Total Net Emissions Research Articles

Greenhouse Gas Fluxes from Cranberry and Highbush Blueberry Plantations on Former Peat Extraction Fields Compared to Active Peat Extraction Fields and Pristine Peatlands in Latvia

Emissions of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4), particularly those from organic soils, need to be reduced in the context of climate change mitigation (CCM). Here, we estimated the greenhouse gas (GHG) fluxes from nutrient-poor organic soils in cranberry (Vaccinium macrocarpon) and highbush blueberry (Vaccinium corymbosum) plantations established on former peat extraction fields compared to active peat extraction fields and pristine raised bogs in Latvia. A two-year study (2016–2018) was conducted using the manual closed chamber method. In berry plantations and active peat extraction fields, annual net CO2 fluxes contributed the most to total GHG emissions, accounting for over 67%, and temperature had the most significant impact on CO2 fluxes. Conversely, annual CH4 fluxes were the primary contributor to total net GHG emissions in the pristine raised bog, which simultaneously acted as a slight CO2 sink. N2O fluxes were relatively low among all studied land use types. This study provided quantitative insights into the variation in GHG fluxes and the environmental variables influencing them, and the obtained data are valuable to estimate the impact of the establishment of berry plantations on former peat extraction fields on CCM in the hemiboreal region of Europe.

An analysis of the impact of CO2 emissions from deforestation and mining in Madre de Dios, Perú

The Madre de Dios Region of Peru faces significant deforestation largely due to a surge in artisanal-small scale gold mining (ASGM), propelled by rising gold prices. This study evaluates the full scope of ASGM activities on net CO2 emissions, accounting for both the deforestation that converts forests into mining territories and the emissions directly resulting from mining and transportation activities. By applying kriging to a comprehensive dataset, we determined the carbon content of the region and the annual loss of CO2 capture due to deforestation. Our analysis also incorporates emissions from the Interoceanic highway, which has contributed to the mining boom. The findings indicate a total net CO2 emission of 429.9 Gigagrams (Gg) per year, underscoring the critical environmental challenge these activities pose. Our study highlights the need for immediate and effective reclamation efforts, including reforestation with indigenous carbon-rich trees, as a counterbalance to the environmental damage inflicted. These efforts are essential to mitigate the adverse impacts and support the global movement towards net-zero emissions.

Exploring the Spatial and Temporal Trajectories of Land Use Carbon Emissions and Influencing Factors in the Aksu River Basin from 1990 to 2020

Land use changes lead to changes in the functions of different types of carbon sources and sinks, which are key sources of carbon emissions. The study of carbon emissions and its influencing factors in the Aksu River Basin from the perspective of land use change is of great importance for the promotion of integrated protection and restoration of mountains, water, forests, fields, lakes, grasslands, sand, and ice in the basin and to help achieve the goal of carbon peaking and carbon neutrality. Based on four periods of land use data and socio-economic data from 1990 to 2020, the total carbon emissions from land use were measured, and the spatial and temporal trajectories of carbon emissions and their influencing factors were explored. The results showed that:① from 1990 to 2020, arable land, forest land, construction land, and unused land showed a general increasing trend, whereas grasslands and water areas showed a decreasing trend. The spatial change in land use types was mainly characterized by the conversion of grasslands and unused land into arable land, and 83.58 % of the arable land conversion areas were concentrated in the southwest of Wensu, Aksu, and the northern part of Awat. ② The total net carbon emissions in the basin showed a continuous growth trend from 1990 to 2020, with a cumulative increase of 14.78×104 t. The increase in arable land was a key factor causing an increase in net carbon emissions in the basin. ③ The spatial distribution pattern of land use carbon emissions in the basin was high in the middle and low in the fourth, with significant changes in net carbon emissions mainly in the southern part of Wensu, Aksu, Awat, and Alaer. ④ Human activities had the strongest driving effect on land use carbon emissions, with their effects gradually increasing from east to west. The contribution of average annual temperature to land use carbon emissions was mainly concentrated in the eastern part of Aksu and the northern part of Awat, whereas average annual rainfall had a strong inhibitory effect on the northern part of Wensu and the western part of Aheqi.

