Burning of rice straw can emit considerable amounts of atmospheric pollutants. We evaluated the effect of rice straw moisture content (5%, 10%, and 20%) on the emission of carbon dioxide (CO2) and on ...the organic and inorganic constituents of released particulate matter (PM): dioxins, heavy metals, and polycyclic aromatic hydrocarbons (PAHs). Four burning tests were conducted per moisture treatment using the open chamber method. Additionally, combustion characteristics, including burning stages, durations, temperature, and relative humidity, were recorded. Burning tests showed flaming and smoldering stages were significantly longer in 20% moisture treatment (P < 0.05) compared with the rest. The amount of burned straw and ashes decreased with increasing straw moisture content (P < 0.001). Carbon dioxide was the main product obtained during combustion with emission values ranging from 692 g CO2 kg dry straw−1 (10% moisture content) to 835 g CO2 kg dry straw−1 (20% moisture content). Emission factors for PM were the highest in 20% moisture treatment (P < 0.005). Fine PM (PM2.5) accounted for more than 60% of total PM mass. Emission factors for dioxins increased with straw moisture content, being the highest in 20% moisture treatment, although showing a wide variability among burning tests (P > 0.05). Emissions factors for heavy metals were low and similar among moisture treatments (P > 0.05). Emission factors for individual PAHs were generally higher in 20% moisture treatment. Overall, emission factors of atmospheric pollutants measured in our study were higher in the 20% moisture content. This difference could be attributed to the incomplete combustion at higher levels of rice straw moisture content. According to our results, rice straw burning should be done after straw drying and under minimal moisture conditions to lower pollutant emission levels.
•We evaluated the effect of rice straw moisture on pollutant emissions during burning.•Atmospheric emissions of CO2, PM, dioxins, heavy metals, and PAHs were monitored.•The main product obtained during the combustion process was CO2, followed by PM.•Emission factors of atmospheric pollutants were higher in 20% moisture treatment.
Intensification of grasslands is necessary to meet the increasing demand of livestock products. The application of nitrogen (N) on grasslands affects the N balance therefore the nitrogen use ...efficiency (NUE). Emissions of nitrous oxide (N2O) are produced due to N fertilisation and low NUE. These emissions depend on the type and rates of N applied. In this study we have compiled data from 5 UK N fertilised grassland sites (Crichton, Drayton, North Wyke, Hillsborough and Pwllpeiran) covering a range of soil types and climates. The experiments evaluated the effect of increasing rates of inorganic N fertiliser provided as ammonium nitrate (AN) or calcium ammonium nitrate (CAN). The following fertiliser strategies were also explored for a rate of 320 kg N ha−1: using the nitrification inhibitor dicyandiamide (DCD), changing to urea as an N source and splitting fertiliser applications. We measured N2O emissions for a full year in each experiment, as well as soil mineral N, climate data, pasture yield and N offtake. N2O emissions were greater at Crichton and North Wyke whereas Drayton, Hillsborough and Pwllpeiran had the smallest emissions. The resulting average emission factor (EF) of 1.12% total N applied showed a range of values for all the sites between 0.6 and 2.08%. NUE depended on the site and for an application rate of 320 kg N ha−1, N surplus was on average higher than 80 kg N ha−1, which is proposed as a maximum by the EU Nitrogen Expert Panel. N2O emissions tended to be lower when urea was applied instead of AN or CAN, and were particularly reduced when using urea with DCD. Finally, correlations between the factors studied showed that total N input was related to Nofftake and Nexcess; while cumulative emissions and EF were related to yield scaled emissions.
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•N2O emissions and NUE were measured at 5 UK grassland sites.•Different fertilisation rates and strategies were tested in all sites.•Average N2O emission factor was 1.12%, but ranged from 0.60% to 2.08%.•Using urea and urea with DCD reduced N2O emission factor.•Yield scaled emissions and emissions relative to herbage N content show similar trend.
