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•First-order kinetic model applied to SMP curves from 3 inocula and 2 substrates.•First-order kinetic constant k differed between inocula for the same substrate.•BMP validation ...criteria were not able to identify an unsuitable inoculum.•SMP curves of blanks were used to identify a suitable inoculum for kinetic analysis.•Validation criteria for estimating first-order kinetic constant k are proposed.
The aim of this study was to improve the quality of estimations of the first-order kinetic constant k, in Biochemical Methane Potential (BMP) tests. The results showed that existing guidelines for BMP tests are not sufficient to improve the estimation of k. The methane production of the inoculum itself exerted a major influence on the estimation of k. A flawed value in k was correlated with a high endogenous methane production. Excluding blanks that showed a distinct lag-phase of >1 day and a mean relative standard deviation >10% during the first ten days of a BMP test helped to retrieve more consistent estimates for k. For improving the repeatability in the determination of k in BMP tests, it is strongly recommended to inspect the methane production rate of the blanks. The proposed threshold values may be applied by other researchers but need further verification with different data.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Three inocula have been tested systematically with four different substrates.•If inoculum’s origin impacts the performance in BMP test depend on the substrate.•Methane yield was not significantly ...influenced by the inoculum except for cellulose.•Degradation velocity was highest for the inoculum adapted to the substrate.
The impact of the inoculum’s origin on the methane yield in Biochemical Methane Potential (BMP) tests was investigated. The three most commonly applied inocula were chosen, originating from (i) a digester of a wastewater treatment plant, (ii) an agricultural biogas plant treating manure and energy crops, and (iii) a biowaste treatment plant. The performance of each inoculum was tested with four different substrates, namely sewage sludge, dried whole crop maize, food waste, and microcrystalline cellulose as a typical reference material. The results revealed that the choice of inoculum had no significant impact on the specific methane yield of the tested substrates except for cellulose. Still, the specific methane production rate was significantly influenced by the choice of the inoculum especially for sewage sludge, but also for food waste and cellulose, whereas it became clear that an inoculum adapted to a substrate is beneficial for a speedy digestion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The use of ornamental flowers and plants is widespread in several regions of the world, but the management of flower (or floral) waste (FW), classified as herbaceous biomasses, is scarcely addressed ...in the literature. However, climate change, population growth and the depletion of resources are expected to push towards the development of FW management strategies, according to principles of flexibility and integration of technologies. This study focuses on the characterization of ten different varieties of flowering plants, of which the wastes are of concern in the Pistoia Province (Italy). The possibility of recovering energy by means of anaerobic digestion is also preliminarily investigated. The interpretation of data through Principal Component Analyses proved to be effective to orientate the selection of technological solutions. The three main parts of each plant variety were analysed separately, showing that the biochemical composition of stems is statistically different from that of leaves and flowers, thus suggesting the viability of adopting different strategies to optimize material (value-added products) recovery from FW. Conversely, regarding biogas generation and energy recovery, the methane yield (in the range 82–330 NmLCH4.gVS−1) is not significantly affected by the type of FW part, nor by the variety of flowering plant or by the use of pesticides during cultivation, whereas lower kinetics were observed for stems compared to leaves and flowers. In view of full-scale application, and depending on FW amounts locally produced, a careful evaluation is required, encompassing aspects of technical feasibility and economic expenses associated with FW parts separation.
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•The management of flower waste is scarcely addressed in the literature.•Principal Component Analysis as practical tool to orientate flower waste management•Stems are different from flowers or leaves as for biochemical composition.•Stems, flowers and leaves are statistically the same as for anaerobic degradability.•Separating stems from flowers/leaves in case of target-oriented resource recovery
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The incomplete degradation of bio-plastics waste is undermining the suitability of current anaerobic digestion (AD) and composting, opening up the exploration of new treatment routes, including mixed ...waste. Bio-plastics are treated with mixed waste in a mechanical-biological treatment (MBT) plant with the production of a dry fraction for incineration and a biologically stable one for landfill. An alternative post-treatment of the bio-stabilised waste based on AD is possible. It follows that the main goal of this study is to verify the feasibility of managing cellulose-based bio-plastics with mixed municipal waste, comparing the AD of the MBT plant outputs with the possible solution of incineration. Experimental lab tests have been carried out to describe the two processes, whose results were the basis for an economic analysis. The values of biochemical methane potential (BMP) and higher heating value (HHV) are used as an index for AD and incineration, respectively. Samples with and without bio-plastics were created; fresh and processed (7 and 14 days of biostabilization) samples were, thus, analysed. For AD, the fresh waste averaged 177 NmL CH4/gVS and a 22% and 33% decrease in BMP value was achieved after 7 and 14 days of biostabilization, respectively. Samples with and without bio-plastics revealed a similar trend. 7 and 14 days of biostabilization increased the HHV of fresh waste (18.01 J/kg) of 16.1% and 19.7%, respectively. Bio-plastics did not significantly change the HHV. The economic analysis revealed the suitability of both AD and incineration, irrespective of the presence of bioplastics.
