Biohydrogen production from cheese factory waste

In questo studio è stata valutata la possibilità di produrre H2 da reflui di caseificio. In particolare, è stato utilizzato il permeato di scotta che è il residuo del recupero delle sieroproteine, mediante ultrafiltrazione, della scotta che, a sua volta, e il residuo della produzione della ricotta da siero di latte. Questo liquido è ancora ricco di lattosio (51 g L-1) da cui si può ricavare H2 mediante la fermentazione al buio (dark fermentation, DF). La DF è regolata da molti parametri e presenta ancora dei punti oscuri. L’attenzione è stata rivolta, in particolare, all’effetto che il pH ha sulla produzione di H2, dei metaboliti prodotti (acidi grassi volatili, etanolo e acido lattico) e sulla popolazione microbica coinvolta nella DF, mediante l’utilizzo della tecnica dell’high-throughput sequencing (HTS), in un sistema non tamponato. La produzione di H2 è stata nettamente influenzata dal pH iniziale tanto che essa è stata molto più alta (+31%) nei reattori a pH alcalino (8 - 10) che nei reattori a pH < 6. Lo studio della comunità microbica ha indicato che la manipolazione del pH iniziale ha influenzato i rapporti interspecifici delle popolazioni presenti all’interno dei reattori. Il pH alcalino ha favorito la proliferazione di un genere in particolare, il Trichococcus. Sebbene questo genere non produca direttamente H2, la sua proliferazione e, dunque, la sua attività metabolica nella fase immediatamente precedente alla DF propriamente detta, ha creato le condizioni ideali per l’attività dei clostridi (produttori di H2) che hanno iniziato a produrre H2 quando il pH era sceso a 5.4. I clostridi sono stati più attivi nei reattori con pH iniziale alcalino, ovvero, dove Trichococcus aveva maggiormente proliferato.In this study, the H2 production from dairy waste was evaluated. Scotta permeate was used as substrate. Scotta permeate is the residue of the recovery of the whey proteins, by means of ultrafiltration, from scotta which is the residue of the production of ricotta from cheese whey. This liquid is still rich in lactose (51 g L-1) and suitable for H2 production in dark fermentation (DF). DF is regulated by many parameters and it has still dark sides. The attention was focused, in particular, on the effect of pH on H2 production, on metabolites production (volatile fatty acids, ethanol and lactic acid) and on the microbial community involved in the DF, by means of high-throughput sequencing (HTS), in an unbuffered system. The production of H2 was strongly influenced by the initial pH: it was much higher (+ 31%) in the reactors at alkaline pH (8 - 10) in comparison with the reactors at pH <6. The study of the microbial community indicated that the manipulation of the initial pH influenced the interspecific relationships of the populations resident in the reactors. The alkaline pH favored the proliferation of one genus in particular, Trichococcus. Although this genus is not an hydrogen-producer, its proliferation and, therefore, its metabolic activity in the phase immediately preceding the DF, has created the optimal conditions for the activity of the clostridia (H2 producers) who have started to produce H2 when the pH had dropped to 5.4. The clostridia were more active in reactors with initial alkaline pH, that is, where Trichococcus were most abundant

Initial pH influences in-batch hydrogen production from scotta permeate

We studied the influence of initial pH on hydrogen (H2) production using permeate from scotta (a partially deproteinized cheese whey from ricotta production) as substrate (51 g L\ue2\u88\u921lactose). Dark fermentation was carried out at 35 \uc2\ub0C in laboratory batch reactors, in an unbuffered system. Hydrogen production and metabolite (volatile fatty acids, ethanol, and lactic acid) evolution during a 96-h period were monitored in reactors with initial pH varying in the range 4\ue2\u80\u9310. In all reactors, H2production started only when pH fell below 6. However, it was much higher (+31%) in the reactors with initial alkaline pH. We conclude that H2production occurs only at acidic pH values, but initial alkaline pH values increase the overall H2production in dark fermentation of lactose-rich substrates

