Optimization of Volatile Fatty Acids Production for Phas Synthesis from Food Wastes

Food wastage is an ethical and environmental wrong practice. Considering a circular economy optic, food waste is a carbon rich substrate, suited for anaerobic fermentation to produce not only biogas, but also highvalue chemical compounds, such as Volatile Fatty Acids (VFAs), that can be recovered in order to synthetize polyhydroxyalkanoates (PHAs). This work represented a step in a larger biorefinery process for food waste treatment, having the aim to explore the production and the profile of VFAs from of three different food waste substrates: Stillage, Condensate and Spent Coffee Ground. The substrates were considered at three different pH conditions (uncontrolled, 7, 12), anaerobically digested in batch reactors for VFAs accumulation. The best VFAs yields belonged to pH 7 tests for all the substrates. The best one on terms of VFAs productivity was Food Stillage with 36.17 gCOD/L of VFAs concentration, corresponding to a VFAs yield of 49.48 % w/w

Production, purification and recovery of caproic acid, Volatile fatty acids and methane from Opuntia ficus indica

Opuntia ficus-indica can grow in arid and semi-arid environments characterized by low water and nutrients availability. These features make it a more sustainable alternative to the common energy crops for biorefinery purposes. This work focused on the potential benefits of anaerobic processes applied to this plant. Specifically, it considered i) the substrate preparation, demonstrating the effect of the apparent viscosity on the process; ii) the evaluation of biomethane, Volatile Fatty Acids (VFAs), and caproic acid production in semi-continuous mode at different hydraulic retention times; iii) the purification of the Fatty Acids-rich output through pressure-driven membrane filtration. The rheology analysis found that a 5 %w/w water dilution of the substrate is needed to lower the apparent viscosity to 173 cP, which is below the acceptable apparent viscosity level of 200 cP for a good bioreactor mixing. Keeping this condition, the semi-continuous trials with the best biomethane performance was at HRT of 20 days, with 210 mLCH4/gVS and 232 mLCH4/gCODin of production and specific yield, respectively. The VFAs and caproic acid production reached their best at Hydraulic Retention Time 5, with 26 and 7.9 gCOD/L of VFAs and caproic acid, corresponding to specific yields of 79 and 30 % respectively. Pressuredriven filtration at 330 kDa allowed to obtain a permeate with a VFAs and caproic acid content of 96.72%w/w. Finally, the adsorption and desorption tests allowed to separate caproic acid from the permeate and to concentrate it from about 7.5 gCOD/L to about 26 gCOD/L

Treatment of food processing wastes for the production of medium chain fatty acids via chain elongation

The production of medium chain fatty acids (MCFAs) through reverse β-oxidation was investigated both on synthetic and real substrates. From preliminary batch tests emerged that caproic acid was maximized under an acetate/ethanol molar ratio of 5:1 at neutral pH. This ratio was then adopted in different semi-continuous tests operating with different amounts of the two reactants. It emerged that the MCFAs yield reached the maximum level of 6.7% when the total molar substrate amount was around 40–45 mmol/d, while the process was inhibited for values higher than 400 mmol/d. Semi-continuous tests using real waste as substrates, namely food waste condensate, cheese whey, and winery wastewater, confirmed the results obtained with the synthetic substrates. Better performances were obtained when an adequate molar ratio of the acetate and the electron-donor compound was naturally present. Therefore, a MCFAs yield of 25% and 10.5% was obtained for condensate of food waste and acidic cheese whey, respectively. Regarding MCFAs composition, caproic acid was the dominant form but small concentrations of octanoic acid were also found in the tests where ethanol was the electron donor (synthetic substrates and food waste condensate). Octanoic acid was not produced in test where lactic acid represented the electron donor molecules (cheese whey). Condensate and synthetic samples were dominated by Pseudoclavibacter caeni with an abundance of 38.19% and 33.38% respectively, while Thomasclavelia (24.13%) and Caproiciproducens (11.68%) was the most representative genus in acidic cheese whey sample

Adherence to antibiotic treatment guidelines and outcomes in the hospitalized elderly with different types of pneumonia

