The carbon footprint of proton therapy-related energy use in the United States

Abstract

There is increasing concern about rising carbon dioxide (CO ) emissions and hazardous impact on human health. This study quantifies the energy utilization of proton therapy, corresponding carbon footprint, and discusses possible offsetting strategies towards carbon-neutral healthcare operations. Patients treated between 07/2020 and 06/2021 using Mevion proton system were evaluated. Current measurements were converted to kilowatt (kW) power consumption. Patients were reviewed for disease, dose, number of fractions, and duration of beam. EPA calculator was used to convert power consumption to tons of CO equivalent (CO e) for scope-based carbon footprint accounting. There were 185 patients treated for total of 5,176 fractions delivered (average 28). Power consumption was 55.8 kW in standby/night mode and 64.4 kW during BeamOn, for annual total of 490 MWh. BeamOn time was 149.6 hours, and BeamOn consumption accounted for 2% of machine total. Power consumption was 52 kWh per patient (breast highest at 140 kWh, prostate lowest at 28 kWh). Annual power consumption of the administrative areas was ∼96 MWh, for a program total of 586 MWh. The carbon footprint for BeamOn time was 4.17 metric tons of CO e, or 23 kg per patient course (breast cancer 60 kg, prostate 12 kg). Annual carbon footprint for the machine was 212.2 tons CO e, and for the proton program 253.7 tons CO e, with attributed footprint 1372 kg CO e per patient. The corresponding CO e offset for the program could be 4,192 new trees planted and grown for 10 years (23 trees per patient). Carbon footprint varied by disease treated and was on average 23 kg of CO e per patient, and 253.7 tons of CO e for the proton program. There are a number of reduction, mitigation and offset strategies possible for radiation oncologists that should be explored such as waste minimization, less treatment commuting, efficient energy use, and renewable electricity power use.

Research highlights

• "With the baseline carbon footprint for energy use of proton therapy energy established, we may begin to assess strategies to lower, mitigate, and possibly offset it."
• "An interesting, if not altogether surprising, finding is that most of the electrical consumption in our study was from the standby 24/7 baseline draw of the proton system, and the actual beam-on time accounted for only 2% of the total power utilization. The largest energy reduction could be made in the reduction of baseline power consumption of the proton therapy system itself..."
• "Our findings highlight the importance of understanding the various sources of energy consumption and their respective carbon footprints in proton therapy systems. By doing so, we can develop effective strategies to reduce and mitigate the overall carbon footprint, including possibly offsetting the residual consumption through carbon sequestration strategies. Overall, these efforts could help to make radiation therapy more sustainable and environ mentally friendly."

Methods & Results

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Citation

Dvorak T, Meeks S, Dvorak L, Rineer J, Kelly P, Ramakrishna N, Henig T, Kucukvar M, Onat NC, Tatari O, Shah A, Salazar J, Zeidan O. Evaluating Carbon Footprint of Proton Therapy Based on Power Consumption and Possible Mitigation Strategies. International journal of radiation oncology, biology, physics. 2023;