived residues are suitable for CO₂ mitigation, but further research on regeneration and scale-up is needed.