BIOGAS PRODUCTION FROM BIODEGRADABLE BIOPLASTICS

In this study, the potential for biogas production from biodegradable bioplastics was evaluated. Mater-Bi\uae (a family of maizestarch based flexible films) and PLA (PolyLactic Acid; a rigid, polylactide-based, polymer) bioplastics were digested in laboratory batch reactors, alone or in co-digestion with pig slurry or scotta (partially deproteinized cheese whey), at 35\ub0C or 55\ub0C. Methane (CH4) and hydrogen (H2) production were monitored during the incubation period. Maximum CH4 (Mmax) or H2 (Hmax) production per reactor, potential CH4 (BMP) or H2 (BHP) production g-1 volatile solids (VS), and residual VS in the digestates were determined. Methane was produced when bioplastics were digested alone or with pig slurry, whereas H2 was produced only in co-digestion with scotta. Mmax, BMP, Hmax and BHP were on average higher at 55\ub0C than at 35\ub0C (+69%, +158%, +51% and +45%, respectively). At 35\ub0C, in monodigestion, small amounts of CH4 (33 mL g-1 VS) were produced with Mater-Bi\uae only. At 55\ub0C, the BMP for Mater-Bi\uae and for PLA were equal to 113 mL and 282 mL CH4 g-1 VS, respectively. Monodigestion of Mater- Bi\uae and PLA at 55\ub0C reduced the initial VS content by 51%. When PLA was in co-digestion with pig slurry, Mmax was 12% higher than the theoretical one, with a synergistic effect. In co-digestion with scotta, a nearly significant 12% increase in H2 production was observed for Mater-Bi\uae incubated at 35\ub0C. The exploitation of bioplastic waste in anaerobic digestion for biogas production, together with or in alternative to conventional composting, appears a promising possibility for a successful waste management

Biophysical factors affecting the anaerobic digestion of waste cooking oil in model systems

The anaerobic digestion (AD) of fat-containing waste is often prolonged in time and problematic. Differences in AD performances could rely in a different probability for microorganisms to access the substrate. The aim of this study was to study the AD of waste cooking oil (WCO) with a biophysical approach. Two laboratory experiments were carried out using model systems consisting of WCO + hydration medium (HM) in 100 mL, static, in-batch reactors. In the first experiment, we assumed the WCO to HM (OtoW) ratio as an indicator of the accessibility of substrate to microorganisms: the higher the ratio, the greater the probability of feeding for the microbial cells. AD performances were evaluated in relation to 5 decreasing OtoW ratios. In the second experiment, we favored the formation of emulsions through alkalinisation, by adding to our model system 5 increasing amounts of KOH 1M (pH range from 6.7 to 10.1). High OtoW ratios (that is, relatively low volumes of aqueous phase) increased the CH4production rate while allowing CH4yields close to the theoretical. However, the highest OtoW ratio resulted in AD failure. A proper amount of alkali halved the time to join the maximum CH4production. Reasoning in terms of biophysical factors, more than in terms of oil concentration or inoculum-to-substrate ratio, could be helpful for the improvement of AD of fat-containing substrates

Biogas production from wheat straw pre-treated with ligninolytic fungi and co-digestion with pig slurry

This study carried out for the first time a comparison among ligninolytic (white-rot) and cellulosolytic or xylanolytic (Trichoderma) pre-treated wheat straw, for biogas production, potential, without or with pig slurry in co-digestion. Methane (CH4) production from wheat straw pre-treated for 4 and 10 weeks with seven different fungal isolates was preliminarily measured. Then, the effects on biogas yield of the co-digestion with pig slurry were checked on straw pre-treated with 3 selected fungal strains. The maximum production of CH4 from pre-treated straw with Ceriporiopsis subvermispora (SUB) for 4 and 10 weeks was higher than the control (16% and 37%, respectively). The accumulation daily rate was higher than control (42% and 81%, respectively). A positive correlation between CH4 accumulation daily rate and straw enzymatic digestibility was found. In co-digestion with pig slurry, SUB pre-treated straw for 10 weeks showed an accumulation daily rate of 17.4 mL d-1 g-1 VS, significantly higher (17%) than that of the control. The time to reach the maximum CH4 production was shortened on average from 34 to 21 days in co-digestion with pig slurry, in comparison with pre-treated mono-digested wheat straw. The biological pre-treatment with selected white-rot fungi appears a promising technology to increase methane production from wheat straw

