Reduce N2O Emissions Research Articles

Symbiotic nitrogen fixation enhanced crop production and mitigated nitrous oxide emissions from paddy crops

Feeding a growing population and preventing dangerous climate change are two challenges facing humanity. Biological nitrogen (N) fixation is considered a sustainable production measure that helps maintain crop production and mitigate climate change by supplementing alternative N nutrients. However, the simultaneous impacts of symbiotic N fixation (SNF) by leguminous green manure crops on rice crop production and nitrous oxide (N2O) emissions remain poorly understood. Here, a field experiment of two annual rotation cycles was conducted to monitor rice yield and the N2O emissions under rice (Oryza sativa subsp. japonica Kato.)-wheat (Triticum aestivum L.) (RW) and rice-hairy vetch (Vicia villosa Roth.) (RV) cropping systems at three N input rates (0 (N0), 50 (N1) and 100 (N2) kg ha−1) for the upland crops and 200 kg ha−1 for the rice crop. Growing hairy vetch introduced a significant amount of N as SNF to the agroecosystem, ranging from 123 to 182 kg ha−1. Compared to the treatments without N for the RV system, the N1 and N2 treatments significantly increased the amount of SNF by 44–47% and 19%− 24%, respectively. The cumulative N2O emissions from SNF ranged from 0.28–0.65 kg ha−1, with the N2O emission factor from SNF (EFSNF) ranging from 0.18%− 0.52% for the RV system. The RV system significantly decreased the N2O emission factor from the total N input (EFTN) by an average of 10.0% compared with the RW system. The RV-N1 treatment produced an obviously lower EFTN, averaging 0.37%, than the other treatments receiving N applications. Compared to the RW system, the RV system slightly increased rice yield by an average of 3.5%. Therefore, the most appropriate N application rate was 50 kg ha−1 for the leguminous crop, and SNF of leguminous green manure could serve as complementary to mineral N fertilizers for reducing N2O emissions while improving soil quality and rice yield in paddy field.

Soil texture, fertilization, cover crop species and management affect nitrous oxide emissions from no-till cropland

Cover crops reduce nitrate leached, but effects on nitrous oxide (N2O) emissions are mixed. Cover crops can reduce N2O emissions by reducing levels of mineral nitrogen (N) and surface soil moisture during spring. Cover crops can also increase N2O emissions by adding organic substrates, releasing N during decomposition, or increasing summer soil water content. Winter-killed cover crops can increase soluble organic C and N during periods of typically low microbial activity. We hypothesized that planting a cover crop mix of radish (Raphanus sativus)-crimson clover (Trifolium incarnatum)-rye (Secale cereale) would increase direct N2O emissions relative to no cover crop, and result in lower direct and indirect N2O emissions than planting radish alone. We also hypothesized that extending the cover crop growing season, by planting earlier and killing later, would increase direct N2O emissions during winter, decrease direct N2O emissions during summer, and decrease indirect N2O emissions. To address these hypotheses, we conducted two field experiments (on sandy and silty soils) over four site-years. We measured cover crop biomass and N content, soil mineral N concentrations, soil moisture, green canopy cover, soil porewater nitrate, direct N2O emissions, and estimated indirect N2O emissions. Nitrous oxide emissions were ~ 7.8 times greater at the silty than the sandy sites due to greater soil moisture retention. Site-years with high radish biomass exhibited greater direct N2O emissions than sites with low radish biomass following winter-kill. Indirect N2O emissions were decreased ~7 % by planting cover crops and by ~70 % by planting cover crops early. Fertilizer induced emission peaks were 8.2 times greater than all previous N2O emissions combined at a silty site. Our results suggested that soil texture and fertilization played an important role in direct N2O emissions, while cover crop species, biomass, and timing played a more important role in NO3 leached, and thus, indirect N2O emissions.

The addition of discrimination inhibitors stimulations discrimination potential and N2O emissions were linked to predation among microorganisms in long term nitrogen application and straw returning systems.

Ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) have been proven to be key microorganisms driving the ammonia oxidation process. However, under different fertilization practices, there is a lack of research on the impact of interaction between predators and AOA or AOB on nitrogen cycling at the multi-trophic level. In this study, a network-oriented microscopic culture experiment was established based on four different long-term fertilization practices soils. We used the nitrification inhibitors 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxide-3-oxyl (PTIO) and 3, 4-Dimethylpyrazole phosphate (DMPP) inhibited AOA and AOB, respectively, to explore the impact of interaction between protists and AOA or AOB on nitrogen transformation. The results showed that long-term nitrogen application promoted the potential nitrification rate (PNR) and nitrous oxide (N2O) emission, and significantly increased the gene abundance of AOB, but had no obvious effect on AOA gene abundance. DMPP significantly reduced N2O emission and PNR, while PTIO had no obvious effect on them. Accordingly, in the multi-trophic microbial network, Cercozoa and Proteobacteria were identified as keystone taxa of protists and AOB, respectively, and were significantly positively correlated with N2O, PNR and nitrate nitrogen. However, Nitrososphaerota archaeon as the keystone species of AOA, had an obvious negative linkage to these indicators. The structural equation model (SEM) showed that AOA and AOB may be competitors to each other. Protists may promote AOB diversity through direct trophic interaction with AOA. The interaction pattern between protists and ammonia-oxidizing microorganisms significantly affects potential nitrification rate and N2O emission, which has important implications for soil nitrogen cycle.

Effects of Biochar Amendment on N2O Emissions from Soils with Different pH Levels

Biochar application has the potential for mitigating N2O emissions from agricultural soils and has been suggested as a management practice to ameliorate soil fertility and increase crop productivity. Nevertheless, the influence of biochar addition on N2O emissions from soils with different pH levels is not yet clear, which results in a poor understanding of the mechanisms regarding biochar application to soil N2O mitigation. A 40-day incubation experiment was carried out in the present study to investigate the impact of biochar on N2O emissions from soils with different natural pH. Four treatments (control, nitrogen fertilizer application, biochar amendment, and N plus biochar amendment) were set up separately in soils with three different natural pH levels (acidic vegetable soil, neutral rice soil, and alkaline soil). Our results showed that adding biochar significantly decreased N2O emissions by 20.8% and 47.6% in acidic vegetable soil for both N and no N addition treatments, respectively. For neutral and alkaline soils, the reduction of N2O emissions by biochar amendment was only significant for N addition treatments in alkaline soil. Soil pH and NO3−-N concentration were significantly affected by biochar amendment (soil pH increased by 1.43–1.56, 0.57–0.70, and 0.29–0.37 units for acidic vegetable soil, neutral rice soil, and alkaline soil, respectively). Thus, biochar amendment could be used as an effective management practice for mitigating N2O emissions from acidic and alkaline soils.

Advancements in greenhouse gas emission reduction methodology for fluorinated compounds and N2O in the semiconductor industry via abatement systems

Greenhouse gases (GHGs), particularly fluorinated compounds (FCs), nitrous oxide (N2O), and nitrogen trifluoride (NF3), contribute significantly to climate change, and the semiconductor industry is a notable emitter of these gases. This report introduces an innovative methodology for GHG emission reduction in the semiconductor industry by utilizing advanced abatement systems, referencing Clean Development Mechanism (CDM) published methods AM0078 and AM0111. The proposed methodology shows promising potential, with substantial reductions in FCs, N2O, and NF3 emissions, positioning the semiconductor industry as a key player in climate change mitigation efforts. The main results indicate that by applying the latest abatement systems, a significant reduction in the targeted GHGs can be achieved. The methodology’s verification process confirms the effectiveness of GHG reduction, ensuring that semiconductor manufacturing’s environmental impact is minimized. Our findings suggest that the implementation of this methodology could lead to industry-wide adoption, resulting in a substantial contribution towards stabilizing atmospheric GHG concentrations.

