In this paper, the anaerobic co-digestion of three different organic wastes, including livestock manure, slaughterhouse waste, and agricultural by-products (ABs), was carried out to enhance the ...efficiency of mono-digestion of livestock manure. The characteristics of co-digestion were evaluated at different mixing ratios. The experiment was performed using the Batch test and was divided into two parts. The first experimental section (EXP. 1) was designed to evaluate the seasonal characteristics of ABs, which are the different ratios of fruits and vegetables, where the mixing ratio of spring (fruits:vegetables = 3:7) showed the highest biogas yield (0.24 m3/kg volatile solids). The second experiment (EXP. 2) was conducted by using ABs in the ratio that gave the highest biogas yield in EXP. 1 in combinations of three wastes livestock manure, slaughterhouse waste, and ABs. The highest CH4 yield was 0.84 m3/kg volatile solids (VS), which was obtained with a mixing ratio that had even amounts of the three feedstocks. In addition, the results of the second biochemical methane potential test, which assessed the digestive efficiency according to the mixing ratio of the three types of organic waste, showed that the CH4 production rate of the merged digestion was approximately 1.03–1.29 times higher than that of the mono-digestion of livestock manure. The results of our experiment were verified using the modified Gompertz model, the results of which were relatively similar to the experimental results.
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•Influence of CO2 in flush gas on the specific methane production was studied.•15 different mixtures of CO2 and N2 were applied on blank samples.•CO2 in the flush gas increased ...significantly the methane production by 30%.•But also a short lag phase was observed suggesting a disturbance of biocenosis.
The influence of carbon dioxide (CO2) in the headspace gas on the specific methane (CH4) production of blank samples with just inoculum during Biochemical Methane Potential (BMP) tests was studied. The headspace of the bottles had been flushed with 15 different ratios of CO2 and N2 prior to incubation, while they were treated otherwise identically. The results revealed that the CH4 yield increased linearly with higher ratio of CO2 in the flush gas reaching a 30% higher yield at pure CO2 relative to pure N2 headspace conditions. However, a slightly distinct lag is noticeable during the initial phase of the degradation process at high ratios of CO2, hypothesizing a reversible disturbance of the biocenosis. Further experiments and analyses need to be performed to elucidate the underlying mechanisms.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Anaerobic co-digestion (ACD) has been used to treat various organic wastes because nutrient balance in the feed can be improved by mixing different organics. Until now, the correlation between ...characteristics of feedstocks and biogas production by ACD has been studied mainly in terms of biochemical methane potential. It has been rarely tried to understand the co-digestion process in terms of microbial community development. This study aimed to evaluate the performance of batch anaerobic digestion (AD) reactors fed with activated sludge (AS), swine slurry (SS) and food waste (FW) individually or in a mixture of the three wastes (FW: SS : AS=1 : 3 : 2). The AD reactors fed with the mixture showed better performance than those fed with a single substrate. Microbial communities of the batch AD reactors fed with a single substrate or the mixture were analyzed and the result was related to the performance of the AD reactors.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Biomethane potential (BMP) test was performed to access the anaerobic degradation of three macrophytes (
Eichhornia crassipes, Pistia stratiotes
and
Salvinia molesta
). Sonication pretreatment was ...evaluated in order to pre-hydrolyze the plants, aiming to remove the lag time and potentially increase the methane production. Two sonication energies were tested: 40,000 and 80,000 kJ kgTS
− 1
. Results indicated that not all the aquatic plants presented the same behavior. Raw biomass of Eichhornia and Pistia required a long lag-phase (11 and 8 days, respectively), while Salvinia did not, being the faster and most productive raw biomass (64% of biomethanization factor). Pretreated biomass was solubilized, however the results did not have a direct translation to the digestion performance. In fact, no substantial improvement on the amount of methane production occurred. The main experimental evidence was the full reduction of the lag-phase for Eichhornia and Pistia, while Salvinia did not exhibited a substantial change neither in methane production or in kinetics. The high biodegradability of Salvinia biomass without pretreatment indicated that ultrasound pretreatment is not required. Energetic Sustainability Index evidenced that sonication pretreatment process was not sustainable, due to the required high water content of the bulk.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This study investigated whether biogas reactor performance, including microbial community development, in response to a change in substrate composition is influenced by initial inoculum source. For ...the study, reactors previously operated with the same grass⁻manure mixture for more than 120 days and started with two different inocula were used. These reactors initially showed great differences depending on inoculum source, but eventually showed similar performance and overall microbial community structure. At the start of the present experiment, the substrate was complemented with milled feed wheat, added all at once or divided into two portions. The starting hypothesis was that process performance depends on initial inoculum source and microbial diversity, and thus that reactor performance is influenced by the feeding regime. In response to the substrate change, all reactors showed increases and decreases in volumetric and specific methane production, respectively. However, specific methane yield and development of the microbial community showed differences related to the initial inoculum source, confirming the hypothesis. However, the different feeding regimes had only minor effects on process performance and overall community structure, but still induced differences in the cellulose-degrading community and in cellulose degradation.
A protocol was developed for determining the biochemical methane potential (BMP) of plant material using the OxiTop(®) system. NaOH pellets for CO(2) absorption and different pretreatment methods ...were tested for their influence in the BMP test. The use of NaOH pellets in the headspace of the bottle negatively affected the stability of the test increasing the pH and inhibiting methanization. Sample comminution increased the biodegradability of plant samples. Our results clearly indicate the importance of test conditions during the assessment of anaerobic biodegradability of plant material, considering BMP differences as high as 44% were found. Guidelines and recommendations are given for screening plant material suitable for anaerobic digestion using the OxiTop(®) system.
The present study aimed at assessing the anaerobic digestion process efficiency on the organic fraction of municipal solids waste. Batch mesophilic and thermophilic biochemical methane potential ...(BMP) tests were carried out and the methane potential as well as the biodegradability of all substrates was determined. The experimental studies indicated that the biological biogas production of organic fraction of municipal solids waste in mesophilic (T=35°C) and thermophilic (T=55°C) temperature were 0.450 m3/kg and 0.481 m3/kg respectively. Moreover, the average biogas composition in percentage for the mesophilic and thermophilic case were (CH4: 61.1%, CO2: 38.9%) and (CH4: 62.3%, CO2: 37.7%) respectively. The experimental study showed that the produced volume of biological biogas and it composition of methane in thermophilic case were higher than the produced volume and methane percentage obtained in mesophilic case (T = 35°C). A possible reason for this could be the temperature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Increased consumption of pharmaceutical compounds compounded by their persistence in biological treatment processes and potential toxicity is becoming a serious concern. The aim of the present study ...was to investigate the fate of an antiepileptic drug, carbamazepine (CBZ), in anaerobic digestion process and its impact on methanogenic metabolism. Biochemical methane potential of CBZ with or without glucose was studied for 40 days in designed batch experiments. About 67.98% and 66.37% of spiked CBZ (about 100 μg l(-1)) were removed during this period from glucose amended or unamended sets, respectively. Loss of CBZ through adsorption onto suspended particles, as in sterilized seed sludge control (16.98%), was significantly lower in comparison to its biotic counterparts (P = 0.002 and P = 0.003). Analysis of methane or biogas production revealed no inhibitory effect of CBZ toward methanogenic process at its tested concentration. Differences in cumulative methane yields between glucose containing sets with or without CBZ were insignificant (P = 0.885). This study suggests that any residual CBZ concentration lower than the present study, if detected in waste-water, might not significantly affect the methanogenic process.
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