Greenhouse Gas Production Research Articles

Biochar as a Soil Amendment for Restraining Greenhouse Gases Emission and Improving Soil Carbon Sink: Current Situation and Ways Forward

The global exponential rise in greenhouse gas (GHG) emissions over the last few decades has triggered an urgent need to contextualize low-cost and evergreen technologies for restraining GHG production and enhancing soil carbon sink. GHGs can be mitigated via incorporating biochar into soil matrix to sequestrate the mineralized carbon in a stable form upon organic matter decomposition in soil. However, the efficiency of using biochar to offset GHG emissions from soil and terrestrial ecosystems is still debatable. Moreover, in the literature, biochar shows high functionality in restraining GHG emissions in short-term laboratory studies, but it shows minimal or negative impacts in field-scale experiments, leading to conflicting results. This paper synthesizes information on the ability of biochar to mitigate carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions from soil and organic biomass, with an emphasis on cropland soils. The feedstock type, pyrolysis temperature, and application rate factors showed significant effects on controlling the effectiveness of biochar in restraining GHG emissions. Our study demonstrates that biochar, taken as a whole, can be seen as a powerful and easy-to-use tool for halting the rising tide of greenhouse gas emissions. Nonetheless, future research should focus on (i) identifying other indirect factors related to soil physicochemical characters (such as soil pH/EH and CaCO3 contents) that may control the functionality of biochar, (ii) fabricating aged biochars with low carbon and nitrogen footprints, and (iii) functionalizing biologically activated biochars to suppress CO2, CH4, and N2O emissions. Overall, our paradoxical findings highlight the urgent need to functionalize modern biochars with a high capacity to abate GHG emissions via locking up their release from soil into the carbonaceous lattice of biochar.

Recycling for deforestation reduction in Tanzania: Why are households not using waste charcoal?

Abstract. Ngowi NJ, Ngalawa AA. 2022. Recycling for deforestation reduction in Tanzania: Why are households not using waste charcoal?. Asian J For 7: 1-8. Charcoal making and the subsequent waste charcoal produced to contribute to deforestation and the production of greenhouse gases, the major drivers for climate change. Whereas climate change is increasingly becoming a public issue, Africa produces 63% of the total global wood charcoal. Since 2004, the demand for wood charcoal on the continent has risen by 30%, the highest in the world. The low efficiency of locally made earth kilns, between 8% and 36%, reported in Africa has contributed to increased waste charcoal production on the continent. However, more information is needed on the cycling use of waste charcoal in low-income countries. In order to improve forest resource use, we investigated the factors influencing the cycling use of wood waste charcoal in the Kilosa District of East-Central Tanzania between 2020 and 2021. A total of 298 randomly selected households were involved in the survey. SPSS version 20 tools were used in the analysis through cross-tab descriptive statistics and the independent sample t-test. Results show that sex, age, expenditure on fuel energy, environment, and technology for cooking significantly affected household use of waste charcoal (p < 0.05). The availability of wastes (v = 0.272) was the most influential factor in the cycling use of waste charcoal. The paper shows that cycling the use of wood waste charcoal would reduce volumes of trees cleared for firewood and improve sanitation by removing rampantly disposed waste from the environment.

Characterization of the number of spot samples required for quantification of gas fluxes and metabolic heat production from grazing beef cows using a GreenFeed.

Enteric fermentation from cattle results in greenhouse gas production that is an environmental concern and also an energetic loss. Several methods exist to quantify gas fluxes; however, an open circuit gas quantification system (OCGQS) allows for unencumbered quantification of methane (CH4), carbon dioxide (CO2), and oxygen (O2) from grazing cattle. While previous literature has proven the accuracy of an OCGQS, little work has been done to establish the minimum number of spot samples required to best evaluate an individual grazing animal's gas fluxes and metabolic heat production. A GreenFeed system (C-Lock Inc.) was used to collect at least 100 spot samples each from 17 grazing cows. The mean gas fluxes and metabolic heat production were computed starting from the first 10 visits (forward) and increasing by increments of 10 until an animal had 100 visits. Mean gas fluxes and metabolic heat production were also computed starting from visit 100 (reverse) in increments of 10 using the same approach. Pearson and Spearman correlations were computed between the full 100 visits and each shortened visit interval. A large increase in correlations were seen between 30 and 40 visits. Thus, mean forward and reverse gas fluxes and metabolic heat production were also computed starting at 30 visits and increasing by 2 until 40 visits. The minimum number of spot samples was determined when correlations with the full 100 visits were greater than 0.95. The results indicated that the minimum numbers of spot samples needed for accurate quantification of CH4, CO2, and O2 gas fluxes are 38, 40, and 40, respectively. Metabolic heat production can be calculated using gas fluxes collected by the OCGQS with 36 spot samples. Practically, calculation of metabolic heat production will require 40 spot samples because the component gases for metabolic heat calculation require up to 40 spot samples. Published literature from nongrazing (confined) environments recommended a similar number of total spot samples. Large variation existed around the average number of spot samples for an animal per day, therefore a wide range of test durations may be needed to meet the same number of spot samples in different populations. For this reason, protocols for the OCGQS should be based on the total number of spot samples, rather than a test duration.

