From Organic Wastes and Hydrocarbons Pollutants to Polyhydroxyalkanoates: Bioconversion by Terrestrial and Marine Bacteria

The use of fossil-based plastics has become unsustainable because of the polluting production processes, difficulties for waste management sectors, and high environmental impact. Polyhydroxyalkanoates (PHA) are bio-based biodegradable polymers derived from renewable resources and synthesized by bacteria as intracellular energy and carbon storage materials under nutrients or oxygen limitation and through the optimization of cultivation conditions with both pure and mixed culture systems. The PHA properties are affected by the same principles of oil-derived polyolefins, with a broad range of compositions, due to the incorporation of different monomers into the polymer matrix. As a consequence, the properties of such materials are represented by a broad range depending on tunable PHA composition. Producing waste-derived PHA is technically feasible with mixed microbial cultures (MMC), since no sterilization is required; this technology may represent a solution for waste treatment and valorization, and it has recently been developed at the pilot scale level with different process configurations where aerobic microorganisms are usually subjected to a dynamic feeding regime for their selection and to a high organic load for the intracellular accumulation of PHA. In this review, we report on studies on terrestrial and marine bacteria PHA-producers. The available knowledge on PHA production from the use of different kinds of organic wastes, and otherwise, petroleum-polluted natural matrices coupling bioremediation treatment has been explored. The advancements in these areas have been significant; they generally concern the terrestrial environment, where pilot and industrial processes are already established. Recently, marine bacteria have also offered interesting perspectives due to their advantageous effects on production practices, which they can relieve several constraints. Studies on the use of hydrocarbons as carbon sources offer evidence for the feasibility of the bioconversion of fossil-derived plastics into bioplastics

Hydrogen and Methane production from OFMSW and sewage sludge by two phases anaerobic codigestion

In this paper a two-phase anaerobic codigestion of organic fraction of municipal solid waste and sewage sludge has been investigated experimentally. The aim of this work is to verify the feasibility and the performance of the process for the hydrogen and methane production. The experimental was carried out at pilot scale using two stirred reactors both maintained at thermophilic temperature (55°C) and fed semicontinuously with separate collected biowaste and sewage sludge. Nor chemicals neither recirculation were used to control the pH in first phase. The study lasted 50 days in which there were no evidences of any instability in the process.It was confirmed the possibility to obtain a stable hydrogen production with a specific average hydrogen production of 40 l per kg of total volatile solid (TVS) fed and a specific biogas production in the second phase of 0.32 m3per kgTVS fed.The biogas produced has a composition characterized by a stable presence of hydrogen over 5%. Therefore, the biogas produced meets the composition characteristic of biohythane

Hydrogen and Methane production from OFMSW and sewage sludge by two phases anaerobic codigestion

In this paper a two-phase anaerobic codigestion of organic fraction of municipal solid waste and sewage sludge has been investigated experimentally. The aim of this work is to verify the feasibility and the performance of the process for the hydrogen and methane production. The experimental was carried out at pilot scale using two stirred reactors both maintained at thermophilic temperature (55°C) and fed semicontinuously with separate collected biowaste and sewage sludge. Nor chemicals neither recirculation were used to control the pH in first phase. The study lasted 50 days in which there were no evidences of any instability in the process.It was confirmed the possibility to obtain a stable hydrogen production with a specific average hydrogen production of 40 l per kg of total volatile solid (TVS) fed and a specific biogas production in the second phase of 0.32 m3per kgTVS fed.The biogas produced has a composition characterized by a stable presence of hydrogen over 5%. Therefore, the biogas produced meets the composition characteristic of biohythane

Thermophilic two-phase anaerobic digestion of source-sorted organic fraction of municipal solid waste for bio-hythane production: effect of recirculation sludge on process stability and microbiology over a long-term pilot-scale experience