ABSTRACT
Gaseous emission in laying hen facilities affects animal production performance and the environment. Emission is ruled by gas concentration and ventilation rate (VR), which are the key ...parameters to estimate precise emission factors. In this work, VR were assessed in a mechanical ventilated laying hen facility under Mediterranean climate conditions. The study was performed during a complete production cycle from July 2015 to October 2016. Direct hot wire anemometer (HWA) and fan rotational speed methods, and indirect CO2 mass balance method were used to assess the VR. Mean VR was 5.3 ± 2.9 m3 h−1 hen−1 for the HWA method. The mean uncertainty of VR based on the HWA method was 8.5%, and it varied among ventilation stages from 2.3 to 12.8%. Uncertainty was higher in warm season (9.6%) than in cold season (5.4%). In relation to fan rotational speed method, mean VR was 5.9 ± 3.3 m3 h−1 hen−1, which accounts for 8.3% more than the HWA method. According to the results, the fan rotational speed method would be less sensitive than the HWA method for assessing VR. VR was 6.3 ± 2.1 m3 h−1 hen−1 for the CO2 balance method, which estimated lower VR values in warm season compared to the laser tachometer (LT) method (-5%) but higher values compared to the HWA method (+5%). In contrast, it estimated higher values in cold season compared to the HWA method (+23%) and LT method (+17%). Correlation analysis showed a strong correlation between the CO2 balance method and both direct methods (R = 0.85 and 0.86 for HWA and LT, respectively).
•Dehydrated citrus pulp is a fibrous by-product generated by the juice industry.•Increasing levels of dehydrated citrus pulp did not affect growth performance.•Dehydrated citrus pulp reduced loin ...depth, backfat gain and carcass weight.•Dehydrated citrus pulp increased methane per litre of slurry, but not per animal.•Dehydrated citrus pulp is a potential ingredient for future pig-sustainable diets.
Using agricultural by-products such as dehydrated orange pulp (DOP) in animal feeds is of interest to increase pig sector sustainability. With this aim, an assay was carried out to assess the effects of increasing inclusion levels of DOP in pig diets regarding animal performance, carcass quality, and environmental impact. Four experimental diets were designed, a control diet (T1) and three more diets with increasing levels of DOP with 80, 160, and 240 g/kg of DOP for diets T2, T3, and T4, respectively. One hundred and sixty growing pigs were used in the experiment. Growth performance (average daily gain, ADG; average daily feed intake, ADFI and feed conversion ratio, FCR) and in vivo backfat thickness (BF) and loin depth (LD) gain were recorded during the finishing phase (from 70 to 130 kg BW). Faecal samples were incubated for bacteria enumeration. At slaughter, carcass characteristics and meat quality traits were measured, and subcutaneous fat was sampled to analyse the fatty acid (FA) profile. Additionally, the slurry excreted by the animals was measured, characterised and subjected to a gaseous emission assay during its storage. The final BW and overall ADFI, ADG and FCR were similar among treatments. In vivo final LD and BF gain decreased (P ≤ 0.10) as the inclusion level of DOP increased. No differences were observed in carcass characteristics with the inclusion of DOP, except carcass weight that decreased linearly (P = 0.05) with DOP. Regarding the FA profile of the subcutaneous fat, the ratio of total monounsaturated to saturated FA increased with the inclusion level of DOP. Neither slurry excretion and characterisation nor bacterial counts from faeces showed any significant difference among treatments. The inclusion of DOP led to greater CH4 emissions in mg per L of slurry and hour, whereas these differences disappeared when expressed in mg per animal and day. In all, it has been demonstrated that the inclusion of DOP up to 240 mg/kg in pig diets had minor effects on growth performance, carcass quality traits or gaseous emissions from slurry, favouring the circular economy strategy and pig sector sustainability.
