Indirect Carbon Research Articles

Design and thermodynamic analysis of a novel structure utilizing coke oven gas for LNG and power cogeneration

Coke oven gas is a by-product of the process of producing coke from coal and contains valuable compounds such as hydrogen and methane. In this study, an improved process was proposed for co-generation of power and LNG from COG with low CO2 emissions and high energy and exergy efficiency. This proposed process includes: LNG Recovery Unit, Organic Rankin Cycle, and the power plant. The results of simulation showed that the exergy and energy efficiencies for this proposed process are 77.9% and 70.29%, respectively, which are considerably higher than other studies. It is found that the total exergy destruction of the proposed process is 4272.95 kW, and the power plant with 3118.1 kW exergy destruction has the largest share in total exergy destruction. Additionally, outcomes showed that ORC recovered 1205 kW of waste heat from compressor exhaust gases and produced 167.4 kW of power. Environmental analysis shows indirect carbon emissions for the proposed process is zero. The CO2 emissions for the total energy and electric power generation were 0.0034 kgCO2/MJ and 406 gCO2/kWhel, respectively which are lower than coal or natural gas power plants.

Indirect carbon emissions from household consumption of middle-income groups: Evidence from Yangtze River Economic Belt in China

Consumption is evidenced to play an increasing significant role accompanied by economic transition in China. Carbon emissions caused by consumption are becoming an important growth point of carbon emissions. The size of China's middle-income groups is growing and is expected to reach 60 % of the population in 2035. However, the amount of indirect carbon emissions from household consumption (ICEHCs) of middle-income groups and the effects of their drivers have not been quantitatively assessed. In response, this paper adopts input-output tables to calculate urban-rural middle-income groups' ICEHCs from 2012 to 2018, and uses structural decomposition analysis to determine the effects of drivers and sectors. Results are as follows: Urban-rural middle-income groups' ICEHCs in the Yangtze River Economic Belt (YREB) are increasing and its differences are significant, and present a spatial pattern of high in the eastern region while low in the western region. S22 (Production and Supply of Electric Power, Steam and Hot Water) becomes the main sector of carbon emissions, which accounts for about 70.00 % of the total middle-income groups' ICEHCs in 2018. Consumption pattern is the predominant driver for promoting urban-rural middle-income groups' ICEHCs, whereas production structure is the predominant restraining driver.

Digital financial development and indirect household carbon emissions: empirical evidence from China

Digital financial development and indirect household carbon emissions: empirical evidence from China

Stackelberg game-based optimal scheduling for multi-community integrated energy systems considering energy interaction and carbon trading

The multi-community integrated energy system (MCIES) has become a practical approach to improve energy efficiency and reduce carbon emissions with the promotion of urbanization. However, the current optimal scheduling of MCIES neither balances the total operation cost of the MCIES and the individual benefits of community microgrids effectively nor considers the carbon emission accounting and carbon trading of terminal integrated energy systems adequately. In this study, a bi-level optimal scheduling framework dominated by the regional dispatching center (RDC) and fully participated by the community integrated energy systems (CIESs) is developed for the scheduling of MCIES, which considers the energy interaction and carbon trading between CIESs. Firstly, a refined carbon emission accounting model considering direct and indirect carbon emissions is proposed, which can calculate the carbon emissions of each CIES in detail from the energy flow perspective based on the definition of virtual and actual carbon flow. Then, a one-master-multi-slave game model is established, where the RDC acts as the leader pursuing the minimum operation cost of the region by formulating energy interaction and carbon trading schemes between CIESs, while the CIESs are regarded as the followers that adjust the energy consumptions to minimize their operation costs. Finally, the effectiveness of the proposed optimization model is validated through the case studies, which are tested in a specific urban area. The simulation results demonstrate that the proposed optimal scheduling model can not only effectively coordinate the benefits between RDC and CIESs, but also reduce the overall operational cost and carbon emission of the MCIES.

