Summary
In this study, productivity and physicochemical and microbiological (454 sequencing) parameters, as well as environmental criteria, were investigated in anaerobic reactors to contribute to ...the ongoing debate about the optimal temperature range for treating animal manure, and expand the general knowledge on the relation between microbiological and physicochemical process indicators. For this purpose, two reactor sizes were used (10 m3 and 16 l), in which two temperature conditions (35°C and 50°C) were tested. In addition, the effect of the hydraulic retention time was evaluated (16 versus 20 days).
Thermophilic anaerobic digestion showed higher organic matter degradation (especially fiber), higher pH and higher methane (CH4) yield, as well as better percentage of ultimate CH4 yield retrieved and lower residual CH4 emission, when compared with mesophilic conditions. In addition, lower microbial diversity was found in the thermophilic reactors, especially for Bacteria, where a clear intensification towards Clostridia class members was evident.
Independent of temperature, some similarities were found in digestates when comparing with animal manure, including low volatile fatty acids concentrations and a high fraction of Euryarchaeota in the total microbial community, in which members of Methanosarcinales dominated for both temperature conditions; these indicators could be considered a sign of process stability.
Stable thermophilic and mesophilic anaerobic digestion of cattle manure has been evaluated in terms of physicochemical, microbiological and environmental criteria as well as productivity.Thermophilic anaerobic digestion showed higher organic matter degradation (especially fiber), higher methane yield and better percentage of ultimate methane yield retrieved and therefore lower residual CH4 emission. In addition, lower microbial diversity was found in the thermophilic reactors, especially for Bacteria, where a clear intensification towards Clostridia class members was evident.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
This study investigated the temperature dependency of CH4 emission from pre-storage of animal manure prior to anaerobic digestion at 15, 20, 25 and 30 °C using lab-scale anaerobic digesters. The ...manure was added and removed daily to simulate the pre-storage process at biogas plants. CH4 emission accounted for 1–46% of total CH4 potential from pig manure (PM) and 1–2% of that from cattle manure (CM) at the investigated temperatures, with significant increases above 25 °C. Addition of food waste (FW) reduced the CH4 emission when storage temperature was 20 °C or lower for PM and 25 °C or lower for CM due to volatile fatty acid accumulation and lower pH (<5.5) but emissions increased with higher storage temperatures.
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•The temperature dependency of CH4 emissions during storage of manure was evaluated.•The effect of co-storage of manure with food waste was investigated.•Food waste addition inhibited CH4 emission at lower temperatures.•Emission at higher temperatures increased with addition of food waste.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Wheat straw and animal wastes are important feedstock for biogas production in Europe. Yet, the high content of lignocellulosic and refractory materials causes the process to be relatively slow. ...Therefore, pretreatment methods have been proposed to shorten the hydrolysis phase. The present study examined the effectiveness of alkali pre-treatment (AP), ultrasonic pre-treatment (UP), and alkali-ultrasonic pre-treatment (AUP) applied on wheat straw (WS), solid fraction of cattle manure (SCM) and solid fraction of slaughterhouse waste (SSHW), by monitoring solubilisation ratio, anaerobic biodegradability and methane yield. The results indicate that the solubilisation ratio of the substrates improved regardless of the types of pre-treatment applied. Though, AP was more effective on WS and SSHW than other pre-treatments (UP and AUP), with approximately 47% and 17% extra methane, respectively. Moreover, AP of SCM caused an increased in methane production rate by 100% and minimised lag phase from 16 days to 1 day during anaerobic digestion. Based on Danish conditions, only AP of WS was economical prior to the biogas process due to high extra methane yield. A positive energy budget of 8 € t
−1
VS
was calculated. High-energy consumption during UP and AUP in laboratory scale hindered the positive benefits of these pre-treatments.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
The objective of the present study was to evaluate the effect of dairy cow diets on feces composition and methane (CH4) potential from manure with emphasis on fat level and roughage type and compare ...these results with the corresponding enteric CH4 emission. In experiment 1 six different diets, divided into two fat levels (low and high) and three different roughage types (early cut grass silage, late cut grass silage and maize silage), were used. The high fat level was achieved by adding crushed rapeseed. In experiment 2, the influence of increasing the fat level by using three different types of rapeseed: rapeseed cake, whole seed and rapeseed oil against a low fat ration with no rapeseed fat supplementation was studied. The diet and fat level had a significant influence on feces composition and CH4 yield. In general, ultimate CH4 yields (B0) were 8–9% higher than the present international default values for diets without extra fat and in feces from diets with extra fat supply the yield was 25–31% higher. It was possible to predict the B0 value from feed and feces characteristics; in fact, the best correlation was obtained by including both feed and feces characteristics. Addition of crude fat to diets to dairy cows reduced enteric CH4 emission but at the same time increased CH4 potential from feces both in terms of organic matter in feces and dry matter intake which might lead to increasing emissions unless proper manure handling such as anaerobic digestion is included. Without subsequent anaerobic digestion to produce energy the positive effect achieved at cow level could be counteracted by increasing manure emissions.
