Biogas, mainly composed of methane (CH4), carbon dioxide (CO2), and trace gases such as hydrogen sulphide (H2S), requires upgrading to enhance its energy content and calorific value for applications like electricity generation and direct heat production. This study presents the development of a cost-effective fixed-bed adsorbent column purification system using biochar (BC) derived from sugarcane bagasse (SB). The BC was produced using a pyrolyser at a heating rate of 10 °C/min, with a residence time of 1 h, at three different temperatures: 350, 450, and 550 °C. Results indicated that BC prepared at higher pyrolysis temperatures demonstrated higher adsorption capacities for CO2 and H2S, with a CO2 removal efficiency of 49.65% at 550 °C, compared to 37.90% for BC produced at 350 °C. The enhanced adsorption is ascribed to the porous structure of BC, which provides an extensive active surface area for CO2 capture. Brunauer–Emmett–Teller (BET) analysis confirmed higher specific surface area (SSA), pore size and pore volume of BC produced at elevated temperatures. Low hydrogen-to-carbon and oxygen-to-carbon ratios indicated a high degree of aromaticity and carbon fixation, further favouring CO2 capture. The presence of surface functional groups (SFG) and alkali and alkaline earth (AAE) elements in the BC also contributed to significant conditions for the biogas purification process. This investigation highlights the potential of BC derived from SB as an effective adsorbent for biogas upgrading.