Sensitivity of carbon sequestration costs to soil carbon rates

Modifying current agricultural management practices as a means of sequestering carbon has been shown to be a relatively low cost way to offset greenhouse gas emissions. In this paper we examine the sensitivity of the estimates of the amount of soil carbon sequestered and the implied costs of sequestering a tonne of carbon to changes in the rates of soil carbon sequestered for alternative production practices. An application is made to the dryland grain production systems of the US Northern Plains where the marginal costs of soil C range from $20 to $100 per MT. We show that the resulting changes in the marginal costs quantities of C sequestered are not a monotonic transformation of the changes in the soil carbon rates. These results underscore the importance of using a linked economic and biophysical simulation model to assess the economic potential for sequestering carbon in agricultural soils.     

The impact of the establishment of carbon emission trade exchange on carbon emission efficiency

Environmental Science and Pollution Research - The China government focuses on changes in carbon emission efficiency with establishing carbon emission trade exchange (CETE). It is meaningful to...     

The impacts of carbon emissions and voluntary carbon disclosure on firm value

Investors and other stakeholders are starting to pay attention to firms’ carbon emissions and carbon disclosure. This study investigated the effects of voluntary carbon disclosure information and carbon emissions on firm value from listed companies in the Shanghai and Shenzhen 300 (CSI 300) Index. We also apply the Probit model to predict the probability of voluntary carbon disclosure information. The results indicate that the increase in carbon emissions has a negative impact on firm value. The action that companies select to disclose carbon emissions has a positive impact on firm value. The effect of leverage ratio on VCDI is increasing year by year. What is more, the probability of the average size firm carbon disclosure was 30.73% in 2020. Company management needs to pay attention to the risks caused by carbon emissions and ensure the quality of carbon disclosure information, especially the authenticity and reliability of the information.

     

Uncertainties and novel prospects in the study of the soil carbon dynamics

Establishment of the Kyoto Protocol has resulted in an effort to look towards living biomass and soils for carbon sequestration. In order for carbon credits to be meaningful, sustained carbon sequestration for decades or longer is required. It has been speculated that improved land management could result in sequestration of a substantial amount of carbon in soils within several decades and therefore can be an important option in reducing atmospheric CO2 concentration. However, evaluation of soil carbon sources and sinks is difficult because the dynamics of soil carbon storage and release is complex and still not well understood. There has been rapid development of quantitative techniques over the past two decades for measuring the component fluxes of the global carbon cycle and for studying the soil carbon cycle. Most significant development in the soil carbon cycle study is the application of accelerator mass spectrometry (AMS) in radiocarbon measurements. This has made it possible to unravel rates of carbon cycling in soils, by studying natural levels of radiocarbon in soil organic matter and soil CO2. Despite the advances in the study of the soil carbon cycle in the recent decades, tremendous uncertainties exist in the sizes and turnover times of soil carbon pools. The uncertainties result from lack of standard methods and incomplete understanding of soil organic carbon dynamics, compounded by natural variability in soil carbon and carbon isotopic content even within the same ecosystem. Many fundamental questions concerning the dynamics of the soil carbon cycle have yet to be answered. This paper reviews and synthesizes the isotopic approaches to the study of the soil carbon cycle. We will focus on uncertainties and limitations associated with these approaches and point out areas where more research is needed to improve our understanding of this important component of the global carbon cycle.     

活性炭纤维的氧化处理研究

采用静态保干器法测定了活性炭纤维对乙醇、丙酮、N-甲基吡咯烷酮的吸附量.研究了酸氧化处理对活性炭纤维吸附性能的影响,并用电位滴定法确定了活性炭纤维氧化前后表面含氧官能团的变化.结果表明,活性炭纤维对3种吸附质的吸附量均随时间延长而增加,但饱和吸附量及达到饱和吸附的时间因吸附质的不同而不同.氧化处理后,活性炭纤维表面含氧官能团发生变化,对乙醇的吸附量增加18%,而对N-甲基吡咯烷酮的吸附量提高了300%.     

活性炭纤维的氧化处理研究

采用静态保干器法测定了活性炭纤维对乙醇、丙酮、N-甲基吡咯烷酮的吸附量。研究了酸氧化处理对活性炭纤维吸附性能的影响,并用电位滴定法确定了活性炭纤维氧化前后表面含氧官能团的变化。结果表明,活性炭纤维对3种吸附质的吸附量均随时间延长而增加,但饱和吸附量及达到饱和吸附的时间因吸附质的不同而不同。氧化处理后,活性炭纤维表面含氧官能团发生变化,对乙醇的吸附量增加18%,而对N-甲基吡咯烷酮的吸附量提高了300%。     

