N2O emissions from municipal solid waste landfills with selected infertile cover soils and leachate subsurface irrigation

This study presents the field investigations into the effects of cover soils and leachate subsurface irrigation on N₂O emissions from municipal solid waste landfills. Landfill Site A and Site B, covered with carefully chosen infertile soils, were selected to monitor their diurnal and seasonal variations of N₂O emissions. The annual average N₂O flux was 469 ± 796 μg N₂O-N m⁻² h⁻¹ in Site B with leachate subsurface irrigation, three times that of Site A without leachate irrigation. When an additional soil containing lower contents of carbon and nitrogen was introduced to cover part of Site B, its N₂O fluxes decreased by 1-2 orders of magnitude compared with the left area of Site B. This suggested that carefully selected cover soils could substantially reduce N₂O emissions even under leachate subsurface irrigation. Statistical analysis proved that the availabilities of soil moisture and mineralized nitrogen were the key parameters controlling landfill N₂O emissions.     

An estimate of the contribution of outdoor concrete yards used by livestock to the UK inventories of ammonia, nitrous oxide and methane

Many farms have unroofed concrete yards used by livestock. These concrete yards have received little attention as sources of gaseous emissions. From 1997 to 1999 measurements were made of emissions of ammonia (NH₃), nitrous oxide (N₂O) and methane (CH₄) from 11 concrete yards used by livestock. A postal survey was carried out to assess the areas of yards on farms in England and Wales to enable the measurements to be scaled up to estimate national emissions. Using the results of this study NH₃-N emissions from farm concrete yards were calculated to be ca. 35×10³ t annually. This is 13% of the current estimated total NH₃-N emission from UK livestock. Concrete yards were an insignificant source of N₂O and CH₄ which were both <0.01% of current estimates of agricultural emissions.     

Ammonia abatement and its impact on emissions of nitrous oxide and methane—Part 2: application for Europe

Agriculture is an important source of NH₃, which contributes to acidification and eutrophication, as well as emissions of the greenhouse gases CH₄ and N₂O. Because of their common sources, emission reduction measures for one of these gases may affect emissions of others. These interrelations are often ignored in policy making. This study presents an analysis of the effects of measures to reduce NH₃ emissions on emissions of N₂O and CH₄ from agriculture in Europe. The analysis combines information from the NH₃ module of the Regional Air pollution INformation and Simulation (RAINS) model for Europe with the IPCC method for national greenhouse gas inventories. The IPCC method for estimating agricultural emissions of N₂O and CH₄ is adjusted in order to use it in combination with the RAINS database for the European agricultural sector. As an example, we applied the adjusted method to the agricultural sector in the Netherlands and found that application of several NH₃ abatement options may result in a substantial increase in N₂O emissions while the effect on CH₄ emissions is relatively small. In Part 2 of this paper we focus on the resulting emissions for all European countries for 1990 and 2010.     

Ammonia abatement and its impact on emissions of nitrous oxide and methane in Europe—Part 1: method

Agriculture is an important source of NH₃, which contributes to acidification and eutrophication, as well as emissions of the greenhouse gases CH₄ and N₂O. Because of their common sources, emission reduction measures for one of these gases may affect emissions of others. These interrelations are often ignored in policy making. This study presents an analysis of the effects of measures to reduce NH₃ emissions on emissions of N₂O and CH₄ from agriculture in Europe. The analysis combines information from the NH₃ module of the Regional Air pollution INformation and Simulation (RAINS) model for Europe with the IPCC method for national greenhouse gas inventories. The IPCC method for estimating agricultural emissions of N₂O and CH₄ is adjusted in order to use it in combination with the RAINS database for the European agricultural sector. As an example, we applied the adjusted method to the agricultural sector in the Netherlands and found that application of several NH₃ abatement options may result in a substantial increase in N₂O emissions while the effect on CH₄ emissions is relatively small. In Part 2 of this paper we focus on the resulting emissions for all European countries for 1990 and 2010.     

N2O Emissions at Solid Waste Disposal Sites in Osaka City

Nitrous oxide (N₂O) is a trace gas contributing to stratospheric ozone depletion and global warming. Although a large quantity of information exists about N₂O emissions from various ecosystems, this study was initiated to demonstrate the features of N₂O emissions from sea-based waste disposal sites in Osaka City in relation to CH₄ emissions.

