scholarly journals Carbon and nitrogen dynamics and greenhouse gas emissions in constructed wetlands treating wastewater: a review

2016 ◽  
Vol 20 (1) ◽  
pp. 109-123 ◽  
Author(s):  
M. M. R. Jahangir ◽  
K. G. Richards ◽  
M. G. Healy ◽  
L. Gill ◽  
C. Müller ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Empirical Evidence ◽  
Constructed Wetlands ◽  
Nutrient Removal ◽  
Management Practices ◽  
N2o Emissions ◽  
Knowledge Gaps ◽  
Ch4 Emissions ◽  
N Removal ◽  
C And N

Abstract. The removal efficiency of carbon (C) and nitrogen (N) in constructed wetlands (CWs) is very inconsistent and frequently does not reveal whether the removal processes are due to physical attenuation or whether the different species have been transformed to other reactive forms. Previous research on nutrient removal in CWs did not consider the dynamics of pollution swapping (the increase of one pollutant as a result of a measure introduced to reduce a different pollutant) driven by transformational processes within and around the system. This paper aims to address this knowledge gap by reviewing the biogeochemical dynamics and fate of C and N in CWs and their potential impact on the environment, and by presenting novel ways in which these knowledge gaps may be eliminated. Nutrient removal in CWs varies with the type of CW, vegetation, climate, season, geographical region, and management practices. Horizontal flow CWs tend to have good nitrate (NO3−) removal, as they provide good conditions for denitrification, but cannot remove ammonium (NH4+) due to limited ability to nitrify NH4+. Vertical flow CWs have good NH4+ removal, but their denitrification ability is low. Surface flow CWs decrease nitrous oxide (N2O) emissions but increase methane (CH4) emissions; subsurface flow CWs increase N2O and carbon dioxide (CO2) emissions, but decrease CH4 emissions. Mixed species of vegetation perform better than monocultures in increasing C and N removal and decreasing greenhouse gas (GHG) emissions, but empirical evidence is still scarce. Lower hydraulic loadings with higher hydraulic retention times enhance nutrient removal, but more empirical evidence is required to determine an optimum design. A conceptual model highlighting the current state of knowledge is presented and experimental work that should be undertaken to address knowledge gaps across CWs, vegetation and wastewater types, hydraulic loading rates and regimes, and retention times, is suggested. We recommend that further research on process-based C and N removal and on the balancing of end products into reactive and benign forms is critical to the assessment of the environmental performance of CWs.

scholarly journals Irrigation and Greenhouse Gas Emissions: A Review of Field-Based Studies

Soil Systems ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 20 ◽  
Author(s):  
Anish Sapkota ◽  
Amir Haghverdi ◽  
Claudia C. E. Avila ◽  
Samantha C. Ying
Keyword(s):  
Greenhouse Gas ◽  
Management Practices ◽  
Irrigation Management ◽  
Management Strategies ◽  
Ghg Emissions ◽  
Field Research ◽  
Sprinkler Irrigation ◽  
N2o Emissions ◽  
Agricultural Field ◽  
Ch4 Emissions

Irrigation practices can greatly influence greenhouse gas (GHG) emissions because of their control on soil microbial activity and substrate supply. However, the effects of different irrigation management practices, such as flood irrigations versus reduced volume methods, including drip and sprinkler irrigation, on GHG emissions are still poorly understood. Therefore, this review was performed to investigate the effects of different irrigation management strategies on the emission of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) by synthesizing existing research that either directly or indirectly examined the effects of at least two irrigation rates on GHG emissions within a single field-based study. Out of thirty-two articles selected for review, reduced irrigation was found to be effective in lowering the rate of CH4 emissions, while flood irrigation had the highest CH4 emission. The rate of CO2 emission increased mostly under low irrigation, and the effect of irrigation strategies on N2O emissions were inconsistent, though a majority of studies reported low N2O emissions in continuously flooded field treatments. The global warming potential (GWP) demonstrated that reduced or water-saving irrigation strategies have the potential to decrease the effect of GHG emissions. In general, GWP was higher for the field that was continuously flooded. The major finding from this review is that optimizing irrigation may help to reduce CH4 emissions and net GWP. However, more field research assessing the effect of varying rates of irrigation on the emission of GHGs from the agricultural field is warranted.