•We model the methane potential from manure by diet and feces composition.•We correlate crude fat in faces with the methane potential.•Increasing fat in the diet increase the methane potential.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Anaerobic co-digestion of cattle manure (CM) with shredded or briquetted wheat straw (SS and BS, respectively) was evaluated in thermophilic continuously stirred tank reactors (CSTR) in two ...experiments (lab and full-scale). Three lab-scale CSTR (15 l) were used with 20 days hydraulic retention time (HRT); one was fed with CM and the other two with mixtures of CM (95% of fresh matter, FM) and SS or BS (5% FM). In the second experiment, two full-scale CSTR (30 m3) were operated with 25 days HRT; one reactor was fed with CM and the other with CM + BS (9% FM). Ultimate CH4 yield was analysed from each substrate. Biochemical CH4 potential at 21 days for CM, SS and BS were 128; 187 and 200 lSTP CH4 kg−1 VS. Anaerobic digestion of CM, CM + SS and CM + BS in lab-scale reactors yielded 165; 214 and 217 lSTP CH4 kg−1 VS. In full scale-reactors, CM and CM + BS yielded 264 and 351 lSTP CH4 kg−1 VS. Increments of 31 and 33% on CH4 yield were achieved in CM + BS compared to CM in lab and full-scale reactors, respectively. Regarding the energy balance, the energy yields were the same for both reactors using straw as co-substrate (CM + SS and CM + BS) after subtracting the energy consumption of the pretreatment, corresponding to 1100 kWh of net energy output. However, briquetting technology could be advantageous for biogas plants where the straw might be transported over longer distances, due to reduction of the transportation costs.
•Straw shredding and briquetting were evaluated in co-digestion with cattle manure.•The use of straw as co-substrate increased cellulose and hemicellulose content.•Shredded and briquetted straws increased specific and volumetric methane yields.•Shredding and briquetting for co-digestion resulted in a positive energy balance.•Briquetting technology can be suitable in decentralised biogas plants.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Anaerobic co-digestion of pig slurry and agricultural substrates was evaluated.•Vegetable substrates showed higher methane yield than fruit substrates.•Higher methane yield were obtained with ...increasing addition of agricultural substrate.•Microbial composition was similar in all combinations.•Methanomicrobiales organisms dominated over the rest of individual archaeal orders.
Anaerobic co-digestion of pig slurry with four agricultural substrates (tomato, pepper, persimmon and peach) was investigated. Each agricultural substrate was tested in co-digestion with pig slurry at four inclusion levels: 0%, 15%, 30% and 50%. Inclusion levels consisted in the replacement of the volatile solids (VS) from the pig slurry with the VS from the agricultural substrate. The effect of substrate type and inclusion level on the biochemical methane potential (BMP) was evaluated in a batch assay performed at 35°C for 100days. Agricultural substrate’s chemical composition was also analyzed and related with BMP. Additionally, Bacteria and Archaea domains together with the four main methanogenic archaeal orders were quantified using quantitative real-time TaqMan polymerase chain reaction (qPCR) at the end of the experiment to determine the influence of agricultural substrate on sludge’s microbial composition. Results showed that vegetable substrates (pepper and tomato) had higher lipid and protein content and lower carbohydrates than fruit substrates (persimmon and peach). Among substrates, vegetable substrates showed higher BMP than fruit substrates. Higher BMP values were obtained with increasing addition of agricultural substrate. The replacement of 50% of VS from pig slurry by tomato and pepper increased BMP in 41% and 44%, respectively compared with pig slurry only. Lower increments in BMP were achieved with lower inclusion levels. Results from qPCR showed that total bacteria and total archaea gene concentrations were similar in all combinations tested. Methanomicrobiales gene concentrations dominated over the rest of individual archaeal orders.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The objective of this study was to compare the total tract (total excreta and marker) and prececal methodologies to determine phosphorus (P) digestibility and to evaluate its variation as a function ...of the physicochemical characteristics of the inorganic phosphate used (monocalcium, MCP and dicalcium, DCP) from different commercial sources. A total of 176 1-day-old male broilers were used in two digestibility experiments. In Experiment 1, one MCP and one DCP were incorporated in the basal diet at two levels. In Experiment 2, MCP and DCP from three commercial sources were incorporated to the basal diet at one level. Physicochemical characteristics of inorganic phosphates were examined, as well. Additionally, bone mineralization and growth performance traits were investigated in both trials. The digestibility of MCP ranged from 75.2 to 87.4% and from 80.5 to 86.6% for DCP amongst methodologies, but differences between total tract and preceal methodologies were not statistically significant. Particle size, surface area, degree of crystallinity and impurities varied amongst commercial sources. The P digestibility of the three tested commercial sources of MCP was 79.6% (MCP1), 70.2% (MCP2) and 65.6% (MCP3);
