1,721,031 research outputs found
Factor-based assessment of continuous bio-H2 production from cheese whey
Get PDFDespite having been widely investigated, dark fermentative H2 production from organic residues is still limited by process-related issues which may hamper the perspectives of full-scale process implementation. Such constraints are mainly due to the process complexity, which is largely affected by multiple and often mutually interacting factors. In the present work, the results of continuous fermentative H2 production experiments using synthetic cheese whey as the input substrate were used to gain detailed knowledge of the process features and identify suitable and critical operating conditions. Specifically, innovative process interpretation involved a combination of analytical characterization of the fermentation broth, mass balance calculations and statistical methods (correlation and principal component analyses) to derive systematic considerations for process characterization and scale-up. The metabolic products mainly included acetate and butyrate, which however were likely to derive (in different proportions depending on the operating conditions) from both hydrogenogenic and competing pathways. For some tests, lactate and succinate were also found to have been formed. It was observed that the main features of the process (H2 yield and rate, stability condition) were correlated with the operational and analytical parameters. The first three principal components identified by the statistical analysis were able to account for: 1) the effect of retention time and total metabolites produced; 2) biogas (H2 and CO2) generation, butyrate production and stability condition; and 3) organic loading rate and propionate production. The results suggested that the main features of hydrogenogenic fermentation can be described by a reduced set of factors that may be usefully adopted for both process monitoring and prediction purposes
Anaerobic digestion of biodegradable plastics: analysis in terms of process conditions and overall performance
No full textIn the present study commercial Polylactic Acid-based disposable cups and plates available on the market were selected for lab scale anaerobic degradability tests. The experiments were carried out under mesophilic and thermophilic conditions at different food to microorganisms (F/M) ratios and test material size, and the specific biogas production and associated kinetics were evaluated. Maximum biogas production was comparable for almost all the experimental runs and only test material size reduction appeared to result in higher yields. Temperature increase influenced particularly the biodegradation degree, ranging between 93 and 100% for thermophilic runs, and the process kinetics resulting in a reduction of residence time by 70%. The specific methane yield ranged from 455 to 545 Nml/gVSfood and from 430 to 505 Nml/gVSfood under mesophilic and thermophilic conditions respectivel
Analysis of parameter effects on fermentative H2 production from cheese whey
No full textCheese whey (CW) is one of the most abundant by-products of cheese manufacturing, with~9.0 kg of CW beinggenerated perkg of cheese produced. Among the different optionsfor CW management, anaerobic digestion can be regarded as one of the most promising, being able to reduce the organic load of CW while harversting its energy content. Recently, an increasing attention has specifically been paid to dark fermentation of CWaimedatbiological H2production. In the present study, the effect of pH conditions and inoculum addition on H2production from CW was investigated under continuously stirred batch conditions by designing the experiments according to the principles of a factorial design. According to this approach, the set-point of the pH values of the system and the amount of inoculum added to CW werevaried over fourvalues. As the inoculum, the aerobic sludge from a wastewater treatment plant was used, after heat-shocking at 110 °C for 30 minutes so as to harvest the hydrogenogenic biomass. Process performance was evaluated in terms of H2production and substrate conversion efficiency, by twoprocess indicators: 1) amount and composition of the produced biogas evolution of the metabolic pathways, 2) evolution of substrate degradation, expressed as the removal total organic carbonand carbohydrates
Continuous fermentative hydrogen production from cheese whey – new insights into process stability