scholarly journals The nitrogen, carbon and greenhouse gas budget of a grazed, cut and fertilised temperate grassland

2016 ◽  
Author(s):  
Stephanie K. Jones ◽  
Carole Helfter ◽  
Margaret Anderson ◽  
Mhairi Coyle ◽  
Claire Campbell ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Soil Layer ◽  
The Body ◽  
Sink Strength ◽  
N2o Emissions ◽  
N Budget ◽  
N Losses ◽  
Enteric Fermentation ◽  
C And N ◽  
Ch4 And N2o

Abstract. Intensively managed grazed grasslands in temperate climates are globally important environments for the exchange of the greenhouse gases (GHGs) carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). We assessed the N and C budget of a mostly grazed, occasionally cut, and fertilized grassland in SE Scotland by measuring or modelling all relevant imports and exports to the field as well as changes in soil C and N pools over time. The N budget was dominated by import from inorganic and organic fertilisers (21.9 g N m2 yr−1) and losses from leaching (5.3 g N m2 yr−1), N2 emissions and NOx and NH3 volatilisation (6.4 g N m2 yr−1). The efficiency of N use by animal products (meat and wool) averaged 11 %. On average over nine years (2002–2010) the balance of N fluxes suggested that 7.2 ± 4.6 g N m−2 y−1 (mean ± confidence interval at p > 0.95) were stored in the soil. The largest component of the C budget was the net ecosystem exchange of CO2 (NEE), at an average uptake rate of 218 ± 155 g C m−2 y−1 over the nine years. This sink strength was offset by carbon export from the field mainly as harvest (48.9 g C m2 yr−1) and leaching (16.4 g C m2 yr−1). The other export terms, CH4 emissions from the soil, manure applications and enteric fermentation were negligible and only contributed to 0.02–4.2 % of the total C losses. Only a small fraction of C was incorporated into the body of the grazing animals. Inclusion of these C losses in the budget resulted in a C sink strength of 163 ± 140 g C m−2 y−1. On the contrary, soil stock measurements taken in May 2004 and May 2011 indicated that the grassland sequestered N in the 0–60 cm soil layer at 4.51 ± 2.64 g N m−2 y−1 and lost C at a rate of 29.08 ± 38.19 g C m−2 y-1, respectively. Potential reasons for the discrepancy between these estimates are probably an underestimation of C and N losses, especially from leaching fluxes as well as from animal respiration. The average greenhouse gas (GHG) balance of the grassland was −366 ± 601 g CO2 eq m−2 y−1 and strongly affected by CH4 and N2O emissions. The GHG sink strength of the NEE was reduced by 54 % by CH4 and N2O emissions. Enteric fermentation from the ruminating sheep proved to be an important CH4 source, exceeding the contribution of N2O to the GHG budget in some years.

scholarly journals Comparing national greenhouse gas budgets reported in UNFCCC inventories against atmospheric inversions

2021 ◽  
Author(s):  
Zhu Deng ◽  
Philippe Ciais ◽  
Zitely A. Tzompa-Sosa ◽  
Marielle Saunois ◽  
Chunjing Qiu ◽  
...  
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Greenhouse Gas ◽  
Wood Products ◽  
Carbon Uptake ◽  
N2o Emissions ◽  
Gulf Region ◽  
Ch4 Emissions ◽  
Atmospheric Inversions