Average N₂O emissions at an active landfill (S-Site) were several times higher than those at a closed landfill (N Site). Average CH₄ emissions were also much greater at the S-Site. Regarding the nature of N₂O emissions, remarkable emissions often were observed with aerobic waste layers at the N-Site, suggesting almost inversely related N₂O emissions with CH₄ production at the N-Site. However, at the S-Site a few exceptionally high N₂O emissions were noted in cases of high CH₄ emissions.     

Seasonal variations of CH(4) and N(2)O emissions in response to water management of paddy fields located in Southeast China

Water management is one of the most important practices that affect methane (CH₄) and nitrous oxide (N₂O) emissions from paddy fields. A field experiment was designed to study the effects of controlled irrigation (CI) on CH₄ and N₂O emissions from paddy fields, with traditional irrigation (TI) as the control. The effects of CI on CH₄ and N₂O emissions from paddy fields were very clear. The peaks of CH₄ emissions from the CI paddies were observed 1-2 d after the water layer disappeared. Afterward, the emissions reduced rapidly and remained low until the soil was re-flooded. A slight increase of CH₄ emission was observed in a short period after re-flooding. N₂O emissions peaks from CI paddies were all observed 8-10 d after the fertilization at the WFPS ranging from 78.1% to 85.3%. Soil drying caused substantial N₂O emissions, whereas no substantial N₂O emissions were observed when the soil was re-wetted after the dry phase. Compared with TI, the cumulative CH₄ emissions from the CI fields were reduced by 81.8% on the average, whereas the cumulative N₂O emissions were increased by 135.4% on the average. The integrative global warming potential of CH₄ and N₂O on a 100-year horizon decreased by 27.3% in the CI paddy fields, whereas no significant difference in the rice yield was observed between the CI and TI fields. These results suggest that CI can effectively mitigate the integrative greenhouse effect caused by CH₄ and N₂O emissions from paddy fields while ensuring the rice yield.     

N2O emissions at municipal solid waste landfill sites: Effects of CH4 emissions and cover soil

Municipal solid waste landfills are the significant anthropogenic sources of N₂O due to the cooxidation of ammonia by methane-oxidizing bacteria in cover soils. Such bacteria could be developed through CH₄ fumigation, as evidenced by both laboratory incubation and field measurement. During a 10-day incubation with leachate addition, the average N₂O fluxes in the soil samples, collected from the three selected landfill covers, were multiplied by 1.75 (p < 0.01), 3.56 (p < 0.01), and 2.12 (p < 0.01) from the soil samples preincubated with 5% CH₄ for three months when compared with the control, respectively. Among the three selected landfill sites, N₂O fluxes in two landfill sites were significantly correlated with the variations of the CH₄ emissions without landfill gas recovery (p < 0.001). N₂O fluxes were also elevated by the increase of the CH₄ emissions with landfill gas recovery in another landfill site (p > 0.05). The annual average N₂O flux was 176 ± 566 μg N₂O–N m^?2 h^?1 (p < 0.01) from sandy soil–covered landfill site, which was 72% (p < 0.05) and 173% (p < 0.01) lower than the other two clay soil covered landfill sites, respectively. The magnitude order of N₂O emissions in three landfill sites was also coincident by the results of laboratory incubation, suggesting the sandy soil cover could mitigate landfill N₂O emissions.     

Nitrous oxide and methane emission from a flooded rice field as influenced by separate and combined application of herbicides bensulfuron methyl and pretilachlor