Optimal performance of stand-alone hybrid microgrid systems based on integrated techno-economic-environmental energy management strategy using the grey wolf optimizer.

Recently, global interest in organizing the functioning of renewable energy resources (RES) through microgrids (MG) has developed, as a unique approach to tackle technical, economic, and environmental difficulties. This study proposes implementing a developed Distributable Resource Management strategy (DRMS) in hybrid Microgrid systems to reduce total net percent cost (TNPC), energy loss (Ploss), and gas emissions (GEM) while taking the cost-benefit index (CBI) and loss of power supply probability (LPSP) as operational constraints. Grey Wolf Optimizer (GWO) was utilized to find the optimal size of the hybrid Microgrid components and calculate the multi-objective function with and without the proposed management method. In addition, a detailed sensitivity analysis of numerous economic and technological parameters was performed to assess system performance. The proposed strategy reduced the system's total net present cost, power loss, and emissions by (1.06%), (8.69%), and (17.19%), respectively compared to normal operation. Firefly Algorithm (FA) and Particle Swarm Optimization (PSO) techniques were used to verify the results. This study gives a more detailed plan for evaluating the effectiveness of hybrid Microgrid systems from a technical, economic, and environmental perspective.

Decarbonizing the sludge treatment industry: Assessing the feasibility of achieving carbon reduction from carbon peaking to carbon neutrality

The significant carbon emissions generated by China's sludge treatment industry cannot be ignored. However, with only a few recent well-executed studies on carbon emission reduction in the sludge treatment field, the literature awaits a more comprehensive assessment and prediction whether the sludge treatment industry can achieve the dual-carbon target. This article aims to fill this gap, holistically examining the carbon emission reduction potential in the industry. Using the moving average method and IPCC method, the projected carbon emission value of sludge treatment in China from 2021 to 2030 indicates a total net carbon emission of 0.3 million tons by 2030. This suggests that the sludge treatment industry is on track to meet the carbon peak target, leaving surplus carbon quotas or credits available to assist other industries for carbon emissions reductions. The study also finds that only incineration and composting demonstrate the potential to be able to partially offset carbon emissions through resource utilization in certain stages or processes. Therefore, the current sludge treatment methods do not yield comprehensive emission reduction effects and cannot provide sufficient contribution to China's dual carbon goals. To address this issue, the paper explores a new scheme that focuses on improving the sludge treatment process. The scheme comparative analysis reveals that, even with all sludge treatment methods optimized, the total net carbon emissions of the industry could only be reduced to 0.058 million tons. This reduction falls short of significantly mitigating carbon emissions to achieve the carbon neutrality goal. Therefore, industries unable to achieve substantial net carbon reduction may need to explore alternative measures, such as carbon sinks, to ultimately attain carbon neutrality.

Numerical simulation and 4E analysis of a steam methane reforming-based multi heat recovery process, producing electricity, methanol, fresh water, heating, and coolant

Natural gas power plants play a pivotal role in power generation; nevertheless, their waste heat contributes to diminished thermodynamic efficiencies and the release of carbon dioxide emissions. One primary approach involves implementing effective heat recovery strategies to generate various products. The present study suggests a novel approach to heat recovery in different stages utilizing series and parallel arrangements within an environmentally friendly design to enhance controllability while expanding the range of products. The present study includes a steam methane reforming process, a Kalina cycle, a multi-effect desalination unit, a methanol synthesis unit, two organic Rankine cycles, and two ammonia Rankine cycles. The primary objective of this system is to efficiently and concurrently produce electricity, hot water, chilled water, fresh water, and methanol. The findings reveal that the newly devised process exhibits energy and exergy efficiencies of 47.55% and 50.58%, respectively, while the total unit cost of products amounts to 7.69 $/GJ. From an environmental perspective, the results indicate that the proposed structure exhibits a total net emission of 87.1 × 103 kg/h and a CO2 footprint of 0.22 kgCO2/kWh. Ultimately, the economic assessment elucidates that the fixed investment cost, total investment cost, total annual cost, and net present value are equivalent to 373.0 M$, 496.1 M$, 207.5 M$, and 598.6 M$, respectively.