Potential side effects of climate change mitigation on poverty and countermeasures

Many countries have set ambitious long-term emissions reduction targets for reaching the goal in alignment with the Paris Agreement. However, large-scale emission reduction efforts may influence poverty by various economic channels. Here, we show the extent to which climate change mitigation, excluding climate change impacts, has the potential to increase poverty, and have identified its factors such as income, price changes, and direct and indirect carbon pricing impacts. We found that the global poverty headcount could increase by 69 million (19%) in 2030 relative to the baseline for climate change mitigation with global uniform carbon prices. Moreover, our decomposition analysis revealed that both price and income change effects were major factors that could increase the poverty headcount, which are 55% and 40%, respectively. This adverse side effect could be mitigated by various measures, such as emission regulations and an enhancement of energy efficiency standards beyond the typical simple carbon tax. Our results imply that global climate change mitigation policy should place more attention on economic development in poor countries.

Are tax revenue recycling schemes based on industry-differentiated carbon tax conducive to realizing the “double dividend”?

Carbon tax policies based on industry differences can produce better emission reductions, but their economic losses have not been fully considered. To guarantee the fairness and economic effectiveness of the carbon emission reduction, this paper explores the policy impacts of revenue recycling schemes based on industry-differentiated carbon taxes using a dynamic CGE model. The findings show that revenue recycling schemes can effectively mitigate the negative macroeconomic and industry output impacts of industry-differentiated carbon taxes, but also affects their carbon reduction effects. The indirect carbon tax revenue recycling schemes are more beneficial than the direct recycling schemes in reducing GDP loss, and corporate income tax reduction is most effective in mitigating the reduction in fixed asset investment. The applicability of different carbon tax revenue recycling schemes varies across industries, and in general corporate income tax reduction and subsidies to clean energy industries are more beneficial to carbon emission reduction, and indirect carbon tax revenue recycling schemes that reduce residential and corporate income taxes can achieve stronger “double dividend”. This paper suggests that China should adopt a industry-differentiated carbon tax with a fair distribution of emission reduction responsibilities, while achieving a “double dividend” through appropriate revenue recycling schemes.

Substitution Estimates for Wood Products in the United States, 1990 to 2020

Abstract Forest carbon stock changes are routinely reported at the national level. Such accounting usually includes carbon sequestered by live trees and stored in living and dead trees, litter, and soil. The carbon stored in harvested wood products (HWPs), while in use and after disposal, may also be reported. However, wood products may provide a further indirect carbon benefit by providing an alternative to materials that require relatively large inputs of fossil-derived carbon. This “substitution impact” of HWPs is not explicitly considered in national reporting for forest carbon accounts because it is not directly comparable with absolute emissions and removals. However, the substitution impact is avoided fossil emissions, which do affect the net climate impact of wood use. Here, we estimate the total substitution impact for wood products harvested recently from forests in the United States. The total substitution impact is based on reported volumes of national wood production and the substitution factors for individual products. The substitution factors are obtained from comparative life-cycle assessments of specific wood products and their nonwood alternatives. The total substitution impact for wood products in the United States in 2020 was 188 TgCO2 equivalents. Calculation of substitution factors is challenged by assumptions about the use of wood products and their alternatives and by limited availability of current and specific life-cycle assessment data; however, our findings indicate that the substitution impact of forest products are a relatively important component of the carbon benefits of wood-based products.

Process simulation and economic evaluation of a biomass oxygen fuel circulating fluidized bed combustor with an indirect supercritical carbon dioxide cycle

In recent years, the utilization of biomass through advanced power technologies has intensified to achieve carbon neutrality. An oxy-fuel circulating fluidized bed combustor of biomass with higher efficiency supercritical carbon dioxide cycle has been developed with the aim of compensating the penalties for carbon capture and storage. The combustor fuelled with waste paper, waste wood, and cow manure, at an input of 200 ton/day is economically evaluated. Waste paper is on the verge of becoming an economically feasible fuel, more so than the other biomass examined. The use of waste paper led to a positive net present value, an internal rate of return of 3.8%, a benefit-cost ratio of 1.025, and a payback period of 17.7 years. Subsequent sensitivity analyses conducted for the waste paper fuelled power plant indicated that the capital cost is the most influential factor; the boiler, supercritical carbon dioxide cycle, and oxygen fuel combustion system were indicated in descending order of related subdivided sensitiveness. Both renewable energy certificate and carbon credit has contributed to the feasible economic of the system, with former one took precedence over later one. Sensitivity from the technical perspective, improvement in air separation unit is likely to greatly improve the economic feasibility of the proposed system. The power consumption of the air separation unit, as well as that of the carbon dioxide compression and purification unit, were highly sensitive to the implementation cost.