Effect of calcium-based additives on NO release of coals under different combustion modes

The nitrogen oxides and sulfur oxides released from coal combustion pose serious environmental hazards, but there exists a contradiction between low-nitrogen combustion and efficient desulfurization, necessitating a deeper understanding of the impact of calcium-based desulfurization agents on NOx release. Based on one-stage and two-stage horizontal furnaces, the effects of temperature, coal types and CaO on the release of NO were explored under the coupled combustion and the separated combustion. The experimental results indicate that: under both conditions, the NO emissions of coals decrease with the increase of temperature. The reaction time of separated combustion is shorter than that of coupled combustion. Under the coupled combustion, the order of NO emissions is: anthracite (AC) > bituminous coal (BC) > lignite (LC) > high chlorine coal (HC), and the order are mainly affected by the content of N in coal. At 800 °C, the fuel-N conversion rates of BC, AC, LC, and HC are all the highest, and the rates are 20.52 %, 25.93 %, 14.90 %, and 15.34 %, respectively. As the temperature rises, both volatile-N and char-N emissions show a downward trend. The NO emissions in the separated combustion are greater and the fuel-N conversion rates of BC, AC, LC, and HC are 44.11 %, 47.31 %, 40.44 % and 32.21 %, respectively. The reduction reaction between char and NO plays a crucial role. After the addition of CaO, there is a significant increase in NO release, indicating that CaO has a catalytic effect on the release of volatile-N and char-N. Under the separated combustion, the impact of CaO on NO emissions is relatively minor, and sometimes it leads to a reduction in NO emission. The role of CaO on the NO release is multifaceted.

Diversifying crop rotation increases food production, reduces net greenhouse gas emissions and improves soil health

Global food production faces challenges in balancing the need for increased yields with environmental sustainability. This study presents a six-year field experiment in the North China Plain, demonstrating the benefits of diversifying traditional cereal monoculture (wheat–maize) with cash crops (sweet potato) and legumes (peanut and soybean). The diversified rotations increase equivalent yield by up to 38%, reduce N2O emissions by 39%, and improve the system’s greenhouse gas balance by 88%. Furthermore, including legumes in crop rotations stimulates soil microbial activities, increases soil organic carbon stocks by 8%, and enhances soil health (indexed with the selected soil physiochemical and biological properties) by 45%. The large-scale adoption of diversified cropping systems in the North China Plain could increase cereal production by 32% when wheat–maize follows alternative crops in rotation and farmer income by 20% while benefiting the environment. This study provides an example of sustainable food production practices, emphasizing the significance of crop diversification for long-term agricultural resilience and soil health.

No-tillage with total green manure mulching: A strategy to lower N2O emissions

ContextGreen manure application in agricultural soil is known to enhance nitrogen use efficiency and crop yield. However, limited research exists on the potential effects of green manure returning on N2O emissions. ObjectiveThis study aims to investigate the effects and underlying mechanisms of N2O emissions in maize fields under different green manure management practices. MethodsA field experiment was conducted using common vetch as a green manure crop following the harvest of spring wheat. The study employed a completely randomized block design and examined four treatments: tillage with total green manure incorporation, no-tillage with total green manure mulching (NTG), tillage with green manure root incorporation (T), and no-tillage with aboveground green manure removal (NT). The study explored both non-biological and biological factors affecting nitrogen conversion to elucidate the mechanisms in N2O emissions. ResultsN2O emissions were 17.7% lower in TG and NTG compared to T and NT (P < 0.01), with NTG showing a 12.2% reduction compared to TG (P < 0.05). NTG also exhibited the lowest average N2O fluxes at 24.2 μg N m−2 h−1. In terms of non-biological factors, N2O emissions were negatively correlated only with aggregate NH4+-N and NO3－-N (P < 0.05). Despite increasing soil mineral nitrogen, NTG had approximately 72.3%− 92.4% of it in the form of aggregate nitrogen. In addition, under NTG, the aggregates have better structure and stability. q-PCR analysis revealed higher nos Z gene abundance in NTG than in other treatments (P < 0.05). Regression analysis showed that N2O emissions were negatively correlated with nos Z's abundance and N2O reductase diversity (P < 0.05). ConclusionsNo-tillage with total green manure mulching (NTG) effectively reduced N2O emissions by enhancing mineral nitrogen in soil aggregates and increasing the abundance of the nos Z gene. ImplicationsOur findings offer valuable insights for long-term agricultural management strategies aimed at improving nitrogen retention and mitigating climate change impacts.

