Biomass Yield and Greenhouse Gas Emissions from a Drained Fen Peatland Cultivated with Reed Canary Grass under Different Harvest and Fertilizer Regimes

Combination of rewetting and wetland crop cultivation (paludiculture) is pursued as a wider carbon dioxide (CO2) mitigation option in drained peatland. However, information on the overall greenhouse gas (GHG) balance for paludiculture is lacking. We investigated the GHG balance of peatlands grown with reed canary grass (RCG) and rewetted to various extents. Gas fluxes of CO2, methane (CH4) and nitrous oxide (N2O) were measured with a static chamber technique for 10 months from mesocosms sown with RCG and manipulated to ground water levels (GWL) of 0, −10, −20, −30 and −40 cm below the soil surface. Gross primary production (GPP) was estimated from the above ground biomass yield. The mean dry biomass yield across all water table treatments was 6 Mg ha−1 with no significant differences between the treatments. Raising the GWL to the surface decreased both the net ecosystem exchange (NEE) of CO2 and N2O emissions whereas CH4 emissions increased. Total cumulative GHG emissions (for 10 months) corresponded to 0.08, 0.13, 0.61, 0.68 and 0.98 kg CO2 equivalents m−2 from the GWL treatments at 0, −10, −20, −30 and −40 cm below the soil surface, respectively. The results showed that a reduction in total GHG emission can be achieved without losing the productivity of newly established RCG when GWL is maintained close to the surface. Further studies should address the practical constrains and long-term productivity of RCG cultivation in rewetted peatlands.

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.

Manure treatment such as anaerobic digestion and solid-liquid separation has shown a potential to abate greenhouse gas (GHG) emissions, but few studies have considered GHG emissions from both storage and field application regarding crop yield. In this study, four different organic fertilizers were studied: untreated cattle manure (CA); digestate of cattle manure anaerobically co-digested with grass-clover (DD); a liquid fraction from the separation of DD (LF); and a liquid fraction derived from a biogas desulfurization biofilter enriched with sulfur and ammonium (NS). The CH4, N2O and NH3 emissions during storage of CA, DD and LF between August and November 2020 (11 weeks) were quantified. Storage continued until April 2021 when these materials, as well as the NS fertilizer and a mineral NKS fertilizer, were applied at a rate of 100 kg total N ha−1 to spring barley. N2O emissions and soil mineral N content were monitored during the growing season. Overall, CH4 emissions during storage were the main source of GHG emissions independent of treatments, accounting for 85 %, 40 % and 11 % of total GHG emissions (based on field application of 100 kg ha−1 total N) from treatments CA, DD and LF, respectively. Anaerobic digestion and separation significantly reduced CH4 emissions during storage due to the diminished content of degradable organic matter available for methanogens. The N2O emissions from treatments CA, DD, and LF during storage were not significantly different. Treatments DD and LF emitted more NH3 than CA during storage, presumably because of higher pH and ammonium content. In the field experiment, the dilute solution of NS emitted the most N2O, while emissions from treatments CA, DD and LF were comparable. Yield-scaled GHG emissions for treatments CA, DD, LF and NS during both periods of storage and field were 44.4, 17.1, 8.5 and 24.3 kg CO2 eq hkg−1 grain yield, respectively. Anaerobic digestion with or without separation were thus effective strategies for the mitigation of GHG emissions from cattle manure in this study. Yields and nitrogen use efficiencies of the processed manure materials were not significantly different from those observed with the same N application rate as inorganic fertilizer, and hence anaerobic digestion with or without separation were promising GHG mitigation strategies.

Effects of water management on greenhouse gas emissions from farmers' rice fields in Bangladesh