Black carbon: the reverse of its dark side

The emission of black carbon is known to cause major environmental problems. Black carbon particles contribute to global warming, carry carcinogenic compounds and cause serious health risks. Here, we show another side of the coin. We review evidence that black carbon may strongly reduce the risk posed by organic contaminants in sediments and soils. Extremely efficient sorption to black carbon pulls highly toxic polycyclic aromatic hydrocarbons, polychlorinated biphenyls, dioxins, polybrominated diphenylethers and pesticides into sediments and soils. This increased sorption is general, but strongest for planar (most toxic) compounds at environmentally relevant, low aqueous concentrations. Black carbon generally comprises about 9% of total organic carbon in aquatic sediments (median value of 300 sediments), and then may reduce uptake in organisms by up to two orders of magnitude. This implies that current environmental risk assessment systems for these contaminants may be unnecessarily safe.     

活性炭纤维脱除二氧化碳的实验研究

采用活性炭纤维(ACF)作为吸附材料,研究了ACF对CO_2和N_2的吸、脱分离特性。结果表明,粘胶基活性炭纤维(V-ACF)和聚丙烯腈基活性炭纤维(PAN-ACF)对CO_2和N_2都表现出较好的吸附效果,其中V-ACF对CO_2和N_2的吸附系数高达9,说明ACF是很好的吸附分离材料。ACF对不同烟气浓度和温度下对CO_2吸附的结果说明,ACF对于高浓度CO_2更易于脱除;讨论了ACF在不同解析温度或时间对吸附的影响和ACF的热稳定性,结果表明,在较高解析温度或者较长解析时间下更加容易脱除CO_2,且再生时间短,最佳的解析时间为15 min。经过相同的多次实验,ACF的性能稳定,再生效率稳定在86%。     

Influence of resorcinol chemical oxidation on the removal of resulting organic carbon by activated carbon adsorption

Activated carbon adsorption and chemical oxidation followed by activated carbon adsorption of resorcinol in water has been studied. Three chemical oxidants have been used: hypochlorite, permanganate and Fenton's reagent. The influence of concentrations of resorcinol and activated carbon on adsorption removal rates has been investigated. Both isotherm and adsorption kinetics have been studied. Results are fit well by Freundlich isotherms and adsorption rates of resorcinol were found to follow a pseudo-second-order kinetic model. However, pyrogallol, an intermediate of resorcinol oxidation with permanganate and Fenton's reagent, showed an unfavourable isotherm type. At the conditions investigated, chemical oxidation allows slight reductions of TOC and intermediates formed were found to inhibit the adsorption rate of TOC in the case of permanganate and Fenton's reagent oxidation, likely due to formation of some polymer pyrogallol product. The adsorption process was found to be controlled by pore internal diffusion, which justifies the poor affinity of oxidation intermediates toward activated carbon since molecules of larger size should diffuse rapidly for the adsorption to be effective.     

Estimating the change of carbon in the terrestrial biosphere from 18 000 BP to present using a carbon cycle model

The authors used a global High Resolution Biosphere Model (HRBM), consisting of a biome model and a carbon cycle model, to estimate the changes of carbon storage in the major pools of the terrestrial biosphere from 18 000 BP to present. The climate change data to drive the biosphere for 18 000 BP were derived from an Atmospheric General Circulation Model. Using the AGCM anomalies interpolated to a 0.5 degrees grid, the HRBM data base of the present climate was recalculated for 18 000 BP. The most important processes which influenced the carbon storage include (1) climate-induced changes in biospheric processes and vegetation distribution, (2) the CO(2) fertilization effect, (3) the inundation of lowland areas resulting from the sea level rise of 100 m. Two scenarios were investigated. The first scenario, which ignored the CO(2) fertilization effect, led to total carbon losses from the terrestrial biosphere of -460 x 10(9) t. Scenario 2, which assumed that the model formulation of the CO(2) fertilization effect as used for preindustrial to present could be extrapolated to the glacial 200 microl litre(-1) (ppmv, parts per million per volume), gave a carbon fixation in the terrestrial biosphere of +213 x 10(9) t. The two scenarios were compared with CO(2) concentration data and isotopic ratios from air in ice cores. The results of Scenario 1 are not in agreement with the data. Scenario 2 gives realistic delta(13)C shifts in the atmosphere but the biospheric carbon storage at the end of the glacial period seems too large. The authors suggest that the low atmospheric CO(2) concentration may have favoured the C-4 plants in ice age vegetation types. As a consequence the influence of the low CO(2) concentration was eventually reduced and the glacial carbon storage in vegetation, litter, and soil was increased.     

