Increased Greenhouse Gas Emissions Research Articles

Influence of the Depth of Nitrogen-Phosphorus Fertilizer Placement in Soil on Maize Yielding and Carbon Footprint in the Loess Plateau of China

Deep fertilization is a beneficial approach for reducing nitrogen losses. However, the effects of various fertilization depths on maize (Zea mays L.) productivity and environmental footprints have not been thoroughly understood. Therefore, a field experiment was conducted to investigate the effects of different fertilization depths of 5 cm (D5), 15 cm (D15), 25 cm (D25), and 35 cm (D35) on maize productivity and environmental footprints. Reactive nitrogen (Nr) losses and greenhouse gas (GHG) emissions were assessed using life cycle analysis. We hypothesized that deep fertilization can obtain lower carbon and nitrogen footprint. The results indicated that deep fertilization decreased the N2O and NH3 emissions while increasing the CH4 uptake. Compared with D5, D15 resulted in an increase in total GHG emissions and carbon footprint (CF), whereas D25 decreased by 13.0% and 23.6%, respectively. Compared with D5, the Nr losses under D15, D25, and D35 conditions was reduced by 11.3%, 17.3%, and 21.0%, respectively, and the nitrogen footprint (NF) was reduced by 16.0%, 27.4%, and 19.0%, respectively. The maize yield under D15 and D25 increased by 5.7% and 13.8%, respectively, compared with the D5 treatment, and the net economic benefits of the ecosystem increased by 7.1% and 17.1%, respectively. In summary, applying fertilizer at a depth of 25 cm can significantly reduce the environmental footprints and increase maize productivity, making it an effective fertilization strategy in the Loess Plateau region of China.

Impact of environmental policy stringency on sectoral GHG emissions: evidence from Finland and Sweden by nonlinear quantile-based methods

ABSTRACT The growing societal concern regarding environmental matters has led to the implementation of many environmental measures intended to protect the environment and address global warming by lessening emissions and mitigating climate change. In line with this movement, this study scrutinizes the impact of these environmental measures on greenhouse gas (GHG) emissions to analyze the cases of Finland and Sweden. More specifically, the study employs the Environmental Policy Stringency (EPS) index as a proxy for environmental measures, explores sector-specific GHG emissions by employing nonlinear quantile-based methodologies (including quantile-on-quantile regression and Granger causality-in-quantiles methods as the primary model and quantile regression for robustness checking) spanning the period from 1991/Q1 to 2020/Q4. The findings show that: (i) EPS lessens GHG emissions from fuel exploitation, industrial combustion, and the power industry sector at lower and middle quantiles in Finland and Sweden; (ii) EPS decreases GHG emissions from processes, transportation, and waste sectors in Finland but increases them in Sweden at higher quantiles; (iii) EPS leads to an increase in GHG emissions from the agriculture and construction sectors at higher quantiles; (iv) EPS has a causal effect on sector-specific GHG emissions across different quantiles; (v) the robustness of the findings is largely confirmed. Hence, the study underscores the varying impacts of EPS on sectoral GHG emissions based on quantiles, sectors, and countries, emphasizing the need for policymakers to adopt environmental policies to comprise these differences and adjust the policy framework accordingly.

Sustainability in dentistry part II: Sustainability and the use of chemicals in dentistry

The world is now in an existential ecological crisis. Our deleterious and unsustainable impact on the planet has, among other things, increased greenhouse gas emissions, with further injury from plastics and other waste in the environment. The evidence for an accelerating biodiversity crisis and serious soil degradation in many parts of the world is irrefutable. The pandemic risk to our species and our planet is not if, but when. We have to change the way we organise society in order to make the future sustainable for all species. Worldwide health systems are a significant contributor to environmental damage. The first article in this series discussed general aspects of sustainability in general practice, and this second article examines the use of chemicals in practice.