Analysis of greenhouse gas generation models at household waste landfills for ecosystem applications

The control and minimization of greenhouse gas emissions is an important task of modern ecology. One of the sources of greenhouse gases is landfills of household waste (LHW). A special feature of LHWs, as a source of greenhouse gases, is the complexity of estimating emissions. The fact is that the production of greenhouse gases (mainly methane) at LHW is a long process, time-consuming and dependent on many factors. In particular, the rate of putrefaction of organic waste depends on environmental parameters, such as temperature, humidity, and precipitation patterns. Knowing the estimates of greenhouse gas emissions, it is possible to develop an appropriate technology for their disposal, taking into account the regional features of the location of landfills. A mathematical model of gas formation on LHWs is required to solve the problem of predicting greenhouse gas emissions from these landfills. Currently, there are several generally accepted models of LHW. This paper reviews the three main models used in world practice: LandGEM, EPER-Germany, and TNO in terms of their universality and applicability for describing LHW from Siberia region. It was shown that the most promising model is LandGEM.

Efeitos dietéticos de caroço de algodão e vitamina E nas emissões de gases de efeito estufa por fezes de bovinos analisadas em biodigestores

Abstract The objective of this work was to evaluate the effect of diets with cottonseed and vitamin E on the greenhouse gas (GHG) emissions of cattle feces analyzed in biodigesters. Animal feces were evaluated in 18 laboratory-scale anaerobic digesters through the following treatments: control, feces from cows fed with a control diet; CS, feces from cows fed with a cottonseed diet; and CSVitE, feces from cows fed with a cottonseed and vitamin E diet. The production of biogas and GHG was measured, and no differences were observed for the emissions of biogas, methane (CH4), and nitrous oxide (N2O). The partition of the gross energy of the anaerobic digestion process was similar among treatments. On average, 28% of gross energy fed was released as CH4, 47% during digestion, and 25% as other gases and heat. The addition of cottonseeds to the cattle diet increases the concentration of CH4 and reduces that of CO2, but it does not affect the total production of CH4, CO2, and N2O in the biodigesters. The inclusion of vitamin E in the diet has no effect on GHG production in the biodigesters.

Analysis of the overall potential for electricity production from farm animals manure in Bulgaria

The increasing energy demand combined with the policies for environmental protection are prerequisite to combine them both into the circular economy conception. The utilization of organic waste which produce greenhouse gases during its disposing through production of electricity by obtained secondary organic compounds is a promising approach for the simultaneously meeting of energy needs and decreasing of carbon footprint from the industry. The successful integration of such technology with well-defined economical and technological benefits is optimization task at local level for each country, city or area. An initial evaluation of the potential of manure generated from farm animals in Bulgaria to be utilized as energy source as a different approach for its treatment to reduce the local generation of greenhouse gases is performed in this study. The well-known and commercialized technology for production of biogas from manure by digestion in biogas reactors where at different treatment conditions could be obtained gas mixtures with up to 65 vol. % content of methane is used. The main challenges in front of the implementation of this technology is the impossibility to collect all of the produced manure and also the high transportation costs for its utilization at a centralized site for biogas production and thereafter its combustion in a large power plant. A conservative analysis of the manure quantity available for utilization from different livestock animals and poultry in Bulgaria is performed based on the statistical data for the available farms and the share of free grazing animals. The contribution of different animals to the biogas production and the calorific value based on the gas mixture content are calculated in details. Unlike most other green energy technologies, this one is characterized by 24-hour availability and according to the calculated data a power plant of 1500 MW thermal power could be realized. The reduction of greenhouse gases emissions and potentially spared CO2 emissions quotas at country level are also calculated. As additionally noted there is a secondary commercial product of the anaerobic manure treatment in bioreactors, the solid residue which is applicable as fertilizer for plants due to its high nutritional value.

