Proportion Of CO2 Emissions Research Articles

Modeling fuel-, vehicle-type-, and age-specific CO2 emissions from global on-road vehicles in 1970–2020

Abstract. Vehicles are among the most important contributors to global anthropogenic CO2 emissions. However, the lack of fuel-, vehicle-type-, and age-specific information about global on-road CO2 emissions in existing datasets, which are available only at the sector level, makes these datasets insufficient for supporting the establishment of emission mitigation strategies. Thus, a fleet turnover model is developed in this study, and CO2 emissions from global on-road vehicles from 1970 to 2020 are estimated for each country. Here, we analyze the evolution of the global vehicle stock over 50 years, identify the dominant emission contributors by vehicle and fuel type, and further characterize the age distribution of on-road CO2 emissions. We find that trucks accounted for less than 5 % of global vehicle ownership but represented more than 20 % of on-road CO2 emissions in 2020. The contribution of diesel vehicles to global on-road CO2 emissions doubled during the 1970–2020 period, driven by the shift in the fuel-type distribution of vehicle ownership. The proportion of CO2 emissions from vehicles in developing countries such as China and India in terms of global emissions from newly registered vehicles significantly increased after 2000, but global CO2 emissions from vehicles that had survived more than 15 years in 2020 still originated mainly from developed countries such as the United States and countries in the European Union. The data are publicly available at https://doi.org/10.6084/m9.figshare.24548008 (Yan et al., 2024).

Effect of Long-term Straw Returning on the Mineralization and Priming Effect of Rice Root-carbon

Long-term straw returning to the field changes the environmental conditions of rice paddy soil, which affects the mineralization and priming effect of residual rice roots in the soil, but the direction and intensity of its influence is not clear. Therefore, based on a long-term fertilization field experiment, 13C-CO2 isotopic labeling technology and laboratorial incubation were used to analyze the characteristics of mineralization of rice roots and native soil organic carbon, the intensity and direction of the priming effect, and the source partitioning of CO2 emissions in three treatments, consisting of no fertilization (CK), chemical fertilizer (CF), and straw returning with chemical fertilizer (CFS). The results showed that after 120 days of flooding incubation, the root residue (R) increased the cumulative CO2 emissions by 617.41-726.27 mg·kg-1. The cumulative CO2 emissions from roots and root mineralized proportions in the CFS+R and CF+R treatments were 470.82 and 444.04 mg·kg-1, respectively, and 18.8% and 17.8%, respectively. These were significantly higher than those in the CK+R treatment (384.19 mg·kg-1, 15.4%). There was no significant difference in the cumulative CO2 emissions from native soil organic carbon among the three treatments. However, the mineralized proportion of native soil organic carbon in the CFS+R treatment (4.2%) was significantly lower than that in the CF+R and CK+R treatments (5.4% and 5.8%). The priming effect in the CFS+R treatment was 29.6%, which was significantly lower than that in the CK+R treatment (42.5%) and higher than that in the CF+R treatment (14.4%). A total of 23.47% to 27.59% of the cumulative CO2 emission of the flooded paddy soil was from the roots, and the remainder was from the soil. In addition, the proportion of CO2 emission caused by the priming effect was smaller in the CFS+R treatment than that in the CK+R treatment and larger than that in the CF+R treatment. In summary, the long-term straw returning in the flooded paddy soil will increase the mineralization potential of rice roots, but it is more conducive to the stability of the native soil organic carbon.

China's provincial CO2 emissions and interprovincial transfer caused by investment demand.

Based on the China's 1997, 2002, 2007, and 2012 multiregional input-output model, this study calculates China's provincial CO2 emissions from investment demand and interprovincial transfer of CO2 emissions caused by investment demand. The findings of this study are as follows: (1) From 1997 to 2012, the CO2 emissions from China's investment demand have seen rapid growth-the CO2 emissions from investment demand has increased by 4.52 times, and the per capita CO2 emissions caused by investment demand has increased by 4.13 times. Investment demand is an important driver of growth of China's CO2 emissions. The proportion of CO2 emissions from investment demand in CO2 emissions from China's three final demands rose from 37.72% in 1997 to 50.68% in 2012. (2) The CO2 emissions from investment demand are relatively large in provinces which have large-scale industries. Affected by investment-driven economic growth, CO2 emissions from investment demand in central, western, and northeastern provinces have increased more rapidly. (3) Large amounts of CO2 are emitted in the less-developed central and western provinces to meet the investment demand of the developed eastern provinces. As China's economy enters the "new normal," economic growth is shifting from investment-driven to consumption-driven, and the growth of CO2 emissions from investment demand will slow down.