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•After biostabilization, MSW decreased potential methane production of about 25%.•Average bio-plastics disintegration after anaerobic digestion range from 60% to 90%.•Bio-drying increased the heating value of MSW of 15–20%.•Cellulose-based bio-plastics reduced their heating value of only 3%.•Anaerobic digestion and incineration are two suitable options for biostabilized MSW.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Anaerobic digestion is a viable method for the conversion of food waste.•The maximum biogas production observed at the pH equal 7.0.•Methane yield variations range from 216 to 1476 mL CH4/ g VS.•The ...range of phosphorus content was: 0–3.66.%•The range of potassium content was: 0–10.45% and that of nitrogen was 0.05–6.15%.
Considerable amounts of expired food waste are generated every day. They are rich in organic carbon and in other elements, including nitrogen, phosphorus and potassium, which cannot be wasted. The present work tested expired food waste in terms of biogas production efficiency in anaerobic digestion (AD) process. A database was extrapolated from the tests carried out in order to obtain a complete list of physico-chemical and biochemical methane potential (BMP) of 88 expired food waste. Many studies are based on the analysis of a small number of samples, which are don't present a complete picture of all the types of food waste. The organic composition and other factors such as pH, temperature, C/N ratio of the samples varies considerably with the region, the season and the processing characteristics, resulting in methane yield variations, ranging from 216 to 1476 mL CH4/gVS. Therefore, knowledge of the appropriate physical and chemical properties of the feedstock, working conditions and the effects of the inhibition of various components on the anaerobic digestion processes is a key element, necessary to optimize energy production from food waste.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The winemaking process generates many by-products besides wastewater, mainly grape marcs, grape stalks, and wine lees. Anaerobic digestion is particularly suitable to treat winery waste because of ...its high content of nutrient-rich organic matter and for its noticeable energetic potential. To date, only results from mesophilic tests have been extensively reported. In this study, potential methane production and kinetic constants were determined by batch trials under thermophilic conditions and compared with mesophilic values already reported in literature. Grape marcs and wine lees appeared to be the most promising substrates with an estimated potential of 0.34 and 0.37 Nm3CH4/kgVSfed, respectively, while grape stalks generated only 0.13 Nm3CH4/kgVSfed. In order to assess the feasibility of a continuous anaerobic digestion process, a lab-scale semi-continuous reactor was constructed. Because of the consumption of buffer capacity, the biological process was difficult to control. On the other hand, biogas was produced when working with a hydraulic retention time of 40 d and with previously fermented grape marcs; a specific biogas production of 0.29 Nm3/kgVSfed was observed. The results of the continuous tests were used to calculate the potential energy recovery from grape marcs produced in Italy (808 thousands of tons per year) in terms of heat and electricity; about 245 GWh of heat and 201 GWh of electricity per annum could be generated in Italian scenario.
•Complete study on thermophilic digestion of winery waste by batch and continuous reactors.•Potential methane production at 55 °C reached 0.360 Nm3/kgVS.•Addiction of a co-substrate improved process stability.•Application of long HRT and previous fermentation double SGP of marcs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Corn stover is a biogas feedstock capable of enhancing agriculture bioenergy potential. Although the influence of growing conditions on biogas yield of corn stover has been reported, the joint ...effects of water and nitrogen on biogas production potential have not been addressed. A two year experiment (Exp. 1 and Exp. 2) was conducted in Balcarce, Argentina to assess nitrogen supply effects on stover composition and potential methane yield of corn crops grown under contrasting water regimes. Treatments were a combination of two nitrogen fertilization doses (0 and 120 kg ha−1) and two water regimes (irrigated and rainfed). Biomass composition (mass closure procedure) was determined, a BMP test was carried out and first-order kinetic parameters were obtained. Interactive effects of nitrogen and water on stover composition were found. BMP tests showed that the biogas production rate (k) decreased upon irrigation while its response to nitrogen depended on water availability. Nitrogen supply decreased specific biogas potential (Bmax) independently of water availability. Methane yield increased with nitrogen fertilization under irrigation, while it decreased under rainfed conditions. The observed water and nitrogen supply interactive effects on stover yield, methane yield and biomass conversion efficiency highlights the importance of considering the joint effects of multiple factors when trying to assess the effects of the environment on biomass quality for bioenergy purposes.