Investigation of the regulatory effects of water and nitrogen supply on nitrogen transport and distribution in wolfberry fields.

Resource-based water shortages, uncoordinated irrigation, and fertilization are prevalent challenges in agricultural production. The scientific selection of appropriate water and fertilizer management methods is important for improving the utilization efficiency of agricultural resources and alleviating agricultural non-point source pollution. This study focused on wolfberry and compared the effects of four irrigation levels [full irrigation (W0, 75%-85% θf), slight water deficit (W1, 65%-75% θf), moderate water deficit (W2, 55%-65% θf), and severe water deficit (W3, 45%-55% θf)] and four nitrogen application levels [no nitrogen application (N0, 0 kg·ha-1), low nitrogen application (N1, 150 kg·ha-1), medium nitrogen application (N2, 300 kg·ha-1), and high nitrogen application (N3, 450 kg·ha-1)] on soil nitrate nitrogen (NO3 --N) transport, plant nitrogen allocation, and soil nitrous oxide (N2O) emissions during the harvest period of wolfberry. And this study used CRITIC-entropy weights-TOPSIS model to evaluate 16 water and nitrogen regulation models comprehensively. The results revealed the following: (1) The NO3 --N content of the soil decreased with increasing horizontal distance from the wolfberry. It initially decreased, then increased, and finally decreased with an increase in soil depth. The average NO3 --N content in the 0-100 cm soil layer ranged from 3.95-13.29 mg·kg-1, indicating that W0 > W1, W2, W3, and N3 > N2 > N1 > N0. (2) The soil NO3 --N accumulation ranged from 64.45-215.27 kg·ha-1 under varying water and nitrogen levels, demonstrating a decreasing trend with increasing horizontal distance. The NO3 --N accumulation at each horizontal distance increased with increasing irrigation and nitrogen application. The NO3 --N accumulation of W0N3 treatment increased by 5.55%-57.60% compared with the other treatments. (3) The total nitrogen content and nitrogen uptake in all wolfberry organs were W1 > W0 > W2 > W3, and N2 > N3 > N1 > N0. The maximum total nitrogen content and nitrogen uptake in W1N2 treatment were 3.25% and 27.82 kg·ha-1 in the roots, 3.30% and 57.19 kg·ha-1 in the stems, 3.91% and 11.88 kg·ha-1 in the leaves, and 2.42% and 63.56 kg·ha-1 in the fruits, respectively. (4) The emission flux and total emission of N2O increased with increasing irrigation and nitrogen application. The emission flux exhibited a transient peak (116.39-177.91 ug·m-2·h-1) after irrigation. The intensity of N2O emissions initially decreased and then increased with an increase in the irrigation amount. It also initially increased with increasing nitrogen application amount, then decreased, and finally increased again. The maximum emission intensity was observed under the W3N3 treatment (0.23 kg·kg-1). The N2O emission coefficients ranged from 0.17%-0.39%, in the order of W0 > W1 > W2 > W3 (except for N1) and N1 > N2 > N3. (5) Under varying water and nitrogen concentrations, N2O emission flux showed a positive linear correlation with soil pore water content and NO3 --N content and a negative linear correlation with soil temperature. The comprehensive evaluation revealed that a slight water deficit (65%-75% θf) combined with medium nitrogen application (300 kg·ha-1) decreased soil NO3 --N leaching, increased nitrogen uptake, and reduced N2O emission. These findings can serve as a reference for improving the efficiency and reducing emissions of wolfberry in the Yellow River irrigation region of Gansu Province and in similar climate zones.

Sources of nitrous oxide emissions from agriculturally managed peatlands.