One of the key factors to improve swine production sustainability is the use of agro-industrial by-products in feeds, such as olive by-products. However, it is necessary to assess its effects on the ...overall production process, including the animal and the environment. With this aim, an experiment was conducted to determine the effects of including a partially defatted olive cake (PDOC) in pig diets on growth performance, faecal microbiota, carcass quality and gas emission from the slurry. Two finishing diets were formulated, a control (C) diet and a diet with PDOC included at 120 g/kg. Eighty finishing male pigs Duroc-Danbred × (Landrace × Large White) of 60.4 ± 7.00 kg BW were divided between these two treatments. During the finishing period (60 to 110 kg BW, 55 days) average daily gain, average daily feed intake and feed conversion ratio were recorded. Faecal samples from the rectum of 16 animals per treatment were incubated for bacteria enumeration. At the end of finishing period, backfat thickness and loin depth (LD) were measured. Animals were slaughtered to obtain carcass weight and carcass composition parameters, and subcutaneous fat was sampled to analyse the fatty acid (FA) profile. In addition greenhouse gas and ammonia emissions were measured during pig slurry storage using the methodology of dynamic flux chambers. An initial slurry characterisation and biochemical methane potential (B0) were also determined. No significant differences between treatments were found in performance, carcass quality and microbial counts with the exception of LD, which was lower in PDOC compared with C animals (45.5 v. 47.5 mm, SEM: 0.62; P = 0.020). The FA profile of the subcutaneous fat did not differ between treatments, but the monounsaturated FA (MUFA) concentration was higher and the polyunsaturated FA was lower in the animals fed PDOC (50.9 v. 48.3, SEM: 0.48, P < 0.001; 17.6 v. 19.3, SEM: 0.30, P < 0.001 in mg/100 g of Total FA, for PDOC and C animals, respectively). The initial pig slurry characterisation only showed differences in ADF concentration that was higher (P < 0.05) in the slurry from PDOC treatment. Regarding gas emission, slurries from both treatments emitted similar amounts of ammonia (NH3), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), as well as B0 values. The results obtained suggest that PDOC may be included in balanced pig diets at rates of up to 120 g/kg without negative effects on performance, carcass quality, gut microflora and slurry gas emission, while improving the MUFA concentration of subcutaneous fat.
The objectives of this paper are: 1) to give an overview of the development of methods for measuring emission rates from naturally ventilated livestock buildings over the last decade, 2) to identify ...and evaluate strengths and weaknesses, 3) to summarise and conclude the current state-of-art of available measurement concepts and their perspectives for improvement. The methods reviewed include determination of concentration and air exchange rate separately, tracer gas ratio, passive flux samplers, flux chambers, and combined downwind measurement and dispersion modelling. It is concluded that passive flux samplers, flux chambers and combined measurement and dispersion modelling are useful, but for limited fields of application only and require further development and validation against reference methods. The most robust method to investigate emission rates available at this stage is the tracer gas ratio method, but improvements are required. They include more detailed estimates of CO2 release rates (when using CO2 as a tracer) and research into optimising dosing performance of tracer gas release systems. The reliability of tracer gas ratio methods applied in buildings with large ventilation openings needs to be improved by a more profound understanding of tracer-pollutant ratios and their spatial variability, and the development of improved sampling methods for concentration ratios. There is a need for a field reference method against which other methods can be evaluated. None of the discussed measurement methods can be marked as a solid reference for all conditions; tracer gas ratio methods are the most likely candidate but need further improvement.
► Measurement methods for emissions from naturally ventilated (NV) livestock barns. ► Several methods are limited in application and need further development. ► The tracer gas ratio method is currently the most reliable and robust method. ► The reliability of the ratio methods in very open NV barns needs to be improved. ► There is a need for a field reference method that evaluates current methods.
Pig slurry is a valuable fertilizer for crop production but at the same time its management may pose environmental risks. Slurry samples were collected from 77 commercial farms of four animal ...categories (gestating and lactating sows, nursery piglets and growing pigs) and analyzed for macronutrients, micronutrients, heavy metals and volatile fatty acids. Emissions of ammonia (NH₃) and biochemical methane potential (BMP) were quantified. Slurry electrical conductivity, pH, dry matter content and ash content were also determined. Data analysis included an analysis of correlations among variables, the development of prediction models for gaseous emissions and the analysis of nutritional content of slurries for crop production. Descriptive information is provided in this work and shows a wide range of variability in all studied variables. Animal category affected some physicochemical parameters, probably as a consequence of different slurry management and use of cleaning water. Slurries from gestating sows and growing pigs tended to be more concentrated in nutrients, whereas the slurry from lactating sows and nursery piglets tended to be more diluted. Relevant relationships were found among slurry characteristics expressed in fresh basis and gas emissions. Predictive models using on-farm measurable parameters were obtained for NH₃ (R² = 0.51) and CH₄ (R² = 0.76), which suggests that BMP may be estimated in commercial farms from easily determined slurry characteristics. Finally, slurry nutrient composition was highly variable. Therefore, complete analyses of slurries should be performed for an effective and environmental friendly land application.