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This study investigates the effect of energy consumption on greenhouse gas (GHG) emissions in 33 African countries from 1995–2017. It contributes to the literature by investigating the effect of disaggregated measures of energy consumption (coal, oil and other liquids, renewable energy, and electricity) on GHG emissions (CO2, N2O, CH4, and total GHG emissions) in Africa and identifies the transmission channels through which energy consumption affects GHG emissions. The system GMM is used in the study as it accounts for possible endogeneity and the potential correlation between the error term and the country fixed effects. The results show that coal consumption significantly increases CO2, CH4, and total GHG emissions and reduces N2O emissions. Oil consumption increases CO2 and total GHG emissions but reduces N2O and CH4 emissions. Renewable energy consumption reduces CO2 and CH4 emissions but increases N2O emissions. Finally, electricity consumption promotes CO2, N2O, CH4 and total GHG emissions in Africa. Further analyses show that foreign trade and economic growth are the channels through which oil consumption increases GHG emissions. The adverse effect of electricity is through urbanization. Renewable consumption could decrease GHG emissions through sustainable urbanization and trade policies. The findings suggest that countries should gradually reduce coal consumption and encourage renewable energy consumption, which has the lowest impact on the environment.

A review on the main affecting factors of greenhouse gases emission in constructed wetlands

Dairy production systems represent a significant source of air pollutants such as greenhouse gases (GHG), that increase global warming, and ammonia (NH3), that leads to eutrophication and acidification of natural ecosystems. Greenhouse gases and ammonia are emitted both by conventional and organic dairy systems. Several studies have already been conducted to design practices that reduce greenhouse gas and ammonia emissions from dairy systems. However, those studies did not consider options specifically applied to organic farming, as well as the multiple trade-offs occurring between these air pollutants. This article reviews agricultural practices that mitigate greenhouse gas and ammonia emissions. Those practices can be applied to the most common organic dairy systems in northern Europe such as organic mixed crop-dairy systems. The following major points of mitigation options for animal production, crop production and grasslands are discussed. Animal production: the most promising options for reducing greenhouse gas emissions at the livestock management level involve either the improvement of animal production through dietary changes and genetic improvement or the reduction of the replacement rate. The control of the protein intake of animals is an effective means to reduce gaseous emissions of nitrogen, but it is difficult to implement in organic dairy farming systems. Considering the manure handling chain, mitigation options involve housing, storage and application. For housing, an increase in the amounts of straw used for bedding reduces NH3 emissions, while the limitation of CH4 emissions from deep litter is achieved by avoiding anaerobic conditions. During the storage of solid manure, composting could be an efficient mitigation option, depending on its management. Addition of straw to solid manure was shown to reduce CH4 and N2O emissions from the manure heaps. During the storage of liquid manure, emptying the slurry store before late spring is an efficient mitigation option to limit both CH4 and NH3 emissions. Addition of a wooden cover also reduces these emissions more efficiently than a natural surface crust alone, but may increase N2O emissions. Anaerobic digestion is the most promising way to reduce the overall greenhouse gas emissions from storage and land spreading, without increasing NH3 emissions. At the application stage, NH3 emissions may be reduced by spreading manure during the coolest part of the day, incorporating it quickly and in narrow bands. Crop production: the mitigation options for crop production focus on limiting CO2 and N2O emissions. The introduction of perennial crops or temporary leys of longer duration are promising options to limit CO2 emissions by storing carbon in plants or soils. Reduced tillage or no tillage as well as the incorporation of crop residues also favour carbon sequestration in soils, but these practices may enhance N2O emissions. Besides, the improvement of crop N-use efficiency through effective management of manure and slurry, by growing catch crops or by delaying the ploughing of leys, is of prime importance to reduce N2O emissions. Grassland: concerning grassland and grazing management, permanent conversion from arable to grassland provides high soil carbon sequestration while increasing or decreasing the livestock density seems not to be an appropriate mitigation option. From the study of the multiple interrelations between gases and between farm compartments, the following mitigation options are advised for organic mixed crop-dairy systems: (1) actions for increasing energy efficiency or fuel savings because they are beneficial in any case, (2) techniques improving efficiency of N management at field and farm levels because they affect not only N2O and NH3 emissions, but also nitrate leaching, and (3) biogas production through anaerobic digestion of manure because it is a promising efficient method to mitigate greenhouse gas emissions, even if the profitability of this expensive investment needs to be carefully studied. Finally, the way the farmer implements the mitigation options, i.e. his practices, will be a determining factor in the reduction of greenhouse gas and NH3 emissions.