The draining and fertilization of peatlands for agriculture is globally an important source of the greenhouse gas nitrous oxide (N2 O). Hitherto, the contribution of major sources to the N2 O emission-that is, fertilization and nitrogen (N) release from peat decomposition-has not yet been deciphered. This hampers the development of smart mitigation strategies, considering that rewetting to halt peat decomposition and reducing N fertilization are promising N2 O emission-reduction strategies. Here, we used machine learning techniques and global N2 O observational data to generalize the distribution of N2 O emissions from agriculturally managed peatlands, to distinguish the sources of N2 O emissions, and to compare mitigation options. N2 O emissions from agriculturally managed croplands were 401.0 (344.5-470.9) kt N year-1 , with 121.6 (88.6-163.3) kt N year-1 contributed by fertilizer N. On grasslands, 64.0 (54.6-74.7) kt N2 O-N year-1 were emitted, with 4.6 (3.7-5.7) kt N2 O-N year-1 stemming from fertilizer N. The fertilizer-induced N2 O emission factor ranged from 1.5% to 3.2%. Reducing the current fertilizer input by 20% could achieve a 10% N2 O emission reduction for croplands but only 3% for grasslands. Rewetting 1.9 Mha cropland and 0.26 Mha grassland would achieve the same N2 O emission reductions. Our results suggest that N2 O mitigation strategies for managed peatlands should be considered separately across land-use types and climatic zones. For croplands, particularly in the tropics, relevant N2 O mitigation potentials are achievable through both fertilizer N reduction and peatland rewetting. For grasslands, management schemes to halt peat degradation (e.g. rewetting) should be considered preferentially for mitigating N2 O and contributing to meeting climate goals.

Estimating Nitrous Oxide (N2O) emissions from managed soils at higher spatial resolution in the Republic of Ireland

This paper aims to define a high spatial resolution model for estimating nitrous oxide (N2O) emissions from agricultural soils in Ireland. In 2020, N2O emissions from the management of agricultural soils represented 10% of the total national agricultural Greenhouse Gas (GHG) emissions. The high spatial resolution model employed here takes account of environmental factors that influence N2O emissions at a more disaggregated spatial scale than the Intergovernmental Panel on Climate Change (IPCC) national inventory-reporting framework. Activity data from the EU Farm Accountancy Data Network (for Ireland) is used in conjunction with biophysical and climatic data in a geographic information system (GIS) framework to estimate N2O emissions at a sub-national level. Results indicate that N2O emissions are 5% lower by applying this high spatial resolution modelling approach at the farm level compared to the baseline model (Tier 2). Nevertheless, 25% of the farms in the sample analysed had an overestimation in their N2O emissions of 20%, and another 25% of the farm sample had an average underestimation in their N2O emissions by 19%, a consequence of the variation of environmental factors among farms. Using a data panel regression, results confirm that the environmental factors examined are statistically significant within the model proposed, and with a simulation, we assessed the switching of 20% of CAN fertiliser for protected urea. According to the high spatial model, this mitigation measure can reduce N2O emissions from inorganic fertilisers by up to 15%. However, the reduction is conditioned by local factors and environmental conditions.

Effects of Central Split Bluff Body on Combustion Characteristics and NOx Emission with Non-Premixed H2/Air Flames

ABSTRACT Considering the safety and flashback problems of hydrogen-fueled micro power generation using premixed combustion for thermophotovoltaic applications, we focused on non-premixed hydrogen/air combustion characteristics. However, the fuel/air mixing is significant in the combustion chamber, so we proposed five bluff bodies and investigated the effects of inlet velocity of the fuel on non-premixed hydrogen/air combustion characteristics and flow patterns. A 21-species and 105-reactions hydrogen/air with NOx extended chemical mechanism is experimentally validated. The results show a significant influence of the inlet velocity and bluff body shape on temperature distribution, flame location, and residence time. All five combustors achieved a 99% energy conversion at the exit of the combustion chamber. Combustors B and D characterized by isosceles triangle-like and right triangle-like shapes excel because of improved hydrogen/air mixing behind the bluff body. Combustor D achieves the highest mean outer wall temperature of 992.03 K and lowest pressure loss of 155.56 Pa when the inlet velocity of fuel is 4 m/s. Moreover, the advanced mixing facilitated by the bluff bodies in Combustors B and D resulted in reduced NO emissions, with reductions of 16.8% and 20.3%, respectively, compared to Combustor C. These findings provide insights into combustion dynamics, leveraging bluff body-induced flow structures to enhance the micro combustor thermodynamics.

