CO2 Emission Rates Research Articles

Towards building clean hydrogen supply chain network in Iran for future domestic demand and exports. Part II: 4E analyses of prioritized scenarios

In continuation of the previous part, this paper comprehensively focuses on energy, exergy, exergo-economic, and environmental (4E) analyses of two prioritized clean hydrogen (H2) supply chains pathways. The first scenario relies on domestic demand, involves blue H2 production and storage using steam methane reforming coupled with carbon capture and storage through H2 conversion to hydrogen carriers in liquid form (ammonia and methanol) aligned with the existing infrastructure. The second scenario involves green H2 production from photovoltaic panels as the power source follows by storing H2 in liquid form which is more suitable to export. The findings indicate that the blue H2 system outperforms the green H2 system in terms of energy and exergy, boasting 41.38% and 22.15% compared to 12.16% and 12.75%, respectively. However, when examining economic parameters, the blue H2 system shows a total cost rate of 1976 US$/h, a net profit of $747.2 million (mn) at the end of its lifetime, and a payback period of approximately nine years. Conversely, the green H2 system demonstrates economic indicators of a 125.2 $/h as a total cost rate, $1.26 billion (bn) net profit, and an 8.17 year payback period. Moreover, the production cost rates for blue and green H2 are 1.32 $/kg and 2.55 $/kg, respectively; while the CO2 emissions rate in the blue H2 system is 10.71 kg/s. The green H2 system prevents 19.84 kg/s of CO2 emissions resulted a significant environmental cost reduction of 2.28 $/kg H2. This analysis facilitates a thorough comparison of these two clean H2 production and storage systems, offering insights for policymakers across performance, economic, and environmental dimensions.

Hybridization in meta-heuristic techniques for green layout design in the tyre manufacturing industry: An optimal analysis

To stop or lessen factory pollution, many academics in the field of study have produced a vast array of strategies to achieve optimization goals. But, it is unable to follow a uniform solution for all production facilities. In this research work, green layout design (GLD) is proposed to minimize total material handling cost (TMHC) and CO2 emissions. The green facility layout refers to the facility layout with minimum CO2 emissions and to eliminate unnecessary energy dissipation from material handling equipments & production machineries, as well as plant re-layout in-term on material handling cost. In this study context, a Lagrangian relaxation model has been used at the allocation level. It computes a suboptimal solution to the dual problem in order to obtain a feasible solution. This enhanced algorithm method iteratively tries to minimize the gap between the dual and feasible solutions on minimal of TMHC and CO2 emission rate. It has been experimentally simulated using the MATLAB (Matrix Laboratory) application and upgraded adaptive salp swarm optimization (ASSO), dragon fly optimization (DFO) and Hybrid (combination) of ASSO-DFO evolutionary optimization techniques. The primary focus of this implementation is to control material handling between departments or cells, production flow between departments, energy consumption (electrical and gas consumption for production), and manpower utilization within and across departments. This research has chosen an existing and acceptable designs from targeted tyre manufacturing company in South India. The hybrid ASSO-DFO implementation TMHC differs from ABC by 60%, DFO by 65%, 58% with simulated annealing (SA), and ASSO by 48%. Emission rate decreased by 26% ABC, 21% DFO, and 24% SA & 18% with ASSO. An average of 50% decrease in TMHC and 25% reduction of CO2 emission rate in GLD have been achieved.

Rainstorm and strong wind weathers largely increase greenhouse gases flux in shallow ponds

