► The maximum hydrogen production is reached at 1.9-days HRT. ► The maximum solubilized organic carbon concentration is reached at 1.9-day HRT. ► The ratio ASC/DOC allows further interpretation of ...process limitations.
The main objective of this work has been to analyze the effect of hydraulic retention time (HRT) on the hydrogen production from the organic fraction of municipal solid waste (OFMSW) coming from a full-scale mechanical–biological-treatment (MBT) plant. Furthermore, it has also been studied, simultaneously, the effect of HRT on the solubilization of organic matter.
Experiments were conducted in an anaerobic continuous stirred tank reactor (CSTR) operating at thermophilic-dry conditions (55°C and 20% in total solids concentration respectively). A decreasing sequence of nine HRTs, from 15days to 1.5days, was imposed to evaluate its influence on the hydrogen production (HP), the specific hydrogen production (SHP) and the solubilized organic matter expressed in form of acidogenic substrate as carbon (ASC), dissolved organic carbon (DOC) and dissolved acid carbon (DAC).
The results have shown that the best results were obtained at 1.9-day HRT with a feeding regime of twice a day (type-C). At these conditions, the HP and the SHP was 1.077L H2/Lreactorday and 24.3mL H2/g VSadded, respectively. Maximum concentrations obtained of solubilized organic matter were: 1201mg/L for ASC, 1936mg/L for DOC and 735mg/L for DAC.
As novelty, the parameter ASC and, specially, the ratio ASC/DOC have shown to be adequate for analyzing and interpreting the behavior of the process and, concretely, to determine if hydrolysis and acidogenesis are coupled (stable process) or decoupled (transitory stage).
We propose an analog-digital quantum simulation of fermion-fermion scattering mediated by a continuum of bosonic modes within a circuit quantum electrodynamics scenario. This quantum technology ...naturally provides strong coupling of superconducting qubits with a continuum of electromagnetic modes in an open transmission line. In this way, we propose qubits to efficiently simulate fermionic modes via digital techniques, while we consider the continuum complexity of an open transmission line to simulate the continuum complexity of bosonic modes in quantum field theories. Therefore, we believe that the complexity-simulating-complexity concept should become a leading paradigm in any effort towards scalable quantum simulations.
A series of batch anaerobic digestion assays were implemented to determine the influence of total solids concentration on the anaerobic digestion of sugar beet by-products and their co-digestion with ...two kind of livestock manures (pig and cow manures). The two total solid concentrations studied were 8% and 5%. Total solids contents above 8% were not evaluated because of the inappropriate rheological behaviour of sugar beet by-products at these concentrations. The best total solid content tested corresponded to 8%, achieving specific methane yields of 464.3 and 451.4mL/g VSadded for co-digestion with pig manure and cow manure respectively. These data were 1.5 times higher than that obtained for reactors operating with 5% total solids content. For individual digestion of sugar beet by-products, final methane yields operating at 8% were also higher than those measured at 5% total solids concentration. However, in these tests, a large delay in the start of biogas production was registered due to the inhibition caused by the accumulation of volatile fatty acids. No significant differences in the organic matter removal efficiencies were observed for the two total solids contents studied.
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•Mesophilic anaerobic digestion of sugar beet byproducts was studied.•Co-digestion of sugar beet byproducts with two livestock manures was conducted.•Influence of two total solid contents of 8% and 5% on the process was evaluated.•Operation at TS content of 8% showed better results than 5% TS.
•H2 was produced from thermophilic anaerobic co-digestion of OFMSW and sewage sludge.•Enhanced H2 production was achieved for OFMSW+sewage sludge co-fermentation.•Mixed sludge was the best ...co-substrate (with OFMSW) among the sludge types studied.•Best hydrogen yield was achieved at 20% TS concentration.•Highest H2 yield was achieved at OFMSW to mixed sludge ratio of 5:1.