Efficacy of grape seed procyanidins for inhibiting denitrification varies by source, soil texture, and cropping history

Plant-derived denitrification inhibitors, such as procyanidins derived from grape seed extract (GSE), hold potential in mitigating nitrous oxide (N2O) emissions, a potent greenhouse gas and stratospheric ozone depleter. A deeper understanding of the effects of GSE – considering aspects like rate, source, application timing, storage, and interactions with soil properties and cropping histories – on denitrification inhibition remains elusive. We conducted a series of laboratory microcosm experiments to assess these effects using denitrification enzyme activity (DEA) and measurements of N2O and carbon dioxide (CO2) production rates under both anaerobic and aerobic conditions, soil inorganic nitrogen (N), and other major soil properties. Our results revealed that one commercial GSE brand (USP GSE) inhibited DEA, while another source was ineffective. Two non-procyanidin compounds in commercial GSE mixtures, tartaric acid and gallic acid, actually enhanced DEA. Inhibition efficiency of the USP GSE varied significantly across soils with differing crop histories and physical properties, exhibiting a positive dose-response in three out of the five soils examined. Greater efficiency was observed in sandy soils compared to silt loam soils and in soils with a history of continuous corn production as opposed to soybean. The GSE application timing relative to urea addition and a one-week room temperature storage had minor effects on denitrification inhibition. In corn-cultivated soil, co-application of GSE and urea reduced cumulative N2O production by 27 % compared to soils treated with urea alone. The CO2 production and nitrate levels remained largely unaffected by GSE application. These findings supported the potential of GSE as a soil amendment to reduce N2O emissions in corn-cultivated soils. However, challenges including purity of procyanidins, cost-effectiveness, and inconsistent performance under various systems warrant consideration for broader field applications.

Modelling future climate effects on N2O emission and soil carbon storage in maize fields under controlled-release urea and straw incorporation

Controlled-release urea application and straw incorporation have been conducted in recent years as environmental-friendly and sustainable farming strategies, but the long-term effects of controlled-release urea application and combination with straw on the dryland maize yield, soil fertility and the environment under future climate scenarios remain unclear. Hence, based on a six-year field experiment, four treatments were used to calibrate and validate the DeNitrification-DeComposition (DNDC) model, including non-nitrogen (CK), split applications of conventional urea (UR), single basal application of conventional urea and controlled-release urea at a ratio of 2:1 (CU), and CU combined with straw (CUS). Subsequently, coupled the well-validated model with future climate to evaluate suitable agricultural production practices under two shared socioeconomic pathways (SSP)-SSP245 and SSP585. The validation results indicated a good fit between the simulated and observed data of greenhouse gas emissions, soil organic carbon (SOC) contents and maize yields. With the anticipation of warmer temperatures and increased precipitation in the future, the yields of UR, CU, and CUS treatment significantly rose. Under SSP585 scenario, the positive impacts of CU treatment on maize yields reduced after the 2050s, exhibiting an average decline of 12.03%. Compared with the UR treatment, the CU treatment markedly reduced cumulative N2O emissions, and both treatments maintained the original state of SOC storages in the 2030s, furthermore, the CUS treatment reduced N2O emissions by 47.10%, 35.07%, 23.80% and 10.04% in the 2030s, 2050s, 2070s and 2090s, respectively. SOC storages for the CUS treatment gradually increased with an average of 464.58, 350.22, 250.87 and 177.75 kg C ha−1 y−1 for two SSP scenarios in the 2030s, 2050s, 2070s and 2090s, which excellently offset the CO2 equivalent of emissions caused by N2O emissions. Therefore, in dryland maize production, combined controlled-release urea with straw incorporation could achieve the best comprehensive effect among increase of yield, improvement of SOC storages and alleviation of greenhouse gas emissions under future climate scenario.

Effects of Extreme Weather Events on Nitrous Oxide Emissions from Rice-Wheat Rotation Croplands.