Biomethanation Potential of Wetland Biomass in Codigestion with Pig Slurry

Constructed wetlands represent an increasingly expanding technology for treatment and reuse of poor quality waters and for the development of marginal areas. The exploitation of herbaceous biomass for biogas production may add further appeal to its adoption. Codigestion of lignocellulosic plant materials with pig slurry could meet the need for biomass hydration and possibly improve biogas yields. The objectives of this study were: (1) to evaluate the biomethanation potential of biomass from several species which are of interest for use in constructed wetlands, and its relationship with plant composition; (2) to evaluate the influence of codigestion of selected wetland species with pig slurry on methane production rate and yield. Biogas production was preliminarily measured in laboratory conditions using as substrates biomass samples belonging to 23 plant species coming from different environments. Eight of them were then tested for biogas production, alone or in codigestion with pig slurry (volatile solid ratio: 1/1). In monodigestion, CH4 yields were on average 213\uc2\ua0mL CH4 g\ue2\u88\u921 volatile solids. Biogas production was positively related with N content and negatively with acid detergent fiber concentration and C to N ratio. The time for the joining of the maximum methane production was 25\uc2\ua0% shorter and the amount of methane was 30\uc2\ua0% higher for wetland biomass in codigestion with pig slurry than in monodigestion. The use of pig slurry as hydration medium for anaerobic digestion can improve the biomethanation potential of wetland biomass

Biogas production from wheat straw pre-treated with hydrolytic enzymes or sodium hydroxide

Lignocellulosic residues are relatively recalcitrant to bioconversion during anaerobic digestion (AD) for biogas production. Pretreatments with cellulolytic enzymes or diluted alkali can facilitate biomass hydrolysis and enhance the process. Both pretreatments require low energy and chemical inputs, without accumulation of inhibitor. Milled wheat straw was pre-treated with hydrolytic enzymes or with diluted NaOH before AD. The pre-treatments were performed on sterilized, stabilized with formic acid or not sterilized wheat straw to evaluate the effect of straw indigenous microorganisms on the sugar concentration before AD. Anaerobic digestion was carried out in batch reactors, at 35 \uc2\ub0C, for 3 months. The maximum cumulated methane production (Mmax) and the daily rate of methane accumulation (R) were estimated by a modified Gompertz equation. The NaOH pretreatment was the most effective, with average increases of 23 and 85 % for Mmax and R, respectively, in comparison with no pre-treatment. The enzymatic pre-treatment only increased Mmax by 14 %. However, the same increase was observed with heatinactivated enzymes, thus it was merely caused by the bioconversion into methane of the organic compounds contained in the enzymatic preparations. Moreover, all the pre-treatments determined a holocellulose conversion into reducing sugars lower than 4 %. In particular, the sugar concentration from not sterilized or stabilized with formic acid straw was lower than from sterilized straw, probably due to straw indigenous microorganisms activity. In conclusion, hydrolytic enzyme addition does not seem to provide a real advantage in terms of methane yield from wheat straw, differently from alkali pre-treatment

Advancements in Giant Reed (<i>Arundo donax</i> L.) Biomass Pre-Treatments for Biogas Production: A Review

Giant reed is a non-food, tall, rhizomatous, spontaneous perennial grass that is widely diffused in warm-temperate environments under different pedo-climatic conditions. In such environments, it is considered one of the most promising energy crops in terms of economic and environmental sustainability, as it can also be cultivated on marginal lands. Owing to its complex and recalcitrant structure due to the lignin content, the use of giant reed as a feedstock for biogas production is limited. Thus, pre-treatment is necessary to improve the methane yield. The objective of this review was to critically present the possible pre-treatment methods to allow the giant reed to be transformed in biogas. Among the studied pre-treatments (i.e., hydrothermal, chemical, and biological), alkaline pre-treatments demonstrated better effectiveness in improving the methane yield. A further opportunity is represented by hybrid pre-treatments (i.e., chemical and enzymatic) to make giant reed biomass suitable for bio-hydrogen production. So far, the studies have been carried out at a laboratory scale; a future challenge to research is to scale up the pre-treatment process to a pilot scale

Potassium Hydroxyde Pre-Treatment Enhances Methane Yield from Giant Reed (Arundo donax L.)

The biogas production through the anaerobic digestion (AD) of giant reed (Arundo donax L.) biomass has received increasing attention. However, due to the presence of lignin, a low CH4 yield can be obtained. Aiming to improve the CH4 yield from giant reed biomass, the effectiveness of a thermo-chemical pre-treatment based on KOH was evaluated in this paper. The usefulness of a washing step before the AD was also assessed. The pre-treatment led to a specific CH4 yield up to 232 mL CH4 g−1 VS which was 21% higher than that from untreated biomass; the maximum daily rate of production was improved by 42%, AD duration was reduced by 10%, and CH4 concentration in the biogas was increased by 23%. On the contrary, the washing step did not improve the AD process. Besides, washing away the liquid fraction led to biomass losses, reducing the overall CH4 production. The use of a KOH-based pre-treatment appears as a good option for enhancing the AD of giant reed, also presenting potential environmental and agronomical benefits, like the avoidance of salty wastewater production and the likely improvement of the digestate quality, due to its enriched K content