Estimating and analyzing the spatial distribution of soil organic carbon in China

Research on the terrestrial carbon cycle is an important component in the study of global change. Soil organic carbon, as the main part of the terrestrial carbon reservoir, plays an important role in the Earth's carbon cycle. To accurately estimate soil organic carbon storage, its composition and dynamic change must be determined. This presents a challenge to research on the soil carbon cycle, especially in China where the nationwide soil organic carbon reservoir largely remains unknown. This paper reports a research project that attempts to estimate the nationwide soil organic carbon reservoir. Data from 2473 soil profiles from the second national soil survey were collected and GIS technology was employed to quantify the national soil carbon reservoir. The analytical results show that the total amount of soil organic carbon is about 92.4 Pg (Pg = 10(15) g) and that the average carbon density is about 10.53 kg C m(-2). The spatial distribution of soil organic carbon was also analyzed and mapped. This study presents basic data and an analysis method for carbon-cycle studies and also provides scientific support for policy-making efforts to control CO2 emissions in China.     

The fate of PAHs in the carbon black manufacturing process

This study measured PAHs contained in the feedstock oil, carbon black products, and stack flue gas, then the fate of PAHs was assessed from the mass balance point of view for a carbon black manufacturing process. Results show the carbon black manufacturing process would result in the depletion of total-PAHs and the summation of top three carcinogenic PAH species (i.e., BbF+BaP+DBA) up to 98.15% and 99.83%, respectively. The above results suggest that the carbon black manufacturing process would result in not only the decrease of the amount of total-PAHs, but also the carcinogenic potencies of PAHs originally contained in the feedstock oil. Regarding PAHs contained in the carbon black products and stack flue gas, this study suggest they might be resulted mostly from high-temperature pyrolytic process, rather than the PAHs originally contained in the feedstock oil. For the carbon black manufacturing industry, since the soot (i.e., the carbon black) was completely collected as its final product, therefore most of carbon black-bearing PAHs did not directly release to atmosphere. On the other hand, PAHs contained in the stack flue gas were directly exhausted to the atmosphere and thus were assessed in this study. The results show the emission rates for total-PAHs and BbF+BaP+DBA for the stack flue gas were 2.18 kg/day and 1.50 g/day, respectively, which were approximately 25% and 40% of those exhausted from a municipal incinerator with a treatment capacity of 300 metric tons/day. It is concluded that the carbon black manufacturing process might not be a significant PAHs emission source, as compared to the municipal incinerator.     

Exploring the influencing factors of carbon neutralization in Chinese manufacturing enterprises

One of the key issues facing the government in achieving carbon neutrality is what methods can be used to effectively reduce carbon emissions. Taking manufacturing enterprises as an example, this paper studies the carbon emission reduction effects of green technology innovation subsidy (GIS), carbon tax (CT), and carbon emission trading (CET). Under the background of social welfare and carbon emission reduction efficiency, we get the results of optimal carbon emission reduction measures in different environments. The results are as follows: (1) In the initial and mature stage of green technology innovation, GIS is the best choice to improve the degree of green manufacturing and maximize social welfare. CT and CET are the best choice to obtain the highest SE (carbon emission reduction efficiency). (2) In the transitional stage, CET and CT can promote the maturity of green technology. However, with the maturity of green technology, the promotion of green technology has weakened. CT is the best choice to achieve the highest SE. (3) When the carbon tax or carbon trading price is at a high or low level, raising the tax rate or carbon trading price can increase the income of enterprises. Therefore, the government should take measures according to the objectives of different stages. When the goal is to maximize social benefits, GIS is the best choice in the initial stage and transition stage, and CET or CT is the best choice in the transition stage. In the initial stage and fertilization stage, when the highest SE, CT, or CET is the best choice, while in the transition stage, CT is the best choice.

     

The ocean as part of the global carbon cycle

The ocean plays a central role in the global carbon cycle being by far the largest active reservoir. Atmospheric CO₂ level depends on the CO₂concentration in the ocean surface layer, which is relatively low compared to mean oceanic values due to biological and physical carbon pumps. Although the ocean may take up much of the carbon released by the increased burning of fossil fuels, this capacity is limited because of the chemical buffering and a mismatch in time scales (oceanic mixing is much slower than anthropogenic perturbations).     

Net carbon flux from agricultural ecosystems: methodology for full carbon cycle analyses

Agricultural ecosystems have the potential to sequester carbon in soils by altering agricultural management practices (i.e. tillage practice, cover crops, and crop rotation) and using agricultural inputs (i.e. fertilizers and irrigation) more efficiently. Changes in agricultural practices can also cause changes in CO2 emissions associated with these practices. In order to account for changes in net CO2 emissions, and thereby estimate the overall impact of carbon sequestration initiatives on the atmospheric CO2 pool, we use a methodology for full carbon cycle analysis of agricultural ecosystems. The analysis accounts for changes in carbon sequestration and emission rates with time, and results in values representing a change in net carbon flux. Comparison among values of net carbon flux for two or more systems, using the initial system as a baseline value, results in a value for relative net carbon flux. Some results from using the full carbon cycle methodology, along with US national average values for agricultural inputs, indicate that the net carbon flux averaged over all crops following conversion from conventional tillage to no-till is -189 kg C ha(-1) year(-1) (a negative value indicates net transfer of carbon from the atmosphere). The relative net carbon flux, using conventional tillage as the baseline, is -371 kg C ha(-1) year(-1), which represents the total atmospheric CO2 reduction caused by changing tillage practices. The methodology used here illustrates the importance of (1) delineating system boundaries, (2) including CO2 emissions associated with sequestration initiatives in the accounting process, and (3) comparing the new management practices associated with sequestration initiatives with the original management practices to obtain the true impact of sequestration projects on the atmospheric CO2 pool.     