Cropland ecosystems are significant emission sources of N2O, but a limited number of studies have focused on the impact of extreme weather events on N2O fluxes from cropland. This present study integrated field observations and model simulations to explore the responses of N2O fluxes to extreme weather events in typical rice and wheat rotation croplands in the middle and lower reaches of the Yangtze River (MLRYR) in China. The findings revealed that the studied rice-wheat rotation cropland exhibited a net source of N2O over the three-year monitoring period, with annual cumulative N2O emissions ranging from 190.4 to 261.8 mg N m-2. N2O emissions during the rice and wheat growing seasons accounted for 29% and 71% of the total yearly emissions, respectively. Extreme heat events led to a 23% to 32% increase in observed N2O emissions from cropland. Observed N2O emissions from irrigated rice fields during extreme precipitation events were 45% lower than those during extreme drought events. In contrast, extreme precipitation events raised observed N2O emissions from rain-fed wheat fields by 36% compared to the multi-year average, while extreme drought events reduced N2O emissions from wheat fields by 20%. Regional simulations indicated that annual cumulative N2O emissions from croplands in the MLRYR are projected to increase from 207.8 mg N m-2 under current climate to 303.4 mg N m-2 in the future. Given the episodic nature and uncertainties associated with N2O emissions from cropland, further validation is necessary for utilizing the model to explore the effects of extreme weather events on N2O in cropland ecosystems.

Influence of introducing clove antioxidant into blends of diesel and biodiesel fuels on engine performance

The utilization of biodiesel as fuel in diesel engines leads to increased NO emissions, which is a significant pollutant that needs to be promptly mitigated. This can be achieved by incorporating natural antioxidants as an additive to suppress the NO emissions. The main focus of the current experimental investigation is to analyze the engine characteristics of Mahua biodiesel by incorporating clove as a natural antioxidant in diesel fuel. The tests encompassed a wide set of engine functioning conditions including varying loads, to ensure comprehensive analysis. The results showed a significant improvement in brake thermal efficiency, with a value of 25.7% for the blend of Mahua biodiesel at 20% concentration with diesel, compared to 24.6% for the blend of Mahua biodiesel at 20% concentration with diesel fuel containing 1000 ppm of clove extract, and 23.9% for the blend of Mahua biodiesel at 20% concentration with diesel fuel containing 2000 ppm of clove extract. The intriguing observation witnessed is that when Mahua biodiesel was blended at a 20% concentration with diesel fuel containing 2000 ppm of clove extract, it resulted in a significant percentage reduction in NO emissions by 7.7%, HC emissions by 8.8%, CO emissions by 28%, and smoke opacity by 9.9% compared to the blend of Mahua biodiesel at 20% concentration with diesel.

Smaller Aerobic Granules Significantly Reduce N2O Production by Ammonia-Oxidizing Bacteria: Evidences from Biochemical and Isotopic Analyses.

The mitigation of nitrous oxide (N2O) is of primary significance to offset carbon footprints in aerobic granular sludge (AGS) systems. However, a significant knowledge gap still exists regarding the N2O production mechanism and its pathway contribution. To address this issue, the impact of varying granule sizes, dissolved oxygen (DO), and nitrite (NO2-) levels on N2O production by ammonia-oxidizing bacteria (AOB) during nitrification in AGS systems was comprehensively investigated. Biochemical and isotopic experiments revealed that increasing DO or decreasing NO2- levels reduced N2O emission factors (by 13.8 or 19.5%) and production rates (by 0.08 or 0.35 mg/g VSS/h) via weakening the role of the AOB denitrification pathway since increasing DO competed for more electrons required for AOB denitrification. Smaller granules (0.5 mm) preferred to diminish N2O production via enhancing the role of NH2OH pathway (i.e., 59.4-100% in the absence of NO2-), while larger granules (2.0 mm) induced conspicuously higher N2O production via the AOB denitrification pathway (approximately 100% at higher NO2- levels). Nitrifying AGS systems with a unified size of 0.5 mm achieved 42% N2O footprint reduction compared with the system with mixed sizes (0.5-2.0 mm) under optimal conditions (DO = 3.0 mg-O2/L and NO2- = 0 mg-N/L).

