Cement substitution with secondary materials can reduce annual global CO2 emissions by up to 1.3 gigatons.

Population and development megatrends will drive growth in cement production, which is already one of the most challenging-to-mitigate sources of CO2 emissions. However, availabilities of conventional secondary cementitious materials (CMs) like fly ash are declining. Here, we present detailed generation rates of secondary CMs worldwide between 2002 and 2018, showing the potential for 3.5 Gt to be generated in 2018. Maximal substitution of Portland cement clinker with these materials could have avoided up to 1.3 Gt CO2-eq. emissions (~44% of cement production and ~2.8% of anthropogenic CO2-eq. emissions) in 2018. We also show that nearly all of the highest cement producing nations can locally generate and use secondary CMs to substitute up to 50% domestic Portland cement clinker, with many countries able to potentially substitute 100% Portland cement clinker. Our results highlight the importance of pursuing regionally optimized CM mix designs and systemic approaches to decarbonizing the global CMs cycle.

Dynamics of economy-wide resource flow and consumption in China, South Korea, and Vietnam-a pan-regional analysis.

The transformation of natural resources across the economy in China, South Korea, and Vietnam has been studied to give a comparative regional perspective based on trends in resource efficiency, bilateral trade dynamics, and progress on regional economic and environmental policy. Consumption of raw materials has been decomposed into economic dynamics and dematerialization, if any, has been tested based on material flow accounting approaches. As per the results, domestic material consumption (DMC) continues to increase in China and Vietnam but has stabilized in South Korea. China and South Korea have become main net importers of raw materials while Vietnam is about to enter this phase. With relatively lower material efficiency in China and Vietnam compared to South Korea, a higher reliance on intensive production and export of raw materials has been identified. As DMC has soared in all three countries, economic affluence is seen as the main driver with marginal contribution from population growth. However, technological improvements have helped reduce material usage with South Korea and China making significant progress. As South Korea has begun to dematerialize, China and Vietnam face the strong challenge of dematerializing economic growth-a reversal that could take several years if resource productivity is not significantly improved. Factors that inhibit better resource efficiency in China and Vietnam include the production and trade of low-end items, energy, and raw materials. However, the increasing economic affluence in China and Vietnam has brought significant environmental improvements from both institutional and technological perspectives-through multiple policy actions. Moreover, as more countries import net resources, regional and global supply chain competition is expected to intensify-making resource efficiency a fundamental economic objective. The results of this study provide important lessons for emerging economies to accelerate resource productivity and reduce the physical intensity of materials for sustainable economic development.

Decarbonization of Vietnam's economy: decomposing the drivers for a low-carbon growth.

Vietnam has witnessed a rapid increase in national-level CO2 emissions due to rising urbanization, economic expansion, export growth, and industrial development. Moreover, to support the ambitious economic growth targets, reliance on and consumption of fossil fuels are increasing by each passing year. With this circumstance, this study aims to analyze the key drivers of CO2 emissions in Vietnam from 1990 to 2016 using the Kaya identity and decomposition method. Following this approach, CO2 emissions have been decomposed into five effect categories comprising population, affluence, energy intensity, fuel mix, and emission intensity. As per the results, CO2 emissions in Vietnam were mainly driven by rising affluence (58.5%) and changing fuel mix (33.2%) which have resulted from improved living standards, rapid industrial development, and higher fossil fuel consumption. Moreover, population (13.8%) and emission intensity (3.1%) exhibited a relatively lower impact on CO2 emissions during 1990-2016. However, energy intensity (- 8.7%) was the only negative driver which has resulted in the slowdown of carbon emissions in Vietnam. Based on the analysis of energy policy development, the share of renewable energy resources was still quite low in the national energy mix with higher reliance on traditional fossil fuels (mainly coal and petroleum). Therefore, to make a transition towards low-carbon economic growth, significant improvements in energy efficiency and emission intensity are necessary together with national energy mix restructuring for low-carbon economic growth.

The metabolic transition of material use and carbon emissions in economically growing Asia: Evidence from 1971 to 2016.

The efficient consumption of material and energy resources, with minimal carbon emissions and maximum economic output, is globally significant. This study examines the metabolic transition of resource use and CO2 emissions in nine of the largest economies of East, South, and Southeast Asia. A data envelopment model has been developed to assess the efficiency of domestic material consumption and CO2 emissions during 1971-2016 at three levels of analysis. The single-country analysis results reveal that China has made the most rapid efficiency transformation during 1971-2016 followed by Japan and South Korea, while the rest of the countries in South and Southeast Asia have not illustrated significant improvements. Results from the analysis of socio-economically grouped countries show that Japan and Bangladesh are the relatively efficient economies in East and South Asia, respectively. Among Southeast Asian countries, both Indonesia and Malaysia were found to be efficient. Based on the regional analysis comparing all nine countries, Japan has consistently remained a relatively efficient economy while China-despite rapid improvements-remains a relatively inefficient economy. To this end, Japan had the lowest material and CO2 intensities compared to all other countries. Based on our results, technological advancement, industry structure, and scale of traded goods and services were found to have a significant impact (the impact of per capita income was less pronounced) on a country's effective resource utilization and carbon mitigation.

Climate co-benefits of alternate strategies for tourist transportation: The case of Murree Hills in Pakistan.

This study explores the climate impacts of on-road tourist transportation with alternate mitigation strategies. To this end, greenhouse gas (GHG) emissions for 2016 and emissions under four "what-if" scenarios were estimated for a popular tourist site in Pakistan, i.e., Murree Hills, using the international vehicle emissions model. Alternate scenarios included occupancy optimization, bus transit system, and Euro II and Euro IV implementation. The emissions were further decomposed using the log mean Divisia index method to study the drivers of global warming potential (GWP) mitigation. As per the results, the total 20-year GWP for 2016 was equal to 51,262 tons CO2 equivalent, and maximum reduction was achieved under the bus transit system scenario having a 20-year GWP of 25,736 tons CO2 equivalent, i.e., 49.8% reduction. Relative to the base year, GWP reductions were also quite significant for Euro IV (46.8%), Euro II (45.8%), and occupancy optimization (32.3%) scenarios. For the base year, CO2 held a share of 87.3% in total emissions; however, its share in the 20-year GWP was 39.7% indicating its reduced impact on total GWP as compared to N2O, CO, NOx, VOC, and CH4. Based on the decomposition results for alternate scenarios, GWP mitigation was mainly driven by CO, CH4, NOx, VOCs, and partially by CO2, while N2O negatively affected GWP mitigation. These results provide several policy-level instruments for developing countries to design a transition to an eco-friendly tourist transport management system. The policy implications from this study can be used to promote an eco-tourism industry.