Total CH4 Emissions Research Articles

Substantial methane emissions from abandoned coal mines in China

China has shut down and abandoned a substantial number of coal mines since 1999, which have been releasing methane (CH4) for many years. However, the characteristics of China's abandoned mine methane (AMM) emissions are still unclear; this is a concerning knowledge gap because coal mines are the largest contributor to China's anthropogenic CH4 emissions. This study used two methods to estimate China's historical AMM emissions over the past 40 years (1980–2020) and to project its AMM emissions to 2060 which is the target year for China's carbon neutrality goal. The results show that China's AMM emissions increased substantially from 0.11 ± 0.03 million tons per year (Mt/yr) (3.1 ± 0.84 Mt/yr CO2-eq) in 1980 to 4.7 ± 0.94 Mt/yr (131 ± 26 Mt/yr CO2-eq) in 2020. An accelerated growth rate was found during 1998–2005, with AMM emissions rapidly increasing by approximately three times, which was consistent with the high number of mine shutdowns. In 2019, we found that AMM emissions had become the fourth largest anthropogenic source in China, higher than the national anthropogenic CH4 emissions of individual United Nations Framework Convention on Climate Change Annex I countries excluding the United States of America and the Russian Federation. If unabated, China's AMM emissions are projected to peak at 8.7 ± 2.6 Mt/yr in 2040 and reach approximately one-third of China's anthropogenic carbon dioxide emissions in 2060. This study reveals that understanding AMM emissions can help more accurately quantify China's total CH4 emissions and guide their future mitigation.

Large increase in CH4 emission following conversion of coastal marsh to aquaculture ponds caused by changing gas transport pathways

Methane emissions from aquatic ecosystems play an important role in global carbon cycle and climate change. Reclamation of coastal wetlands for aquaculture use has been shown to have opposite effects on sediment CH4 production potential and CH4 emission flux, but the underlying mechanism remained unclear. In this study, we compared sediment properties, CH4 production potential, emission flux, and CH4 transport pathways between a brackish marsh and the nearby reclaimed aquaculture ponds in the Min River Estuary in southeastern China. Despite that the sediment CH4 production potential in the ponds was significantly lower than the marsh, CH4 emission flux in the ponds (17.4 ± 2.7 mg m−2 h−1) was 11.9 times higher than the marsh (1.3 ± 0.2 mg m−2 h−1). Plant-mediated transport accounted for 75% of the total CH4 emission in the marsh, whereas ebullition accounted for 95% of the total CH4 emission in the ponds. CH4 emission fluxes in both habitat types were highest in the summer. These results suggest that the increase in CH4 emission following the conversion of brackish marsh to aquaculture ponds was not caused by increased sediment CH4 production, but rather by eliminating rhizospheric oxidation and shifting the major transport pathway to ebullition, allowing sediment CH4 to bypass oxidative loss. This study improves our understanding of the impacts of modification of coastal wetlands on greenhouse gas dynamics.

Rice straw decomposition in paddy surface water potentially reduces soil methane (CH4) emission

Background: Rice cultivation is considered significant methane (CH4) emission source. Rice straw (RS) incorporation into the soil is a critical factor that produces higher CH4 emissions. The RS waterlogging approach on the soil surface potentially reduces CH4 emissions due to increasing RS decomposition in aerobic conditions. However, the hypothesis has not been entirely determined. The study aimed to examine CH4 emissions under RS waterlogging on surface water compared with RS incorporation into the soil. Methods: We carried out a microcosm experiment in a screen-house with two treatments, including (i) RS incorporation into the soil and (ii) RS waterlogging on the soil surface in triplicates. We compared the CH4 emissions and CH4 accumulation for the off-growing and rice-sowing periods. Yield-scaled CH 4 emission was assessed based on total methane emission and rice yield. Results: The results demonstrated that RS waterlogging reduced CH4 emissions by 16.9% compared to RS incorporation. During the rice-growing period, total CH4 emissions from RS waterlogging accounted for 36% of the incorporation treatment. Under RS waterlogging, high CH4 emissions during the off-sowing stage were disclosed. The difference between yield-scaled CH4 emissions was not significant. Conclusions: RS waterlogging is a feasible option to alternate conventional RS incorporation toward lower CH4 emissions from rice production. Ameliorating CH4 emission mitigation by RS waterlogging during off-sowing is recommended for future works.