Ozonation of aniline promoted by activated carbon

The removal of aniline from aqueous solutions by simultaneous use of ozone and activated carbon was investigated at different solution pH. For comparative purposes, single ozonation and adsorption on activated carbon were carried out in the same experimental set-up. In order to evaluate the role of the activated carbon surface chemistry during ozonation, a commercial activated carbon, Norit GAC 1240 PLUS, was submitted to oxidation in the liquid phase with HNO(3). The texture and surface chemistry of the activated carbon samples were characterized. During ozonation, complete conversion of aniline was achieved after approximately 20 min, regardless of the presence of activated carbon. In all cases, several by-products were formed during ozonation. Nitrobenzene, o- and p-aminophenol were the primary aromatic oxidation by-products identified. In terms of TOC removal, best results were achieved by the simultaneous use of ozone and activated carbon. Though there is a strong contribution of adsorption, a considerable synergetic effect between ozone and activated carbon is observed. In general, activated carbon promotes the reaction of ozonation enhancing the efficiency of this treatment process. The basic activated carbon presented greater activity in this process leading to higher mineralization rates.     

Comparative analysis of the structure of carbon materials relevant in combustion

The determination of the structure of carbon materials is an analytical problem that join the research scientific communities involved in the chemical characterization of heavy fuel-derived products (heavy fuel oils, coal-derived fuels, shale oil, etc.) and of carbon materials (polycyclic aromatic compounds, tar, soot) produced in many combustion processes.

The knowledge of the structure of these “difficult” fuels and of the carbon materials produced by incomplete combustion is relevant to research for the best low-environmental impact operation of combustion systems; but an array of many analytical and spectroscopic tools are necessary, and often not sufficient, to attempt the characterization of such complex products and in particular to determine the distribution of molecular masses.

In this paper the size exclusion chromatography using N-methyl-pyrrolidinone as eluent has been applied for the characterization of different carbon materials starting from typical carbon species, commercially available like polyacenaphthylene, carbon black, naphthalene pitch up to combustion products like soot and soot extract collected in fuel-rich combustion systems. Two main fractions were detected, separated and molecular weights (MWs) determined by comparison with polystyrene standards: a first fraction consisted of particles with very large molecular masses (>100 000 u); a second fraction consisted of species in a relatively small MW range (200–600 u). The distribution of these fractions changes in dependence on the carbon sample characteristics.

Fluorescence spectroscopy applied on the fractions separated by size-exclusion chromatography has been used and comparatively interpreted giving indications on the differences and similarities in chemical structure of such different materials.     

Methodology for estimating soil carbon for the forest carbon budget model of the United States, 2001

The largest carbon (C) pool in United States forests is the soil C pool. We present methodology and soil C pool estimates used in the FORCARB model, which estimates and projects forest carbon budgets for the United States. The methodology balances knowledge, uncertainties, and ease of use. The estimates are calculated using the USDA Natural Resources Conservation Service STATSGO database, with soil dynamics following assumptions based on results of site-specific studies, and area estimates from the USDA Forest Service. Forest Inventory and Analysis data and national-level land cover data sets. Harvesting is assumed to have no effect on soil C. Land use change and forest type transitions affect soil C. We apply the methodology to the southeastern region of the United States as a case study.     

Closing the carbon cycle through rational use of carbon-based fuels

In this paper, a brief overview is presented of natural gas as a fuel resource with subsequent carbon capture and re-use as a means to facilitate reduction and eventual elimination of man-made carbon emissions. A particular focus is shale gas and, to a lesser extent, methane hydrates, with the former believed to provide the most reasonable alternative as a transitional fuel toward a low-carbon future. An emphasis is placed on the gradual elimination of fossil resource usage as a fuel over the coming 35 to 85 years and its eventual replacement with renewable resources and nuclear power. Furthermore, it is proposed that synthesis of chemical feedstocks from recycled carbon dioxide and hydrogen-rich materials should be undertaken for specific applications in the transport sector which require access to high energy density fuels. To achieve the latter, carbon dioxide capture is imperative and possible synthetic routes for chemical feedstock production are briefly reviewed.