Abstract. In support of the Global Stocktake of the Paris Agreement on Climate change, this study presents a comprehensive framework to process the results of atmospheric inversions in order to make them suitable for evaluating UNFCCC national inventories of land-use carbon dioxide (CO2) emissions and removals, corresponding to the Land Use, Land Use Change and Forestry and waste sectors. We also deduced anthropogenic methane (CH4) emissions regrouped into fossil and agriculture and waste emissions, and anthropogenic nitrous oxide (N2O) emissions from inversions. To compare inversions with national reports, we compiled a new global harmonized database of national emissions and removals from periodical UNFCCC inventories by Annex I countries, and from sporadic and less detailed emissions reports by Non-Annex I countries, given by National Communications and Biennial Update Reports. The method to reconcile inversions with inventories is applied to selected large countries covering 78 % of the global land carbon uptake for CO2, as well as emissions and removals in the land use, land use change and forestry sector, and top-emitters of CH4 and N2O. Our method uses results from an ensemble of global inversions produced by the Global Carbon Project for the three greenhouse gases, with ancillary data. We examine the role of CO2 fluxes caused by lateral transfer processes from rivers and from trade in crop and wood products, and the role of carbon uptake in unmanaged lands, both not accounted for by the rules of inventories. Here we show that, despite a large spread across the inversions, the median of available inversion models points to a larger terrestrial carbon sink than inventories over temperate countries or groups of countries of the Northern Hemisphere like Russia, Canada and the European Union. For CH4, we find good consistency between the inversions assimilating only data from the global in-situ network and those using satellite CH4 retrievals, and a tendency for inversions to diagnose higher CH4 emissions estimates than reported by inventories. In particular, oil and gas extracting countries in Central Asia and the Persian Gulf region tend to systematically report lower emissions compared to those estimated by inversions. For N2O, inversions tend to produce higher anthropogenic emissions than inventories for tropical countries, even when attempting to consider only managed land emissions. In the inventories of many non-Annex I countries, this can be tentatively attributed to either a lack of reporting indirect N2O emissions from atmospheric deposition and from leaching to rivers, or to the existence of natural sources intertwined with managed lands, or to an under-estimation of N2O emission factors for direct agricultural soil emissions. The advantage of inversions is that they provide insights on seasonal and interannual greenhouse gas fluxes anomalies, e.g. during extreme events such as drought or abnormal fire episodes, whereas inventory methods are established to estimate trends and multi-annual changes. As a much denser sampling of atmospheric CO2 and CH4 concentrations by different satellites coordinated into a global constellation is expected in the coming years, the methodology proposed here to compare inversion results with inventory reports could be applied regularly for monitoring the effectiveness of mitigation policy and progress by countries to meet the objective of their pledges.

scholarly journals Carbon and nitrogen dynamics and greenhouse gases emissions in constructed wetlands: a review

2014 ◽  
Vol 11 (7) ◽  
pp. 7615-7657 ◽  
Author(s):  
M. M. R. Jahangir ◽  
O. Fenton ◽  
L. Gill ◽  
C. Müller ◽  
P. Johnston ◽  
...  
Keyword(s):  
Constructed Wetlands ◽  
Surface Waters ◽  
Current Knowledge ◽  
Sustainable Use ◽  
Transformation Products ◽  
Detailed Examination ◽  
Dissolved Carbon ◽  
N Removal ◽  
Carbon And Nitrogen Dynamics ◽  
C And N

Abstract. The nitrogen (N) removal efficiency of constructed wetlands (CWs) is very inconsistent and does not alone explain if the removed species are reduced by physical attenuation or if they are transformed to other reactive forms (pollution swapping). There are many pathways for the removed N to remain in the system: accumulation in the sediments, leaching to groundwater (nitrate-NO3- and ammonium-NH4+), emission to atmosphere via nitrous oxide- N2O and ammonia and/or conversion to N2 gas and adsorption to sediments. The kinetics of these pathways/processes varies with CWs management and therefore needs to be studied quantitatively for the sustainable use of CWs. For example, the quality of groundwater underlying CWs with regards to the reactive N (Nr) species is largely unknown. Equally, there is a dearth of information on the extent of Nr accumulation in soils and discharge to surface waters and air. Moreover, CWs are rich in dissolved organic carbon (DOC) and produce substantial amounts of CO2 and CH4. These dissolved carbon (C) species drain out to ground and surface waters and emit to the atmosphere. The dynamics of dissolved N2O, CO2 and CH4 in CWs is a key "missing piece" in our understanding of global greenhouse gas budgets. In this review we provide an overview of the current knowledge and discussion about the dynamics of C and N in CWs and their likely impacts on aquatic and atmospheric environments. We suggest that the fate of various N species in CWs and their surface emissions and subsurface drainage fluxes need to be evaluated in a holistic way to better understand their potential for pollution swapping. Research on the process based N removal and balancing the end products into reactive and benign forms are critical to assess environmental impacts of CWs. Thus we strongly suggest that in situ N transformation and fate of the transformation products with regards to pollution swapping requires further detailed examination.