A two-stage thermophilic anaerobic digestion process for the concurrent production of hydrogen and methane through the treatment of the source-sorted organic fraction of municipal solid waste was carried out over a long-term pilot scale experience. Two continuously stirred tank reactors were operated for about 1 year. The results showed that stable production of bio-hythane without inoculum treatment could be obtained. The pH of the dark fermentation reactor was maintained in the optimal range for hydrogen-producing bacteria activity through sludge recirculation from a methanogenic reactor. An average specific bio-hythane production of 0.65 m3 per kg of volatile solids fed was achieved when the recirculation flow was controlled through an evaporation unit in order to avoid inhibition problems for both microbial communities. Microbial analysis indicated that dominant bacterial species in the dark fermentation reactor are related to the Lactobacillus family, while the population of the methanogenic reactor was mainly composed of Defluviitoga tunisiensis. The archaeal community of the methanogenic reactor shifted, moving from Methanothermobacter-like to Methanobacteriales and Methanosarcinales, the latter found also in the dark fermentation reactor when a considerable methane production was detected

Thermophilic two-phase anaerobic digestion of source-sorted organic fraction of municipal solid waste for bio-hythane production: effect of recirculation sludge on process stability and microbiology over a long-term pilot-scale experience

A two-stage thermophilic anaerobic digestion process for the concurrent production of hydrogen and methane through the treatment of the source-sorted organic fraction of municipal solid waste was carried out over a long-term pilot scale experience. Two continuously stirred tank reactors were operated for about 1 year. The results showed that stable production of bio-hythane without inoculum treatment could be obtained. The pH of the dark fermentation reactor was maintained in the optimal range for hydrogen-producing bacteria activity through sludge recirculation from a methanogenic reactor. An average specific bio-hythane production of 0.65 m3 per kg of volatile solids fed was achieved when the recirculation flow was controlled through an evaporation unit in order to avoid inhibition problems for both microbial communities. Microbial analysis indicated that dominant bacterial species in the dark fermentation reactor are related to the Lactobacillus family, while the population of the methanogenic reactor was mainly composed of Defluviitoga tunisiensis. The archaeal community of the methanogenic reactor shifted, moving from Methanothermobacter-like to Methanobacteriales and Methanosarcinales, the latter found also in the dark fermentation reactor when a considerable methane production was detected

Hydrogen and Methane production from OFMSW and sewage sludge by two phases anaerobic codigestion.

In this paper a two-phase anaerobic codigestion of organic fraction of municipal solid waste and sewage sludge has been investigated experimentally. The aim of this work is to verify the feasibility and the performance of the process for the hydrogen and methane production. The experimental was carried out at pilot scale using two stirred reactors both maintained at thermophilic temperature (55\ub0C) and fed semicontinuously with separate collected biowaste and sewage sludge. Nor chemicals neither recirculation were used to control the pH in first phase. The study lasted 50 days in which there were no evidences of any instability in the process.It was confirmed the possibility to obtain a stable hydrogen production with a specific average hydrogen production of 40 l per kg of total volatile solid (TVS) fed and a specific biogas production in the second phase of 0.32 m3per kgTVS fed.The biogas produced has a composition characterized by a stable presence of hydrogen over 5%. Therefore, the biogas produced meets the composition characteristic of biohythane

Pilot scale comparison of single and double-stage thermophilic anaerobic digestion of food waste

This study compared the performances of single and two-stage anaerobic digestion processes of food waste. The processes were monitored by taking into account both the steady state process performances and the transient conditions. In addition to a conventional univariate analysis, a multivariate analysis to increase the validity of the results of the comparison study was also performed. The transient states caused peaks due to a high organic loading rate, simulating possible overloading events and the recovery capacity of both processes (resilience). The specific gas production of the methanogenic reactor of the two-stage process was higher (0.88 m3 biogas/kgVS) than for the single-stage process (0.75 m3 biogas/kgVS). This finding was related to the increase in the removal efficiency (of 17%). Considering the pilot-scale results, a comparison of mass and energy balance, and costs (assuming the upgrading of the biogas produced) was also discussed

Changes in microbial community during hydrogen and methane production in two-stage thermophilic anaerobic co-digestion process from biowaste