Shallow-water ponds represent the hotspots of greenhouse gas (GHG) emissions. Most current studies focus on the temporal dynamics for GHGs in water, with little consideration given to the effects of weather changes. In this study, we measured and compared the concentrations and fluxes of CO2, CH4, and N2O from a pond in Northeast China under different meteorological conditions. Results showed that the rates of CO2, CH4, and N2O emissions from pond into the atmosphere during strong winds were 85.85 ± 7.55 mmol m−2 d−1, 22.05 ± 6.80 mmol m−2 d−1, and 10.87 ± 0.72 μmol m−2 d−1, respectively, significantly higher than those measured during non-rain weather. Among which, over 88 % of CH4 emissions were contributed by ebullition. Meanwhile, the CO2 and N2O flux were also significantly higher during heavy rainfall, reaching 100.05 ± 19.76 mmol m−2 d−1 and 5.90 ± 1.03 μmol m−2 d−1, respectively. Strong winds and precipitation induced sediment disturbances, high gas transport coefficients, reduced photosynthesis and oxygen greatly promoted the GHGs escape evasion. Wind speed, air pressure, solar radiation, and dissolved oxygen in water were important influencing factors. Our results emphasize the importance of capturing short-term weather disturbance events, especially rainstorm and strong winds, to accurately assess the annual GHG budget from these shallow water ecosystems.

Regional emissions of soil greenhouse gases across Tibetan alpine grasslands

Soil greenhouse gas (GHG) emissions play an important role in regional climate feedback on the Qinghai-Tibetan Plateau (QTP). Previous studies have focused on soil GHGs based on observations within a limited space on the QTP, however, the regional GHG emissions remain unclear. Analyzing soil samples from 25 sites along a 2,700 km transect across QTP, we showed significantly higher soil CO2 and N2O emission rates in alpine meadows than other upland grassland types, but similar soil CH4 uptake rates across all grassland types. The spatial variations of total soil GHG balance were dominated by CO2 emission. We found that CO2 emission was primarily constrained by high soil pH, low soil moisture and nutrient availability, and fungal abundance, N2O emission was inhibited by high soil pH, while CH4 uptake was dominated by methanotrophic abundance. Furthermore, we estimated a current regional total soil GHG balance of 144.4 Tg CO2-eq yr−1 for surface soil across Tibetan alpine grasslands, which increased by 17.6%, 24.8%, and 38.9% under warming scenarios of 1.5℃, 2℃ and 3℃, respectively. Our results provide a baseline for regional soil GHG emissions responding to climate warming on the QTP.

Lotic‐SIPCO2: Adaptation of an open‐source CO2 sensor system and examination of associated emission uncertainties across a range of stream sizes and land uses

AbstractRiver networks play a crucial role in the global carbon cycle, as relevant sources of carbon dioxide (CO2) to the atmosphere. Advancements in high‐frequency monitoring in aquatic environments have enabled measurement of dissolved CO2 concentration at temporal resolutions essential for studying carbon variability and evasion from these dynamic ecosystems. Here, we describe the adaptation, deployment, and validation of an open‐source and relatively low‐cost in situ pCO2 sensor system for lotic ecosystems, the lotic‐SIPCO2. We tested the lotic‐SIPCO2 in 10 streams that spanned a range of land cover and basin size. Key system adaptations for lotic environments included prevention of biofouling, configuration for variable stage height, and reduction of headspace equilibration time. We then examined which input parameters contribute the most to uncertainty in estimating CO2 emission rates and found scaling factors related to the gas exchange velocity were the most influential when CO2 concentration was significantly above saturation. Near saturation, sensor measurement of pCO2 contributed most to uncertainty in estimating CO2 emissions. We also found high‐frequency measurements of pCO2 were not necessary to accurately estimate median emission rates given the CO2 regimes of our streams, but daily to weekly sampling was sufficient. High‐frequency measurements of pCO2 remain valuable for exploring in‐stream metabolic variability, source partitioning, and storm event dynamics. Our adaptations to the SIPCO2 offer a relatively affordable and robust means of monitoring dissolved CO2 in lotic ecosystems. Our findings demonstrate priorities and related considerations in the design of monitoring projects of dissolved CO2 and CO2 evasion dynamics more broadly.