No full textContinuous dark fermentation experiments for hydrogen production from synthetic cheese whey were conducted at different HRTs and OLRs. The study mainly aimed at developing a novel criterion to quantitatively assess stability and relating it to the evolution of microbial pathways and associated metabolic products. For HRTs = 6–8 h and OLRs = 65–97.5 g TOC/(L·d), the best hydrogen generation performance was attained, yielding 42–50 L H2/kg TOC. Instead of using a stability index for the entire test length, accounting for the fluctuations of hydrogen production over 1-HRT periods (dynamic stability index) provided a more accurate assessment of process stability showing a clear correlation with the hydrogen yield. The analysis of the metabolic reactions provided evidence of a competition among acidogenic, hydrogen-consuming and hydrogen-neutral microbial species. This explained the lower process performance in comparison to the theoretical yield expected, pointing out at the need for further investigation on suitable strategies to effectively inhibit undesired metabolic pathways
Agroindustrial residues utilization as a feedstock for biorefineries
No full textIn order to reduce the amount of landfilled waste and to attain the valorization of the material and energy content of organic wastes, the integrated approach based on the biorefinery concept appearsto be the most promising in terms of potential for resource recovery, technical feasibility as well as overall environmental and economic benefits. Biorefineries are aimed at converting biomass into biofuels and bio-based products, thus they can contribute to reducing the overall consumption of fossil fuels and minimizing the global carbon footprint of both energy and material production. Compared to conventional refineries, the bio-basedconfiguration allows to produce gaseous/liquid fuels, plastics and other valuable chemicalsstarting from organic biomass instead of hydrocarbons. Irrespectiveof the specific outputs, microbial fermentation, possibly controlled so as to increase the process yields and the products quality, represents the core process in the biorefinery concept. As for the biomass to be treated, an intense debate has grown over the utilization of food crops for biofuels and biomaterials production since the end of 1900, when the opponents stated that such a practice involve turning food for the poor into fuel for the rich, worsen soil erosion and may result into marginal replacement of fossil fuels. A strategy to overcome the food vs. fuel dilemma may involvethe utilization of residual biomass, such as the biodegradable fraction of municipal waste and agro-industrial residues, as a feedstock for biorefineries. The present paper presents an overview of the most interesting metabolic pathways for liquid and gaseous biofuels. Conceptual schemes for integrating different fermentation processes aimed at biofuels and bioplastics production will also be shown
Anaerobic co-digestion of single-use bioplastics and food waste
No full textThe present paper aims at describing the behaviour of disposable bioplastic items undergoing lab-scale anaerobic degradability tests. Single-use PLA and Mater-Bi products were selected and tested under thermophilic conditions at different food to microorganisms (F/M) ratios (0.5 and 1 gVS/gVS) and in co-digestion with synthetic food waste (FW). The tests were evaluated in terms of specific biogas production and associated kinetics. All PLA runs showed virtually complete biodegradability, with a biogas yield of 1550-1670 Nml/gTOC. On the other hand, Mater-Bi cup’s yields ranged between 570 and 640 Nml/gTOC but doubled to 1300 Nml/gTOC with the addition of FW
Fermentative hydrogen production from cheese whey with in-line, concentration gradient-driven butyric acid extraction
No full textHydrogen (H2) generation from cheese whey with simultaneous production and extraction
of volatile fatty acids (VFAs) was studied in UASB reactors at two temperatures (20 and
35 C) and pH values (5.0 and 4.5). The extraction module, installed through a recirculation
loop, was a silicone tube coil submerged in water, which allows concentration-driven
extraction of undissociated VFAs. Operating conditions were selected as a compromise
for the recovery of both H2 and VFAs. Batch experiments showed a higher yield (0.9 mol H2
mol 1 glucoseeq.) at 35 C and pH 5.0, regardless of the presence of the extraction module,
whereas lower yields were obtained at pH 4.5 and 20 C (0.5 and 0.3 mol H2 mol 1 glucoseeq., respectively). VFAs crossed the silicone membrane, with a strong preference for butyric
over propionic and acetic acid due to its higher hydrophobicity. Sugars, lactic acid and
nutrients were retained, resulting in an extracted solution of up to 2.5 g L 1 butyric acid
with more than 90% purity. Continuous experiment confirmed those results, with production
rates up to 2.0 L H2 L 1 d 1 and butyric acid extraction both in-line (from the UASB
recirculation) and off-line (from the UASB effluent). In-line VFA extraction can reduce the
operating costs of fermentation, facilitating downstream processing for the recovery of
marketable VFAs without affecting the H2 production
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