Decoupling analysis to assess the impact of land use patterns on carbon emissions: A case study in the Yellow River Delta efficient eco-economic zone, China

Investigating how land use patterns impact on carbon emissions is crucial, as land use change is a major cause of increased carbon emission. High Efficiency Eco-economic Zone of Yellow River Delta (HEEZ-YRD) are typical of land use patterns affecting carbon emissions due to the fact they have greater dramatic land use changes. Here, we used carbon emission model and the decoupling analysis to assess the impact of land use patterns on carbon emissions based on the 30-m Global Land Cover Dataset (GlobeLand30) and socio-economic data from 2000 to 2019. The results showed that construction land increased while cropland decreased. The construction land area increased from cropland was 9.03 × 104ha from 2000 to 2010 and 1.44 × 105ha from 2010 to 2019, indicating that the increase in construction land mainly from cropland. Moreover, the HEEZ-YRD was the carbon source area. The total net carbon emissions increased from 9155.68 Gg CO2 equivalents (CO2e) in 2000–45817.44 Gg CO2e in 2019, but the increase declined. In the HEEZ-YRD, the land-use mix degree was highest in the east and north and lowest in the west and south. Zouping had the highest carbon emissions of all the cities. The decoupling of land use patterns and carbon emissions was dynamic. During the study period, the decoupling between land use patterns and carbon emissions shifted from an extended negative decoupling to a weak or even a strong decoupling. The consequences will make contributions to the establishment and implementation of low-carbon insurance policies and supply a theoretical framework for sustainable land use.

A novel trigeneration model using landfill gas upgrading process and waste heat recovery: Application of methanol, desalinated water, and oxygen production

In this paper, an integrated process for coproduction of methanol (122500 kgh), desalinated water (40.56 m3h), and oxygen (13420 Nm3h) using landfill gas upgrading is presented. The process embraces negative carbon dioxide (CO2) emission framework, high thermodynamic efficiency, and low product cost. The proposed process consists of nine subsystems, which are utilized for heat recovery in addition to production of electricity and desalinated water. Results showed that the total energy and exergy efficiencies of the trigeneration system are 59.19% and 48%, respectively. According to the conducted analysis, the total exergy destruction rate equals 973291 kW in which the biogas upgrading unit has an 80% contribution. In addition, it is demonstrated that the combustor of the biogas upgrading unit is responsible for 57.96% of the total exergy destruction rate. Moreover, the sensitivity analysis illustrates that the increase in the H2CO2 ratio is an important factor in increasing the carbon efficiency and total energy efficiency, and decreasing the CO2 emission. From the environmental perspective, it is deduced that the total net emission of the proposed process is −0.6773 kgCO2kgMeOH, which is significantly lower than other methanol production technologies. Economic analysis is performed for the integrated structure and its results showed that the total annual cost and methanol production cost rate are 124,660,373 $ and 0.124 $kg, respectively. This value is 91.68% lower than the renewable methanol production technology.

Saudi Arabia’s Journey toward Net-Zero Emissions: Progress and Challenges

Combating climate change by reducing greenhouse gas (GHG) emissions has become an obligation for countries that ratified the Paris Agreement. Saudi Arabia, as a member of the Paris Agreement, pledged to achieve net zero emissions (NZE) by 2060. This endeavor is challenging for all countries. This paper provides an analysis and assessment of the Saudi measures to achieve NZE by 2060. The analysis reveals that Saudi Arabia will reduce the total net emissions to 49.67 Mt of CO2eq, whereas under a business-as-usual scenario, the emissions would reach 1.724 million tons (Mt) of CO2 equivalent (CO2eq). The study reveals that sectors conducting environmental, social, and governance ratings (ESG) and those where the government is a stakeholder are on the right track and will facilitate the government’s efforts in reaching NZE. The gap in reaching NZE will be mainly due to the Saudi steel and cement industries.