Effect of banana tree leaves ash as cementitious material on the durability of concrete against sulphate and acid attacks

The construction industry's rapid growth poses challenges tied to raw material depletion and increased greenhouse gas emissions. To address this, alternative materials like agricultural residues are gaining prominence due to their potential to reduce carbon emissions and waste generation. In this context this research optimizes the use of banana leaves ash as a partial cement substitution, focusing on durability, and identifying the ideal cement-to-ash ratio for sustainable concrete. For this purpose, concrete mixes were prepared with BLA replacing cement partially in different proportions i.e. (0 %, 5 %, 10 %, 15 %, & 20 %) and were analyzed for their physical, mechanical and Durability (Acid and Sulphate resistance) properties. Compressive strength, acid resistance and sulphate resistance testing continued for 90 days with the intervals of 7, 28 and 90 days. The results revealed that up to 10 % incorporation of BLA improved compressive strength by 10 %, while higher BLA proportions (up to 20 %) displayed superior performance in durability tests as compared to the conventional mix. The results reveal the potentials of banana leave ash to refine the concrete matrix by formation of addition C–S–H gel which leads towards a better performance specially in terms of durability aspect. Hence, banana leaf ash (BLA) is an efficient concrete ingredient, particularly up to 10 % of the mix. Beyond this threshold, it's still suitable for applications where extreme strength isn't the primary concern, because there may be a slight reduction in compressive strength.

On the energy impact of cool roofs in Dubai

Urban warming can significantly increase the energy demand for building cooling. As temperatures rise, buildings require additional energy for air conditioning, which can lead to higher electricity demand and increased greenhouse gas emissions. This can create a positive feedback loop, as increased energy demand leads to increased waste heat and further exacerbates the urban warming effect. To solve this issue, this study integrates high-resolution meteorological data from the Weather Research and Forecasting coupled with Single Layer Urban Canopy Model (WRF/SLUCM) into CitySim for the first time to evaluate the building energy demands at various building types in Dubai metropolis. Examining how cool materials reduced cooling loads was achievable utilizing modified albedo in Dubai's downtown buildings. An increase of urban albedo from 0.2 to 0.8 significantly lowers the urban heating effect, as well as the building cooling needs. The study shows that for albedo scenario 0.8, Low-rise residential buildings experienced cooling load reductions of about 13.1 kWh/m2 and 6 kWh/m2 for buildings without insulation and those with insulation, respectively, compared to the base case. Additionally, high-rise residential buildings saw cooling load reductions ranging from 7.7 kWh/m2 to 11.7 kWh/m2 for buildings without insulation and a cooling load reduction of 3.6 kWh/m2 to 5.4 kWh/m2 for insulated buildings. This study provides a tool for regulating the energy impact of cool roofs in different urban settings using energy simulation, which could help policymakers control the energy needs in subtropical desert urban environments.

Potential Torrefaction of Tropical Forest Fruits Waste

Biomass torrefaction can improve the quality of raw biomass as fuel. Tropical forest fruit waste that is not managed properly will become waste that contributes to increasing greenhouse gas emissions. Conversion of tropical forest fruit waste into biomass fuel by torrefaction can be used as coal co-firing. In this research, torrefaction was carried out on the biomass from the cocoa pod shell, coffee husks, and mangosteen pod shell. The samples used in this study came from tropical forest fruits in Lampung Province. Samples were chopped and dried using the hot sun. The samples were then torrefied in a tubular reactor at temperatures of 250, 275, and 300°C and their calorific values were tested. Torrefaction at 275°C has increased the calorific value of tropical forest fruit waste to exceed the calorific value of sub-bituminous A. Torrefaction of tropical forest fruit waste has the potential to be used as fuel for co-firing coal in power plants. Thus, it can indirectly reduce the rate of CO2 emissions from power generation and waste accumulation. In addition, it also has the potential to become a competitive sustainable export commodity.