CO2 flux from the French Massif Central groundwaters: Modelling and quantitative estimation of the degassing process

Passive rift systems are often characterized by CO2 degassing, witnessed by the presence of mineral and thermal springs, bubbling pools, mofetes. Despite these field manifestations, the quantitative estimation of the CO2 budget released to the atmosphere from these geodynamic structures is not well constrained. Here, we examine the chemistry of 169 springs, the isotopic composition of the dissolved carbon (δ13CTDIC) of 33 springs and the dissolved gases composition of 6 springs from the French Massif Central, part of the European Cenozoic Rift System (ECRIS), in order to describe the CO2 degassing process and to compute the CO2 emission rate released from groundwaters at regional scale. Water-gas-rock models reveal that the separation of gas from the liquid phase occurs at P-T conditions between 10 bar-180 °C and 1 bar-10 °C. The carbon mass and isotopic balance of spring waters of the French Massif Central allow us to compute a total deeply-sourced CO2 emission rate of 1.52 ± 0.14 × 109 mol yr−1, suggesting that the CO2 release from passive rift systems is significant at global scale and should be considered in the present-day global Earth degassing budget. The comparison of our data to other continental rift systems shows a high variability of CO2 emission rates, highlighting that more detailed studies are needed to constrain the CO2 flux from this geodynamic setting that, at present, is likely underestimated.

How can there be an economic transition to a green ecosystem by adapting plastic-to-fuel technologies through renewable energy?

Plastics partially help define the way humanity lives today and plastic waste is an increasing phenomenon. It seems to be a serious concern that causes economic inefficiencies and environmental degradation that result in high CO2 emissions rates. To overcome this issue, regulations and policies on the production and behavior of plastics and energy should be reconsidered in the growing world economy. To this end, this study aims to foster economic pathways for decision-makers and answers the question of “How can there be an economic transition to a green eco-system by adapting plastic-to-fuel technologies through renewable energy?”. This strategy is introduced by an autoregressive distributed lag (ARDL) time-series methodology with the worldwide data from 1950 to 2022, considering energy production, economic growth, and CO2 emissions as independent variables; and plastic production as a dependent variable. The findings reveal the existence of a long-run cointegration relationship. An increase in renewable energy production (REP) and CO2 emissions causes a decrease in plastic production, while the opposite is valid for non-renewable energy production (NREP). The relationships between environmental degradation, energy production and economic growth are conducted through a global perspective. Therefore, this pioneering aspect of the article is expected to become a reference study for many studies in the future, in mitigating global warming by adapting plastic-to-fuel technologies. The paper shows how the production and use of renewable energy have critical importance in terms of the economic development levels of countries and therefore, can benefit countries (i.e., particularly developing and least developed countries) for environmentally friendly production and consumption patterns through a very important good: plastic.

Seasonal dynamics of soil CO2 emissions from different semi-arid land-use systems

ABSTRACT Soil carbon dioxide (CO2) fluxes are a critical component in understanding carbon sequestration. In sub-Saharan Africa, empirically measured CO2 emissions data from diverse land-use systems is limited. Soil CO2 emission rates were measured in the Limpopo Province, South Africa for 12 months at two-week intervals in natural systems (forest and shrubland) and commercially managed orchards (avocado and citrus) to establish seasonal dynamics of soil CO2 emissions across these land-use systems. The results showed a variation in emission rates with the variation depending on the season. In the spring and winter, soil CO2 emission rates in citrus were four times higher than in the shrubland due to higher moisture levels. However, in the summer season, the forest emission rates were 40% higher than in citrus due to higher soil organic carbon content. Organic carbon stocks were higher in the forest (1.19 kg/m2) compared to the other land uses. This study revealed differences in soil CO2 emission rates among land-use systems, with the cumulative amount of CO2 emitted over a 12-month period following the order: forest (39.3 tons/ha) > citrus (36.1 tons/ha) > shrubland (28.1 tons/ha) > avocado (26.9 tons/ha). Thus, understanding the emission patterns from various ecosystems can inform strategies for mitigating greenhouse gas emissions.