Combination of divergent active principles to achieve broad-spectrum control is gaining popularity to manage the weed menace in intensive agriculture. However, such application could have non-target impacts on the soil processes affecting soil ecology and environmental interactions. A field experiment was conducted to investigate the impact of separate and combined applications of herbicides bensulfuron methyl and pretilachlor on the emission of N₂O and CH₄, and related soil and microbial parameters in a flooded alluvial field planted to rice cv Lalat. Single application of the herbicide bensulfuron methyl or pretilachlor resulted in a significant reduction of N₂O and CH₄ emissions while the combination of these two herbicides distinctly increased N₂O and CH₄ emissions. Cumulative N₂O emissions (kg N₂O-N) followed the order of bensulfuron methyl (0.35 kg ha⁻¹) < pretilachlor (0.36 kg ha⁻¹) < control (0.45 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% single dose (0.49 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% double dose (0.54 kg ha⁻¹). Cumulative CH₄ emissions (kg CH₄), on the other hand, followed the order of bensulfuron methyl (47.89 kg ha⁻¹) < pretilachlor (73.17 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% single dose (93.50 kg ha⁻¹) < control (106.54 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% double dose (124.67 kg ha⁻¹). The inhibitory effect of separate application of herbicides bensulfuron methyl 0.6% and pretilachlor 6.0% on N₂O emission was linked to lower mineral N, lower denitrifying and nitrifying activity and low denitrifier and nitrifier populations. Inhibitory effect on CH₄ emission, on the contrary, was linked to prevention in the drop of redox potential, lower readily mineralizable carbon (RMC) and microbial biomass carbon (MBC) contents as well as lower methanogenic and higher methanotrophic bacterial population. Admittedly, stimulatory effect of combined application of herbicides bensulfuron methyl 0.6% and pretilachlor 6.0% at double dose on N₂O and CH₄ emission was related to reversal of the identified indicators of inhibition. Results indicate that while individual application of herbicides bensulfuron methyl 0.6% or pretilachlor 6.0% can reduce N₂O and CH₄ emission from flooded soil planted to rice, their combined application at normal dose can keep the emission at a comparatively lower level with significantly higher grain yield as compared to the herbicides applied alone.     

Protection from wintertime rainfall reduces nutrient losses and greenhouse gas emissions during the decomposition of poultry and horse manure-based amendments

Manure-based soil amendments (herein “amendments”) are important fertility sources, but differences among amendment types and management can significantly affect their nutrient value and environmental impacts. A 6-month in situ decomposition experiment was conducted to determine how protection from wintertime rainfall affected nutrient losses and greenhouse gas (GHG) emissions in poultry (broiler chicken and turkey) and horse amendments. Changes in total nutrient concentration were measured every 3 months, changes in ammonium (NH₄⁺) and nitrate (NO₃^?) concentrations every month, and GHG emissions of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) every 7–14 days. Poultry amendments maintained higher nutrient concentrations (except for K), higher emissions of CO₂ and N₂O, and lower CH₄ emissions than horse amendments. Exposing amendments to rainfall increased total N and NH₄⁺ losses in poultry amendments, P losses in turkey and horse amendments, and K losses and cumulative N₂O emissions for all amendments. However, it did not affect CO₂ or CH₄ emissions. Overall, rainfall exposure would decrease total N inputs by 37% (horse), 59% (broiler chicken), or 74% (turkey) for a given application rate (wet weight basis) after 6 months of decomposition, with similar losses for NH₄⁺ (69–96%), P (41–73%), and K (91–97%). This study confirms the benefits of facilities protected from rainfall to reduce nutrient losses and GHG emissions during amendment decomposition.

Implications: The impact of rainfall protection on nutrient losses and GHG emissions was monitored during the decomposition of broiler chicken, turkey, and horse manure-based soil amendments. Amendments exposed to rainfall had large ammonium and potassium losses, resulting in a 37–74% decrease in N inputs when compared with amendments protected from rainfall. Nitrous oxide emissions were also higher with rainfall exposure, although it had no effect on carbon dioxide and methane emissions. Overall, this work highlights the benefits of rainfall protection during amendment decomposition to reduce nutrient losses and GHG emissions.     