Relationships between different types of biochar and N2O emissions during composting based on roles of nosZ-carrying denitrifying bacterial communities enriched on compost and biochar particles

Biochar has demonstrated the potential in mitigating N2O emissions during composting. However, little is known about how microbial communities on biochar particles interact with N2O emissions. This study selected three types of biochar (corn stalk biochar (CSB), rape straw biochar (RSB), and bamboo charcoal (BC)) to investigate the relationship between N2O emissions and denitrifying bacterial communities on compost and biochar particles. The results showed that N2O emissions rate were higher in the thermophilic phase, and the average emissions rate of BC treatment were lower 40% and 26% than CSB and RSB, respectively. The nosZ-carrying denitrifying bacterial community played a key role in reducing N2O emissions, and the network indicated that Rhizobium and Paracoccus on compost particles may have played major roles in reducing N2O emissions, but only Paracoccus on biochar particles. Notably, BC enhanced the efficiency of N2O emission reduction by enhancing the abundance of these key genera.

Fertilizer nitrogen substitution using biochar-loaded ammonium-nitrogen reduces nitrous oxide emissions by regulating nitrous oxide-reducing bacteria

Biochar has been extensively demonstrated as an abundant, cost-effective, and highly efficient adsorbent material for removing ammonium (NH4+) from non-point source-polluted water. The new technology of biochar-loaded NH4+-N (BLN) is urgently needed. However, the underlying mechanisms of BLN in regulating N2O emissions by substituting chemical fertilizer nitrogen (CFN) were poorly understood. Based on the substitution rate of CFN with BLN, a soil column experiment was designed with six treatments: CFN-only (BLN0), 20% BLN plus 80% CFN (BLN20), 40% BLN plus 60% CFN (BLN40), 60% BLN plus 40% CFN (BLN60), 80% BLN plus 20% CFN (BLN80), and BLN only (BLN100). BLN application significantly decreased cumulative N2O emissions by 20.50–40.78% compared to the BLN0 treatment. The optimal ratio of CFN substitution was 66.10%, which was supported by the lowest N2O emissions in the BLN60 treatment. In BLN-treated soil, the abundance of nosZ played a dominant role in N transformation, followed by ammonia-oxidizing bacteria (AOB). Particularly, BLN60 significantly increased nosZ abundance. The high substitution ratio (BLN60–100) promoted N2O reduction by increasing the overall abundance of nosZ-harboring communities, however, low substitution ratio (BLN0–40) promoted it by increasing nosZ cluster Ⅸ abundance and the connectivity of operational taxonomic units within the module. Soil pH and C/N ratio were critical influencing factors to alter the nosZ community structure. These findings highlighted that BLN substitution treatments reduced N2O emissions, while the microbiological mechanism of emission reduction varied with the proportion of substitution. An appropriate substitution ratio (60%) mainly reduced N2O emissions by increasing nosZ abundance.

Synergistic effect and volatile emission characteristics during co-combustion of biomass and low-rank coal

Mass loss behaviours, volatile emissions (NO, HCN, NH3, CO, and CO2), and the O2 consumption characteristics during co-combustion of Naomaohu coal (NMH coal) and pine sawdust (PS) are studied using a TG-FTIR and a specially designed fixed-bed reactor. The results reveal that the trends of CO and CO2 in the TG-FTIR and fixed bed reactor results were similar, while the NO trends showed opposite behavior. In an inert atmosphere, there was no significant interaction during co-combustion of NMH coal and PS. However, a synergistic effect was observed under air atmosphere, leading to enhanced oxidation reactions and a notable reduction in ignition time. Specifically, the ignition time of NMH coal reduced from 5 s to 0.5 s when PS was added in the proportion of 75 %. Furthermore, the replacement of 25 % NMH coal with PS resulted in an 8.9 % reduction in NO emissions. This research provides a valuable framework for the thermal conversion of blends consisting of lignocellulosic biomass and low-rank coal.