Investigating the impact of high-altitude on vehicle carbon emissions: A comprehensive on-road driving study

This study addresses the literature gap concerning accurately identifying vehicle carbon emission characteristics in high-altitude areas. Utilizing a portable emission measurement system (PEMS) for real-world testing, we quantified the influence of altitude on carbon emissions from light-duty gasoline (LDGV) and diesel vehicles (LDDV). The Random Forest (RF) algorithm was employed to analyze the complex nonlinear relationships between altitude, meteorological conditions, driving patterns, and carbon dioxide (CO2) emissions, enabling predictions across different altitudes. The results showed that CO2 emissions progressively increase with elevation. Furthermore, as altitude increases, combustion efficiency declines, and the overall impact of driving conditions on emission rates diminishes. Altitude and meteorological factors significantly contributed to CO2 emissions, whereas driving conditions and road grades contributed less. Compared with the COPERT model, the RF model demonstrates strong accuracy in predicting carbon emissions at different altitudes. Specifically, the CO2 emission rate nearly triples as altitude increases from 2.0 km to 4.5 km. This research bridges a critical gap in the understanding carbon emissions from high-altitude vehicles, offering insights into policy development for emission reduction strategies in such regions. Future studies should integrate diverse testing methodologies and comprehensive surveys to validate and extend the findings.

Seasonal Wetlands Make a Relatively Limited Contribution to the Dissolved Carbon Pool of a Lowland Headwater Tropical Stream

AbstractWetlands process large amounts of carbon (C) that can be exported laterally to streams and rivers. However, our understanding of wetland inputs to streams remains unclear, particularly in tropical systems. Here we estimated the contribution of seasonal wetlands to the C pool of a lowland headwater stream in the Australian tropics. We measured dissolved organic and inorganic C (DOC and DIC) and dissolved gases (carbon dioxide—CO2, methane—CH4) during the wet season along the mainstem and in wetland drains connected to the stream. We also recorded hourly measurements of dissolved CO2 along a ‘stream–wetland drain–stream’ continuum, and used a hydrological model combined with a simple mass balance approach to assess the water, DIC and DOC sources to the stream. Seasonal wetlands contributed ∼15% and ∼16% of the DOC and DIC loads during our synoptic sampling, slightly higher than the percent area (∼9%) they occupy in the catchment. The riparian forest (75% of the DOC load) and groundwater inflows (58% of the DIC load) were identified as the main sources of stream DOC and DIC. Seasonal wetlands also contributed marginally to stream CO2 and CH4. Importantly, the rates of stream CO2 emission (1.86 g C s−1) and DOC mineralization (0.33 g C s−1) were much lower than the downstream export of DIC (6.39 g C s−1) and DOC (2.66 g g C s−1). This work highlights the need for further research on the role of riparian corridors as producers and conduits of terrestrial C to tropical streams.

Development of a continuous UAV-mounted air sampler and application to the quantification of CO2 and CH4 emissions from a major coking plant

Abstract. The development in uncrewed aerial vehicle (UAV) technologies over the past decade has led to a plethora of platforms that can potentially enable greenhouse gas emission quantification. Here, we report the development of a new air sampler, consisting of a pumped stainless coiled tube of 150 m in length with controlled time stamping, and its deployment from an industrial UAV to quantify CO2 and CH4 emissions from the main coking plant stacks of a major steel maker in eastern China. Laboratory tests show that the time series of CO2 and CH4 measured using the sampling system is smoothed when compared to online measurement by the cavity ring-down spectrometer (CRDS) analyzer. Further analyses show that the smoothing is akin to a convolution of the true time series signals with a heavy-tailed digital filter. For field testing, the air sampler was mounted on the UAV and flown in virtual boxes around two stacks in the coking plant of the Shagang Group (steel producer). Mixing ratios of CO2 and CH4 in air and meteorological parameters were measured from the UAV during the test flight. A mass-balance computational algorithm was used on the data to estimate the CO2 and CH4 emission rates from the stacks. Using this algorithm, the emission rates for the two stacks from the coking plant were calculated to be 0.12±0.014 t h−1 for CH4 and 110±18 t h−1 for CO2, the latter being in excellent agreement with material-balance-based estimates. A Gaussian plume inversion approach was also used to derive the emission rates, and the results were compared with those derived using the mass-balance algorithm, showing a good agreement between the two methods.