Effects of straw returning and feeding on greenhouse gas emissions from integrated rice-crayfish farming in Jianghan Plain,China

Great efforts have been devoted to assessing the effects of straw managements on greenhouse gas (GHG) emissions, global warming potential (GWP), and net economic budget in rice monoculture (RM). However, few studies have evaluated the effects of straw managements on GHG emissions and net ecosystem economic budget (NEEB) in integrated rice-crayfish farming (RC). Here, a randomized block field experiment was performed to comprehensively evaluate the effects of aquatic breeding practices (feeding or no feeding of forage) and straw managements (rice straw returning or removal) on soil NH₄⁺–N and NO^?₃–N contents, redox potential (Eh), CH₄ and N₂O emissions, GWP, and NEEB of fluvo-aquic paddy soil in a rice-crayfish co-culture system in Jianghan Plain of China. We also compared the differences in CH₄ and N₂O emissions, GWP, and NEEB between RM and RC. Straw returning significantly increased CH₄ and N₂O emissions by 34.9–46.1% and 6.2–23.1% respectively compared with straw removal. Feeding of forage decreased CH₄ emissions by 13.9–18.7% but enhanced N₂O emissions by 24.4–33.2% relative to no feeding. Compared with RM treatment, RC treatment decreased CH₄ emissions by 18.1–19.6% but increased N₂O emissions by 16.8–21.0%. Moreover, RC treatment decreased GWP by 16.8–22.0% while increased NEEB by 26.9–75.6% relative to RM treatment, suggesting that the RC model may be a promising option for mitigating GWP and increasing economic benefits of paddy fields. However, the RC model resulted in a lower grain yield compared with the RM model, indicating that more efforts are needed to simultaneously increase grain yield and NEEB and decrease GWP under RC model.

     

Gaseous emissions from outdoor concrete yards used by livestock

Measurements of ammonia (NH₃), nitrous oxide (N₂O) and methane (CH₄) were made from 11 outdoor concrete yards used by livestock. Measurements of NH₃ emission were made using the equilibrium concentration technique while closed chambers were used to measure N₂O and CH₄ emissions. Outdoor yards used by livestock proved to be an important source of NH₃ emission. Greatest emission rates were measured from dairy cow feeding yards, with a mean of 690 mg NH₃-N m⁻² h⁻¹. Smaller emission rates were measured from sheep handling areas, dairy cow collecting yards, beef feeding yards and a pig loading area, with respective mean emission rates of 440, 280, 220 and 140 mg NH₃-N m⁻² h⁻¹. Emission rates of N₂O and CH₄ were much smaller and for CH₄, in particular, emission rates were influenced greatly by the presence or absence of dung on the measurement area.     

Effects of land use conversion and fertilization on CH<Subscript>4</Subscript> and N<Subscript>2</Subscript>O fluxes from typical hilly red soil

Land use conversion and fertilization have been widely reported to be important managements affecting the exchanges of greenhouse gases between soil and atmosphere. For comprehensive assessment of methane (CH₄) and nitrous oxide (N₂O) fluxes from hilly red soil induced by land use conversion and fertilization, a 14-month continuous field measurement was conducted on the newly converted citrus orchard plots with fertilization (OF) and without fertilization (ONF) and the conventional paddy plots with fertilization (PF) and without fertilization (PNF). Our results showed that land use conversion from paddy to orchard reduced the CH₄ fluxes at the expense of increasing the N₂O fluxes. Furthermore, fertilization significantly decreased the CH₄ fluxes from paddy soils in the second stage after conversion, but it failed to affect the CH₄ fluxes from orchard soils, whereas fertilizer applied to orchard and paddy increased soil N₂O emissions by 68 and 113.9 %, respectively. Thus, cumulative CH₄ emissions from the OF were 100 % lower, and N₂O emissions were 421 % higher than those from the PF. Although cumulative N₂O emissions were stimulated in the newly converted orchard, the strong reduction of CH₄ led to lower global warming potentials (GWPs) as compared to the paddy. Besides, fertilization in orchard increased GWPs but decreased GWPs of paddy soils. In addition, measurement of soil moisture, temperature, dissolved carbon contents (DOCs), and ammonia (NH₄ ⁺-N) and nitrate (NO₃ ^?-N) contents indicated a significant variation in soil properties and contributed to variations in soil CH₄ and N₂O fluxes. Results of this study suggest that land use conversion from paddy to orchard would benefit for reconciling greenhouse gas mitigation and citrus orchard cultivation would be a better agricultural system in the hilly red soils in terms of greenhouse gas emission. Moreover, selected fertilizer rate applied to paddy would lead to lower GWPs of CH₄ and N₂O. Nevertheless, more field measurements from newly converted orchard are highly needed to gain an insight into national and global accounting of CH₄ and N₂O emissions.     