A new integrated circular economy index and a combined method for optimization of wood production chain considering carbon neutrality

The wood industry is potentially advantageous to applying the concepts of circular economy for sustainable development and can contribute to the commitment of carbon neutrality. This study developed an integrated circular economy index based on five different quantitative indicators for assessment of the wood production chain: heat recovery rate, CO2 sequestration rate, fossil fuel substitution rate, renewable electricity usage rate, and revenue increase from the by-products. A combination of best-worst method (BWM) and linear goal programming (LGP) techniques was investigated to develop an optimal circular economy model of wood processing chain for reduction in CO2 emission. The integrated circular economy index and the combined method were tested in a case-study of a rubberwood processing chain in Vietnam. The proposed model suggests that the woodchips and biomass from the harvesting and processing of rubberwood could be collected and treated using microwave thermolysis techniques; the enzyme hydrolysis technique is appropriate for bioethanol and biomethane recovery from the sawdust; and the hot air technique is preferable in the drying process. The proposed model could result in a significant reduction of the total net carbon emission from +552,750 tons CO2eq to −1,145,940 tons CO2eq per year. This could support the achievement of Vietnam's zero CO2 emission goal and hopefully contribute to the country's commitment to carbon emission neutrality by the year 2050.

Methanol production from natural gas reforming and CO2 capturing process, simulation, design, and technical-economic analysis

In this paper, a methanol production process with high thermodynamic efficiency and a low production cost is presented. The proposed process is based on steam methane reforming, in which carbon dioxide (CO2) captured from a power plant flue gas is employed to improve the stoichiometric number, methanol efficiency, and carbon efficiency and increase CO2 conversion. In addition to the sensitivity analysis, comprehensive technical, economic, and environmental analyses are performed. Furthermore, the obtained results of this paper are compared to those of previous studies. A parametric study showed that the optimum steam-to-methane ratio is 3.75, and the optimum flow rate for CO2 utilization is 140 kmol/h. From the economic point of view, it is demonstrated that the total annual cost is 11,799,484 USD, and the total production cost rate is 0.1 $/kg. The environmental analysis showed that the total net CO2 emission in this process is 6580.64 kg/h, and for producing 1 kg of methanol, 0.41 kg of CO2 is emitted.

Geo-referenced building stock analysis as a basis for local-level energy and climate mitigation strategies

A geo-referenced building stock model was used to analyse the energy and climate performance of the Knowledge Axis in Trondheim, Norway, by 2050. Strategies for energy upgrades, construction of more energy-efficient new constructions, changes in heating technologies, and their implications in terms of energy savings and greenhouse gas (GHG) emissions associated with energy and materials are assessed through various scenarios.Thematic maps were used to display the development of the total floor area and energy use. Compared to the baseline scenario for the same year, the energy savings range from 2 to 9%, 2–14%, and 2–19% in 2030, 2040, and 2050, respectively. New passive house constructions combined with energy upgrades in renovation projects and the maximum use of heat pumps have the greatest energy-saving potential.Our results displayed a large variation in the total net GHG emissions as a result of the alternative emission factors. The total net GHG emissions are primarily affected by the energy savings (amplified by assuming fossil fuel as the marginal mix), electricity mix (Norwegian or European), and allocation chosen for the incinerated waste to feed the district heating system.