Aeroponics vertical indoor farming

Aeroponics vertical indoor farming is a farming that involves growing crops in layers that are piled vertically. Aeroponics is a method of growing plants without soil. Vertical indoor farming is climate controlled so it can be done year-round regardless of environmental challenges. Emerging problems of food security, urbanization, farmland shortage, food miles increased greenhouse gas emissions focus on the need for vertical farming physiological constraints that occur within hydroponic systems. Today, agriculture especially in India to concentrate in some situation such as how to increase the productivity and profit. This paper presents a methodology for developing the plants are submerged in a nutrient-rich mist solution. This study challenges is cultivating the plant by organic farming natural nutrition.

Comparative evaluation of Artificial intelligence based models and kinetic studies in the prediction of biogas from anaerobic digestion of MSW

The generation of biogas from the decomposition of MSW increases greenhouse gas emissions, contributing to global warming. However, the produced biogas can be effectively captured for conversion into a renewable energy resource. This study demonstrates the utility of artificial neural networks (ANN), adaptive network-fuzzy inference systems (ANFIS), and kinetic models in predicting biogas production from the anaerobic digestion of MSW. The digestion time, volatile solids, pH, temperature, and moisture content were selected as the independent variables. Furthermore, kinetic studies were conducted to predict the biogas yield using First-order, modified Gompertz, Logistic, and Transference models. To assess the efficacy of these models, their performance was evaluated using the coefficient of determination (R2) and root mean square error (RMSE). Upon comparing the results, it was evident that for set IX under 100 % field capacity (FC), the ANFIS network exhibited superior performance with RMSE and R2 values of 0.670 and 0.999, respectively. In comparison, the ANN and modified Gompertz models yielded RMSE values of 0.863 and 21.705, and R2 values of 0.999 and 0.998, respectively. While the coefficient of determination (R2 ≥ 0.99) suggested satisfactory agreement between all the models and experimental data, the ANFIS and ANN models achieved notably lower RMSE values, demonstrating their competitive performance.

Energy Management Strategy for DC Micro-Grid System with the Important Penetration of Renewable Energy

This paper presents an energy management strategy using a Stateflow controller related to DC microgrids with the important penetration of renewable energy. The increase in world electricity demand is one of the principal drivers of the exhaustion of fossil fuels and increased greenhouse gas emissions. To solve these problems, several countries have adopted actions for widespread renewable energy deployment, which includes wind energy, solar power, biomass power, tidal, and hydropower. These sources are considered as significant in delivering clean energy and reducing greenhouse gas emissions for sustainable improvement. As these sources play an increasingly vital role in the global energy landscape, the efficient management of these intermittent sources is essential for grid stability and sustainability. This paper aimed to develop an energy management strategy for DC microgrids to supply power to a DC microgrid system. The main objective of this paper was to implement an energy management system to ensure the proper operation of DC microgrid systems utilizing Simulink blocks available in MATLAB/Simulink 2020b software. The simulation results demonstrated that the developed energy management algorithm was unconditionally reliable, ensuring the proper operation of the microgrid systems. Additionally, the results demonstrated that the energy management strategy exhibited robust performance across different scenarios, effectively balancing energy generation and consumption while ensuring the reliable operation of the microgrid system. Moreover, the developed algorithm model presents another advantage, as it enables users to access and to change any control parameters within the DC microgrid. By comparing these results with the literature, the developed energy management algorithm provides safety and the automatic control of the microgrid.

Ecological niche shift and suitable area expansion of a globally invasive species Phthorimaea operculella.