Carbon emission efficiency evaluation of wastewater treatment plants: evidence from China.

A scientific evaluation of the carbon emission efficiency is crucial for ensuring the sustainable development of wastewater treatment plants (WWTPs). In this paper, we applied a non-radial data envelopment analysis (DEA) model to calculate the carbon emission efficiency of 225 WWTPs located in China.The results showed that the average carbon emission efficiency of China's WWTPs was 0.59, indicating that the efficiencies of most samples still require improvement. The carbon emission efficiency of WWTPs from 2015 to 2017 decreased because of the decrease in technology efficiency. Among the influencing factors, different treating scales had positive impact on carbon emission efficiency improvement. WWTPs with anaerobic oxic process and the first-class A standard were likely to have higher carbon emission efficiency in the 225 WWTPs. By incorporating direct and indirect carbon emissions into WWTP efficiency evaluation, this study helped decision-makers and related water authorities to better understand the contribution of WWTPs to the aquatic and atmospheric environments.

Efficient conversion of waste-to-SNG via hybrid renewable energy systems for circular economy: Process design, energy, and environmental analysis

Developing an efficient and environment-friendly route for waste valorization is extremely significant in accelerating the transition toward a circular economy. A novel waste-to-synthetic natural gas (SNG) conversion process comprising hybrid renewable energy systems is proposed for this purpose. This includes thermochemical waste conversion and power-to-gas technologies for simultaneous waste utilization and renewable energy storage applications. The energy and environmental performances of the proposed waste-to-SNG plant are assessed and optimized. Results indicated that the implementation of a thermal pretreatment unit prior to the plasma gasification (two-step) is beneficial to improve the yield of hydrogen in the syngas, thereby leading to less renewable energy requirement for green hydrogen production used in the methanation process. This also enhances SNG yield by a factor of 30% as compared to the case without thermal pretreatment (one-step). The overall energy efficiency (OE) of the proposed waste-to-SNG plant is in the range of 61.36–77.73%, while the energy return on investment (EROI) ranges between 2.66 and 6.11. Most environmental impacts are mainly contributed by the indirect carbon emissions as a consequence of the power requirement for thermal pretreatment, plasma gasifier, and auxiliary equipment. The value of specific electricity consumption for SNG production of the treated RDF exhibits 1.70–9.25 % less than that of raw RDF when the pretreatment temperature is less than 300 °C. The OE of the system declines by 4.52% when 50 wt% of biomass is mixed in the fuel, whereas an enhancement of 18.33% in EROI and a reduction of 16.19% in specific CO2 emissions are obtained.

Identification of Key Basic Parameters Involved in Carbon Emissions in Full-Scale Wastewater Treatment Plants

In this study, carbon emissions in three full-scale wastewater treatment plants were determined by the emission factor method. Moreover, the correlation between basic parameters (influent water parameters and pollutant removal efficiency) and carbon emissions was examined via a structural equation model (SEM). The results showed a significant variation in the total carbon emission intensity of plants over time. The average total carbon emission intensity of plants A, B and C were 0.314, 0.404 and 0.363 kg eqCO2/m³, respectively. Meanwhile, the indirect carbon emission caused by energy and chemical agent consumption accounts for the majority of total carbon emissions (about 85%). Generally, statistical analysis results show that carbon emission intensity is positively correlated with pollutant removal efficiency. Notably, RTN showed the highest positive correlation with Eind, followed by RTN > RCODCr > RTP > TN > RNH3-N > NH3-N > TP. Moreover, capacity showed the greatest negative contribution to Eind, followed by CODCr. In contrast, the positive contribution to Edir was followed by the sequence of RTN > RCODCr > TN > RNH3-N > NH3-N. Notably, CODCr showed a significantly negative correlation with Edir, while TP and its removal showed little correlation with Edir.