Tree mortality and carbon emission as a function of wildfire severity in south-eastern Australian temperate forests

Disturbance trends over recent decades indicate that climate change is resulting in increased fire severity and extent in Australia's temperate Eucalyptus forests. As disturbance cycles become shorter and more severe, empirical measurements are required to identify potential change in forest carbon (C) stock and emissions. However, such estimates are rare in the literature.The 2019–2020 wildfires burnt through 6 to 7 million ha of mainly temperate open Eucalyptus forest in south-east Australia, with top down emission estimates ranging from 97 to 130 tonnes CO2 ha−1. Study sites that had been assessed for all aboveground C pools prior to the wildfires, were burnt in January 2020 by wildfire that varied in severity. Here we quantify the impact of high and low/moderate fire severities on tree mortality, C loss and C redistribution and assess implications for future C storage in these temperate Eucalyptus forests.Higher fire severity resulted in greater overstorey tree mortality but not understorey or loss of dead standing trees than in low/moderate severity fires. High severity fires combusted almost twice as much C from live trees (42 Mg C ha−1) as low/moderate severity fires (25 Mg C ha−1), while C loss from dead standing trees was similar among fire severity classes (average 17 Mg C ha−1). Total aboveground C lost across study sites was 42 Mg C ha−1 for high and 47 Mg C ha−1 for low/moderate severity, with an average of 45 Mg C ha−1 equivalent to 15 % (high severity) and 14 % (low/moderate severity) of AGC.Extrapolating our findings to other tall to medium open Eucalyptus forests across Victoria revealed that 37.33 ± 12.25 Tg C (mean ± s.e.) or 152 ± 50 Mg CO2 ha−1 was lost to the atmosphere from the 0.9 million ha of these productive forests, equating to about 20 % of Australia's total net annual emissions.

Crisp and fuzzy optimization models for sustainable municipal solid waste management

Increasing municipal solid waste (MSW) generation in the city has caused a serious problem to the authority, especially for emerging countries. Improper management of MSW will increase greenhouse gas (GHG) emissions. Apart from landfill, there are other options to convert MSW into valuable products or energy, such as recycling and incineration. This paper presents crisp and fuzzy optimization models for designing optimal supply chain networks for sustainable MSW management, considering economic (cost minimization) and environmental objectives (emissions reduction). The crisp model is based on a superstructure and consists of material balances, capacity limits and planning constraints for MSW transfer stations, disposal sites and treatment technologies. Fuzzy optimization with max-min aggregation is then incorporated to handle conflicting economic and environmental objectives, as well as uncertainties in GHG emission factors and cost coefficients of MSW treatment. A case study for the design of an optimal MSW supply chain network in the city of Qingdao, China is presented to illustrate the proposed approach. The conflicting objectives of minimizing the total net cost and GHG emissions for MSW transport and treatment are analyzed using the crisp model, yielding a set of Pareto optimal solutions. A compromise solution achieving a 21.6% cost reduction and a 28.4% emissions reduction is identified using the fuzzy model. An inferior solution is also found with smaller cost (19.1%) and emissions reductions (25.1%) due to the use of conservative estimates of uncertain cost coefficients and emission factors. These results demonstrate the effectiveness of the proposed models in dealing with the MSW management problem.

Multi-Objective Optimal Economic Dispatch of a Fuel Cell and Combined Heat and Power Based Renewable Integrated Grid Tied Micro-grid Using Whale Optimization Algorithm

Micro-grids are practical solution for combining distributed energy resources and combined heat and power units in order to satisfy the system power and heat demands. Nowadays, in order to integrate both renewable and non-renewable energy resources like photovoltaic, wind turbine, combined heat and power systems and fuel-cell unit; micro-grid seems to be a good idea. The aim of this paper is to obtain optimal scheduling of proposed generating units and to reduce the total operational cost and net emission of the system through economic/environmental power dispatch, while considering the impact of grid tied and autonomous mode of operation and satisfying the operational constraints. In this paper, a novel whale optimization algorithm is employed to solve this multi-objective problem. The obtained optimal results through this proposed whale optimization algorithm represents the efficiency, feasibility and capability of handling non-linear optimization problems in an efficient way compared to other optimization techniques. The proposed system is studied in a 24-h time horizon. The results obtained from this proposed technique are compared with other techniques which are recently employed.