Carbon Dioxide Emission Evaluation of Porous Vegetation Concrete Blocks for Ecological Restoration Projects

The purpose of this study is to determine the mix proportions that can minimize CO2 emissions while satisfying the target performance of porous vegetation concrete. The target performance of porous vegetation concrete was selected as compressive strength (>15 MPa) and void ratio (>25%). This study considered the use of reinforcing fiber and styrene butadiene (SB) latex to improve the strength of porous vegetation concrete, as well as the use of blast furnace slag aggregate to improve the CO2 emissions-reducing effect, and analyzed and evaluated the influence of fiber reinforcing, SB latex, and blast furnace slag aggregate on the compressive strength and CO2 emissions of porous vegetation concrete. The CO2 emissions of the raw materials were highest for cement, followed by aggregate, SB latex, and fiber. Blast furnace slag aggregate showed a 30% or more CO2 emissions-reducing effect versus crushed aggregate, and blast furnace slag cement showed a 78% CO2 emissions-reducing effect versus Portland cement. The CO2 emissions analyses for each raw material showed that the CO2 emissions during transportation were highest for the aggregate. Regarding CO2 emissions in each production stage, the materials stage produced the highest CO2 emissions, while the proportion of CO2 emissions in the transportation stage for each raw material, excluding fiber, were below 3% of total emissions. Use of blast furnace slag aggregate in porous vegetation concrete produced CO2 emissions-reducing effects, but decreased its compressive strength. Use of latex in porous vegetation concrete improved its compressive strength, but also increased CO2 emissions. Thus, it is appropriate to use latex in porous vegetation concrete to improve its strength and void ratio, and to use a blast furnace slag aggregate replacement ratio of 40% or less.

Soil aggregate fraction-based 14C analysis and its application in the study of soil organic carbon turnover under forests of different ages

There still exist uncertainties in the trend, magnitude and efficiency of carbon sequestration with regard to the changes in soil organic carbon (SOC) pools after afforestation. In this study, SOC turnover times of the meadow steppe and planted forests at Saihanba Forest Station of Hebei Province, China are estimated by means of the radiocarbon (14C) method. Our results show that the SOC turnover times can be as long as from 70 to 250 years. After planting the Pinus sylvestri var. mongolica in the Leymus chinensis meadow steppe, the turnover times of organic carbon in both bulk samples and soil aggregate fractions of the topsoils are decreased with an increase of the stand age. Such a lowering of the turnover time would cause an increase in soil CO2 flux, implying that afforestation of grassland may reduce the capacity of topsoil to sequestrate organic carbon. Combined stable isotope and 14C analyses on soil aggregate fractions suggest that there are different responses to afforestation of grassland between young and old carbon pools in topsoils. In the young and middle-age planted forests, the proportion of CO2 emission from the older soil carbon pool shows an increasing trend. But in the mature planted forest, its proportion tends to decline, indicating that the stand age may influence the soil carbon sequestration mechanism. The CO2 emission from the topsoils estimated using the 14C method is relatively low compared to those by other methods and may be caused by the partial isolation of the young carbon component from the soil aggregates. For more accurate estimation of CO2 flux, future studies should therefore employ improved methodology for more effective separation of different soil carbon components before isotope analyses.

The Role of CO<sub>2</sub> Emission in Energy Demand and Supply

Problem statement: During the last few years in Malaysia, the amount of Carbon Dioxide (CO2) released into the atmosphere has been rising extensively. The main source of CO2 is power source of automobile and industry that are contributing the main role for these CO2 emissions. But these sectors are also very important for economic growth and developments. The aim of this study is to examine the current status and identify the future trend of energy demand and supply and its impacts on CO2 emissions in Malaysia. Approach: The data for analysis was obtained from the secondary sources. Results: The study discovered that the highest proportion of CO2 emissions comes from energy sector. The future trend of energy demand and supply was estimated by the forecasting polynomial curve fitting method. The increase rate of energy supply and demand can rich up to 170 and 160% respectively during the year 2020 if the current situation last long. The study showed a linear trend of increasing intensity of energy and CO2 emission with respect to Gross Domestic Product (GDP) by the year 2020. Conclusion: A significant share of CO2 emissions can be avoided through improved energy efficiency while providing the same or higher level of energy services. In this regard, greater use of energy efficient, renewable energy and green technologies or options and behavioural changes can substantially reduce CO2 emissions from the energy sector.

マイクロＸ線ＣＴを用いたコークス組織の三次元解析

The performance of coke in blast furnace (BF) used to prefer a high strength and low reactivity, generally. One of the reasons is in the importance of the gas and liquid permeability in BF, which are related to the stable operation of BF. On the other hand, the energy saving on the BF will contribute the decrease of CO2 emission, because the proportion of CO2 emission in the iron making field is quite large. To decrease the reducing agent ratio the reaction efficiency in the BF should increase more and more. It is recognized that the reactivity and the strength of coke contradict each other. The high reactivity coke generally has a low strength. To overcome the contradiction, we are going to use the catalytic effect on the coke gasification. Therefore, it is important to clarify the mechanism of coke gasification concerning to the coke microstructure and porosity. In this study, the coke gasification were analyzed using μ-X-ray CT. The optimum conditions for the image processing of the data from the μ-X-ray CT were obtained through the comparison with the cross section of the coke embedded in the resin. Nondestructive observation became possible. It was found that the relatively larger structure (carbon and pore: ~0.5 mm) were almost the same between the μ-X-ray CT and the cross section of the sample embedded in resin, but smaller structure could not observed appropriately. The problems (ex.: existence of iron catalysts, difference of thickness for X-ray absorption, etc.) to get a proper image by μ-X-ray CT still remained.