Comparative Study of CO2 Storage Capacity Estimation in Depleted Oil & Gas Reservoir: A Case Study in Vermillion Basin Gulf of Mexico

CO2 emissions rates have seen an exponential growth from the 19th century up till date, if no drastic measures and plans are implemented to prevent this exponential growth the consequence will be devastating. The notion of achieving net-zero greenhouse gas emissions gained prominence through the Paris Agreement, a groundbreaking accord reached at the United Nations Climate Change Conference. This agreement was devised to mitigate the impact of greenhouse gas emissions. To execute the net-zero CO2 emission plan, the USDOE has set a new goal to remove gigatons of carbon dioxide (CO2 ) from the atmosphere and durably store it for less than $100/ton of net CO2 -equivalent. Making such a goal a reality requires an accurate estimation of CO2 storage capacity for the successful implementation of Carbon Capture and Storage (CCS) technologies, and the assessment of the impact of CCS to the reduction of CO2 emissions. Hence this paper serves as a template for accurately estimating CO2 storage capacity in depleted saturated oil reservoirs with initial gas cap using three approaches: Volumetric, Production and Correlation-based methods and compares the accuracy of the estimates. A case study was conducted on a depleted VR273_Q combination sand in the Vermillion Basin, Gulf of Mexico (GOM). The deterministic and stochastic (P50) CO2 storage capacity estimates from the Volume-based method are 1.21 million tonnes (Mt) and 1.23 Mt respectively, while the deterministic CO2 storage capacity estimates from the Production and Correlationbased method are 1.32 Mt and 1.41 Mt respectively. All three approaches showed similar results, with little deviations attributed to petrophysical uncertainties arising from data gaps i.e., absence of well logs to key wells. However, these uncertainties are captured by Stochastic (P90) CO2 storage capacity estimates of 1.47 Mt from the Volume-based method. Although the Correlation-based approach slightly overestimates the CO2 storage capacity, it can be used as a starting point for quick estimation as it only requires production data which are readily available on various databases for GOM. Finally, through this paper, opportunities for concerned agencies to make well-informed energy-related policies and business decisions are made possible.

Temperature Matters More than Fertilization for Straw Decomposition in the Soil of Greenhouse Vegetable Field

As the largest organic carbon input to agroecosystems, crop straw can solve the problem of soil quality degradation in greenhouse vegetable fields, harmonize the balance between soil nutrients and energy, and improve soil quality to maintain the sustainable production of greenhouse vegetables. However, the microbial mechanism of the straw decomposition process under different temperatures and fertilization treatments in greenhouse vegetable soils has not been clarified. Soil samples were used to investigate the biology of straw decomposition in the soil at three incubation temperatures (15, 25, and 35 °C) through a soil incubation experiment (60 d) under different fertilization treatments. Fertilization treatments for this long-term field experiment included chemical fertilizer (CF), substitution of half of the chemical N fertilizer with manure (CM), straw (CS), or combined manure and straw (CMS). The results showed that soil hydrolase activities tended to decrease with increasing temperature during straw decomposition. Compared with the CF, organic substitutions (CM, CMS, and CS) increased soil β-glucosidase, β-cellobiosidase, N-acetyl-glucosaminidase, and β-xylosidase activities during straw decomposition. Soil CO2 emission rates were the highest at each incubation temperature on the first day, rapidly declining at 25 °C and 35 °C and slowly declining at 15 °C. The soil CO2 cumulative emissions tended to increase with increasing temperature under different fertilization treatments. PCA showed that the responses of soil enzyme activities to temperature at 7, 15, and 30 d of straw decomposition were stronger than those of fertilization. In summary, both fertilization treatment and incubation temperature could influence soil CO2 emissions by affecting soil physicochemical properties and enzyme activities during straw decomposition, whereas incubation temperature had a stronger effect on straw decomposition than fertilization, as indicated by PLS-PM and three-way ANOVA. Considering the influence for fertilization on the straw decomposition process at different incubation temperatures, the straw applications (CMS and CS) were more suitable to temperature changes.