Phthorimaea operculella is a major potato pest of global importance, early warning and detection of which are of significance. In this study, we analyzed the climate niche conservation of P. operculella during its invasion by comparing the overall climate niche from three dimensions, including the differences between native range (South America) and entire invaded region (excluding South America), the differences bwtween native range (South America) and five invaded continents (North America, Oceania, Asia, Africa, and Europe), as well as the differences between native region (South America) and an invaded region (China). We constructed ecological niche models for its native range (South America) and invaded region (China). The results showed that the climatic niche of the pest has expanded to varying degrees in different regions, indicating that the pest could well adapt to new environments during the invasion. Almost all areas of South America are suitable for P. operculella. In China, its suitable area is mainly concentrated in Shandong, Hebei, Tianjin, Beijing, Henan, Hubei, Yunnan, Guizhou, Sichuan, Hainan, northern Guangxi, southern Hunan, Anhui, Guangdong, Jiangsu, southern Shanxi, and southern Shaanxi. With increasing greenhouse gas emissions and global temperature, its suitable area will decrease at low latitude and increase gradually at high latitude. Specifically, the northern boundary will extend to Liaoning, Jilin, and the southeastern region of Inner Mongolia, while the western boundary extends to Sichuan and the southeast Qinghai-Tibet Plateau. The suitable area in the southeast Yunnan-Guizhou Plateau, Hainan Island, and the south of Yangtze River, will gradually decrease. The total suitable habitat area for P. operculella in China is projected to increase under future climate condition. From 2081 to 2100, under the three greenhouse gas emissions scenarios of ssp126, ssp370, and ssp585, the suitable area is expected to increase by 27.78, 165.54, and 140.41 hm2, respectively. Therefore, it is crucial to strengtehen vigilance and implement strict measures to prevent the further expansion of P. operculella.

Subsidizing Grid-Based Electrolytic Hydrogen Will Increase Greenhouse Gas Emissions in Coal Dominated Power Systems.

Clean hydrogen has the potential to serve as an energy carrier and feedstock in decarbonizing energy systems, especially in "hard-to-abate" sectors. Although many countries have implemented policies to promote electrolytic hydrogen development, the impact of these measures on costs of production and greenhouse gas emissions remains unclear. Our study conducts an integrated analysis of provincial levelized costs and life cycle greenhouse gas emissions for all hydrogen production types in China. We find that subsidies are critical to accelerate low carbon electrolytic hydrogen development. Subsidies on renewable-based hydrogen provide cost-effective carbon dioxide equivalent (CO2e) emission reductions. However, subsidies on grid-based hydrogen increase CO2e emissions even compared with coal-based hydrogen because grid electricity in China still relies heavily on coal power and likely will beyond 2030. In fact, CO2e emissions from grid-based hydrogen may increase further if China continues to approve new coal power plants. The levelized costs of renewable energy-based electrolytic hydrogen vary among provinces. Transporting renewable-based hydrogen through pipelines from low- to high-cost production regions reduces the national average levelized cost of renewables-based hydrogen but may increase the risk of hydrogen leakage and the resulting indirect warming effects. Our findings emphasize that policy and economic support for nonfossil electrolytic hydrogen is critical to avoid an increase in CO2e emissions as hydrogen use rises during a clean energy transition.

Rapidly increased greenhouse gas emissions by Pacific white shrimp aquacultural intensification and potential solutions for mitigation in China

The Pacific white shrimp (Litopenaeus vannamei) plays a crucial role in global aquaculture, contributing significantly to farmed shrimp production, with China being a major contributor. In the last two decades, China's production of farmed L. vannamei experienced substantial growth due to expanded aquaculture areas and intensification. These processes can lead to increases in greenhouse gas emissions. However, the magnitude of greenhouse gas emissions from L. vannamei aquaculture systems remains unclear. Therefore, in this study, we systematically quantified greenhouse gas (carbon dioxide, methane, and nitrous oxide) emissions in L. vannamei farming systems with different levels of intensification. Various emission sources were assessed, including infrastructure, energy use, feed production, and pond aquatic emissions. The estimates indicate that greenhouse gas emissions increased from 6159.35 ± 475.24 kg CO2e/t of L. vannamei in semi-intensive systems to 24,059.81 ± 3846.31 kg CO2e/t of L. vannamei in super-intensive systems. The increase in greenhouse gas emissions was primarily due to energy use (2395% increase) and infrastructure (15,939% increase). As a result, the greenhouse gas emissions from China's shrimp farming industry increased three-fold (from 5633.37 ± 177.40 to 19,730.68 ± 635.52 million kg CO2e) from 2003 to 2022, mainly contributed by coastal provinces. As the demand for high-quality aquatic products continues to increase, coupled with the urgent necessity to reduce greenhouse gas emissions, there is a crucial requirement to lower the emissions associated with each unit of L. vannamei production. The results of this study suggest that reducing fossil fuel use, improving feed efficiency, promoting biofloc technology, and integrated multi-trophic aquaculture systems may help to build climate-resilient sustainable aquaculture.