Gas emissions from broiler production have been the subject of intensive research. However, little experimental information exists for farms under the particular management and environmental ...conditions of the European Mediterranean area. In this study, ammonia, carbon dioxide, methane, and nitrous oxide concentrations and emissions were measured in a commercial broiler farm located in Spain. Gas concentrations were measured using a photoacoustic gas monitor, whereas the ventilation flow was evaluated by controlling the operation status of each fan. Two rearing periods were studied, one in summer and one in winter. All gas emissions increased with bird age. Ammonia emission rates averaged 19.7 and 18.1 mg/h per bird in the summer and winter, respectively, and increased with indoor temperature (r² = 0.51 in summer; r² = 0.42 in winter). Average CO₂ emission rates were 3.84 and 4.06 g/h per bird, CH₄ emission was 0.44 and 1.87 mg/h per bird, and N₂O emission was 1.74 and 2.13 mg/h per bird in summer and winter, respectively. A sinusoidal daily variation pattern was observed in all emissions except for CH₄. These patterns were characterized in terms of time of maximum emission and amplitude of the daily variation.
Standardized measurement protocols are required to reduce ammonia (NH
3
) emissions. In vitro measurement of NH
3
emissions consists in trapping the emission from an emitting source in an acidic ...solution under controlled conditions. The objective of this study was to assess the in vitro NH
3
measurement method from pig slurry with acid wet traps, as regards to the following: (i) the variation between replicates of NH
3
emissions measured in vitro, (ii) the relationships between partial and accumulated emissions, and (iii) the reduction of measurement frequency. For this study, a total of 60 pig slurry samples from different animal types (sows and growing animals) were collected from commercial farms. The coefficient of variation among replicates of accumulated NH
3
emission during 15 days was 6.73 %. Emissions tended to decrease with time, and an average reduction of NH
3
emissions about 16 % was found in the period 96–240 h with respect to the 0–96-h period. However, samples continued emitting considerable amounts of NH
3
after 360 h. Linear regression models allowed predicting emissions accumulated for 15 days using only the first 8 days (
R
2
> 0.90). Reducing NH
3
measurement frequency (from 24 to 48 h) did not significantly affect measured emissions (
P
> 0.05). The results of this study confirm that replication of measurements is required and a coefficient of variation of 10 % may be established as quality control requirement. The study also suggests that reducing the duration and frequency of measurements is a tangible option to simplify this methodology.
Among the factors influencing dust production on the farms, animal activity is probably the least studied. Animal activity is strongly affected by circadian rhythms and it is altered by the rearing ...conditions, especially the management of light and the feeding strategy. In this study, a broiler flock was evaluated until 35 d of age with the general objective of studying the factors influencing the production of dust, particularly the effect of animal activity, as affected by the lighting program. In an experimental room, 2 daily dark periods of 6 and 4 h with 158 birds divided in 12 groups, reared on wood shavings, were evaluated. A TEOM analyzer was used to measure dust concentrations, whereas animal activity was determined by observation of birds on video tapes. Animal activity was defined by an activity index, which was determined by direct evaluation of birds on video tapes. The animal activity index was closely related to the lighting program (0.084 and 0.556 during dark and light periods, respectively) and was maximum at wk 4 of the rearing period. The dust concentrations during light periods were on average 4 times higher than during dark periods, with a maximum average concentration of 2.82 mg·m⁻³ during the last week of the cycle. Particulate matter emission was on average 2.08 mg·animal⁻¹·hour⁻¹. Dust concentration increased linearly with bird weight and daily variations in dust production were characterized. As a result, a direct cause-effect relationship between animal activity and dust concentration was obtained (r² = 0.89).
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