Greenhouse gas emissions from coastal freshwater wetlands in Veracruz Mexico: Effect of plant community and seasonal dynamics

Abstract. This article provides an overview of the effects of land-use on the fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) and from peatlands in the Nordic countries based on the field data from about 100 studies. In addition, this review aims to identify the gaps in the present knowledge on the greenhouse gas (GHG) balances associated with the land-use of these northern ecosystems. Northern peatlands have accumulated, as peat, a vast amount of carbon from the atmosphere since the last glaciation. However, the past land-use and present climate have evidently changed their GHG balance. Unmanaged boreal peatlands may act as net sources or sinks for CO2 and CH4 depending on the weather conditions. Drainage for agriculture has turned peatlands to significant sources of GHGs (mainly N2O and CO2). Annual mean GHG balances including net CH4, N2O and CO2 emissions are 2260, 2280 and 3140 g CO2 eq. m−2 (calculated using 100 year time horizon) for areas drained for grass swards, cereals or those left fallow, respectively. Even after cessetion of the cultivation practices, N2O and CO2 emissions remain high. The mean net GHG emissions in abandoned and afforested agricultural peatlands have been 1580 and 500 g CO2 eq. m−2, respectively. Peat extraction sites are net sources of GHGs with an average emission rate of 770 g CO2 eq. m−2. Cultivation of a perennial grass (e.g., reed canary grass) on an abandoned peat extraction site has been shown to convert such a site into a net sink of GHGs (−330 g CO2 eq. m−2). In contrast, despite restoration, such sites are known to emit GHGs (mean source of 480 g CO2 eq. m−2, mostly from high CH4 emissions). Peatland forests, originally drained for forestry, may act as net sinks (mean −780 g CO2 eq. m−2). However, the studies where all three GHGs have been measured at an ecosystem level in the forested peatlands are lacking. The data for restored peatland forests (clear cut and rewetted) indicate that such sites are on average a net sink (190 g CO2 eq. m−2). The mean emissions from drained peatlands presented here do not include emissions from ditches which form a part of the drainage network and can contribute significantly to the total GHG budget. Peat soils submerged under water reservoirs have acted as sources of CO2, CH4 and N2O (mean annual emission 240 g CO2 eq. m−2). However, we cannot yet predict accurately the overall greenhouse gas fluxes of organic soils based on the site characteristics and land-use practices alone because the data on many land-use options and our understanding of the biogeochemical cycling associated with the gas fluxes are limited.

Dairy production systems represent a significant source of air pollutants such as greenhouse gases (GHG), that increase global warming, and ammonia (NH3), that leads to eutrophication and acidification of natural ecosystems. Greenhouse gases and ammonia are emitted both by conventional and organic dairy systems. Several studies have already been conducted to design practices that reduce greenhouse gas and ammonia emissions from dairy systems. However, those studies did not consider options specifically applied to organic farming, as well as the multiple trade-offs occurring between these air pollutants. This article reviews agricultural practices that mitigate greenhouse gas and ammonia emissions. Those practices can be applied to the most common organic dairy systems in northern Europe such as organic mixed crop-dairy systems. The following major points of mitigation options for animal production, crop production and grasslands are discussed. Animal production: the most promising options for reducing greenhouse gas emissions at the livestock management level involve either the improvement of animal production through dietary changes and genetic improvement or the reduction of the replacement rate. The control of the protein intake of animals is an effective means to reduce gaseous emissions of nitrogen, but it is difficult to implement in organic dairy farming systems. Considering the manure handling chain, mitigation options involve housing, storage and application. For housing, an increase in the amounts of straw used for bedding reduces NH3 emissions, while the limitation of CH4 emissions from deep litter is achieved by avoiding anaerobic conditions. During the storage of solid manure, composting could be an efficient mitigation option, depending on its management. Addition of straw to solid manure was shown to reduce CH4 and N2O emissions from the manure heaps. During the storage of liquid manure, emptying the slurry store before late spring is an efficient mitigation option to limit both CH4 and NH3 emissions. Addition of a wooden cover also reduces these emissions more efficiently than a natural surface crust alone, but may increase N2O emissions. Anaerobic digestion is the most promising way to reduce the overall greenhouse gas emissions from storage and land spreading, without increasing NH3 emissions. At the application stage, NH3 emissions may be reduced by spreading manure during the coolest part of the day, incorporating it quickly and in narrow bands. Crop production: the mitigation options for crop production focus on limiting CO2 and N2O emissions. The introduction of perennial crops or temporary leys of longer duration are promising options to limit CO2 emissions by storing carbon in plants or soils. Reduced tillage or no tillage as well as the incorporation of crop residues also favour carbon sequestration in soils, but these practices may enhance N2O emissions. Besides, the improvement of crop N-use efficiency through effective management of manure and slurry, by growing catch crops or by delaying the ploughing of leys, is of prime importance to reduce N2O emissions. Grassland: concerning grassland and grazing management, permanent conversion from arable to grassland provides high soil carbon sequestration while increasing or decreasing the livestock density seems not to be an appropriate mitigation option. From the study of the multiple interrelations between gases and between farm compartments, the following mitigation options are advised for organic mixed crop-dairy systems: (1) actions for increasing energy efficiency or fuel savings because they are beneficial in any case, (2) techniques improving efficiency of N management at field and farm levels because they affect not only N2O and NH3 emissions, but also nitrate leaching, and (3) biogas production through anaerobic digestion of manure because it is a promising efficient method to mitigate greenhouse gas emissions, even if the profitability of this expensive investment needs to be carefully studied. Finally, the way the farmer implements the mitigation options, i.e. his practices, will be a determining factor in the reduction of greenhouse gas and NH3 emissions.KeywordsAgricultureGreenhouse gasAmmoniaAbatementMixed crop-dairy systemsOrganicLivestockManureGrasslandCarbon storageSoil carbon sequestration