A Coupled CH4, CO and CO2 Simulation for Improved Chemical Source Modeling

Understanding greenhouse gas–climate processes and feedbacks is a fundamental step in understanding climate variability and its links to greenhouse gas fluxes. Chemical transport models are the primary tool for linking greenhouse gas fluxes to their atmospheric abundances. Hence, accurate simulations of greenhouse gases are essential. Here, we present a new simulation in the GEOS-Chem chemical transport model that couples the two main greenhouse gases—carbon dioxide (CO2) and methane (CH4)—along with the indirect greenhouse gas carbon monoxide (CO) based on their chemistry. Our updates include the online calculation of the chemical production of CO from CH4 and the online production of CO2 from CO, both of which were handled offline in the previous versions of these simulations. In the newly developed coupled (online) simulation, we used consistent hydroxyl radical (OH) fields for all aspects of the simulation, resolving biases introduced by inconsistent OH fields in the currently available uncoupled (offline) CH4, CO and CO2 simulations. We compare our coupled simulation with the existing v12.1.1 GEOS-Chem uncoupled simulations run the way they are currently being used by the community. We discuss differences between the uncoupled and coupled calculation of the chemical terms and compare our results with surface measurements from the NOAA Global Greenhouse Gas Reference Network (NOAA GGGRN), total column measurements from the Total Carbon Column Observing Network (TCCON) and aircraft measurements from the Atmospheric Tomography Mission (ATom). Relative to the standard uncoupled simulations, our coupled results suggest a stronger CO chemical production from CH4, weaker production of CO2 from CO and biases in the OH fields. However, we found a significantly stronger chemical production of CO2 in tropical land regions, especially in the Amazon. The model–measurement differences point to underestimated biomass burning emissions and secondary production for CO. The new self-consistent coupled simulation opens new possibilities when identifying biases in CH4, CO and CO2 source and sink fields, as well as a better understanding of their interannual variability and co-variation.

Dynamic Scenario Predictions of Peak Carbon Emissions in China’s Construction Industry

As the largest carbon emitter in the world, China aims to reach its peak carbon emissions goal by the year 2030, while the construction industry makes a significant contribution to carbon emissions, directly affecting the country’s commitment to meet its target. The present paper investigates the dynamic characteristics of carbon emissions released by China’s construction industry under single- and multiple-scenario settings with altering economic growth rates, optimizing energy structures, adjusting industrial structures, and modifying carbon emission policy factors. The research results show that the total carbon emissions generally present a steady increase from the year 2000 and will reach 12,880.40 million tons (MT) by 2030 under a scenario without any intervention. Indirect carbon emissions released from associated industries account for over 96% of the total carbon emissions, while direct carbon emissions make a minor contribution to the total. Single and comprehensive scenarios have positive effects on reducing emissions; it was also observed that only under energy structure scenario III and comprehensive scenario III could carbon emissions released from the construction sector reach a peak value by 2030. The effects of emissions reductions as a result of single policies can be presented in the following order: energy structure, economic growth, carbon emissions policy factor, and industrial structure. All of the emissions reduction effects of multiple scenarios are superior to the single scenarios. The research results provide a basis and guidance for policymakers to adopt the correct steps to fulfill China’s aim of achieving peak carbon emissions by the projected date.

Direct ammonium recovery from the permeate of a pilot-scale anaerobic MBR by biochar to advance low-carbon municipal wastewater reclamation and urban agriculture

The rapidly evolving global climate change has an unprecedented impact sustainable water supply, but also challenges and water shortage global food security. In such a dynamic situation, this study explored direct recovery of ammonium from the effluent of a pilot-scale anaerobic membrane bioreactor (AnMBR) treating actual municipal wastewater via biochar adsorption, while the use of produced ammonium-loaded biochar for urban agriculture was also demonstrated. Results showed that modified biochar could remove almost all ammonium in the pilot AnMBR permeate at an empty bed contact time of 30 mins. Results showed that ammonium extracted from the ammonium-loaded biochar could promote the germination of Daikon radish seeds. It was further observed that the fresh weight of Pak Choi (a typical leafy vegetable) planted in the soils augmented with the ammonium-loaded biochar was 42.5 g per vegetable versus 18.5 g per vegetable in the control, indicating a 130 % of increase in the Pak Choi productivity. In addition, the Pak Choi in grown the ammonium-loaded biochar augmented soils appeared to be much bigger with larger leaves compared to the control. It was also worth to note that the ammonium-loaded biochar could significantly stimulate the root development of Pak Choi, i.e., 20.7 cm over 10.5 cm obtained in the control. More importantly, the amount of carbon emission reduced through returning ammonium-loaded biochar to urban agriculture could offset the treatment process-associated direct and indirect carbon emission.