Batch dry-thermophilic anaerobic co-digestion (55°C) of organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) for hydrogen production was studied under several sludge combinations (primary sludge, PS; waste activated sludge, WAS; and mixed sludge, MS), TS concentrations (10–25%) and mixing ratios of OFMSW and SS (1:1, 2.5:1, 5:1, 10:1). The co-digestion of OFMSW and SS showed a 70% improvement in hydrogen production rate over the OFMSW fermentation only. The co-digestion of OFMSW with MS showed 47% and 115% higher hydrogen production potential as compared with OFMSW+PS and OFMSW+WAS, respectively. The maximum hydrogen yield of 51mLH2/gVSconsumed was observed at TS concentration of 20% and OFMSW to MS mixing ratio of 5:1, respectively. The acetic and butyric acids were the main acids in VFAs evolution; however, the higher butyric acid evolution indicated that the H2 fermentation was butyrate type fermentation.
•Two-phase olive-mill waste and cattle manure were anaerobically co-digested.•Start-up and stabilization stages were studied in semicontinuous stirred tank reactor.•Propionic accumulation was the key ...factor in the methanogenic phase inhibition.•Total period of 140 days was required to start-up and stabilization the process.•During the stable period the methane productivity was 0.34 LCH4/LRd at 40-d HRT.
In this work, the start-up and stabilization stages of mesophilic anaerobic co-digestion of 2POMW and CM in a semi-continuously fed stirred tank reactor (SSTR) were analyzed. Volatile fatty acids (VFAs) were monitored and used as the main control parameter for the start-up and stabilization stages, as well as to evaluate the potential inhibition episodes. The results showed that accumulation of propionic acid was the key factor in the inhibition of the methanogenic phase, leading to process imbalance. To avoid the problems associated with inhibition by high VFA concentrations, several reinoculations were performed using a suitable inoculum adapted to VFA degradation. The start-up phase was carried out in batch conditions for 97 days, reaching a final concentration of propionic acid of 12.77 mg/L. From that moment, the reactor was fed in a semi-continuous mode with a hydraulic retention time (HRT) of 40 days. A total period of 140 days was required to achieve a stable performance of the reactor with a methane productivity of 0.34 LCH4/LRd.
•HRT of 1.2days led to the maximum hydrogen production of 3.67L H2/L reactor/day.•Maximum specific hydrogen production was 33.8mL H2/gVSadded (1.2-days HRT).•Two indirect parameters NSC and ASC ...determine the balance in hydrolytic phase.•At HRTs between 2.9 and 1.2-days the system operates stable.•Failure of the hydrolytic phase occurs at HRTs lower than 1.2days.
Effect of hydraulic retention time (HRT) on bio-hydrogen production from co-digestion of organic fraction of municipal solid waste (OFMSW) and mixed sludge (MS) in dry thermophilic conditions (55°C and 20% total solids) was investigated. A decreasing sequence of six HRTs, from 2.9 to 0.8-days, was performed to evaluate the stability of the system and the influence of HRT on the organic matter solubilization, the daily hydrogen production (HP) and the specific hydrogen production (SHP).
Best results were obtained operating at 1.2-days HRT: HP of 3.67L H2/Lreactor/day, SHP of 33.8mL H2/gVSadded and hydrogen percentage in biogas of 52.4%. However, HRTs lower than 1.2-days induce failure in the system due to an unbalance of the hydrolytic phase. This fact was corroborated through the evaluation of two indirect parameters, “non-solubilized carbon” (NSC) and “acidogenic substrate as carbon” (ASC), and the relationships of NSC/TOC and ASC/TOC.
The work presented here concerns the start-up and stabilization stages of a Continuous Stirred Tank Reactor (CSTR) semicontinuously fed for the treatment of the Organic Fraction of Municipal Solid ...Waste (OFMSW) through anaerobic digestion at thermophilic temperature range (55
°C) and dry conditions (30% Total Solids). The procedure reported involves two novel aspects with respect to other start-up and stabilization protocols reported in the literature. The novel aspects concern the adaptation of the inoculum to both the operating conditions (thermophilic and dry) and to the type of waste by employing a modified SEBAC (Sequential Batch Anaerobic Composting) system and, secondly, the direct start-up of the process in a thermophilic temperature regime and feeding of the system from the first day of operation. In this way a significant reduction in the start-up time and stabilization is achieved i.e. 110
days in comparison to 250
days for the processes reported by other authors for the same type of waste and digester. The system presents suitable operational conditions to stabilize the reactor at SRT of 35
days, with a maximum biogas production of 1.944 LR/L·d with a CH
4 and CO
2 percentage of 25.27% and 68.15%, respectively.
