1,720,981 research outputs found
Economic Evaluation of a Large-Scale PHBV Production Facility: Impact of Polymer Content on the Final Selling Price
No full textPoly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biodegradable polymer with excellent thermal and mechanical properties comparable to fossil-based plastics. Scaling up the production of this polymer could provide a viable solution for reducing the use of fossil-based materials. However, its current production capacities are limited, with only a few facilities implementing the process at pilot or semi-industrial scales. The primary challenge lies in the high production costs, with 40% of the expenses attributed to the feedstock used for fermentation. Additionally, the energy required for sterilization in processes using pure methanotrophic cultures further reduces its economic viability. In this study, the economic aspects of the PHBV production process were assessed at an industrial level (100,000 t/y PHBV), using cheap and renewable substrates such as valeric acid and methane. A mixed methanotrophic consortium was used to reduce the need for sterility. The techno-economic analysis was based on estimating both fixed investment and operating costs. Then, a sensitivity analysis was performed to analyse the effect that the polymer content has on the final selling price: the initial biomass concentration was set to 30 g L-1 and the PHBV content was considered to be 20, 30, 40, 50 and 70% wt on a dry weight basis. The results revealed that increasing the polymer content beyond 40% wt led to a more competitive PHBV selling price, thus opening significant market opportunities
Exploring 1,3-Dioxolane Extraction of Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from Methylocystis hirsuta and Mixed Methanotrophic Strain: Effect of Biomass-to-Solvent Ratio and Extraction Time
No full textThe increasing need for biodegradable polymers demands efficient and environmentally friendly extraction methods. In this study, a simple and sustainable method for extracting polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHB-co-HV) from Methylocystis hirsuta and a mixed methanotrophic consortium with different biopolymer contents was presented. The extraction of biopolymers with 1,3-dioxolane was initially investigated by varying the biomass-to-solvent ratio (i.e., 1:2 w v−1, 1:4 w v−1, 1:6 w v−1, 1:8 w v−1 and 1:10 w v−1) and extraction time (6, 8 and 10 h) at the boiling point of the solvent and atmospheric pressure. Based on the results of the preliminary tests, and only for the most efficient biomass-to-solvent ratio, the extraction kinetics were also studied over a time interval ranging from 30 min to 6 h. For Methylocystis hirsuta, the investigation of the extraction time showed that the maximum extraction was reached after 30 min, with recovery yields of 87% and 75% and purities of 98.7% and 94% for PHB and PHB-co-HV, respectively. Similarly, the extraction of PHB and PHB-co-HV from a mixed methanotrophic strain yielded 88% w w−1 and 70% w w−1 recovery, respectively, with 98% w w−1 purity, at a biomass-to-solvent ratio of 6 in 30 min
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Polyhydroxyalkanoate recovery overview: properties, characterizations, and extraction strategies
No full textDue to their excellent properties, polyhydroxyalkanoates are gaining increasing recognition in the biodegradable polymer market. These biogenic polyesters are characterized by high biodegradability in multiple environments, overcoming the limitation of composting plants only and their versatility in production. The most consolidated techniques in the literature or the reference legislation for the physical, chemical and mechanical characterisation of the final product are reported since its usability on the market is still linked to its quality, including the biodegradability certificate. This versatility makes polyhydroxyalkanoates a promising prospect with the potential to replace fossil-based thermoplastics sustainably. This review analyses and compares the physical, chemical and mechanical properties of poly-β-hydroxybutyrate and poly-β-hydroxybutyrate-co-β-hydroxyvalerate, indicating their current limitations and strengths. In particular, the copolymer is characterised by better performance in terms of crystallinity, hardness and workability. However, the knowledge in this area is still in its infancy, and the selling prices are too high (9–18 $ kg−1). An analysis of the main extraction techniques, established and in development, is also included. Solvent extraction is currently the most widely used method due to its efficiency and final product quality. In this context, the extraction phase of the biopolymer production process remains a major challenge due to its high costs and the need to use non-halogenated toxic solvents to improve the production of good-quality bioplastics. The review also discusses all fundamental parameters for optimising the process, such as solubility and temperature