Bioenergy from perennial grasses mitigates climate change via displacing fossil fuels and storing atmospheric CO2 belowground as soil carbon. Here, we conduct a critical review to examine whether increasing plant diversity in bioenergy grassland systems can further increase their climate change mitigation potential. We find that compared with highly productive monocultures, diverse mixtures tend to produce as great or greater yields. In particular, there is strong evidence that legume addition improves yield, in some cases equivalent to mineral nitrogen fertilization at 33–150 kg per ha. Plant diversity can also promote soil carbon storage in the long term, reduce soil N2O emissions by 30%–40%, and suppress weed invasion, hence reducing herbicide use. These potential benefits of plant diversity translate to 50%–65% greater life-cycle greenhouse gas savings for biofuels from more diverse grassland biomass grown on degraded soils. In addition, there is growing evidence that plant diversity can accelerate land restoration. Bioenergy from perennial grasses mitigates climate change via displacing fossil fuels and storing atmospheric CO2 belowground as soil carbon. Here, we conduct a critical review to examine whether increasing plant diversity in bioenergy grassland systems can further increase their climate change mitigation potential. We find that compared with highly productive monocultures, diverse mixtures tend to produce as great or greater yields. In particular, there is strong evidence that legume addition improves yield, in some cases equivalent to mineral nitrogen fertilization at 33–150 kg per ha. Plant diversity can also promote soil carbon storage in the long term, reduce soil N2O emissions by 30%–40%, and suppress weed invasion, hence reducing herbicide use. These potential benefits of plant diversity translate to 50%–65% greater life-cycle greenhouse gas savings for biofuels from more diverse grassland biomass grown on degraded soils. In addition, there is growing evidence that plant diversity can accelerate land restoration.

To mitigate greenhouse gas (GHG) emissions of intensified agriculture, conservation practices are gradually being implemented in Chinese wheat–maize cropping systems. However, the effects of different tillage practices on agricultural field GHG emissions and subsequent global warming potential (GWP) are poorly documented. In this study, a three-year field experiment was conducted from 2019 to 2021 to assess the effects of tillage on the emissions of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and eventually GWP. Compared to conventional tillage (CT), no-tillage (NT) significantly decreased CO2, CH4, and N2O emissions by 35.43%, 67.33%, 339.07%, respectively, which resulted in a decrease of 37.25% in GWP during three annual cycles. Based on the results of this study, soil could potentially act as a net source of CO2 and CH4 under both CT and NT, and a net sink of N2O under NT. Annually, non-growing season contributed 16.9%, 15.6%, and 13.8% soil CO2, CH4, and N2O fluxes, and 16.6% GWP under CT and 17.3%, 16.4%, 21.6%, and 17.3% under NT, respectively. Compared to CT, NT improved the aboveground biomass and grain yields of wheat by 21.3% and 13.3% from averaged results, respectively; no significant differences were found for maize yields. Although principal component analysis showed that soil temperature had higher correlations with CO2 emissions and GWP as compared to soil moisture, soil moisture affected GHG emissions more than soil temperature as demonstrated by the structural equation model. The modeling analysis found that NT increased soil moisture, pH, and bulk density, thus increasing soil organic carbon and decreasing total nitrogen content, eventually inhibiting GHG emissions. This research demonstrated that NT had the potential to mitigate GHG emissions, yet stability needed further investigation on long-term scales.∙Graphical