•Nitrogen supply did not increase corn stover yield in water limited environments.•Nitrogen supply decreased specific biogas potential disregarding water availability.•Water and nitrogen interact in their effects on final methane yield.•Irrigation increased methane yield at any nitrogen status.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The evaluated factors introduce significant systematic errors (10–38%) in BMP tests.•Ambient temperature (T) has the most substantial impact (∼10%) at low altitude.•Ambient pressure (p) has the most ...substantial impact (∼68%) at high altitude.•Continuous monitoring of T and p is not necessary for kinetic calculations.
The Biochemical Methane Potential (BMP) test is increasingly recognised as a tool for selecting and pricing biomass material for production of biogas. However, the results for the same substrate often differ between laboratories and much work to standardise such tests is still needed. In the current study, the effects from four environmental factors (i.e. ambient temperature and pressure, water vapour content and initial gas composition of the reactor headspace) on the degradation kinetics and the determined methane potential were evaluated with a 24 full factorial design. Four substrates, with different biodegradation profiles, were investigated and the ambient temperature was found to be the most significant contributor to errors in the methane potential. Concerning the kinetics of the process, the environmental factors’ impact on the calculated rate constants was negligible. The impact of the environmental factors on the kinetic parameters and methane potential from performing a BMP test at different geographical locations around the world was simulated by adjusting the data according to the ambient temperature and pressure of some chosen model sites. The largest effect on the methane potential was registered from tests performed at high altitudes due to a low ambient pressure. The results from this study illustrate the importance of considering the environmental factors’ influence on volumetric gas measurement in BMP tests. This is essential to achieve trustworthy and standardised results that can be used by researchers and end users from all over the world.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The biochemical methane potential (BMP) test is significant for the landfill industry as it provides a means to evaluate the gas potential, and therefore potential degradability, of both incoming and ...in-place municipal solid waste (MSW). However, the BMP test is not standardized making comparison of BMP results across sites problematic. For example, the BMP test duration has historically ranged from 20 days to several months with most current BMP tests lasting 60 days. However, the gas generation data can potentially be modelled for any of those durations to produce a prediction of the ultimate BMP value (BMP
). Currently, the predicted BMP
values of 23 long-duration (115-150 days) BMP tests were used to determine the required quantity of data (i.e. number of days) needed to produce an accurate BMP
prediction. Results showed that no single test duration produced both accurate and efficient results, so a novel performance-based endpoint was proposed. The relative change in predicted BMP
values with respect to time (dBMP
/d
) was chosen as a potential performance-based completion metric. Results indicate that once the absolute normalized dBMP
/d
value is within <2.5, <1.5 and <0.6% day
that the predicted BMP
is within 20, 10 and 5% of the true BMP
, respectively. Overall, the use of performance-based metrics for determining BMP test completion will allow for the collection of partial data sets, reduced experimental times and verification of results.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Boosting biomethane production makes it possible to offset the required energy in a wastewater treatment plant. In this research, using batch biomethane potential assays, various techniques including ...pretreatment, co-digestion, and digestion temperature rise were evaluated to increase the methane productivity of municipal sewage sludge (SS). Between thermal and sonication pretreatment methods, thermal pretreatment was shown to be more efficient and there was no need to pretreat SS for more than 0.5 h. Thermophilic digestion of SS led to 160.8% rise in the methane productivity, compared to mesophilic digestion. The most suitable co-substrate for co-digestion with SS was food waste (FW). FW and SS had little negative synergistic effect, however higher FW concentration caused to higher specific methane yield. Thermal pretreatment was not effective on FW. To evaluate the techniques, a combined cooling, heat and power plant was suggested. The energy recovery balance was positive for all the techniques, but co-digestion was not successful to reduce the levelized cost of energy (LCOE). Unlike co-digestion, thermal pretreatment and digestion temperature rise decreased the LCOE. The thermophilic digestion of SS, pretreated at 90 °C for 0.5 h, resulted in the lowest amount of LCOE by 43.70% reduction, compared to the mesophilic single digestion of non-treated SS.
•Evaluation of various techniques to increase biogas productivity of sewage sludge.•For the same energy applied, thermal pretreatment was more effective than sonication.•Digestion temperature rise led to significant increase in the methane productivity.•Co-digestion with food waste could not reduce the levelized cost of energy (LCOE).•Thermal pretreatment before thermophilic digestion significantly decreased the LCOE.
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