Growth Study and Biological Hydrogen Production by novel strain Bacillus paramycoides

Industrial revolution has created high dependent on fossil fuels for energy creation. However, combustion of fossil fuels has created excessive amount of greenhouse gases, hence led to climate change. Thus, renewable energy has been proposed to alleviate the environmental pollution issues around the globe. One of the promising renewable energies is green hydrogen energy. Commercialized technologies such as electrolysis and thermochemical reaction are utilized to form hydrogen energy. Nonetheless, these processes require high energy and yet producing greenhouse gases that harm the environment. In this study, biodegradation process to produce hydrogen energy has been explored. To our knowledge, Bacillus paramycoides strain has not yet been investigated for biological hydrogen evolution. Therefore, in this paper, the ability of Bacillus paramycoides to produce biological hydrogen has been studied. The rod-shaped and gram-positive Bacillus paramycoides was identified under scanning electron microscope and gram staining procedure. Furthermore, biological hydrogen generation by Bacillus sp. was experimented for 96 hours. The result shows that 4668 ± 120 ppm cumulative hydrogen gas was generated through dark fermentation process. For Bacillus sp. growth study, lag, log, and stationary phase have been achieved in 96 hours. In a summary, metabolic engineering to degrade abundant biomass wastes is a sustainable pathway to produce hydrogen energy, simultaneously resolve waste management issue around the globe.

A Service Level Agreement Aware Online Algorithm for Virtual Machine Migration

The demand for cloud computing has increased manifold in the recent past. More specifically, on-demand computing has seen a rapid rise as organizations rely mostly on cloud service providers for their day-to-day computing needs. The cloud service provider fulfills different user requirements using virtualization - where a single physical machine can host multiple Virtual Machines. Each virtual machine potentially represents a different user environment such as operating system, programming environment, and applications. However, these cloud services use a large amount of electrical energy and produce greenhouse gases. To reduce the electricity cost and greenhouse gases, energy efficient algorithms must be designed. One specific area where energy efficient algorithms are required is virtual machine consolidation. With virtual machine consolidation, the objective is to utilize the minimum possible number of hosts to accommodate the required virtual machines, keeping in mind the service level agreement requirements. This research work formulates the virtual machine migration as an online problem and develops optimal offline and online algorithms for the single host virtual machine migration problem under a service level agreement constraint for an over-utilized host. The online algorithm is analyzed using a competitive analysis approach. In addition, an experimental analysis of the proposed algorithm on real-world data is conducted to showcase the improved performance of the proposed algorithm against the benchmark algorithms. Our proposed online algorithm consumed 25% less energy and performed 43% fewer migrations than the benchmark algorithms.

The path to climate neutrality for California dairies

Abstract In recent years, dairy farms have come under scrutiny with pressure to curb their environmental impacts. Since 1950, the California dairy industry has made strides in reducing greenhouse gas (GHG) emissions per kilogram of milk produced. However, total GHG emissions have remained near constant over the past 15 years. Most on-farm dairy production emissions are in the form of methane (CH 4 ) emissions produced via enteric fermentation, where CH 4 is produced as a byproduct of feed digestion, and manure management. Methane is a powerful but short-lived GHG. Historically, GWP100 has been utilized to describe a GHG emission’s warming impact over a 100-year time span. To better characterize the impact of CH 4 on atmospheric warming, a relatively new accounting system named global warming potential star (GWP*) has been proposed to consider the production and degradation of this short-living GHG. Characterizing greenhouse gases by how they warm our atmosphere instead of the number of emissions produced is a better metric for the true impact of the emissions on atmospheric warming. The goal of this research is to use GWP* to analyze the impact of potential GHG emissions scenarios from California dairy and the impact of those scenarios on atmospheric warming. Utilizing GWP* can help discern when an industry or sector has achieved climate neutrality or no annual warming contributions from industry. This paper also investigates the necessary amount of CH 4 reduction needed and the time point at which the dairy sector can achieve climate neutrality. The scenarios are business-as-usual (BAU), 40% reduction in manure CH 4 emissions (40 MAN) by applying anaerobic digestion and its alternative technologies, and 40 MAN along with a 10.6% reduction in enteric fermentation CH 4 emissions via 1/3 of California’s cows fed the feed additive 3-nitrooxypropanol (40 MAN+EF). Under GWP100 in 2030, carbon dioxide equivalents (CO 2 e) for the 40 MAN and the 40 MAN + EF scenarios were reduced by 18 and 22%, respectively compared to the BAU. For all three scenarios, the relative warming impact of the industry decreased over time due to constant herd sizes and total annual emissions. By aggressively decreasing CH 4 emissions under the 40 MAN and 40 MAN+EF scenarios, there is the possibility for the California dairy industry to reach climate neutrality by the year 2027. These scenarios have more CH 4 naturally removed in the atmosphere than is emitted, thus lowering atmospheric contributions from the industry. These scenarios could be adopted by dairies in other states and countries to help the global dairy industry to achieve climate goals through persistent CH 4 mitigation.