scholarly journals Effect of reed canary grass cultivation on greenhouse gas emission from peat soil at controlled rewetting

2015 ◽  
Vol 12 (2) ◽  
pp. 595-606 ◽  
Author(s):  
S. Karki ◽  
L. Elsgaard ◽  
P. E. Lærke
Keyword(s):  
Land Use ◽  
Greenhouse Gas ◽  
Ecosystem Respiration ◽  
Water Levels ◽  
Bioenergy Crops ◽  
N2o Emissions ◽  
Reed Canary Grass ◽  
Ghg Emission ◽  
Ch4 Emissions ◽  
Canary Grass

Abstract. Cultivation of bioenergy crops in rewetted peatland (paludiculture) is considered as a possible land use option to mitigate greenhouse gas (GHG) emissions. However, bioenergy crops like reed canary grass (RCG) can have a complex influence on GHG fluxes. Here we determined the effect of RCG cultivation on GHG emission from peatland rewetted to various extents. Mesocosms were manipulated to three different ground water levels (GWLs), i.e. 0, −10 and −20 cm below the soil surface in a controlled semi-field facility. Emissions of CO2 (ecosystem respiration, ER), CH4 and N2O from mesocosms with RCG and bare soil were measured at weekly to fortnightly intervals with static chamber techniques for a period of 1 year. Cultivation of RCG increased both ER and CH4 emissions, but decreased the N2O emissions. The presence of RCG gave rise to 69, 75 and 85% of total ER at −20, −10 and 0 cm GWL, respectively. However, this difference was due to decreased soil respiration at the rising GWL as the plant-derived CO2 flux was similar at all three GWLs. For methane, 70–95% of the total emission was due to presence of RCG, with the highest contribution at −20 cm GWL. In contrast, cultivation of RCG decreased N2O emission by 33–86% with the major reductions at −10 and −20 cm GWL. In terms of global warming potential, the increase in CH4 emissions due to RCG cultivation was more than offset by the decrease in N2O emissions at −10 and −20 cm GWL; at 0 cm GWL the CH4 emissions was offset only by 23%. CO2 emissions from ER were obviously the dominant RCG-derived GHG flux, but above-ground biomass yields, and preliminary measurements of gross photosynthetic production, showed that ER could be more than balanced due to the photosynthetic uptake of CO2 by RCG. Our results support that RCG cultivation could be a good land use option in terms of mitigating GHG emission from rewetted peatlands, potentially turning these ecosystems into a sink of atmospheric CO2.

scholarly journals Net global warming potential and greenhouse gas intensity in a double cropping cereal rotation as affected by nitrogen and straw management

2013 ◽  
Vol 10 (8) ◽  
pp. 13191-13229 ◽  
Author(s):  
T. Huang ◽  
B. Gao ◽  
P. Christie ◽  
X. Ju
Keyword(s):  
Greenhouse Gas ◽  
Management Practices ◽  
Cropping System ◽  
N2o Emissions ◽  
Summer Maize ◽  
Straw Management ◽  
Double Cropping ◽  
Straw Return ◽  
Greenhouse Gas Intensity ◽  
N Management

Abstract. The effects of nitrogen and straw management on global warming potential (GWP) and greenhouse gas intensity (GHGI) in a winter wheat–summer maize double-cropping system on the North China Plain were investigated. We measured nitrous oxide (N2O) emissions and studied net GWP (NGWP) and GHGI by calculating the net exchange of CO2 equivalent (CO2-eq) from greenhouse gas emissions, agricultural inputs and management practices, and changes in soil organic carbon (SOC), based on a long-term field experiment established in 2006. The field experiment includes six treatments with three fertilizer N levels (zero-N control, optimum and conventional N) and straw removal (i.e. N0, Nopt and Ncon) or return (i.e. N0, Nopt and SNcon). Optimum N management (Nopt, SNopt) saved roughly half of the fertilizer N compared to conventional agricultural practice (Ncon, SNcon) with no significant effect on grain yields. Annual mean N2O emissions reached 3.90 kg N2O-N ha−1 in Ncon and SNcon, and N2O emissions were reduced by 46.9% by optimizing N management of Nopt and SNopt. Straw return increased annual mean N2O emissions by 27.9%. Annual SOC sequestration was 0.40–1.44 Mg C ha−1 yr−1 in plots with N application and/or straw return. Compared to the conventional N treatments the optimum N treatments reduced NGWP by 51%, comprising 25% from decreasing N2O emissions and 75% from reducing N fertilizer application rates. Straw return treatments reduced NGWP by 30% compared to no straw return because the GWP from increments of SOC offset the GWP from higher emissions of N2O, N fertilizer and fuel after straw return. The GHGI trends from the different nitrogen and straw management practices were similar to the NGWP. In conclusion, optimum N and straw return significantly reduced NGWP and GHGI and concomitantly achieved relatively high grain yields in this important winter wheat–summer maize double-cropping system.