Physiology or Psychology: What Drives Human Emissions of Carbon Dioxide and Ammonia?

Humans are the primary sources of CO2 and NH3 indoors. Their emission rates may be influenced by human physiological and psychological status. This study investigated the impact of physiological and psychological engagements on the human emissions of CO2 and NH3. In a climate chamber, we measured CO2 and NH3 emissions from participants performing physical activities (walking and running at metabolic rates of 2.5 and 5 met, respectively) and psychological stimuli (meditation and cognitive tasks). Participants' physiological responses were recorded, including the skin temperature, electrodermal activity (EDA), and heart rate, and then analyzed for their relationship with CO2 and NH3 emissions. The results showed that physiological engagement considerably elevated per-person CO2 emission rates from 19.6 (seated) to 46.9 (2.5 met) and 115.4 L/h (5 met) and NH3 emission rates from 2.7 to 5.1 and 8.3 mg/h, respectively. CO2 emissions reduced when participants stopped running, whereas NH3 emissions continued to increase owing to their distinct emission mechanisms. Psychological engagement did not significantly alter participants' emissions of CO2 and NH3. Regression analysis revealed that CO2 emissions were predominantly correlated with heart rate, whereas NH3 emissions were mainly associated with skin temperature and EDA. These findings contribute to a deeper understanding of human metabolic emissions of CO2 and NH3.

Greenhouse gas emissions and their trends over the last 3 decades across Africa

Abstract. A key goal of the Paris Agreement (PA) is to reach net-zero greenhouse gas (GHG) emissions by 2050 globally, which requires mitigation efforts from all countries. Africa's rapidly growing population and gross domestic product (GDP) make this continent important for GHG emission trends. In this paper, we study the emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in Africa over 3 decades (1990–2018). We compare bottom-up (BU) approaches, including United Nations Convention Framework on Climate Change (UNFCCC) national inventories, FAO, PRIMAP-hist, process-based ecosystem models for CO2 fluxes in the land use, land use change and forestry (LULUCF) sector and global atmospheric inversions. For inversions, we applied different methods to separate anthropogenic CH4 emissions. The BU inventories show that, over the decade 2010–2018, fewer than 10 countries represented more than 75 % of African fossil CO2 emissions. With a mean of 1373 Mt CO2 yr−1, total African fossil CO2 emissions over 2010–2018 represent only 4 % of global fossil emissions. However, these emissions grew by +34 % from 1990–1999 to 2000–2009 and by +31 % from 2000–2009 to 2010–2018, which represents more than a doubling in 30 years. This growth rate is more than 2 times faster than the global growth rate of fossil CO2 emissions. The anthropogenic emissions of CH4 grew by 5 % from 1990–1999 to 2000–2009 and by 14.8 % from 2000–2009 to 2010–2018. The N2O emissions grew by 19.5 % from 1990–1999 to 2000–2009 and by 20.8 % from 2000–2009 to 2010–2018. When using the mean of the estimates from UNFCCC reports (including the land use sector) with corrections from outliers, Africa was a mean source of greenhouse gases of 262221863239 Mt CO2 eq. yr−1 from all BU estimates (the subscript and superscript indicate min–max range uncertainties) and of +263717615873 Mt CO2 eq. yr−1 from top-down (TD) methods during their overlap period from 2001 to 2017. Although the mean values are consistent, the range of TD estimates is larger than the one of the BU estimates, indicating that sparse atmospheric observations and transport model errors do not allow us to use inversions to reduce the uncertainty in BU estimates. The main source of uncertainty comes from CO2 fluxes in the LULUCF sector, for which the spread across inversions is larger than 50 %, especially in central Africa. Moreover, estimates from national UNFCCC communications differ widely depending on whether the large sinks in a few countries are corrected to more plausible values using more recent national sources following the methodology of Grassi et al. (2022). The medians of CH4 emissions from inversions based on satellite retrievals and surface station networks are consistent with each other within 2 % at the continental scale. The inversion ensemble also provides consistent estimates of anthropogenic CH4 emissions with BU inventories such as PRIMAP-hist. For N2O, inversions systematically show higher emissions than inventories, on average about 4.5 times more than PRIMAP-hist, either because natural N2O sources cannot be separated accurately from anthropogenic ones in inversions or because BU estimates ignore indirect emissions and underestimate emission factors. Future improvements can be expected thanks to a denser network of monitoring atmospheric concentrations. This study helps to introduce methods to enhance the scope of use of various published datasets and allows us to compute budgets thanks to recombinations of those data products. Our results allow us to understand uncertainty and trends in emissions and removals in a region of the world where few observations exist and where most inventories are based on default IPCC guideline values. The results can therefore serve as a support tool for the Global Stocktake (GST) of the Paris Agreement. The referenced datasets related to the figures are available at https://doi.org/10.5281/zenodo.7347077 (Mostefaoui et al., 2022).