Physiological processes affecting methane transport by wetland vegetation – A review

Wetland plants transport oxygen to belowground tissues to survive in anoxic sediments, and simultaneously conduct methane (CH4) from the sediment to the atmosphere. Although plant-mediated transport is the main CH4 emission pathway in vegetated wetlands, the contribution of vegetated areas to total emissions in wetlands remains uncertain. To accurately quantify these emissions, understanding the physiological processes driving plant-mediated CH4 transport is crucial. This review describes the state of the art understanding of CH4 transport through trees, emergent, floating-leaved, and submerged freshwater macrophytes. Gas transport mechanisms in plants include diffusion, pressurized flow, and transpiration-driven flow. Pressurized flow in the gas-filled aerenchyma leads to higher gas transport rates than diffusion, and mostly occurs in plants standing in deeper water. Transpiration-driven flow occurs in the xylem tissue of trees, whereby dissolved CH4 is transported by sap flow. Pressurized flow and transpiration-driven flow both result in diel cycles in CH4 emission, with higher emissions during the day than at night. The total CH4 emission through a wetland plant depends on its growth stage, transport mechanisms and the balance between sediment and in-plant CH4 production and oxidation. Although plants contribute substantially to total CH4 emissions, soil carbon content, soil temperature, nutrient availability, and water depth are often stronger driving factors than plant species. Nevertheless, accurate quantification of emissions from vegetated wetlands requires standardization of measurement protocols which capture diurnal and seasonal variation in emissions. Knowledge on CH4 transport through trees and submersed and free-floating macrophytes is scarce and warrants further research.

Mitigation of methane emissions from three Danish landfills using different biocover systems

The establishment of biocover systems is an emerging methodology in reducing methane (CH4) emissions from landfills. This study investigated the performance of three biocover systems with different designs (biowindow and passively and actively loaded biofilters) in mitigating CH4 emissions from three landfills in Denmark. A series of field tests were carried out to evaluate the functionality of each system, and total CH4 emissions from relevant landfill sections or the entire landfill were measured before and after biocover implementation. Surface CH4 concentration screening and local CH4 fluxes showed generally low emissions from the biowindow/biofilters (mostly < 5 g CH4 m−2 d−1), although some hotspots were identified on two actively loaded biofilters. One passively loaded biofilter exhibited high CH4 emissions, mainly due to gas overloading into the system. Gas concentration profiles measured at different locations suggested uneven gas distribution in the biofilters, and significant CH4 oxidation occurred in both the gas distribution layer (when oxygen was fed into the system) and the CH4 oxidation layer. High CH4 oxidation efficiencies of above 95% were found in all systems except for one biofilter (55%). Whole-site emission measurements showed CH4 reduction efficiencies between 29 and 72% after implementing biocover systems at the three landfills, suggesting that they were efficient in reducing CH4 emissions. The most challenging task for the passively loaded biocover systems was to control gas flow and secure homogenous gas distribution, while for actively loaded biocovers, it might be more important to eliminate emission hotspots for better functionality.

Unexpected Methane Emissions From Old Small Fishing Vessels in China

Diesel-fueled ships have long been considered to contribute a marginal fraction of the global methane (CH4) emission budget compared to liquified natural gas (LNG)-fueled ships. Here, based on real-world measurements, we find that a specific yet-overlooked group of diesel-fueled ships–the old small fishing vessels (OSFVs)–is associated with high levels of CH4 emissions. The emission factors of CH4 from OSFVs is on average 5.2 ± 6.4 g CH4 per 1 kg fuel consumed, approaching EFCH4 of LNG-fueled ships (5.3–30.1 g/kg) and being at least six times EFCH4 of other types of diesel-fueled ships (0.0–0.9 g/kg). We estimate that CH4 emissions from OSFVs in China amount to 570–2,240 t per year, which is comparable to the total CH4 emission from all LNG-fueled ships worldwide. Our results thus call for revision of the global CH4 emission inventory for shipping.