A synthesis of the evidence regarding the efficacy of alternative field management practices in rice cultivation using life cycle assessment

Field management practices are an important factor in mitigating climate change and increasing agricultural production. However, no study has synthesized the evidence on the efficacy of alternative field management practices and reviewed life cycle assessments that consider all emissions over the entire or part of the life cycle of rice production. Thus, 68 papers were reviewed and grouped into 13 field management categories. The management practices were evaluated in terms of yield, area-scaled greenhouse gas (GHG) emissions, and yield-scaled GHG emissions against base management practices. The yield increase of these field management practices was between −6 % and 12 %, with some exceptions. It was only nonpuddling that simultaneously increased the yield and reduced both the area-scaled GHG and yield-scaled GHG emissions with respect to the base category. Water management, including alternate wetting and drying or single and multiple drainage and no-tillage, performed well in reducing the average area-scaled GHG and yield-scaled GHG emissions, although the average yield was reduced slightly. For the remaining many management practices, the increase in area-scaled GHG emissions was larger than the change in yield, so the yield change had little impact on yield-scaled GHG emissions. The higher increase in area-scaled GHG emissions than the change in yield requires innovative and new approaches, such as implementing alternative management together with water management, of which the effect was observed in some of the papers reviewed in this study. Therefore, this study recommends selecting nonpuddling, water management or no-tillage as climate mitigation management options. The evaluation of field management will be more robust if more impact categories are considered, including missing aspects (i.e., soil fertility).

Critical review of the role of ash content and composition in biomass pyrolysis

In the face of environmental challenges (e.g., dramatically increasing greenhouse gas emissions and climate change), it is utmost of importance to sustainable energy systems. Biomass consisting of agricultural and forest waste, municipal solid waste, and aquatics, has been identified as alternative and promising fuel sources. Thermochemical conversion approaches like pyrolysis can turn various types of biomass into three valuable product streams, namely, bio-oil, biochar, and syngas. To date, past review articles have considered the major operating parameters of kinetics, chemistry, and the application of pyrolysis products. However, ash content is one of the key biomass components that lacks investigation on its influence during biomass pyrolysis with respect to products yield and properties. This review article examines: i) the ash content and composition in different types of biomass; ii) effects of ash content on catalytic pathway and biomass thermal degradation; iii) ash related problems in the thermal degradation of biomass; and iv) available deashing techniques for biomass. The review aims to provide new understandings and insights regarding the effects of ash content and composition on biomass pyrolysis.

Assessing the effect of the aquaculture industry, renewable energy, blue R&D, and maritime transport on GHG emissions in Ireland and Norway

The assessment of the effects of aquaculture and fisheries on greenhouse gas (GHG) emissions is crucial, especially within the framework of environmental sustainability and global efforts to mitigate climate change. This study investigates the effect of the aquaculture industry, Blue R&D, green energy, and maritime transport on GHG emissions in Ireland and Norway from 2000 to 2019 using quantile-on-quantile regression (QQR) and wavelet coherence (WC). The results of the QQR model indicate a negative effect of aquaculture production at a lower quantile in Ireland. However, the effect turns positive at upper quantiles, showing that aquaculture increases GHG emissions. The strict regulation and efforts to address sustainable aquaculture practices can explain the impact of aquaculture production on GHG emissions in Norway. Maritime transport positively affects GHG emissions in both countries, yet the blue R&D seems more considerable in Norway than in Ireland. The causal relationship between variables implies a substantial impact of the explanatory factors on GHG emissions that have policy directions for policymakers and investment managers.

