## 4 Discussion  
The estimation of the CF of healthcare systems is a field of ever-growing interest and importance. The healthcare GHG footprint as a percentage of the national GHG footprint is 8-10% in the US [28,29], 3% in England [30,31], and 5% in Canada [32], thus representing a significant contributor in a country's GHG emissions. [PERSON] et al. published the first study assessing specialty-level CO\({}_{2}\) emissions, quantifying the CF of a renal unit in a UK hemodialysis ward [33,34]. This growing interest in carbon reduction has also permeated healthcare policy; for instance, the UK National Health Service (NHS) has committed to becoming the world's first \"net zero\" carbon national health service [6]. Surgical departments and operating theaters rank among hospitals' most energy-intensive and waste-generating departments [35]. A recent systematic review by [PERSON] et al. [36] identified several major sources of carbon emissions in surgical care, such as anesthetic gases, the sterilization processes, the use of disposable materials, and resistance to adopting greener practices among surgical staff. Various strategies have been proposed to mitigate their environmental impact without compromising patient safety, including avoiding desflurane and adopting occupancy-based ventilation systems [37]. Building on this foundation, our initial study focused on prostate cancer [38]. To the best of our knowledge. This study was the first to compare CO\({}_{2}\) emissions from two MIS approaches [6,39,40,41]. Notably, robot-assisted surgery demonstrated an 11% reduction in emissions compared to laparoscopy, saving 12.36 kg CO\({}_{2}\) per procedure, equivalent to the emissions from driving 50 km in a petrol car [42]. These results prompted our group to investigate whether this trend was confirmed in MIS kidney surgery. Similar to our previous study, the difference in CO\({}_{2}\) emissions between the two robot-assisted procedures and the laparoscopic procedures was statistically significant due to the use of reusable materials and lower total energy consumption. RAPN and RANN produce on average 4 kg and 3 kg of CO\({}_{2}\) less than their laparoscopic counterparts. Our findings highlight how the robot-assisted approach allows for the use of reusable instruments, as the main surgical instrumentation of the Da Vinci Xi System has a lifespan of up to 15 procedures. In contrast, laparoscopy relies heavily on single-use instruments in our institutions, resulting in higher energy consumption due to slightly longer surgical times and the need for closer postoperative monitoring. Single-use instruments, primarily composed of plastics, have a significantly higher CF than reusable instruments. In both laparoscopic arms of this study, the CO\({}_{2}\) emissions from plastics alone accounted for \(\sim\)1.8 and \(\sim\)2.2 kg CO\({}_{2}\). This discrepancy is largely attributed to the greater variety and quantity of single-use instruments required for laparoscopy. These results align with the existing literature [6], which emphasizes the advantages of hybrid instruments over single-use components. Although the per-case savings may seem modest, when multiplied across thousands of procedures in high-volume institutions, the cumulative environmental benefit could be substantial. While the robotic system consumes more energy intraoperatively compared to the laparoscopic column, the shorter hospitalization period compensated for this, leading to lower overall CO\({}_{2}\) emissions. Initiatives like the \"Power Down\" program (turning off unused anesthesia and OR lights) have shown promise, saving USD 33,000 and reducing 234.3 metric tons of CO\({}_{2}\) annually [42]. While we acknowledge that both hybrid and reusable instruments are used in laparoscopic procedures, these are not available in our institutions. In clinical and surgical settings resembling ours, robot-assisted surgery seems more environmentally sustainable. However, more systemic changes are essential to significantly reduce healthcare-related GHG emissions.