Sensing and Analysis of Greenhouse Gas Emissions from Rice Fields to the Near Field Atmosphere.

Greenhouse gas (GHG) emissions from rice fields have huge effects on climate change. Low-cost systems and management practices to quantify and reduce GHGs emission rates are needed to achieve a better climate. The typical GHGs estimation processes are expensive and mainly depend on high-cost laboratory equipment. This study introduces a low-cost sensor-based GHG sampling and estimation system for rice fields. For this, a fully automatic gas chamber with a sensor-integrated gas accumulator and quantifier unit was designed and implemented to study its performance in the estimation efficiency of greenhouse gases (CH4, N2O, and CO2) from rice fields for two crop seasons. For each crop season, three paddy plots were prepared at the experimental site and then subjected to different irrigation methods (continuous flooding (CF), intermittent flooding (IF), and controlled intermittent flooding (CIF)) and fertilizer treatments to study the production and emission rates of GHGs throughout the crop growing season at regular intervals. A weather station was installed on the site to record the seasonal temperature and rainfall events. The seasonal total CH4 emission was affected by the effects of irrigation treatments. The mean CH4 emission in the CIF field was smaller than in other treatments. CH4 and N2O emission peaks were high during the vegetative and reproductive phases of rice growth, respectively. The results indicated that CIF treatment is most suitable in terms of rice productivity and higher water use efficiency. The application of nitrogen fertilizers produced some peaks in N2O emissions. On the whole, the proposed low-cost GHGs estimation system performed well during both crop seasons and it was found that the adaption of CIF treatment in rice fields could significantly reduce GHG emissions and increase rice productivity. The research results also suggested some mitigation strategies that could reduce the production of GHGs from rice fields.

Soil-tree-atmosphere CH4 flux dynamics of boreal birch and spruce trees during spring leaf-out

AimsStudies on tree CH4 exchange in boreal forests regarding seasonality and role of tree canopies are rare. We aimed to quantify the contribution of boreal trees to the forest CH4 budget during spring leaf-out and to reveal the role of microbes in the CH4 exchange.MethodsMethane fluxes of downy birch and Norway spruce (Betula pubescens and Picea abies) growing on fen and upland sites were measured together with soil CH4 flux, environmental variables and microbial abundances involved in the CH4 cycle. Tree CH4 fluxes were studied from three stem heights and from shoots.ResultsThe trees emitted CH4 with higher stem emissions detected from birch and higher shoot emissions from spruce. The stem CH4 emissions from birches at the fen were high (mean 45 µg m−2 h−1), decreasing with stem height. Their dynamics followed soil temperature, suggesting the emitted CH4 originated from methanogenic activity, manifested in high mcrA gene copy numbers, in the peat soil. Methanogens were below the quantification limit in the tree tissues. Upscaled tree CH4 emissions accounted for 22% of the total CH4 emissions at the fen.ConclusionsThe variation in stem CH4 flux between the trees and habitats is high, and the emissions from high-emitting birches increase as the spring proceeds. The lack of detection of methanogens or methanotrophs in the aboveground plant tissues suggests that these microbes did not have a significant role in the observed tree-derived fluxes. The stem-emitted CH4 from birches at the fen is presumably produced microbially in the soil.

Ebullitive CH4 flux and its mitigation potential by aeration in freshwater aquaculture: Measurements and global data synthesis