Impact of raw pig slurry and pig farming practices on physicochemical parameters and on atmospheric N2O and CH4 emissions of tropical soils,Uvéa Island (South Pacific)

Emissions of CH₄ and N₂O related to private pig farming under a tropical climate in Uvéa Island were studied in this paper. Physicochemical soil parameters such as nitrate, nitrite, ammonium, Kjeldahl nitrogen, total organic carbon, pH and moisture were measured. Gaseous soil emissions as well as physicochemical parameters were compared in two private pig farming strategies encountered on this island on two different soils (calcareous and ferralitic) in order to determine the best pig farming management: in small concrete pens or in large land pens. Ammonium levels were higher in control areas while nitrate and nitrite levels were higher in soils with pig slurry inputs, indicating that nitrification was the predominant process related to N₂O emissions. Nitrate contents in soils near concrete pens were important (≥55 μg N/g) and can thus be a threat for the groundwater. For both pig farming strategies, N₂O and CH₄ fluxes can reach high levels up to 1 mg N/m²/h and 1 mg C/m²/h, respectively. CH₄ emissions near concrete pens were very high (≥10.4 mg C/m²/h). Former land pens converted into agricultural land recover low N₂O emission rates (≤0.03 mg N/m²/h), and methane uptake dominates. N₂O emissions were related to nitrate content whereas CH₄ emissions were found to be moisture dependent. As a result relating to the physicochemical parameters as well as to the gaseous emissions, we demonstrate that pig farming in large land pens is the best strategy for sustainable family pig breeding in Uvéa Islands and therefore in similar small tropical islands.     

Regional and sectoral assessment of greenhouse gas emissions in India

In this paper the authors have estimated for 1990 and 1995 the inventory of greenhouse gases CO₂, CH₄ and N₂O for India at a national and sub-regional district level. The district level estimates are important for improving the national inventories as well as for developing sound mitigation strategies at manageable smaller scales. Our estimates indicate that the total CO₂, CH₄ and N₂O emissions from India were 592.5, 17, 0.2 and 778, 18, 0.3 Tg in 1990 and 1995, respectively. The compounded annual growth rate (CAGR) of these gases over this period were 6.3, 1.2 and 3.3%, respectively. The districts have been ranked according to their order of emissions and the relatively large emitters are termed as hotspots. A direct correlation between coal consumption and districts with high CO₂ emission was observed. CO₂ emission from the largest 10% emitters increased by 8.1% in 1995 with respect to 1990 and emissions from rest of the districts decreased over the same period, thereby indicating a skewed primary energy consumption pattern for the country. Livestock followed by rice cultivation were the dominant CH₄ emitting sources. The waste sector though a large CH₄ emitter in the developed countries, only contributed about 10% the total CH₄ emission from all sources as most of the waste generated in India is allowed to decompose aerobically. N₂O emissions from the use of nitrogen fertilizer were maximum in both the years (more than 60% of the total N₂O). High emission intensities, in terms of CO₂ equivalent, are in districts of Gangetic plains, delta areas, and the southern part of the country. These overlap with districts with large coal mines, mega power plants, intensive paddy cultivation and high fertilizer use. The study indicates that the 25 highest emitting districts account for more than 37% of all India CO₂ equivalent GHG emissions. Electric power generation has emerged as the dominant source of GHG emissions, followed by emissions from steel and cement plants. It is therefore suggested, to target for GHG mitigation, the 40 largest coal-based thermal plants, five largest steel plants and 15 largest cement plants in India as the first step.     

Practical Incinerator Implications

This paper discusses a number of results obtained from a hazardous waste flat flame combustion study with implications to full scale incinerators. The results demonstrate that it is possible to obtain DREs of up to 99.95 percent firing mixtures of CH₂Cl₂/CH₄ and air in such a facility. These results are significant since residence times are at the millisecond level. The paper presents DRE results obtained with this CH₂Cl₂ flat flame system when systematically varying the chlorine loading and equivalence ratio within the flames. Additionally, a PIC DRE is defined as an alternative approach to measure total stack emissions. PIC DRE results are presented for systematic variation of chlorine loading and equivalence ratio. Based upon the data of the paper, a suggested two-stage incineration process is presented which may be both economically advantageous and result in less total PIC emissions as compared with conventional incinerators for certain wastes. The data of this work further indicate that it is kinetically possible to obtain high DREs with corresponding high CO levels for select wastes. Finally, an interpretation of the data suggests that, for a class of liquid wastes, it may be beneficial to vaporize the waste and premix it with gaseous fuel and oxidizer streams, thereby avoiding the need to atomize the waste.     