Critical Analysis of Sustainable Development Goal 13 Climate Action: A Case Study of Amazon

It is well known that the massive production of greenhouse gases is causing global temperatures to rise. It is worth considering whether Amazon, the world's leading e-commerce company and one of the most popular brands, is currently taking steps to support Sustainable Development Goal 13(SDG 13) on climate change. This research will examine Amazon's stakeholder efforts to support SDG 13 and explore stakeholder behavior using a disciplined stakeholder analysis. This research will make recommendations for Amazon.com to reduce the number of deliveries and invest in new technologies, but it is clear that the downsides of these recommendations are also evident.

An Overview on Microbial Enzymes and their Industrial Applications

The application of enzymes for commercial interests is a very well-known practice over centuries. A diverse range of new enzymes have been discovered with the progression of technologies and some of these are yet unexplored. The environment-friendly nature of microbial enzymes gained interest of researchers because they reduce the production of greenhouse gases, during industrial processing. There are so many applications for microbial enzymes in a variety of industries for example (textiles, leather, paper and pulp, pharmaceutical, agriculture, detergent, waste, biorefineries, photography and food industries. There is a preference for microbial enzymes over plants and animals’ sources because of some of their specific characteristics e.g.- inexpensive production value, short time taken procedure and high yield. This review focuses on to reveal some industrial enzymes listed in comprehensive manner with their microbial origins and a diverse range of commercial implementation.

Photofixation of N2 to ammonia utilizing Ni@TPP-HPA nanocomposite under visible-light illumination.

The production of ammonia as an important raw material in the chemical, agricultural, and food industries has been always a significant concern. However, conventional ammonia production methods require high energy consumption and costs. The photocatalytic rotes use green light sources and cost-effective photocatalysts to obtain ammonia from water under aerobic conditions and preventing production of greenhouse gases in the environment. To produce an effective heterogeneous catalyst, a new tetraphenylporphyrin-heteropolyacid (TPP-HPA) nanohybrid material is synthesized and loaded onto Ni nanoparticles in this work. Then, FE-SEM, EDS, XRD, and FT-IR analyses were applied to characterize the prepared nanohybrid material Ni@TPP-HPA. After that, the new inorganic-organic nanohybrid photocatalyst was introduced as an effective, environmental friendly, and recyclable mediator for N2 photofixation. The results showed that Ni@TPP-HPA is a good photocatalyst for the N2 fixation reaction and can be easily recycled without losing its activity for at least five runs. The Ni@TPP-HPA nanocomposite demonstrated the maximum ammonia generation by 2760 μmol L-1 g-1 under mild conditions when using methanol as a hole scavenger. Additionally, effects of solvent type, temperature, reaction time, irradiation source, solution pH, and other electron scavengers on the rate of NH4+ production were investigated and discussed.

Transportation Biofuels in Latvia: A Life Cycle Thinking Approach

Abstract Transport consumes around one-third of Latvia’s final energy demand being the largest sector that produces greenhouse gas emissions. In Latvia, in the year 2019, the share of renewable energy sources in the transport sector was only 4.8 % of the total gross consumption with a target of 7 % of not food-based biofuels by 2030. To tackle climate change problems, one significant task is reducing pollution in the transport sector by substituting fossil with biomass-based fuels. The goal of this study is to develop a methodology for evaluating biofuel production in Latvia considering economic, social, environmental, and technological aspects. A total of 16 specific criteria were selected for biofuel comparison. The methodology is based on a combination of two quantitative approaches, namely Life Cycle Assessment and Multi-Criteria Analysis. The proposed method aims to identify the most sustainable biofuel in Latvia according to a set of specific indicators.