Background: Few studies evaluated the clinical outcomes of Community Acquired Pneumonia (CAP), Hospital-Acquired Pneumonia (HAP) and Health Care-Associated Pneumonia (HCAP) in relation to the adherence of antibiotic treatment to the guidelines of the Infectious Diseases Society of America (IDSA) and the American Thoracic Society (ATS) in hospitalized elderly people (65 years or older). Methods: Data were obtained from REPOSI, a prospective registry held in 87 Italian internal medicine and geriatric wards. Patients with a diagnosis of pneumonia (ICD-9 480-487) or prescribed with an antibiotic for pneumonia as indication were selected. The empirical antibiotic regimen was defined to be adherent to guidelines if concordant with the treatment regimens recommended by IDSA/ATS for CAP, HAP, and HCAP. Outcomes were assessed by logistic regression models. Results: A diagnosis of pneumonia was made in 317 patients. Only 38.8% of them received an empirical antibiotic regimen that was adherent to guidelines. However, no significant association was found between adherence to guidelines and outcomes. Having HAP, older age, and higher CIRS severity index were the main factors associated with in-hospital mortality. Conclusions: The adherence to antibiotic treatment guidelines was poor, particularly for HAP and HCAP, suggesting the need for more adherence to the optimal management of antibiotics in the elderly with pneumonia

Volatile Fatty Acid Recovery from Anaerobic Fermentate: Focusing on Adsorption and Desorption Performances

The purification and concentration of volatile fatty acids (VFAs) after acidogenic fermentation represent the key steps for their industrial use. In this study, different batch adsorption tests were performed on single VFAs using powdered activated carbon (PAC), Lewatit VP OC 1065, Amberlyst A21, and VFA mixtures using Lewatit and Amberlyst. Adsorption yields of approximately 70% for PAC and 86-96% for Lewatit and Amberlyst were achieved on the single VFA tests at an initial concentration of 5 g/L. The VFA mixture tests at 25 g/L showed lower yields: 40 and 27% for Lewatit and Amberlyst, respectively. Batch desorption tests were performed adopting two desorbents, ethanol, and water at various NaOH concentrations (1, 0.1, and 0.01 M) and at decreasing volumes (5, 3, and 2 mL). The optimization of the adsorption and desorption operations allowed the final VFA concentrations of 85-90 g/L to be reached. The best adsorbent, Lewatit, and the best desorption conditions were applied on a real fermentate with an initial VFA concentration of approximately 18 g/L, obtaining a final VFA content three times higher than in the original solution

Volatile fatty acids production from waste rich in carbohydrates: Optimization of dark fermentation of pasta by products

Pasta is one of the most appreciated Italian products around the world. The 31% of the global production of pasta is made by Italian companies: here, about 120 companies assure an annual production of 5.3 million tons of pasta. The pasta not compliant with the required selling standards (for example size, weight) is usually crushed, grounded to power, and used for animals feeding. This study offered a more advantageous alternative for the valorization of pasta by-products, whose mono-fermentation for Volatile Fatty Acids (VFAs) production was not investigated before. In particular, we considered pasta residues to optimize the operational parameters both in batch and in continuous conditions. The first round consisted in batch tests at different Total Solids (TS) con- centration (1.5–10% TS w/w). The 2% TS w/w emerged as the best one, able to assure a VFAs yield close to the 80%. Consequently, this concentration was chosen for the conduction of continuous tests dedicated to the optimization of the best HRT and SRT for the process. The HRT of 3 d and a SRT of 4.4 d allowed the best process performances with a VFAs productivity of 3.48 gVFAs_COD per L of reactor and per day. The optimization of the process conditions for VFAs production led to a greater concentration of butyric acids (about 10% w/w) instead of the mere acetic acid production. Because of the economic value of butyric acid, this result is of particular interes

Decarbonization of the European natural gas grid using hydrogen and methane biologically produced from organic waste: A critical overview

The global CO2 emissions are above 35 GtCO2/year. Recently, the European Commission approved the Green Deal with the aim to reduce the greenhouse gases emissions. Hydrogen, because of its capacity to burn without CO2 formation, is considered one of principal energy option for the future to obtain decarbonization. In 2020, total hydrogen demand was estimated at 8.6 Mt but over 90% of all hydrogen production plants use fossil fuels as feedstock. In perspective, a relatively small part of this hydrogen can be of biological origin. Anaerobic digestion, in particular two stages processes, can assure biological hydrogen and methane productions using organic waste and waste effluents as feedstock. Carbon dioxide in biogas can be removed to obtain a gas blend of methane and hydrogen with typical concentrations of 90:10–70:30% v/v. This review aims to provide an overview on biohythane production in Europe at Technology Readiness Level greater or equal to 5 (technology validated in relevant environment). At the moment, there are few examples of biohythane plants at pilot or higher scales, mainly located in Italy, France and United Kingdom. Here reactors with volumes in the range 20–350 L and 300-1000 L were able to assure a stable hydrogen and methane, respectively, production. The highest volumes of 700 and 3800 L for acidogenic and methanogenic phases, respectively, were successfully tested close Milan (Italy)