Assessing the performance of synthetic co-cultures during the conversion of methane into Poly(3-hydroxybutyrate)
No full textSynthetic co-cultures can enhance pollutant bioconversion performance through synergistic effects among co-existing species. In this study, the potential of Methylocystis hirsuta and Methylocystis parvus to support poly(3-hydroxybutyrate) (PHB) production in co-cultivation with Rhodococcus opacus and Pseudomonas putida under a CH4:O2 atmosphere was assessed batchwise. The metabolic activation of almost all co-cultures studied was faster than that of single strain cultures, bringing higher methane and oxygen consumption rates. Higher PHB yields were achieved when coupling M. hirsuta with R. opacus (63 % w w−1) or with R. opacus and P. putida (64.4 % w w−1) compared to M. hirsuta alone (38.5 % w w−1). Interestingly, the combination of both R. opacus and P. putida with M. parvus reduced PHB accumulation to 42.2 % w w−1 compared to the content observed in M. parvus monocultures (62.2 % w w−1) and M parvus + R. opacus co-cultures (66.6 % w w−1)
Solubility of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in sustainable and green solvents: Effect of HV content and comparison between experimental results and theoretical prediction
No full textFor the first time, a quantitative analysis of the solubility of poly-3hydroxybutyrrate-co-3hydroxyvalerate (PHBV) in green solvents is proposed. The solubility of two commercial co-polymers, with hydroxyvalerate (HV) contents of 8 %mol and 12 %mol, in 1,3-dioxolane, dimethyl carbonate and butyl acetate was experimentally determined using chloroform as the benchmark and water as the control. The results showed a direct correlation between solubility and temperature, with a maximum at the boiling point of the solvent. For PHBV with an HV content of 8 %mol, solubilities of 265 mg mL−1 for 1,3-dioxolane and dimethyl carbonate and 274 mg mL−1 for butyl acetate were measured; for PHBV with an HV content of 12 %mol, solubilities of 225 mg mL−1, 197 mg mL−1 and 137 mg mL−1 for 1,3-dioxolane, dimethyl carbonate and butyl acetate were measured, respectively. Following Hansen's theory, the PHBV solubility sphere was defined to predict the solubility of the co-polymers in solvents qualitatively. The validation of the sphere was performed by the experimental results herein obtained
Techno-economic assessment of biopolymer production from methane and volatile fatty acids: effect of the reactor size and biomass concentration on the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) selling price
No full textPoly(3-hydroxybutyrate-co-3-hydroxyvalerate) is a biobased and biodegradable polymer that could efficiently replace fossil-based plastics. However, its widespread deployment is slowed down by the high production cost. In this work, the techno-economic assessment of the process for producing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from low-cost substrates, such as methane and valeric acid derived from the anaerobic digestion of organic wastes, is proposed. Several strategies for cost abatement, such as the use of a mixed consortium and a line for reagent recycling during downstream, were adopted. Different scenarios in terms of production, from 100 to 100,000 t/y, were analysed, and, for each case, the effect of the reactor volume (small, medium and large size) on the selling price was assessed. In addition, the effect of biomass concentration was also considered. Results show that the selling price of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is minimum for a production plant with 100,000 t/y capacity, accounting for 18.4 €/kg, and highly influenced by the biomass concentration since it can be reduced up to 8.6 €/kg by increasing the total suspended solids from 5 to 30 g/L, This adjustment aligns the breakeven point of PHBV with the reported average commercial price
Study of the vortex dynamics as a function of frequency in the microwave range
No full textThe frequency dependence of the transport properties provides noticeable informations on the vortex matter in superconductors. In particular, low (<100 MHz) and high (of order 10 GHz) frequency response give different informations on the vortex dynamics: while at low frequency large distance motion of vortices is predominant, at higher frequencies vortices tend to oscillate around their equilibrium positions. Few reports have been presented in the past related to the study of the intermediate frequency regime, and to the evolution of one regime into the other. We present here an experimental study as a function of frequency, in the range 1-20 GHz, over a continuous frequency spectrum (Corbino disc technique), in presence of an applied magnetic field. Data are presented for both YBa2Cu3O7-delta and MgB2 superconductors. We also discuss the data as a function of frequency and show to what extent existing theories are able to fit the measured data. (C) 2004 Elsevier B.V. All rights reserved
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