Analysis of CO_2 utilization into synthesis gas based on solar thermochemical CH_4-reforming

In this study, the solar thermochemical reactor performance for CO_2 utilization into synthesis gas(H_2+ CO) based on CH_4 reforming process was investigated in the context of carbon capture and utilization(CCU) technologies. The P1 radiation heat transfer model is adopted to establish the heat and mass transfer model coupled with thermochemical reaction kinetics. The reactor thermal behavior with direct heat transfer between gaseous reactant and products evolution and the effects of different structural parameters were evaluated. It was found that the reactor has the potential to utilize by ～60% of CO_2 captured with 40% of CH_4 co-fed into syngas(72.9% of H_2 and 27.1% of CO) at 741.31 k W/mof incident radiation heat flux. However, the solar irradiance heat flux and temperature distribution were found to significantly affect the reactant species conversion efficiency and syngas production. The chemical reaction is mainly driven by the thermal energy and higher species conversion into syngas was observed when the temperature distribution at the inner cavity of the reactor was more uniform. Designed a solar thermochemical reactor able to volumetric store concentrated irradiance could highly improve CCU technologies for producing energy-rich chemicals. Besides, the mixture gas inlet velocity, operating pressure and CO_2/CH_4 feeding ratio were crucial to determining the efficiency of CO_2 utilization to solar fuels. Catalytic CO_2-reforming of CH_4 to chemical energy is a promising strategy for an efficient utilization of CO_2 as a renewable carbon source.

脱贫对中国实现碳中和目标的影响

China is facing challenges to tackle the threat of climate change while reducing social inequality.Poverty eradication requires improvement in the living conditions of low-income households,which leads in turn to higher carbon footprints and may undermine the efforts of climate change mitigation.Previous studies have assessed the climate impacts of poverty eradication,but few have quantified how the additional carbon emissions of poverty eradication are shared at the subnational level in China and the impact on China’s climate targets.We investigated the recent trend of carbon footprint inequality in China’s provinces and estimated the climate burden of different poverty reduction schemes,measured by increased carbon emissions.The results indicate that poverty eradication will not impede the achievement of national climate targets,with an average annual household carbon footprint increase of 0.1%–1.2%.However,the carbon emissions growth in less developed provinces can be 4.0%,five times that in wealthy regions.Less developed regions suffer a greater climate burden because of poverty eradication,which may offset carbon reduction efforts.Therefore,interregional collaboration is needed to coordinate inequality reduction with investments in low-carbon trajectories in all provinces.

The rebound effect on energy efficiency improvements in China’s transportation sector:A CGE analysis

Energy use is becoming more efficient due to technological innovations.We focused on the transportation sector in China to develop a national multisector computable general equilibrium(CGE)model for analyzing the rebound effect from an improvement of 10%in the energy efficiency.We compared the size of the energy rebound effect at both the macroeconomic and sectoral levels in different transportation modal subsectors,namely rail,road,water,and air travel.The findings showed that the magnitude of the rebound effect varies across the transportation modes.This is particularly true for the air transportation sector,which has an economy-wide rebound effect of 30.1%and an own-sector rebound effect of 74.6%because of a sharp increase in the export demand for air transport services.We also quantitatively evaluated the contribution of energy efficiency improvement in the transportation sector to China’s economic growth and carbon reductions and found a positive dividend effect on the economy as well as the environment.The modeling results suggest that improving overall transportation energy efficiency by 10%generates an economy-wide welfare gain of approximately 29 billion yuan,while 19 billion yuan are attributable to a more efficient road transportation subsector.Furthermore,to offset the effects of these mode-specific rebound effects,we simulated the effectiveness of different policies and solutions.These included economic instruments in the form of energy,environmental,and carbon taxes,household transport consumption structure adjustments,and energy structure adjustments.This study revealed that combining these sustainable development policies offers opportunities for economy-wide multisectoral improvements in energy savings,emissions reduction,and economic benefits.

Multi-objective optimization of environmental tax for mitigating air pollution and greenhouse gas

Government macro-control through various policies is an important way to mitigate air pollution and greenhouse gases.Therefore,environmental tax is used worldwide as an important measure.However,few studies have considered the interaction between carbon and environmental protection taxes.Additionally,different sectors differ in their energy structure,pollution emission intensity,and economic status,and previous studies rarely proposed differentiated environmental tax rates based at the sectoral level.A model framework combining the computable general equilibrium(CGE)model and Bayesian optimization(BO)algorithm is proposed to maximize GDP,meet environmental planning objectives,and explore the optimal environmental taxation scheme to realize the multi-objective optimization of the economy and environment.Meanwhile,this study compares the different impact mechanisms of environmental protection tax and carbon tax.It discusses the impacts of differentiated environmental tax rates in different sectors on the environment and economy.For example,the results show that the coordinated implementation of environmental protection and carbon tax policies and the sectoral differentiated environmental tax rates in China could better balance economic development and environmental governance.Additionally,the optimal taxation scheme could mitigate air pollution and greenhouse gases,promote economic growth,and realize sustainable economic and environmental development.Furthermore,the optimized taxation scheme positively affects the energy and industrial structures.

ENERGY CONSUMPTION,ENVIRONM ENTAL IMPACTS AND EFFECTIVE MEASURES OF GREEN OFFICE BUILDINGS:ALIFE CYCLE APPROACH

The last few decades have witnessed a rapid development of green buildings in China especially the office sector.The life cycle assessment(LCA)approach has potential to weigh the benefits and costs associated with green building developments.Essentially,the LCA method evaluates the costs and benefits across a building’s life cycle with a system approach.In this study,a green office building in Beijing,China,was analyzed by life cycle assessment to quantify its energy use and evaluate the environmental impacts in each life cycle stage.The environmental impacts can be reduced by 7.3%,1.6%and 0.8%by using 30%gas-fired electricity generation,increasing the summer indoor temperature by 1℃,and switching off office equipment and lighting during lunchtime,respectively.Similarly,by reusing 80%of the selected materials when the building is finally demolished,the three major adverse environmental impacts on human health,ecosystem quality,and resource depletion can be reduced by 11.3%12.7%,and 7.1%respectively.Sensitivity analysis shows that electricity conservation is more effective than materials efficiency in terms of a reduction in environmental impacts.These findings are useful to inform decision makers in different stages of the green building life cycle.