scholarly journals Effect of Manure from Cattle Fed 3-Nitrooxypropanol on Anthropogenic Greenhouse Gas Emissions Depends on Soil Type

Agronomy ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 371
Author(s):  
Tien L. Weber ◽  
Xiying Hao ◽  
Cole D. Gross ◽  
Karen A. Beauchemin ◽  
Scott X. Chang
Keyword(s):  
Life Cycle ◽  
Greenhouse Gas ◽  
Best Management Practices ◽  
Soil Type ◽  
Ghg Emissions ◽  
Soil Types ◽  
N2o Emissions ◽  
Enteric Fermentation ◽  
Ch4 Emissions ◽  
Gray Luvisol

Cattle production is a large source of greenhouse gas (GHG) emissions from the Canadian livestock sector. Efforts to reduce CH4 emissions from enteric fermentation have led to modifications of diet composition for livestock, resulting in a corresponding change in manure properties. We studied the effect of applying manure from cattle fed a barley-based diet with and without the methane inhibitor supplement, 3-nitrooxypropanol (3-NOP), on soil GHG emissions. Three soils common to Alberta, Canada, were used: a Black Chernozem, a Dark Brown Chernozem, and a Gray Luvisol. We compared the supplemented (3-NOPM) and non-supplemented manure (BM) amendments to a composted 3-NOPM (3-NOPC) amendment and a control with no manure amendment (CK). In an 84-day laboratory incubation experiment, 3-NOPM had significantly lower cumulative CO2 emissions compared to BM in both the Black Chernozem and Gray Luvisol. The cumulative N2O emissions were lowest for 3-NOPC and CK and highest for 3-NOPM across all soil types. Cumulative CH4 emissions were only affected by soil type, with a net positive flux from the fine-textured Gray Luvisol and Dark Brown Chernozem and a net negative flux from the coarse-textured Black Chernozem. Cumulative anthropogenic GHG emissions (CO2-equivalent) from soil amended with 3-NOPM were significantly higher than those for both BM and CK amendments in the Black Chernozem, while the cumulative anthropogenic GHG emissions from the 3-NOPC treatment were similar to or significantly lower than those for the BM and CK treatments across all soil types. We conclude that soil GHG emissions resulting from the 3-NOPM amendment are dependent on soil type and 3-NOPM could potentially increase soil GHG emissions compared to BM or CK. Although we show that the composting of 3-NOPM prior to soil application can reduce soil GHG emissions, the composting process also releases GHGs, which should also be considered in assessing the life-cycle of manure application. Our results provide a first look at the potential effect of the next stage in the life cycle of 3-NOP on GHG emissions. Further research related to the effect of soil properties, particularly in field studies, is needed to assess the best management practices related to the use of manure from cattle-fed diets supplemented with 3-NOP as a soil amendment.

Can management practices provide greenhouse gas abatement in grain farms in New South Wales, Australia?