Freshwater aquaculture ponds constitute one of the important anthropogenic sources of atmospheric methane (CH4). Nevertheless, estimates of global CH4 emissions from freshwater aquaculture have large uncertainties due to a lack of data from different aquaculture types. Furthermore, despite that ebullition is a major pathway of CH4 in aquatic systems, the quantification of ebullitive CH4 fluxes from typical freshwater aquaculture ponds has been poorly represented. Here, field measurements of CH4 fluxes over two years were taken to quantify ebullitive CH4 fluxes from inland freshwater fish and crab aquaculture ponds in subtropical China. Ebullitive CH4 fluxes averaged 15.97 ± 1.57 and 11.22 ± 1.26 mg m−2 d−1 in the fish and crab ponds in the first experimental year, respectively, and were 22.86 ± 2.30 and 21.95 ± 2.19 mg m−2 d−1 in the second year. During aquaculture period, ebullition dominated the emission pathways of CH4, accounting for 83% and 98% of the total CH4 emissions in the fish and crab ponds, respectively. Ebullitive CH4 fluxes exhibited considerable spatial variations, with the lowest flux rates captured at the aeration area due to aerator-use in both the fish and crab ponds. Dissolved oxygen and dissolved organic carbon were the two primary factors that drove ebullitive CH4 fluxes in both aquaculture ponds. By incorporating global measurement data, we further assessed the CH4 mitigation potential of aerator use in freshwater aquaculture and revealed the dominant role of ebullition in this mitigation contribution. Together with the rice-based aquaculture, aerator use could reduce CH4 emissions from freshwater aquaculture ponds globally by 71% and in China by 63%.

Potential role of submerged macrophytes for oxic methane production in aquatic ecosystems

AbstractMethane (CH4) from aquatic ecosystems contributes to about half of total global CH4emissions to the atmosphere. Until recently, aquatic biogenic CH4production was exclusively attributed to methanogenic archaea living under anoxic or suboxic conditions in sediments, bottom waters, and wetlands. However, evidence for oxic CH4production (OMP) in freshwater, brackish, and marine habitats is increasing. Possible sources were found to be driven by various planktonic organisms supporting different OMP mechanisms. Surprisingly, submerged macrophytes have been fully ignored in studies on OMP, yet they are key components of littoral zones of ponds, lakes, and coastal systems. High CH4concentrations in these zones have been attributed to organic substrate production promoting classic methanogenesis in the absence of oxygen. Here, we review existing studies and argue that, similar to terrestrial plants and phytoplankton, macroalgae and submerged macrophytes may directly or indirectly contribute to CH4formation in oxic waters. We propose several potential direct and indirect mechanisms: (1) direct production of CH4; (2) production of CH4precursors and facilitation of their bacterial breakdown or chemical conversion; (3) facilitation of classic methanogenesis; and (4) facilitation of CH4ebullition. As submerged macrophytes occur in many freshwater and marine habitats, they are important in global carbon budgets and can strongly vary in their abundance due to seasonal and boom‐bust dynamics. Knowledge on their contribution to OMP is therefore essential to gain a better understanding of spatial and temporal dynamics of CH4emissions and thus to substantially reduce current uncertainties when estimating global CH4emissions from aquatic ecosystems.

Spatial and temporal variation of air pollutant emissions from forest fires in China

Warm and dry climate conditions favor the occurrence of forest fires. Forest burning leads to the discharge of large amounts of particles and trace gases that play an important role in air quality degradation and have impact on human health. To date, most studies on China's forest fire emissions have concentrated in certain regions, also with a relatively coarse temporal resolution. In this study, we used the INteractive Fire and Emission algoRithm for Natural envirOnments (INFERNO), as well as high-resolution land cover data to compile a forest fire emission inventory for China in 2020. The variations of forest combustion emissions were then analyzed at the provincial and seasonal level. The results show that forest fires were concentrated in southern China and northeastern China, which are in agreement with MODIS observations. Total CO2, CO, CH4, NOx, SO2, PM2.5, OC, and BC emissions were estimated to be 3.06 × 104, 1.87 × 103, 96.92, 34.95, 13.84, 208, 116.03, and 9.95 Gg, respectively. Provinces with higher emissions were found in Yunnan, Guangdong, Hunan, and Sichuan. Peak emission from forest fire occurred in spring and winter, mainly from January to April, during which contributed 70% of the total forest fire contaminants emissions. The algorithm used in this study can be easily coupled in the meteorological model and air quality model to estimate the occurrence of fire and calculate pollutant emission online. This study updated emissions information that may support future research and policy development on greenhouse gas reduction and air pollution control.

