Background: The National Health System is responsible for 8–10% of total greenhouse gas emissions. Operating rooms are responsible for 60–70% of all hospital waste. Over the last 30 years abdominal surgery transcended from a laparoscopic approach toward a robot-assisted approach. The role of robot-assisted laparoscopic surgery is still debated in some procedures, such as colorectal surgery. The studies available in scientific literature comparing laparoscopic and robot-assisted left hemicolectomy are focused on clinical outcomes. The environmental sustainability of these procedures remains largely unexplored, representing a key area that our study seeks to investigate. Methods: In this pilot study consecutive patients scheduled for a minimally invasive left hemicolectomy for diverticular disease or cancer were recruited and randomly assigned 1:1 to the laparoscopic or robotic groups. The “Green Team” supported the operating room staff in separate waste collection during the surgical procedures. Primary end point was CO₂ consumption and secondary endpoints the specific mass of the most important waste stream. Results: Ten patients were enrolled. Robot-assisted left hemicolectomy required more CO₂ consumption in liters to maintain pneumoperitoneum (p = 0.03) compared with laparoscopic left hemicolectomy and required a longer operation time (p = 0.04). In total, the robot and laparoscopic approaches produced a total of 74.5 and 54 kg of plastic, non-woven fabric (TNT), unsorted waste bins, and biohazardous waste combined, which cost €92 and €71 to dispose of. Conclusion: Robot-assisted left hemicolectomy seems to have a greater environmental impact compared with laparoscopic left hemicolectomy in terms of both CO₂ emissions and waste production. Given the growing focus on operating room sustainability, further studies are needed to compare laparoscopic and robotic techniques to inform surgical decisions.