Multi‐objective economic/emission optimal energy management system for scheduling micro‐grid integrated virtual power plant

AbstractDue to rapid socioeconomic growth and current environmental concerns, reducing global greenhouse gas emissions is a key step toward sustainable development. In recent years, some researchers have begun to adopt new grid management technologies such as virtual power plants (VPP) that allow them to improve energy management and cost and reduce gas emissions. The integration of distributed energy resources (DER), such as solar photovoltaic and wind power, combined with micro‐turbines and energy storage systems and with the support of VPP intelligence, will contribute immensely to improving micro‐grids (MGs) energy performance and reducing gas emissions. In this paper, an expert multi‐objective feasibility enhanced particle swarm optimization algorithm is adopted for the optimal scheduling of energy management system to reduce the total operating cost and net emission simultaneously. The proposed algorithm is tested on an Algerian reel building‐MG integrated VPP with DERs and combined cooling, heat, and power generation. Finally, different cases are simulated for a 24‐h time and discussed to demonstrate the validity of the proposed VPP energy system and the effectiveness of the adopted algorithm to reduce gas emissions and the total operating cost.

Greenhouse gas emissions from Mexican inland waters: first estimation and uncertainty using an upscaling approach

ABSTRACT The traditional upscaling approach to greenhouse gas (GHG) emission estimates of inland waters is imprecise, but more precise methods based on environmental drivers are a longstanding challenge. Mexico lacks GHG emission estimates for its inland waters, and only sparse but scientifically validated information is available. This study provides the first GHG emission estimates from Mexican inland waters using 4275 GHG flux measurements from 26 distinctive waterbodies and one local and another global surface area dataset (INEGI and HydroLAKES). GHG emission factors were calculated and subsequently upscaled to estimate total national GHG emissions from the inland waters and compare to other emission measures based on mean global emission factors or size-productivity weighted (SPW) models. Mean (standard error) annual fluxes from all inland waters were 2.2 (5.3) kg CO2 m−2 yr−1, 0.6 (1.14) kg CH4 m−2 yr−1, and 1.0 × 10−3 (6.0 × 10−4) kg N2O m−2 yr−1. Estimates for natural waterbodies are annual average release rates between 74 (87) and 139 (163.23) Tg CO2eq while artificial waterbodies reach between 32 (2) and 21 (21) Tg CO2eq according to INEGI and HydroLAKES datasets, respectively. Considerable uncertainty was determined in the calculated mean emission factor, mostly for anthropogenic emissions. Waterbody area and chlorophyll a concentration were used as proxies to model CO2 and CH4 fluxes through regression analysis. According to SPW and IPCC models, computed mean annual CH4 emission factors were close to our estimates and exhibited a strong influence from eutrophication. In a likely scenario of increased eutrophication in Mexico, an increase in total net emissions from inland waters could be expected.

Assessing the spatial and temporal variability of greenhouse gas emissions from different configurations of on-site wastewater treatment system using discrete and continuous gas flux measurement

Abstract. Global emissions linked to wastewater treatment are estimated to account for up to 1.5 % of total greenhouse gas (GHG) emissions globally. However, few studies have measured GHG emissions from domestic on-site treatment systems (DWWTSs) directly. In this study, two DWWTSs were monitored for 446 d and > 42 000 gas flux measurements were conducted using both discrete spot measurements and continuous flux chamber deployments. The observed GHG fluxes from biological activity in the soil and water phase were found to be highly spatially and temporally variable and correlated to environmental factors, water usage patterns and system design. In total, the results show that a septic tank discharging effluent into a well-designed soil treatment unit is estimated to emit a net 9.99 kg-CO2eq.cap-1yr-1, with approximately 63 %, 27 % and 10 % of the total CO2-equivalent net emissions in the form of CO2, CH4 and N2O, respectively. Emissions from the septic tank surface contributed over 50 % of total emissions and tended to be strongly underestimated by one-off discrete measurements, especially when episodic ebullitive events are to be considered. Fluxes from the soil treatment unit (STU) stemmed from both the soil surface and the vent system. Soil fluxes were mostly influenced by temperature but peaked regularly under conditions of rapidly changing soil water content. Vent fluxes were mostly governed by effluent, quality and a low number of high-emission events were responsible for the majority of total observed vent emissions. Owing to the strong overall spatial and temporal heterogeneity of observed fluxes from DWWTSs across all modules, future studies should focus on continuous deployments of a number of flux chambers over discrete measurements to accurately assess GHG emissions from on-site systems. This study also provided insights into managing GHG emissions from DWWTSs by different system configuration design, as well as indicating that the current IPCC emission factors for CH4 and N2O significantly overestimate emissions for on-site wastewater treatment systems.