Methane emissions from US low production oil and natural gas well sites

Eighty percent of US oil and natural gas (O&G) production sites are low production well sites, with average site-level production ≤15 barrels of oil equivalent per day and producing only 6% of the nation’s O&G output in 2019. Here, we integrate national site-level O&G production data and previously reported site-level CH4 measurement data (n = 240) and find that low production well sites are a disproportionately large source of US O&G well site CH4 emissions, emitting more than 4 (95% confidence interval: 3—6) teragrams, 50% more than the total CH4 emissions from the Permian Basin, one of the world’s largest O&G producing regions. We estimate low production well sites represent roughly half (37—75%) of all O&G well site CH4 emissions, and a production-normalized CH4 loss rate of more than 10%—a factor of 6—12 times higher than the mean CH4 loss rate of 1.5% for all O&G well sites in the US. Our work suggests that achieving significant reductions in O&G CH4 emissions will require mitigation of emissions from low production well sites.

Spatiotemporal changes in greenhouse gas emissions and soil organic carbon sequestration for major cropping systems across China and their drivers over the past two decades

Chinese agricultural systems have experienced dramatic changes in crop planting area, cropping system, irrigation and fertilization managements, and crop yields in recent decades. These changes can substantially affect greenhouse gases (GHG) emissions and soil organic carbon (SOC) sequestration in croplands. However, the spatiotemporal patterns, as well as their driving factors and mechanisms, have not been well understood. Here, the Denitrification-Decomposition model is calibrated and validated to estimate nitrous oxide (N2O) and methane (CH4) emissions and SOC sequestration for seven major cropping systems in China during 2001–2020. The Logarithmic Mean Divisia Index method is further applied to attribute the net GHG emissions (NGEs) trend to various drivers. The results show that the total N2O emissions, CH4 emissions, and SOC sequestration were approximately 23.7, 182.0, and 177.6 Tg CO2-eq/year in the croplands across China. The national average NGEs per unit area ranged from −8705 to 8431 kg CO2-eq ha−1 year−1 across the major cropping systems. During 2001–2020, the trend in national annual NGEs was 0.66 kg CO2-eq ha−1 year−2, ranging from −78.9 to 82.2 kg CO2-eq ha−1 year−2 across the major cropping systems. The paddy lands were mainly a carbon source due to the large amount of CH4 emissions while the uplands could be a carbon sink owing to SOC sequestration. As a whole, the cropland in China was a carbon source with the NGEs equal to 28.4 Tg CO2-eq/year, and the NGEs increased by 0.047 Tg CO2-eq/year2 in the past 20 years. Nationally, changes in crop planting area and yields reduced the NGEs whereas changes in nitrogen use efficiency and cropping systems increased them, although the major factors and their impacts varied greatly among regions. Optimizing cropping systems and nitrogen fertilization based on the local genotype, environment and management should be the most effective method to reduce the NGEs in croplands.

Evaluating the use of an Unmanned Aerial Vehicle (UAV)-based active AirCore system to quantify methane emissions from dairy cows

Enteric fermentation and manure methane emissions from livestock are major anthropogenic greenhouse gas emissions. In general, direct measurements of farm-scale methane emissions are scarce due to the source complexity and the limitations of existing atmospheric sampling methods. Using an innovative UAV-based active AirCore system, we have performed accurate atmospheric measurements of CH4 mole fractions downwind of a dairy cow farm in the Netherlands on four individual days during the period from March 2017 to March 2019. The total CH4 emission rates from the farm were determined using the UAV-based mass balance approach to be 1.1–2.4 g/s. After subtracting estimated emission factors of manure onsite, we derived the enteric emission factors to be 0.20–0.51 kgCH4/AU/d (1 AU = 500 kg animal weight) of dairy cows. We show that the uncertainties of the estimates were dominated by the variabilities in the wind speed and the angle between the wind and the flight transect. Furthermore, nonsimultaneous sampling in the vertical direction of the plume is one of the main limiting factors to achieving accurate estimate of the CH4 emissions from the farm. In addition, a N2O tracer release experiment at the farm was performed when both a UAV and a mobile van were present to simultaneously sample the N2O tracer and the CH4 plumes from the farm, improving the source quantification with a correction factor of 1.04 and 1.22 for the inverse Gaussian approach and for the mass balance approach, respectively. The UAV-based active AirCore system is capable of providing useful estimates of CH4 emissions from dairy cow farms. The uncertainties of the estimates can be improved when combined with accurate measurements of local wind speed and direction or when combined with a tracer approach.