Production Inventory Optimization Considering Direct and Indirect Carbon Emissions under a Cap-and-Trade Regulation

Background: The latest global agreement on net-zero emissions encourages new studies on production inventory optimization that promote carbon emissions reduction without harming a company’s profit performance, particularly because certain carbon-pricing regulations bind manufacturing companies. Methods: This study aims to develop a production inventory model that considers direct and indirect emissions in three emission scopes. It incorporates emissions from production, material handling, transportation, and waste disposal for further treatment under a carbon cap-and-trade regulation. With the help of Maple software, a convex total cost function was solved. Results: The results show that the optimum production quantity depends on the values of demand, setup cost, holding cost, fixed cost per delivery, fixed cost for waste disposal, and other parameters related to carbon prices. This study also found that the total cost was highly dependent on the values of the carbon cap, carbon price, and delivery distance. Meanwhile, changes in the delivery distance and fuel emissions standard significantly impacted total emissions. Conclusions: The proposed model can guide manufacturing companies in setting the optimum production quantity per cycle. Moreover, they must carefully manage the delivery and setting of the carbon cap and carbon price from the government.

Feasibility study of using cogeneration plants at Kuzbass coal mines

The paper considers the problem of reducing greenhouse gas emissions in the process of coal mining during the coal mine methane utilization in power supply systems. An algorithm to form recommendations for the implementation of CMM generation is presented. A simulation model for one of the Kuzbass coal mines was developed in the PowerFactory software application. The simulation model considers the uneven nature of the power consumption of mining equipment. As a result of modeling, daily power consumption profiles and voltage levels in the coal mine power supply system were determined before and after the implementation of the proposed measures. Based on the results, the technical and economic effects was estimated, which consisted in reducing the direct and indirect carbon footprint, electricity and capacity fees. It has been established that the cost of carbon dioxide emission quotas significantly affects the investment attractiveness of cogeneration projects. Based on the results, recommendations are given to stimulate the development of small generation in coal mines.

Economic policy uncertainty and carbon footprint: International evidence

Economic policy uncertainty is an evolving area of research that may affect environmental issues such as the carbon footprint. However, from a global perspective, it is not known whether economic policy uncertainty is significantly related to it. Motivated by this gap in the literature, we investigate the impact of economic policy uncertainty on carbon footprint. Using a sample of 2782 firms from 60 countries, our cross-sectional regression analysis finds that economic policy uncertainty is positively associated with the carbon footprint. This applies to the total, direct, and indirect carbon emissions measurements. However, we find that countries with better institutional governance alleviate the significant association between economic policy uncertainty and carbon footprint.

Systematic Evaluation of Low-carbon Operation of Typical A2O Processes in Municipal Sewage Plant

Under the "Carbon Peak, Carbon Neutral" goal, the systematic evaluation of the carbon emission equivalent (CO2eq) and its compositions of the typical A2O process has important guiding significance for the low-carbon operation of most municipal sewage plants in China. Based on the operational data on the first municipal sewage plant of Jiaozuo in 2020 and the methods presented in "2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, " a systematic evaluation of the CO2eq of the typical A2O process was established, including direct emissions that were built on the Arrhenius model introducing the water temperature factor and indirect emissions from the three aspects of electricity consumption, agent addition, and sludge transportation. The results showed that the daily emission intensities of CH4 and N2O were (115±56) kg·d-1 and (30±18) kg·d-1, respectively. Additionally, indirect carbon emissions from electricity consumption and agent addition accounted for 48.4% and 51.3% in the biochemical treatment section, respectively. In 2020, CO2eq amounts of total research plant and per unit sewage were 2.17×104 t and (0.63±0.07) kg·m-3, respectively. The magnitude of the proportion of different carbon emission compositions was as follows:sewage electricity (36.5%)>sewage agent (26.6%)>N2O direct (15.4%)>sludge agent (9.6%)>sludge electricity (6.7%)>CH4 direct (4.9%)>sludge transportation (0.3%). System import/export fluxes of carbon and nitrogen elements were calculated, followed by the carbon to nitrogen mass ratio in the sewage plant. Direct carbon emission characteristics of CH4 and N2O and their influencing factors were discussed, respectively. Based on the balance theory of carbon and nitrogen elements in the system, it is proposed that the selective introduction of industrial wastewater may become an important reference measure for the low-carbon operation of municipal sewage plants in the future.