Developing optimal energy management of integrated energy systems in the hybrid electricity and gas networks

Coordination of different energy resources provide specific opportunities to improve energy efficiency, higher service reliability, better power quality, reduce environmental pollution and flexibility of the energy supply. This paper presents a novel optimal operation and planning for the integrated energy systems (IESs). The IES inherits several forms of energy supply, energy storage system and energy conversion equipment, and achieves the coupling of different types of energy in different links such like network, charge and source. The main challenge and complicate of the operation of IESs is determining the optimal interaction between different energy types for supplying electric and thermal loads in order to improve overall energy utilization efficiency. To implement this challenge, an integration of natural gas network with a modified IEEE 33 bus electricity system connected to the upstream power grid has been used to examine the system performance over a wide range. In this research, the multi-objective optimization problem is employed in order to reduce total net emissions and operating costs simultaneously. Due to the uncertainty related to day-ahead forecasts (24 h), a Monte Carlo simulation is utilized to estimate renewable energy resources, thermal, and electric loads. The adaptive particle swarm optimization (APSO) technique is used to minimized the IES's operating costs. Using the APSO method, the operational costs are reduced by 2.96% and 4.62%, in comparison with PSO and genetic algorithm (GA), respectively. Also, the amounts of emissions are reduced by 4.68% and 6.03% than the PSO and GA methods, respectively. The proposed method can outperform others on system operating cost and distributed energy resource utilization with satisfactory energy-efficiency and environmental performance.

Dominant influence of non-thawing periods on annual CO2 emissions from Zoige peatlands: Five-year eddy covariance analysis

Changes in freeze–thaw processes as a result of climate change significantly affect the carbon balance of terrestrial ecosystems, especially peatlands. The Qinghai-Tibetan Plateau contains substantial permafrost and seasonal frozen soils and its peatlands feature a huge carbon stock highly sensitive to global change. In this paper, we used an eddy covariance flux tower to monitor carbon fluxes on the Zoige peatlands with seasonal frozen soils on the eastern Qinghai-Tibetan Plateau from 2013 to 2017. Total net emissions (g C m−2 yr−1) over the monitoring period were 64.1, 106.7, 126.5 and 103.2 in the frozen, frozen-thawing, thawing and thawing-freezing periods; the corresponding weighted mean emission rates (g C m−2 d−1) were 0.36, 0.44, 0.64 and 0.38. Although net CO2 emissions were highest in the thawing period, emissions during the other periods accounted for approximately 68.4% of annual emissions. In fact, emissions during the two freeze–thaw periods were 1.7 times those during the thawing period despite the freeze–thaw periods lasting fewer days. CO2 emission correlated significantly with volumetric water content and soil temperature in the frozen period, with soil temperature and precipitation in the frozen-thawing period, and with precipitation in the thawing and thawing-freezing periods. Annual net CO2 emissions during each of the years were 57.2 g C m−2 yr−1 (2013), 108.3 g C m−2 yr−1 (2014), 41 g C m−2 yr−1 (2015), 62.9 g C m−2 yr−1 (2016) and 131.1 g C m−2 yr−1 (2017), and hydrological conditions were the primary determinant of interannual variations. Long-term continuous monitoring of carbon is essential to understand how freeze–thaw processes affect the ability of alpine peatland ecosystems to act as carbon sources and sinks.