Effect of a Blend of Essential Oils, Bioflavonoids and Tannins on In Vitro Methane Production and In Vivo Production Efficiency in Dairy Cows.

Simple SummaryThe dairy system is facing many environmentally related issues, such as green-house gas emissions (GHG), as well as an increased demand for milk by the growing world population. Dairy cow farming must evolve towards more efficient and sustainable ways of production. Strategies to reduce ruminal methane emissions must be considered, due both to methane’s direct involvement in global warming and its negative relationship with productivity. Besides being the most important GHG arising from dairy cows, methane is also correlated with a loss of energy and a reduction in production efficiency that further worsen the environmental impact. The use of natural extracts, such as essential oils, bioflavonoids, and tannins may be useful to reduce methane production and to modulate the ruminal microbiota toward more efficient fermentation, increased feed efficiency and improved overall productivity.Two trials were performed to evaluate the efficacy of a blend of essential oils, bioflavonoids and tannins on methane (CH4) emissions (in vitro) and on the production efficiency of dairy cows (in vivo). The in vitro trial tested the production of total gas and CH4 at 16, 20 and 24 h of incubation, and volatile fatty acids (VFA) at 16 and 24 h, through biochemical methane potential (BMP) assays. In the in vivo trial, milk yield, dry matter intake (DMI), feed conversion rate (FCR), milk quality and apparent total tract digestibility (aTTD) were evaluated in 140 lactating Holstein Friesian cows. Animals were allocated into two groups: (i) Control, standard diet; (ii) Treatment, standard diet plus 10 g/head/d of a powder with a 10% concentration of a blend of essential oils, bioflavonoids and tannins. Statistical analysis was performed using the mixed procedure of SAS either for single or repeated measures. For all the parameters a p-value ≤ 0.05 was considered statistically significant. The blend significantly reduced the in vitro total gas and CH4 emissions at 16, 20 and 24 h of incubation (p < 0.001). In addition, acetic acid was reduced (p < 0.001), while propionic acid concentration was increased (p < 0.001) at 16 h and 24 h. In the in vivo trial, the Treatment group showed significantly raised milk yield, DMI, FCR (p < 0.001), and of the aTTD of cellulose and starch (p ≤ 0.002), while the milk quality traits were not affected. Overall, the results from the study indicated that the blend of essential oils, bioflavonoids, and tannins significantly reduced in vitro total gas and CH4 production and improved the production efficiency of lactating dairy cows in vivo.

Rice straw decomposition in paddy surface water potentially reduces soil methane (CH4) emission

Background: Rice cultivation is a significant methane (CH4) emission source. Rice straw (RS) incorporation into the soil is a key factor that produces higher CH4 emission. The RS waterlogging approach on the soil surface possibly reduces CH4 emission due to not being buried into the soil. However, evaluation of CH4 emission by this approach has not been determined. The objective of this study was to examine CH4 emission under RS waterlogging on surface water compared with RS incorporation into the soil. Methods: We carried out a microcosm experiment in a screen-house with two treatments, including (i) RS incorporation into the soil and (ii) RS waterlogging on the soil surface in triplicates. We compared the CH4 emissions and CH4 accumulation for the rice-growing and off-sowing periods. Yield-scaled CH4 emission was assessed based on total methane emission and rice yield. Results: The results demonstrated that RS waterlogging reduced CH4 emission by 16.9% compared to RS incorporation into the soil. During the rice-growing period, total CH4 emission from RS waterlogging accounted for 36% of the incorporation treatment. However, RS waterlogging is caused by high emissions during the off-sowing stage. The difference between yield-scaled CH4 emissions was insignificant. Conclusions: This study demonstrated that the treatment of RS by waterlogging is an appropriate alternative to conventional RS practices known as incorporation, which increases greenhouse CH4 emission. However, high CH4 emission during the off-sowing period, and RS accumulation in the field are key drivers that possibly contribute to greenhouse gas emissions. Therefore, further evaluation is needed to determine the long-term effects of this approach.