> 0.05. The P digestibility of the 3 tested commercial sources of DCP was 80.1% (DCP1), 77.4% (DCP2) and 71.4% (DCP3);
> 0.05.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Forty pigs of 76.8 ± 4.2 kg body weight were fed four different diets varying in ensiled citrus pulp (ECP) inclusion level (0, 50, 100, and 150 g of ECP/kg of diet on dry matter base). The trial ...lasted 5 weeks. During the last week, faecal samples were obtained to calculate apparent nutrient digestibility; also volatile fatty acids (VFA) content in faeces was determined. The digestible energy and protein of ECP was estimated by regression analysis. During the trial faecal samples were collected to determine enterobacteria and lactobacilli counts. At slaughter, carcass characteristics were registered. The inclusion of ECP in the diets decreased energy digestibility but increased neutral and acid detergent fibre digestibility linearly (p<0.05). The estimated digestible energy and protein of ECP were lower than expected (7.0 MJ/kg dry matter (DM) and 33.8 g/kg DM, respectively). Total VFA production in faeces was not affected by the diet. Both enterobacteria and lactobacilli counts were lower (p<0.01) with than without ECP inclusion at the end of the study. Carcass yield decreased linearly (p<0.05) and backfat at gluteus medius increased quadratically (p<0.05) with the inclusion of ECP in the diet. The polyunsaturated fatty acid content of the internal subcutaneous fat layer decreased quadratically (p<0.05) with the inclusion of ECP. Thus, the nutritive value of ECP for finishing pigs is low and levels of 150g/kg can negatively affect carcass yield. However, including up to 100 g of ECP/kg in finishing pig diets did not affect nutrient digestibility, carcass yield and subcutaneous fat FA profile. Additionally, increasing ECP levels in diets decreases faecal enterobacteria and lactobacilli counts in faeces.
This study aimed to analyse several factors of variation of slurry composition and to establish prediction equations for potential methane (CH4) and ammonia (NH3) emissions. Seventy-nine feed and ...slurry samples were collected at two seasons (summer and winter) from commercial pig farms sited at two Spanish regions (Centre and Mediterranean). Nursery, growing-fattening, gestating and lactating facilities were sampled. Feed and slurry composition were determined, and potential CH4 and NH3 emissions measured at laboratory. Feed nutrient contents were used as covariates in the analysis. Near infrared reflectance spectroscopy (NIRS) was evaluated as a predicting tool for slurry composition and potential gaseous emissions. A wide variability was found both in feed and slurry composition. Mediterranean farms had a higher pH (p<0.001) and ash (p=0.02) concentration than those located at the Centre of Spain. Also, type of farm affected ether extract content of the slurry (p=0.02), with highest values obtained for the youngest animal facilities. Results suggested a buffer effect of dietary fibre on slurry pH and a direct relationship (p<0.05) with fibre constituents of manure. Dietary protein content did not affect slurry nitrogen content but decreased (p=0.003) total and volatile solids concentration. Prediction models of potential NH3 emissions (R2=0.89) and CH4 yield (R2=0.61) were obtained from slurry composition. Predictions from NIRS showed a high accuracy for most slurry constituents (R2>0.90) and similar accuracy of prediction of potential NH3 and CH4 emissions (R2=0.84 and 0.68, respectively) to models using slurry characteristics, which can be of interest to estimate emissions from commercial farms and establish mitigation strategies or optimize biogas production.
Sampling techniques to detect airborne Salmonella species (spp.) in two pilot scale broiler houses were compared. Broilers were inoculated at seven days of age with a marked strain of Salmonella ...enteritidis. The rearing cycle lasted 42 days during the summer. Airborne Salmonella spp. were sampled weekly using impaction, gravitational settling, and impingement techniques. Additionally, Salmonella spp. were sampled on feeders, drinkers, walls, and in the litter. Environmental conditions (temperature, relative humidity, and airborne particulate matter (PM) concentration) were monitored during the rearing cycle. The presence of Salmonella spp. was determined by culture-dependent and molecular methods. No cultivable Salmonella spp. were recovered from the poultry houses' surfaces, the litter, or the air before inoculation. After inoculation, cultivable Salmonella spp. were recovered from the surfaces and in the litter. Airborne cultivable Salmonella spp. Were detected using impaction and gravitational settling one or two weeks after the detection of Salmonella spp. in the litter. No cultivable Salmonella spp. were recovered using impingement based on culture-dependent techniques. At low airborne concentrations, the use of impingement for the quantification or detection of cultivable airborne Salmonella spp. is not recommended. In these cases, a combination of culture-dependent and culture-independent methods is recommended. These data are valuable to improve current measures to control the transmission of pathogens in livestock environments and for optimising the sampling and detection of airborne Salmonella spp. in practical conditions.
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