A comparison of CH4, N2O and CO2 emissions from three different cover types in a municipal solid waste landfill

High-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.     

Composting of spent pig litter in turned and forced-aerated piles

A study was carried out to compare the compositing efficiency of spent litter (a mixture of partially decomposed pig manure and sawdust) in turned and forced-aerated piles. Duplicate piles were built with manual turning (every 4 days) during composting, and duplicate piles were set up with forced aeration using an air pump. The present study demonstrated that the efficiency of composting in the turned and forced-aerated piles was similar. Spent litter in these piles reached maturity at the same time (60 days). The forced-aerated piles went through similar physical, chemical, and microbial changes with the turned piles during composting. The forced-aerated composting system was also as effective as the turned system in eliminating Salmonella sp. in the spent litter. These results suggest that a forced-aerated composting system could be used as an alternative method in composting spent litter. The similarities in temporal changes in temperature, chemical, and microbiological properties of the forced-aerated piles, compared with the turned piles, indicate that addition of a bulking agent under forced aerated composting of spent litter is not necessary. The partially decomposed sawdust in the spent litter provided enough free air space, allowing the delivery of oxygen for the microorganisms in the spent litter piles.     

Carbon dioxide and methane emissions from the scale model of open dairy lots

To investigate the impacts of major factors on carbon loss via gaseous emissions, carbon dioxide (CO₂) and methane (CH₄) emissions from the ground of open dairy lots were tested by a scale model experiment at various air temperatures (15, 25, and 35 °C), surface velocities (0.4, 0.7, 1.0, and 1.2 m sec^?1), and floor types (unpaved soil floor and brick-paved floor) in controlled laboratory conditions using the wind tunnel method. Generally, CO₂ and CH₄ emissions were significantly enhanced with the increase of air temperature and velocity (P < 0.05). Floor type had different effects on the CO₂ and CH₄ emissions, which were also affected by air temperature and soil characteristics of the floor. Although different patterns were observed on CH₄ emission from the soil and brick floors at different air temperature-velocity combinations, statistical analysis showed no significant difference in CH₄ emissions from different floors (P > 0.05). For CO₂, similar emissions were found from the soil and brick floors at 15 and 25 °C, whereas higher rates were detected from the brick floor at 35 °C (P < 0.05). Results showed that CH₄ emission from the scale model was exponentially related to CO₂ flux, which might be helpful in CH₄ emission estimation from manure management.

Implications: Gaseous emissions from the open lots are largely dependent on outdoor climate, floor systems, and management practices, which are quite different from those indoors. This study assessed the effects of floor types and air velocities on CO₂ and CH₄ emissions from the open dairy lots at various temperatures by a wind tunnel. It provided some valuable information for decision-making and further studies on gaseous emissions from open lots.     

接种比对餐厨垃圾干式厌氧发酵启动的影响

针对不同接种比对餐厨垃圾干式厌氧发酵启动的影响,对比分析了VS接种比分别为0.36和0.90两种情况下,餐厨垃圾干式厌氧发酵启动过程中pH、NH4-N、COD、VFA、甲烷含量等指标的变化。实验结果表明,启动初期2组样品pH分别快速降至4.74和5.68,均呈酸化状态,经碱液调整后,接种比为0.36的处理仍无法正常产气,接种比为0.90的处理,pH逐步提高,系统正常运行,经72 d的发酵实验,COD去除率达90.29%,甲烷含量高于60%的沼气产量达255.4 L,分析可见,VS接种比是干式厌氧发酵处理的重要参数;此外,与传统湿式厌氧发酵处理相比,餐厨垃圾干式厌氧发酵在较高的VFA和氨氮浓度下,仍能正常运行,采用干式厌氧发酵技术处理餐厨垃圾是可行的。