Efficient recycling and conversion of CO2 to methanol: Process design and environmental assessment

Carbon capture and carbon reuse in the chemical plants is one of the attractive prospective approaches to decrease the concerns about global warming and climate change. In the present study, is focused on the synthesis gas production from carbon dioxide in a methanol synthesis plant. In this regard, two methanol processes are proposed based on CO2 separation, recycling, and reforming. In the first scenario, CO2 is separated and recycled to the conventional reformer, while the process is equipped by a CO2 separation unit and dry methane reformer in the second scenario. The proposed processes are simulated and a sensitivity analysis is performed to investigated the effect of inputs on methanol productivity and carbon conversion. The operational parameters of proposed processes are optimized to enhance methanol productivity and CO2 conversion. Then, the processes are compared from energy efficiency, carbon efficiency, CO2 emission rate and methanol productivity viewpoints. The results showed that, in the second proposed scenario, methanol production rate approach to 5367 tons per day in comparison to 5030 tons per day for industrial unit. In addition, modification of conventional methanol process based on the second scenario could decrease CO2 emission rate about 56 tons per day.

Microorganisms in subarctic soils are depleted of ribosomes under short-, medium-, and long-term warming.

Physiological responses of soil microorganisms to global warming are important for soil ecosystem function and the terrestrial carbon cycle. Here, we investigate the effects of weeks, years, and decades of soil warming across seasons and time on the microbial protein biosynthesis machineries (i.e. ribosomes), the most abundant cellular macromolecular complexes, using RNA:DNA and RNA:MBC (microbial biomass carbon) ratios as proxies for cellular ribosome contents. We compared warmed soils and non-warmed controls of 15 replicated subarctic grassland and forest soil temperature gradients subject to natural geothermal warming. RNA:DNA ratios tended to be lower in the warmed soils during summer and autumn, independent of warming duration (6weeks, 8-14years, and > 50years), warming intensity (+3°C, +6°C, and +9°C), and ecosystem type. With increasing temperatures, RNA:MBC ratios were also decreasing. Additionally, seasonal RNA:DNA ratios of the consecutively sampled forest showed the same temperature-driven pattern. This suggests that subarctic soil microorganisms are depleted of ribosomes under warm conditions and the lack of consistent relationships with other physicochemical parameters besides temperature further suggests temperature as key driver. Furthermore, in incubation experiments, we measured significantly higher CO2 emission rates per unit of RNA from short- and long-term warmed soils compared to non-warmed controls. In conclusion, ribosome reduction may represent a widespread microbial physiological response to warming that offers a selective advantage at higher temperatures, as energy and matter can be reallocated from ribosome synthesis to other processes including substrate uptake and turnover. This way, ribosome reduction could have a substantial effect on soil carbon dynamics.