Greenhouse gas production, diffusion and consumption in a soil profile under maize and wheat production

Agricultural soil emissions are a balance between sinks and sources of greenhouse gases (GHGs). The fluxes of GHGs from soils are complex and spatially and temporally heterogenous. While the soil surface is the exchange site with the atmosphere and is commonly where GHG fluxes are measured, it is important to consider processes occurring throughout the soil profile. To reduce emissions and improve agricultural sustainability we need to better understand the drivers and dynamics (production, consumption, diffusion) of these gases within the soil profile. Due to the heterogeneous nature of GHG processes at small to large scales, it is important to test how these processes differ with depth in different systems. In this study, we measured in situ CO2, N2O and CH4 concentration gradients as a function of soil depth over subsequent maize and wheat growing seasons with active gas samplers inserted into an arable field at 10, 20, 30 and 50 cm depths. We found N2O and CH4 concentrations increased with depth, but only CO2 concentrations differed with depth between growing seasons due likely to differences in soil diffusivity driven by soil conditions. Using the concentration gradient method (GM), the CO2 fluxes at each depth and their contribution to the surface flux were calculated and validated against a chamber method (CM) measured surface flux. We found the GM estimated surface CO2 flux was only 6 % different in the wheat, but 28 % lower than the surface measured flux in the maize growing season, due to drought conditions reducing the accuracy of the GM. Finally, we measured fluxes of CO2, N2O and CH4 in ambient and highly concentrated headspaces in laboratory mesocosms over a 72 h incubation period. We provide evidence of depth dependent CH4 oxidation and N2O consumption and possibly CO2 fixation. In conclusion, our study provides valuable information on the applicability of the GM and further evidence of the GHG production, consumption and diffusion mechanisms that occur deeper in the soil in a temperate arable context.

Open source IoT-based collection bin applied to local plastic recycling

Plastic waste is a major challenge for policy making; it has a terrible impact on the environment if it is not properly managed. In order to mitigate this issue, recycling industries have emerged with the associated logistics chain that also has an environmental impact, notably with the production of greenhouse gas. In addition to using energy to transform plastic waste into source material, energy is also wasted to transport it. In parallel to reducing plastic waste, it may be recycled at a very local scale, reducing transportation and allowing potential improvement of the collecting process. Assuming that local transformation of plastic waste is possible, this article describes the design, assembly, and setup of the hardware, system architecture, and software of collectors that may be used by these recycling units. The specificity of these collectors is that they produces on-line data related to the quantity of waste collected. Once implemented, a network of smart collectors should allow the reduction of travel to collect waste as it notifies when the collectors are full. It also produces data on the scale of a territory to optimize the supply chain related to plastic waste collection. This article presents the design and engineering aspects as well as limitations induced by technical choices, but also potential improvements for future developments.

Variability and drivers of CO2, CH4, and N2O concentrations in streams across the United States

AbstractStreams and rivers are major sources of greenhouse gases (GHGs) to the atmosphere, as carbon and nitrogen are converted and outgassed during transport. Although our understanding of drivers of individual GHG fluxes has improved with numerous site‐specific studies and global‐scale compilations, our ability to parse out interrelated physical and biogeochemical drivers of gas concentrations is limited by a lack of consistently collected, temporally continuous samples of GHGs and their associated drivers. We present a first analysis of such a dataset collected by the National Ecological Observatory Network across 27 streams and rivers across ecoclimatic domains of the United States. Average concentrations of CO2 ranged from 36.9 ± 0.88 to 404 ± 33 μmol L−1, CH4 from 0.003 ± 0.0003 to 4.99 ± 0.72 μmol L−1, and N2O from 0.015 to 0.04 μmol L−1 and spanned ranges of previous global compilations. Both CO2 and CH4 were strongly affected by physical drivers including mean air temperature and stream slope, as well as by dissolved oxygen and total nitrogen concentrations. N2O was exclusively correlated with total nitrogen concentrations. Results suggested that potential for gas exchange dominated patterns in gas concentrations at the site level, but contributions of in‐stream aerobic and anaerobic metabolism, and groundwater also likely varied across sites. The highest gas concentrations as well as highest variability occurred in low‐gradient, warmer, and nonperennial systems. These results are a first step in providing unprecedented, continuous estimates of GHG flux constrained by temporally variable physical and biogeochemical drivers of GHG production.