Soybean vs. Pea Bean in the Diet of Medium-Growing Broiler Chickens Raised under Semi-Intensive Conditions of Inner Mediterranean Areas: Growth Performance and Environmental Impact.

Simple SummaryGrowth performance of medium-growing broiler chickens raised under semi-intensive conditions was evaluated comparing two different dietary treatments and two different genotypes. Starting from the dietary ingredients traditionally used, soybean was totally replaced by pea bean. The experimental diets were also compared from an environmental point of view simulating the annual global warming potential of the diets. Neither genotype nor dietary treatment affected feed consumption and growth performance, suggesting that the total replacement of soybean with pea bean can be a valuable feeding strategy, also from the economic point of view. A diet containing pea slightly reduced the total greenhouse gas and carbon dioxide emitted on a yearly basis. The results of the present study suggest that replacing soybean with pea bean can be a sustainable feeding strategy in broiler chicken production of inner Mediterranean areas, from both economic and environmental perspectives.The effects of Glycine max L. (SOY) vs. Pisum sativum L. (PEA) in the diet were investigated on in vivo performance of two medium-growing broiler genotypes and on environmental impact. Sixty Kabir Red Plus and sixty New Red chickens were randomly allocated in 20 pens (n = 6 birds per pen). Each pen, i.e., experimental unit, received 1.18 kg dry matter (DM) including soybean (3.39%) in SOY, or pea bean (6.78%) in PEA groups. DM intake, DM refusals and bodyweight (BW) were recorded on pen basis, and average daily gain (ADG) and feed conversion rate (FCR) were calculated. Data on in vivo performance were processed by ANOVA General Linear Model followed by Student–Newman–Keuls post hoc test. Greenhouse gas (GHG) emissions were evaluated on a year basis by GLEAM-i software. The diet did not affect (p > 0.05) DM intake and DM refusals, BW, ADG and FCR. Diet x genotypes affected (p < 0.05) DM intake and DM refusals. PEA diet, cheaper than SOY diet, allowed the reduction in total GHG and CO2, and of meat emission intensity. However, an increase in total CH4 and N2O emissions was observed. The replacement of soybean with pea bean can represent a possible management strategy to reach trade-off between good farming practices and environmental protection on small-scale poultry farms of inner Mediterranean areas.

Supplementation of Oilseeds to an Herbage Diet High in Condensed Tannins Affects Methane Production with Minimal Impact on Ruminal Fermentation in Continuous Culture

Condensed tannins (CT) have been observed to reduce enteric CH4 production when added to ruminant diets. However, high concentrations of CT in forages such as sericea lespedeza (SL; Lespedeza cuneata (Dum. Cours.) G. Don) may depress nutrient digestibility. Oilseed crops, high in lipid concentration, also reduce enteric CH4 via toxicity to methanogenic bacteria with less depression of nutrient digestibility. However, it is unclear whether combining these two feeds would result in even greater decreases in CH4 without impairing ruminal fermentation. This study used an in vitro continuous culture fermentor system to determine if supplementation of ground oilseeds would further reduce enteric CH4 production while improving nutrient digestibility of high-CT forages. The experimental design was a 4 × 4 Latin square, with four diets containing (dry matter basis) 45% orchardgrass (OCH; Dactylis glomerata L.), 45% sericea lespedeza (SL; Lespedeza cuneata (Dum. Cours.) G. Don), and 10% oilseed supplements, using canola (CAN; Brassica napus L.), soybean (SOY; Glycine max L.), sunflower (SUN; Helianthus annuus L.), or a mix of all three species (MIX; in equal proportions). Fermentors were fed 82 g of dry matter/d in four equal feedings over four 10 d periods. Methane was recorded every 10 min, and effluent samples were analyzed for pH, volatile fatty acids, dry matter, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber to determine apparent and true nutrient digestibilities. The CAN, SUN, and MIX diets had greater concentrations of crude fat (7–8 g/kg) than the SOY diet (5.7 g/kg), which contributed to the greater reduction in enteric CH4 production in those diets (13–27 mg/d) compared to the SOY diet (84 mg/d). Apparent and true nutrient digestibilities were not affected by the addition of ground oilseeds. While N intake increased concomitant with crude protein increases in the diets, there were no additional effects on N flows. While supplementing a high-CT diet with any of the three oilseeds (canola, soybean, sunflower, or a mixture of the three oilseeds) reduced total CH4 emission without depressing nutrient digestibility, canola and mixes containing canola were most effective. Further research is needed in vivo to evaluate whether these results translate to greater feed efficiency and animal production.