Amendment of straw with decomposing inoculants benefits the ecosystem carbon budget and carbon footprint in a subtropical wheat cropping field

The incorporation of straw with decomposing inoculants into soils has been widely recommended to sustain agricultural productivity. However, comprehensive analyses assessing the effects of straw combined with decomposing inoculants on greenhouse gas (GHG) emissions, net primary production (NPP), the net ecosystem carbon budget (NECB), and the carbon footprint (CF) in farmland ecosystems are scant. Here, we carried out a 2-year field study in a wheat cropping system with six treatments: rice straw (S), a straw-decomposing Bacillus subtilis inoculant (K), a straw-decomposing Aspergillus oryzae inoculant (Q), a combination of straw and Bacillus subtilis inoculant (SK), a combination of straw and Aspergillus oryzae inoculant (SQ), and a control with no rice straw or decomposing inoculant (Control). We found that all the treatments resulted in a positive NECB ranging between 838 and 5065 kg C ha−1. Relative to the Control, the S treatment increased CO2 emissions by 16%, while considerably enhancing the NECB by 349%. This difference might be attributed to the straw C input and an increase in plant productivity (NPP, 30%). More importantly, in comparison to that in S, the NECB in SK and SQ significantly increased by 27–35% due to the positive response of NPP to the decomposing inoculants. Although the combination of straw and decomposing inoculants yielded a 3% increase in indirect GHG emissions, it also exhibited the lowest CF (0.18 kg CO2-eq kg−1 of grain). This result was attributed to the synergistic effects of straw and decomposing inoculants, which reduced direct N2O emissions and increased wheat productivity. Overall, the findings of the present study suggested that the combined amendment of straw and decomposing inoculants is an environmentally sustainable management practice in wheat cropping systems that can generate win–win scenarios through improvements in soil C stock, crop productivity, and GHG mitigation.

Feasibility Investigation of Geothermal Energy Heating System in Mining Area: Application of Mine Cooling and Aquifer Thermal Energy Exploitation Technique

Mine heat hazards have resulted in large amounts of high-quality coal resources in deep that cannot be mined. The mining industry is paying more and more attention to the extraction and utilization of geothermal energy in mines, while at the same time reducing the underground temperature to realize co-extraction of coal and heat. In addition, coal mines tend to burn large amounts of coal to heat mine buildings and provide hot water for workers’ daily baths, creating operating costs and increasing greenhouse gas emissions. Therefore, it is of great significance to investigate the feasibility of extracting geothermal energy to provide the daily heat load for mines. Currently, there is little research on the feasibility of geothermal energy extraction and utilization in productive mines instead of abandoned mines. In this study, according to the actual situation of Xinhu mine in eastern China, a combined geothermal water system and heat-pump heating system is proposed, aiming to effectively realize mine cooling and geothermal exploitation and utilization. The geothermal storage capacity in the area is analyzed, and an economic analysis is developed. The economic analysis indicates that the main factors affecting the feasibility of the system are the number of mine users, the distance from the geothermal production well to the mine buildings, and the coal price. The research shows that the economic efficiency of the system is better when the heating scale is larger and the distance is smaller. As coal prices rise, the combined geothermal water and heat-pump heating system will be more economical than traditional coal heating. If a mine has 2000 workers, the application of this system can prevent 334.584 t of CO2 emissions per year.