Greenhouse gas emissions studies commonly focus on temperate and subtropical regions. As a result, greenhouse gas emissions from agricultural soils in tropical areas are often neglected. Therefore, greenhouse gas fluxes in a Hainan paddy field under different fertilization regimes were studied. This research provides an accurate assessment of CH4 and N2O emissions from paddy fields in China and sound mitigation measures. Through static chamber/gas chromatography techniques, CH4 and N2O emissions, global warming potential (GWP), and greenhouse gas emissions intensity (GHGI) in late rice season under five fertilizer treatments were measured. The treatments included:control (CK), conventional treatment (CON), optimized fertilization treatment (YH), optimized fertilization combined with controlled slow-release fertilizer treatment (ZHY1), optimized fertilization combined with controlled slow-release fertilizer and organic fertilizer treatment (ZHY2). The results showed that the cumulative CH4 emissions in the CK, CON, YH1, ZYH1, and ZYH2 treatments were 175.70, 60.30, 63.00, 62.80, and 56.60kg·hm-2, and the cumulative N2O emissions were 0.78, 3.40, 1.03, 1.44, and 0.44kg·hm-2, respectively. Correlation analysis showed that soil temperature and Eh were the main factors driving CH4 emission. Compared with CK, CON, YH, and ZYH1, the yield of rice in ZYH2 treatment increased by 29.69%, 11.81%, 6.74%, and 10.36%, respectively. While GWP of ZYH2 decreased by 64.80%, 43.23%, 12.93%, and 15.15%, and GHGI decreased by 76.49%, 52.52%, 20.54%, and 23.87%, respectively. Therefore, in terms of yield and greenhouse gas emissions, optimal fertilization combined with sheep manure and slow release fertilizer treatment (ZYH2) is feasible in this region.

ABSTRACTHigh-density polyethylene (HDPE) membranes are commonly used as a cover component in sanitary landfills, although only limited evaluations of its effect on greenhouse gas (GHG) emissions have been completed. In this study, field GHG emission were investigated at the Dongbu landfill, using three different cover systems: HDPE covering; no covering, on the working face; and a novel material-Oreezyme Waste Cover (OWC) material as a trial material. Results showed that the HDPE membrane achieved a high CH4 retention, 99.8% (CH4 mean flux of 12 mg C m-2 h-1) compared with the air-permeable OWC surface (CH4 mean flux of 5933 mg C m-2 h-1) of the same landfill age. Fresh waste at the working face emitted a large fraction of N2O, with average fluxes of 10 mg N m-2 h-2, while N2O emissions were small at both the HDPE and the OWC sections. At the OWC section, CH4 emissions were elevated under high air temperatures but decreased as landfill age increased. N2O emissions from the working face had a significant negative correlation with air temperature, with peak values in winter. A massive presence of CO2 was observed at both the working face and the OWC sections. Most importantly, the annual GHG emissions were 4.9 Gg yr-1 in CO2 equivalents for the landfill site, of which the OWC-covered section contributed the most CH4 (41.9%), while the working face contributed the most N2O (97.2%). HDPE membrane is therefore, a recommended cover material for GHG control.Implications: Monitoring of GHG emissions at three different cover types in a municipal solid waste landfill during a 1-year period showed that the working face was a hotspot of N2O, which should draw attention. High CH4 fluxes occurred on the permeable surface covering a 1- to 2-year-old landfill. In contrast, the high-density polyethylene (HDPE) membrane achieved high CH4 retention, and therefore is a recommended cover material for GHG control.