Rebound effects undermine carbon footprint reduction potential of autonomous electric vehicles.

Autonomous vehicles offer greater passenger convenience and improved fuel efficiency. However, they are likely to increase road transport activity and life cycle greenhouse emissions, due to several rebound effects. In this study, we investigate tradeoffs between improved fuel economy and rebound effects from a life-cycle perspective. Our results show that autonomy introduces an average 21.2% decrease in operation phase emissions due to improved fuel economy while manufacturing phase emissions can surge up to 40%. Recycling efforts can offset this increase, cutting emissions by 6.65 tons of Carbon dioxide equivalent per vehicle. However, when examining the entire life cycle, autonomous electric vehicles might emit 8% more greenhouse gas emissions on average compared to nonautonomous electric vehicles. To address this, we suggest; (1) cleaner and more efficient manufacturing technologies, (2) ongoing fuel efficiency improvements in autonomous driving; (3) renewable energy adoption for charging, and (4) circular economy initiatives targeting the complete life cycle.

Evaluating Carbon Footprint of Proton Therapy Based on Power Consumption and Possible Mitigation Strategies.

PURPOSE: There is increasing concern about rising carbon dioxide (CO2) emissions and their hazardous effect on human health. This study quantifies the energy utilization of proton therapy, assesses the corresponding carbon footprint, and discusses possible offsetting strategies toward carbon-neutral health care operations. METHODS AND MATERIALS: Patients treated between July 2020 and June 2021 using the Mevion proton system were evaluated. Current measurements were converted to kilowatts of power consumption. Patients were reviewed for disease, dose, number of fractions, and duration of beam. The Environmental Protection Agency calculator was used to convert power consumption to tons of CO2 equivalent (CO2e) for scope-based carbon footprint accounting. RESULTS: There were 185 patients treated and a total of 5176 fractions delivered (average, 28). Power consumption was 55.8 kW in standby/night mode and 64.4 kW during BeamOn, for an annual total of 490 MWh. BeamOn time was 149.6 hours, and BeamOn consumption accounted for 2% of the 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 approximately 96 MWh, for a program total of 586 MWh. The carbon footprint for BeamOn time was 4.17 metric tons of CO2e, or 23 kg per patient course (breast cancer, 60 kg; prostate, 12 kg). The annual carbon footprint for the machine was 212.2 tons CO2e, and for the proton program, 253.7 tons CO2e, with an attributed footprint of 1372 kg CO2e per patient. The corresponding CO2e offset for the program could be 4192 new trees planted and grown for 10 years (23 trees per patient). CONCLUSIONS: The carbon footprint varied by disease treated. On average, the carbon footprint was 23 kg of CO2e per patient and 253.7 tons of CO2e 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.

Green Concrete for a Circular Economy: A Review on Sustainability, Durability, and Structural Properties.

A primary concern of conventional Portland cement concrete (PCC) is associated with the massive amount of global cement and natural coarse aggregates (NCA) consumption, which causes depletion of natural resources on the one hand and ecological problems on the other. As a result, the concept of green concrete (GC), by replacing cement with supplementary cementitious materials (SCMs) such as ground granulated blast furnace slag (GGBFS), fly ash (FA), silica fume (SF), and metakaolin (MK), or replacing NCA with recycled coarse aggregates, can play an essential role in addressing the environmental threat of PCC. Currently, there is a growing body of literature that emphasizes the importance of implementing GC in concrete applications. Therefore, this paper has conducted a systematic literature review through the peer-reviewed literature database Scopus. A total of 114 papers were reviewed that cover the following areas: (1) sustainability benefits of GC, (2) mechanical behavior of GC in terms of compressive strength, (3) durability properties of GC under several environmental exposures, (4) structural performance of GC in large-scale reinforced beams under shear and flexure, and (5) analytical investigation that compares the GC shear capacities of previously tested beams with major design codes and proposed models. Based on this review, the reader will be able to select the optimum replacement level of cement with one of the SCMs to achieve a certain concrete strength range that would suit a certain concrete application. Also, the analysis of durability performance revealed that the addition of SCMs is not recommended in concrete exposed to a higher temperature than 400 °C. Moreover, combining GGBFS with FA in a concrete mix was noticed to be superior to PCC in terms of long-term resistance to sulfate attack. The single most striking observation to emerge from the data comparison of the experimentally tested beams with the available concrete shear design equations is that the beams having up to 70% of FA as a replacement to OPC or up to 100% of RCA as a replacement to NCA were conservatively predicted by the equations of Japan Society of Civil Engineers (JSCE-1997), the American Concrete Institute (ACI 318-19), and the Canadian Standards Association (CSA-A23.3-14).

Evaluating environmental impacts of alternative construction waste management approaches using supply-chain-linked life-cycle analysis.

Waste management in construction is critical for the sustainable treatment of building-related construction and demolition (C&D) waste materials, and recycling of these wastes has been considered as one of the best strategies in minimization of C&D debris. However, recycling of C&D materials may not always be a feasible strategy for every waste type and therefore recycling and other waste treatment strategies should be supported by robust decision-making models. With the aim of assessing the net carbon, energy, and water footprints of C&D recycling and other waste management alternatives, a comprehensive economic input-output-based hybrid life-cycle assessment model is developed by tracing all of the economy-wide supply-chain impacts of three waste management strategies: recycling, landfilling, and incineration. Analysis results showed that only the recycling of construction materials provided positive environmental footprint savings in terms of carbon, energy, and water footprints. Incineration is a better option as a secondary strategy after recycling for water and energy footprint categories, whereas landfilling is found to be as slightly better strategy when carbon footprint is considered as the main focus of comparison. In terms of construction materials' environmental footprint, nonferrous metals are found to have a significant environmental footprint reduction potential if recycled.