Resource use efficiencies, environmental footprints and net ecosystem economic benefit of direct-seeded double-season rice in central China

Intensive cropping systems with two or three harvests per year are vital to produce sufficient food for the growing population. Improvements in the sustainability of these systems are critical for global food security. Transplanted double-season rice (TPD), an important cropping system in China, is seriously threatened by various challenges such as labor shortage, poor resource use efficiency, high environmental footprint, and low profitability. These challenges could be potentially alleviated by shifting TPD to direct-seeded double-season rice (DSD). Due to the limited thermal energy, ultrashort-duration cultivars matured within 95 days have to be used in DSD in central China. However, it is unknown whether DSD with ultrashort-duration cultivars (DSDS) can improve resource use efficiency and reduce environmental costs compared with TPD in this region. This study aimed to compare the resource use efficiency (energy, water, labor, and fertilizer), carbon and nitrogen footprints, and net ecosystem economic benefit of DSDS and TPD with ultrashort-duration (TPDS) and medium-duration cultivars (TPDM). Results showed that total energy output was 222.0 GJ ha−1 in DSDS, which was comparable to that of TPDM but was significantly increased by 9.5% compared with TPDS. Compared with TPD (i.e. both TPDS and TPDM), the total energy input, labor input, water input, and nitrogen surplus in DSDS reduced by 16.9%, 53.2%, 36.8%, and 31.4%, respectively, leading to significant increases in energy use efficiency, labor productivity, water use efficiency, and nitrogen use efficiency. Furthermore, DSDS decreased direct CH4 and NH3 emissions and indirect carbon emission and reactive nitrogen losses from agronomic inputs, and consequently reduced carbon footprint by 28.6–42.7% and nitrogen footprint by 12.9–14.8% compared with TPD. As a result, the net ecosystem economic benefit in DSDS was significantly increased by 65.9–188.2% relative to TPD. These findings suggest that DSDS is a highly promising strategy to maintain high productivity with less resource inputs and environmental pressures but high economic benefits in central China.

Remediation of benzo[a]pyrene contaminated soils by moderate chemical oxidation coupled with microbial degradation

Chemical oxidation is a promising technology for the remediation of organics-contaminated soils. However, residual oxidants and transformation products have adverse effects on microbial activities. This work aimed at moderate chemical oxidation coupled with microbial degradation (MOMD) for the removal of benzo[a]pyrene (BaP) by optimizing the type and dosage of oxidants. Potassium permanganate (KMnO4), Fe2+ + sodium persulfate (Fe2+ + PS), Fenton's reagent (Fe2+ + H2O2), and hydrogen peroxide (H2O2) were compared for BaP removal from loam clay and sandy soils. Overall, the removal efficiency of BaP by a moderate dose of oxidant coupled indigenous microorganism was slightly lower than that by a high dose of relevant oxidant. The contributions of microbial degradation to the total removal of BaP varied for different oxidants and soils. The removal efficiency of BaP from loam clay sandy soil by a moderate dose of KMnO4 (25 mmol/L) was 94.3 ± 1.1 % and 92.5 ± 1.8 %, respectively, which were both relatively higher than those under other conditions. The indirect carbon footprint yielded by the moderate dose of oxidants was 39.2–72.8 % less than that by the complete oxidation. A moderate dose of oxidants also reduced disturbances to soil pH and OC. The microbial communities after MOMD treatment were dominated by Burkholderiaceae, Enterobacteriaceae, Alicyclobacillaceae, and Oxalobacteraceae. These dominant microorganisms promoted the removal of BaP through the expression of polycyclic aromatic hydrocarbon-ring hydroxylated dioxygenase gene. Compared with complete chemical oxidation, MOMD is also a promising technique with the utilization of indigenous microorganism for remediating BaP-contaminated soils.