A critical review on the techno-economic feasibility of nutrients recovery from anaerobic digestate in the agricultural sector

The unsustainable environmental impact of fossil derived fertilizers and the depletion of raw materials for their production make the research of alternative sources for fertilizers production one of the main priorities of the international agenda. Agricultural digestate, especially if derived from livestock manure, is considered a potential candidate for the recovery of bio-based fertilizers: 180 M tonnes of digestate, which contain high concentrations of nitrogen (2–5 kg/m3) and phosphorous (0.5–1.5 kg/m3), are produced annually in the EU. This paper overviews different technologies, their robustness and yields in terms of nutrients recovery for different biobased fertilizers. Ammonia stripping and struvite precipitation are the technologies more developed at full scale allowing an average removal and recovery yield of 80–90 % for nitrogen and phosphorous, respectively. Due to their high degree of development, costs for ammonia stripping and struvite precipitation are relatively low, ranging from 2 to 7 € per kg of nutrient recovered. However, other technologies are rapidly developing and spreading. Pressure-driven membrane technologies (ultrafiltration and reverse osmosis) are emerging as important processes for nutrient recovery, although not selective. Nitrogen and phosphorous removal efficiencies for these technologies are around 75–95 % and 85–99 %, respectively. The main drawback of membrane processes is represented by the membrane fouling which prevents their large diffusion at full scales because of management difficulties. Moreover, the operational cost of this process is higher compared to other available technologies, ranging from 4 to 12 € per m3 of digestate. Full-scale applications for membrane technologies are available, but still limited, while several studies at laboratory and pilot scale are currently under development. Membrane contactors are receiving attention for the possibility to strip ammonia directly in the membrane with high ammonia recovery (over the 95 %). But this technology is currently developed at low TRL in the EU with several studies at laboratory and pilot scale. Ion exchange, adsorption, evaporation, and electrodialysis are also discussed in this review paper. The difficulty to have solid matrices able to assure a selective nitrogen/phosphorous compound adsorption and the need for regeneration has limited the ion exchange process at full TRL for treatment of agricultural digestate. However, some pilot scale applications of this technology have been investigated for wastewater treatment. Similarly, the high economic and energetic costs for evaporation and electrodialysis have prevented further applications of these techniques for pilot and full scale operation

A groundbreaking biorefinery loop for the valorization of cigarette butts into fermentable sugars and bioethanol

Cigarette Butts are one of the most diffused and toxic waste in urban contexts. They are composed by a cellulose acetate filter, used to retain toxic compounds during the smoking of cigarette, and eventual tobacco's residues. This work had the ambitious to exploit cigarette butts in a biorefinery scheme to produce fermentable sugars and bioethanol. Cigarette butts followed different sequential operations. Deacetylation of cellulose acetate was optimized by a lipase treatment, which played an important role in the biological degradation and deacetylation of cellulose acetate. The following cellulase addition allowed the conversion of the deacetylated cellulose into fermentable sugars. In particular, the best performances were obtained with a cellulase addition of 10% of the cigarette butts, which led to a final fermentable sugars' concentration of about 12 g/L, corresponding to a cigarette butts' conversion of about 70% w/w. Then, the fermentable sugars were used as substrates for bioethanol production by three different yeasts: Metschnikowia pulcherrima MALV5, Lachancea fermentati LS16 and Saccharomyces cerevisiae EC1118. Metschnikowia pulcherrima MALV5, Lachancea fermentati LS16 achieved similar results with a bioethanol production of 2.14 and 2.44 g/L, respectively, corresponding to a fermentable sugars conversion of about 20% w/w

Toward the Transition of Agricultural Anaerobic Digesters into Multiproduct Biorefineries

Anaerobic digestion allows for the proper management of agro-waste, including manure. Currently, more than 18,000 anaerobic digestion plants are under operation in EU, 80% of which are employed in the rural context. Tariff schemes for power generation from biogas produced during anaerobic digestion of agricultural feedstocks in Germany, Italy and Austria are coming to an end and new approaches are needed to exploit the existing infrastructures. Digesters in the rural context can be implemented and modified to be transformed into sustainable multi-feedstock and multi-purpose biorefineries for the production of energy, nutrients, proteins, bio-chemicals such as carboxylic acids, polyesters and proteins. This paper describes how the transition of agricultural anaerobic digesters into multi-products biorefineries can be achieved and what are the potential benefits originating from the application of a pilot scale platform able to treat cow manure and other crop residues while producing volatile fatty acids, polyhydroxyalkanoates, microbial protein material, hydrogen, methane and a concentrated liquid stream rich in nitrogen, potassium and phosphorus