2017 ◽  
Vol 68 (4) ◽  
pp. 390 ◽  
Author(s):  
Jeda Palmer ◽  
Peter J. Thorburn ◽  
Elizabeth A. Meier ◽  
Jody S. Biggs ◽  
Brett Whelan ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Management Practices ◽  
New South ◽  
New South Wales ◽  
N2o Emissions ◽  
Soil C ◽  
C Storage ◽  
South Wales ◽  
Greenhouse Gas Abatement ◽  
Summer Crop

Greenhouse gas abatement in the agricultural cropping industry can be achieved by employing management practices that sequester soil carbon (C) or minimise nitrous oxide (N2O) emissions from soils. However, C sequestration stimulates N2O emissions, making the net greenhouse-gas abatement potential of management practices difficult to predict. We studied land-management practices that have potential to mitigate greenhouse gas emissions by increasing soil C storage and/or decreasing soil N2O emissions for a diverse range of broadacre grain cropping sites in New South Wales. Carbon sequestration and N2O emissions were simulated with the Agricultural Production Systems Simulator (APSIM) for a baseline crop-management scenario and alternative scenarios representing management practices for greenhouse gas abatement, for 15 rainfed or irrigated sites. The global warming potential of the scenarios was quantified at 25 and 100 years after commencement of the alternative practices. Soil C and N2O emissions were predicted to increase with the use of practices that increased organic matter additions to the soil (e.g. adding a summer crop to the rotation). However, in only a few cases did the increase in soil C storage counter the N2O emissions sufficiently to provide net greenhouse gas abatement. For rainfed sites, inclusion of a summer crop and/or a pasture in the rotation was predicted to provide greenhouse gas abatement after 25 years, whereas after 100 years, only practices that included a summer crop provided abatement for some sites. For irrigated sites after 25 years, practices that reduced N fertiliser rate while retaining stubble were predicted to provide small abatement, and practices that included a summer crop provided abatement for some sites. After 100 years, practices likely to provide abatement included those that reduced N2O emissions, such as reducing N fertiliser rate. These findings suggest that a few management practices are likely to abate greenhouse gas emissions across New South Wales grain production sites and that these practices differ for irrigated and rainfed sites.

scholarly journals Drainage and tillage practices in the winter fallow season mitigate CH<sub>4</sub> and N<sub>2</sub>O emissions from a double-rice field in China

2016 ◽  
Vol 16 (18) ◽  
pp. 11853-11866 ◽  
Author(s):  
Guangbin Zhang ◽  
Haiyang Yu ◽  
Xianfang Fan ◽  
Yuting Yang ◽  
Jing Ma ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Rice Field ◽  
Rice Fields ◽  
N2o Emissions ◽  
No Tillage ◽  
Ch4 Emissions ◽  
Double Rice ◽  
Ch4 And N2o ◽  
Late Rice ◽  
Winter Fallow

Abstract. Traditional land management (no tillage, no drainage, NTND) during the winter fallow season results in substantial CH4 and N2O emissions from double-rice fields in China. A field experiment was conducted to investigate the effects of drainage and tillage during the winter fallow season on CH4 and N2O emissions and to develop mitigation options. The experiment had four treatments: NTND, NTD (drainage but no tillage), TND (tillage but no drainage), and TD (both drainage and tillage). The study was conducted from 2010 to 2014 in a Chinese double-rice field. During winter, total precipitation and mean daily temperature significantly affected CH4 emission. Compared to NTND, drainage and tillage decreased annual CH4 emissions in early- and late-rice seasons by 54 and 33 kg CH4 ha−1 yr−1, respectively. Drainage and tillage increased N2O emissions in the winter fallow season but reduced it in early- and late-rice seasons, resulting in no annual change in N2O emission. Global warming potentials of CH4 and N2O emissions were decreased by 1.49 and 0.92 t CO2 eq. ha−1 yr−1, respectively, and were reduced more by combining drainage with tillage, providing a mitigation potential of 1.96 t CO2 eq. ha−1 yr−1. A low total C content and high C / N ratio in rice residues showed that tillage in the winter fallow season reduced CH4 and N2O emissions in both early- and late-rice seasons. Drainage and tillage significantly decreased the abundance of methanogens in paddy soil, and this may explain the decrease of CH4 emissions. Greenhouse gas intensity was significantly decreased by drainage and tillage separately, and the reduction was greater by combining drainage with tillage, resulting in a reduction of 0.17 t CO2 eq. t−1. The results indicate that drainage combined with tillage during the winter fallow season is an effective strategy for mitigating greenhouse gas releases from double-rice fields.

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