Ground-based remote sensing of CH4 and N2O fluxes from a wastewater treatment plant and nearby biogas production with discoveries of unexpected sources.

This study is an attempt to assess CH4 and N2O emissions from all the treatment steps of a wastewater treatment plant (WWTP) in Sweden, serving 145000 persons, and an adjacent biogas production facility. We have used novel mid-IR ground-based remote sensing with a hyperspectral camera to visualize and quantify the emissions on 21 days during a year, with resulting yearly fluxes of 90.4±4.3 tonne CH4/yr and 10.9±1.3 tonne N2O/yr for the entire plant. The most highly emitting CH4 source was found to be sludge storage, which is seldom included in literature as in-situ methods are not suitable for measuring emissions extended over large surfaces, still contributing 90% to the total CH4 emission in our case. The dominating N2O source was found to be a Stable High rate Ammonia Removal Over Nitrite reactor, contributing 89% to the total N2O emissions. We also discovered several unexpected CH4 sources. Incomplete flaring of CH4 gave fluxes of at least 30kg CH4/min, corresponding to plume concentrations of 2.5%. Such highly episodic fluxes could double the plant-wide yearly emissions if they occur 2 days per year. From a distance of 250m we found a leak in the biogas production facility, corresponding to 1.1% of the CH4 produced, and that loading of organic material onto trucks from a biofertilizer storage tank contributed with high emissions during loading events. These results indicate that WWTP emissions globally may have been grossly underestimated and that it is essential to have effective methods that can measure all types of fluxes, and discover new potential sources, in order to make adequate priorities and to take effective actions to mitigate greenhouse gas emissions from WWTPs.

Influencing mechanism of non-CO2 greenhouse gas emissions and mitigation strategies of livestock sector in developed regions of eastern China: a case study of Jiangsu province

The livestock sector not only provides people with meat, eggs, milk, and other nutrients but also causes a large number of non-CO2 greenhouse gas emissions. It is urgent to explore the influence mechanism of non-CO2 greenhouse gas emission from the livestock sector and formulate effective mitigation strategies. Taking Jiangsu province as an example, we analyzed the influencing factors of non-CO2 greenhouse gas emissions from the livestock sector based on sources and modified the STIRPAT (stochastic impact by regression on population, affluence, and technology) model, proposed the directions, designed the generally circular path, and determined the focus of non-CO2 greenhouse gas emissions reduction from the livestock sector. The results demonstrated: (1) the top priority of emission reduction of livestock sector in Jiangsu province was the reasonable treatment of manure produced by livestock (non-CO2 greenhouse gas emissions from manure had accounted for more than 60% of the total emissions from the livestock sector since 2007.), and the core was pig manure management (the CH4 and N2O emissions from pig manure accounted for more than 90 and 50% of the total CH4 and N2O emissions from all livestock manure, respectively). (2) The decrease of the agricultural population, the increase of livestock output value per capita of the agricultural population, and the improvement of livestock carbon productivity all reduced non-CO2 greenhouse gas emissions of the livestock sector. For every 1% decrease in agricultural population, for every 1% increase in livestock carbon productivity and livestock output value per capita of the agricultural population, non-CO2 greenhouse gas emissions from the livestock sector would be reduced by 0.0859%, 0.1748%, and 0.0400%, respectively. (3) To construct and improve the low carbon industrial chain of the livestock sector, to promote low carbon technology research and development and introduction are two focuses for non-CO2 greenhouse gas emission reduction in the livestock sector. The research can provide a basis for non-CO2 greenhouse gas emissions reduction from the livestock sector in China, especially in the developed eastern regions.