Algorithm for Monitoring Emissions Based on Actual Speed of Ships Participating in the Korean Vessel Speed Reduction Program

The vessel speed reduction program (VSRP) was first introduced in the Port of Los Angeles in 2001 to improve air quality. In this study, an algorithm was developed to calculate ship emissions with a bottom-up approach based on ship activity using automatic identification system (AIS) data. The target vessel applied to the emission calculation was a vessel participating in Korea’s VSRP. Factors considered for the calculation of emissions were ship type, speed, gross tonnage, engine power, load, sulfur content of fuel, and fuel consumption rate by engine age. The algorithm is designed to calculate the reduction amount by VSRP by simultaneously calculating the emission amount of the actual speed and the emission amount of the cruise speed when not participating in VSRP. The emission results of ships that participated in the VSRP in 2020 revealed that their speed was reduced by 47% and carbon dioxide emissions by 71.9%. These results were verified through comparison with the fuel consumption report of the container fleet presented by the International Maritime Organization. Our findings can be used to monitor the air pollutant emissions of ships entering major ports in Korea and to develop policies envisaged at reducing the production and effect of greenhouse gases and air pollutants. Moreover, we recommend that this model be replicated in other countries for monitoring ship-induced emissions.

Production and possible reduction of greenhouse gases produced during GI endoscopy activity: a systematic review of available literature

Background and aimsGreenhouse gases (GHGs) that trap heat in the atmosphere are composed of carbon dioxide (CO2), methane, nitrous oxide and fluorinated gases (synthetic hydrofluorocarbons, perfluorocarbons and nitrogen trifluoride). In...

Neural network to quantify the amount of greenhouse gases produced by flue gases affecting climatic conditions in Iran's southern areas

The present research was conducted using neural network to investigate the climatic changes resulted by the production of greenhouse gases from flue gas condensates in the petroleum regions of southern Iran. The climatic data (humidity, wind speed, and temperature) and the activity of flue gases in an 11-year period (2008–2018) were collected to train the network. The emission of greenhouse gases and the global warming potential (GWP) values were calculated using IPCC 2006. The climatic conditions in a specific period were determined using Ivanov's climatic index. Initially, the prediction of climatic variation (by the emission of greenhouse gases from the flue gas condensates) was investigated by the linear regression of GWP and Ivonov's index lacking the suitable precision (R = 0.088). Accordingly, neural network of multilayer perceptron (MLP) and radial basis function (RBF) were used to test the correlation of GWP and Ivonov's index. The function of linear axon and the momentum training algorithm were utilized. The collected data were used for training (76%), validating (15%) and testing the network (9%). The R2 values by MLP and RBF were equal to 0.83 (mean of square error (MSE) = 0.170792332) and 0.96 (MSE = 0.063481847), indicating the two networks precisely predicted the climatic variation (global warming) resulted by the emission of greenhouse gases from the flue gas condensates. Such results are of environmental, health and economic significance, and can be used for the development of strategies, which can mitigate the climatic changes resulted by the production of greenhouse gases.

Landscape Change Affects Soil Organic Carbon Mineralization and Greenhouse Gas Production in Coastal Wetlands

AbstractPlant invasion and aquaculture activities have drastically modified the landscape of coastal wetlands in many countries, but their impacts on soil organic carbon (SOC) mineralization and greenhouse gas production remain poorly understood. We measured SOC mineralization rate and soil CO2 and CH4 production rates in three habitat types from 21 coastal sites across the tropical and subtropical zones in China: native mudflats (MFs), Spartina alterniflora marshes (SAs), and aquaculture ponds (APs). Landscape change from MFs to SAs or APs increased total and labile fraction of SOC, as well as carbon mineralization rate and greenhouse gas production, but there were no discernible differences in SOC source‐sink dynamics between SAs and APs. SOC mineralization rate was highest in SAs (20.4 μg g−1 d−1), followed by APs (16.9 μg g−1 d−1) and MFs (11.9 μg g−1 d−1), with CO2 as the dominant by‐product. Bioavailable SOC was less than 2% and was turned over within 60 days in all three habitat types. Proliferation of S. alterniflora marshes and expansion of AP construction had resulted in a net increase in soil CO2‐eq production of 0.4–4.3 Tg yr−1 in the last three decades. Future studies will benefit from better census and monitoring of coastal habitats in China, complementary in situ measurements of greenhouse gas emissions, and more sampling in the southern provinces to improve spatial resolution.