► Methane generation may be modeled by means of modified product generation model of Romero García (1991). ► Organic matter content and particle size influence the kinetic parameters. ► Higher ...organic matter content and lower particle size enhance the biomethanization.
The influence of particle size and organic matter content of organic fraction of municipal solid waste (OFMSW) in the overall kinetics of dry (30% total solids) thermophilic (55°C) anaerobic digestion have been studied in a semi-continuous stirred tank reactor (SSTR). Two types of wastes were used: synthetic OFMSW (average particle size of 1mm; 0.71g Volatile Solids/g waste), and OFMSW coming from a composting full scale plant (average particle size of 30mm; 0.16g Volatile Solids/g waste).
A modification of a widely-validated product-generation kinetic model has been proposed. Results obtained from the modified-model parameterization at steady-state (that include new kinetic parameters as K, YpMAX and θMIN) indicate that the features of the feedstock strongly influence the kinetics of the process. The overall specific growth rate of microorganisms (μmax) with synthetic OFMSW is 43% higher compared to OFMSW coming from a composting full scale plant: 0.238d−1 (K=1.391d−1; YpMAX=1.167L CH4/gDOCc; θMIN=7.924 days) vs. 0.135d−1 (K=1.282d−1; YpMAX=1.150L CH4/gDOCc; θMIN=9.997 days) respectively.
Finally, it could be emphasized that the validation of proposed modified-model has been performed successfully by means of the simulation of non-steady state data for the different SRTs tested with each waste.
In this paper, a destabilization episode in a semicontinuous dry thermophilic acidogenic reactor was induced. The reactor was fed with different mixtures of organic fraction of municipal solid waste ...(OFMSW) and food waste (FW). The aim was to determinate the effect of the organic loading rate (OLR) and cosubstrate ratio on biohydrogen production by dark fermentation. OLR was increased from 21.0 to 88.8 g TVS/L/day testing three mixture ratios (OFMSW:FW) from 80:20 to 50:50 and four hydraulic retention times (HRTs; 6.6, 4.4, 2.4, and 1.9 days). Results have shown that an increment in the OLR (from 21.0 to 59.8 g TVS/L/day) and FW proportion (from 80:20 to 50:50) improves the yield process in terms of solubilized organic matter. However, from 50:50 ratio combined with OLRs higher than 70.3 g TVS/L/day and HRTs lower than 4.4 days showed a clear destabilization episode due to an imbalance of the hydrolytic phase. This fact has been corroborated by the values of two indirect parameters, “nonsolubilized carbon” and “acidogenic substrate as carbon”.
The influence of the soluble substrates over the anaerobic processes has been extensively investigated, but little is known about the effects of particulate substrate. The biodegradation of these ...substrates starts with the hydrolytic step, this process is slower than the other ones involved in the biodegradation of particulate substrates and usually becomes the rate-limiting step. This study investigate the effect of the initial total solids (TS) concentration on the anaerobic co-digestion of two slowly biodegradable organic substrates. The wastes mixtures were prepared at different dilutions in the range from 10% to 28% TS. From these experiments it was observed that as TS concentration increased, the methane production decreased. These results were modelled and it was observed that neither hydrolysis nor fermentation stages controlled the methane production rate. Being a substrate inhibition event experienced at the methanogenic stage the responsible of the lower methane production when operating at high TS concentrations.
•Anaerobic digestion stages at different solid concentrations were studied.•Hydrolysis presented the lower rate, 0.70 d−1.•Methanogenic rate was slightly higher than that of the hydrolysis, 0.75 d−1.•High solids concentrations inhibit methanogenic stage, becoming the limiting stage.
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