In this paper, the microbial community in a two-phase thermophilic anaerobic co-digestion process was investigated for its role in hydrogen and methane production, treating waste activated sludge and treating the organic fraction of municipal solid waste. In the acidogenic phase, in which hydrogen is produced, Clostridium sp. clusters represented 76% of total Firmicutes. When feeding the acidogenic effluent into the methanogenic reactors, these acidic conditions negatively influenced methanogenic microorganisms: Methanosaeta sp., (Methanobacteriales, Methanomicrobiales, Methanococcales) decreased by 75%, 50%, 38% and 52%, respectively. At the same time, methanogenic digestion lowered the numbers of Clostridium sp. clusters due to both pH increasing and substrate reduction, and an increase in both Firmicutes genera (non Clostridium) and methanogenic microorganisms, especially Methanosaeta sp. (208%). This was in accordance with the observed decrease in acetic (98%) and butyric (100%) acid contents. To ensure the activity of the acetate-utilizing methanogens (AUM) and the acetogens, high ratios of H-2-utilizing methanogens (HUM)/AUM (3.6) were required. (C) 2016 Elsevier Ltd. All rights reserved

Anaerobic Codigestion of Algal Material with Two Different Co-Substrates, Biowaste and Sewage Sludge: Process Yields and Behaviour Comparison

The problem of algae disposing, especially in coastal and lagoon areas where eutrophication occurs in all its gravity, makes necessary to seek appropriate methods for the treatment of this organic material. The anaerobic digestion for the treatment of this biomass is currently of considerable interest, due the low environmental impact and the energy recovery at the same time. After a pre-screening analysis, it is possible to say that algal biomass completely meets the requirements needed for anaerobic digestion process. In this paper are reported the feasibility results of the anaerobic codigestion treatment of algal biomass. Pilot-scale continuous stirred tank reactors with working volumes of 3 and 1 m3 were used, and full-scale digestion operational conditions were applied. Anaerobic digestion process with algae and organic fraction of municipal solid waste was inhibited by high concentration of hydrogen sulfide. This process was feasible if the algae content in the feeding mixture was equal to 10 % (in terms of solids) and with addition of iron powder; on the other hand the co-treatment of sewage sludge appeared very interesting, in fact the biogas production rate increased from 0.4 to 0.8 m3/m3reactord and methane content reached 71 %.The problem of algae disposing, especially in coastal and lagoon areas where eutrophication occurs in all its gravity, makes necessary to seek appropriate methods for the treatment of this organic material. The anaerobic digestion for the treatment of this biomass is currently of considerable interest, due the low environmental impact and the energy recovery at the same time. After a pre-screening analysis, it is possible to say that algal biomass completely meets the requirements needed for anaerobic digestion process. In this paper are reported the feasibility results of the anaerobic codigestion treatment of algal biomass. Pilot-scale continuous stirred tank reactors with working volumes of 3 and 1 m(3) were used, and full-scale digestion operational conditions were applied. Anaerobic digestion process with algae and organic fraction of municipal solid waste was inhibited by high concentration of hydrogen sulfide. This process was feasible if the algae content in the feeding mixture was equal to 10 % ( in terms of solids) and with addition of iron powder; on the other hand the co-treatment of sewage sludge appeared very interesting, in fact the biogas production rate increased from 0.4 to 0.8 m(3)/m(reactor)(3)d and methane content reached 71 %

FIRST- AND SECOND-GENERATION VALORISATION OF WASTES AND RESIDUES OCCURRING IN THE FOOD SUPPLY CHAIN

Despite the high potential to increase sustainability of food systems, wastes and by-products occurring in the food supply chain are currently only partially valorised at different value-added levels. First-generation valorisation strategies that aim at utilisation of complete material streams for production of animal feed, energy, compost and/or specific consumer applications are already widely implemented and experience further dissemination and/or development (e.g. biohydrogen/biohythane production) – either in the form of single processes or as part of cascade utilisations. Second-generation valorisation strategies comprise various forms of fractionised utilisation of material streams. They rely on integration of adapted recovery and conversion procedures for specific components in order to obtain sequentially different classes of products, e.g. fine chemicals, commodity products and biofuels. Such advanced strategies are particularly suitable for wastes and by-products occurring during industrial food processing. Valorisation of food by-products for functional food is an emerging trend