Post-fire soil carbon emission rates along boreal forest fire chronosequences in northwest Canada show significantly higher emission potentials from permafrost soils compared to non-permafrost soils

Boreal forests are one of the most important biomes storing carbon (C). Wildfires burn yearly on average more than 1% of the boreal forest, and it is expected that the fire return intervals will shorten due to climate change. Fire is one of the most influential factors affecting soil organic matter quantity and quality, soil C pools, and presumably also the time C resides in the soil (soil C turnover time in years). We compared the potential effects of forest fire through post-fire succession on soil carbon dioxide (CO2) emission rates and soil C turnover time in two fire chronosequences, one with underlying permafrost soil and the other without permafrost. We found that fire had a significant effect on potential soil C turnover times, but surprisingly there was no significant difference in soil C turnover times between the permafrost and non-permafrost areas, although the soil CO2 emissions rates in permafrost areas are approximately three times higher compared to non-permafrost areas. In recently burned areas the potential soil C turnover times were two times longer compared to control areas located in forests burned more than 100 years ago. The longest potential soil C turnover times were recorded in mineral soil layers (30 cm) of permafrost soils, and the shortest potential soil C turnover times were recorded in humus layers of non-permafrost areas.

The mutual effect between dual thermal power units under the advanced configuration of two units sharing one dry cooling tower and the energy-efficient and low-emission operation strategy

For a thermal power plant configuration of two power units sharing one dry cooling tower, a comprehensive computational framework was developed to reveal the mutual effect between dual units via analyzing the competition between the air-cooled radiators which are owned by two units and coupled by the shared tower, under various environmental factors and unit power load schemes. Results showed that an increase in crosswind speed vcw aggravates the uneven performance distribution among radiators, but variations in ambient temperature ta have little impact. Each growth of 10 °C in ta results in a drop of ∼1.4% in power cycle efficiency ηe for both units operating at rated load, corresponding to increases of ∼9 g/(kW·h) and ∼26 g/(kW·h) in coal consumption and CO2 emission rates. ηe of the unit with its radiators facing towards ambient crosswind is 0.3% higher than ηe of the other unit as vcw exceeds 8 m/s. When both units operate with equal power load rate Np, a decline in Np aggravates the unevenness of air inflow among radiators and amplifies the predominance of air intake of windward radiators for the shared tower. An increase in Np causes a growth in ηe for both units, but this growth becomes slight as Np exceeds 75%. For both units operating with different Np, ηe declines more sharply with vcw for the unit with a higher Np, especially when radiators of the other unit face towards ambient crosswind. To maximize the overall operation economic efficiency, load difference between dual units should be minimized and radiators owned by the unit with a higher Np should be positioned against ambient crosswind. For dual units operating at a total Np = 150% on a strong-wind summer day with ta = 32.5 °C and vcw = 12 m/s, a maximum saving of 87.9 t standard-coal can be achieved by applying the optimal operating strategy, reducing daily CO2 emission by 250.3 t.

Effect of biochar addition on CO2 emission from salt-affected soils under drying-rewetting conditions

Under the conditions of global climate change, soils have undergone more complex and frequent cycles of wetting and drying, which has had a significant impact on soil respiration. In order to explore the response of CO2 emissions from salt-affected soils to biochar (BC) at different pyrolysis temperatures under drying-rewetting conditions, an indoor microcosmic culture experiment was conducted to add maize straw BC at different pyrolysis temperatures (300°C and 600°C) to salt-affected soils to study the influence of BC at different pyrolysis temperatures on the characteristics of CO2 emissions under drying-rewetting conditions. The results indicated that the addition of BC significantly altered the CO2 emission rate from the soil, subsequently influencing the mineralization of soil organic carbon. BC produced at varying pyrolysis temperatures exhibited distinct effects on the CO2 emission rates. Specifically, BC pyrolyzed at high temperatures inhibited the mineralization of soil organic carbon, whereas BC produced at low temperatures facilitated this mineralization process. This finding will provide a theoretical and scientific foundation for assessing the carbon sequestration potential of coastal wetlands and for the development of carbon sequestration technologies.