Modern anthropogenic drought in Central Brazil unprecedented during last 700 years

A better understanding of the relative roles of internal climate variability and external contributions, from both natural (solar, volcanic) and anthropogenic greenhouse gas forcing, is important to better project future hydrologic changes. Changes in the evaporative demand play a central role in this context, particularly in tropical areas characterized by high precipitation seasonality, such as the tropical savannah and semi-desertic biomes. Here we present a set of geochemical proxies in speleothems from a well-ventilated cave located in central-eastern Brazil which shows that the evaporative demand is no longer being met by precipitation, leading to a hydrological deficit. A marked change in the hydrologic balance in central-eastern Brazil, caused by a severe warming trend, can be identified, starting in the 1970s. Our findings show that the current aridity has no analog over the last 720 years. A detection and attribution study indicates that this trend is mostly driven by anthropogenic forcing and cannot be explained by natural factors alone. These results reinforce the premise of a severe long-term drought in the subtropics of eastern South America that will likely be further exacerbated in the future given its apparent connection to increased greenhouse gas emissions.

Enhancing Sustainability in Potato Crop Production: Mitigating Greenhouse Gas Emissions and Nitrate Accumulation in Potato Tubers through Optimized Nitrogen Fertilization

The complex ramifications of global climate change, which is caused by heightened concentrations of greenhouse gases in the Earth’s atmosphere, are deeply concerning. Addressing this crisis necessitates the immediate implementation of adaptive mitigation strategies, especially within the agricultural sector. In this context, this study aimed to assess how the supply of nitrogen (N) (0, 70, 140, and 210 kg N ha−1) in the forms of ammonium nitrate and urea affects the agronomic performance, food quality, greenhouse gas emissions (GHG), and carbon footprint of potato plants. The examined hypothesis was that by precisely calibrating N doses alongside appropriate sourcing, over-fertilization in potato cultivation can be mitigated. A decline in stomatal conductance and net photosynthetic rate disturbs physiological mechanisms, reflecting in biomass production. Application of 136 kg N ha−1 as urea showed a remarkable yield increase compared to other doses and sources. The highest nitrate content in potato tubers was achieved at 210 kg N ha−1 for both sources, not exceeding the limit (200 mg kg−1 of fresh mass) recommended for human consumption. The lowest carbon footprint was obtained when 70 kg N ha−1 was applied, around 41% and 26% lower than when 210 kg N ha−1 and 140 kg N ha−1 were applied, respectively. The results demonstrated that over-fertilization not only worsened the yield and tuber quality of potato plants, but also increased greenhouse gas emissions. This information is valuable for establishing an effective fertilization program for the potato crop and reducing carbon footprint.

Earthworms and plants can decrease soil greenhouse gas emissions by modulating soil moisture fluctuations and soil macroporosity in a mesocosm experiment.

Earthworms can stimulate microbial activity and hence greenhouse gas (GHG) emissions from soils. However, the extent of this effect in the presence of plants and soil moisture fluctuations, which are influenced by earthworm burrowing activity, remains uncertain. Here, we report the effects of earthworms (without, anecic, endogeic, both) and plants (with, without) on GHG (CO2, N2O) emissions in a 3-month greenhouse mesocosm experiment simulating a simplified agricultural context. The mesocosms allowed for water drainage at the bottom to account for the earthworm engineering effect on water flow during two drying-wetting cycles. N2O cumulative emissions were 34.6% and 44.8% lower when both earthworm species and only endogeic species were present, respectively, and 19.8% lower in the presence of plants. The presence of the endogeic species alone or in combination with the anecic species slightly reduced CO2 emissions by 5.9% and 11.4%, respectively, and the presence of plants increased emissions by 6%. Earthworms, plants and soil water content interactively affected weekly N2O emissions, an effect controlled by increased soil dryness due to drainage via earthworm burrows and mesocosm evapotranspiration. Soil macroporosity (measured by X-ray tomography) was affected by earthworm species-specific burrowing activity. Both GHG emissions decreased with topsoil macropore volume, presumably due to reduced moisture and microbial activity. N2O emissions decreased with macropore volume in the deepest layer, likely due to the presence of fewer anaerobic microsites. Our results indicate that, under experimental conditions allowing for plant and earthworm engineering effects on soil moisture, earthworms do not increase GHG emissions, and endogeic earthworms may even reduce N2O emissions.