Exploitation of Solar Energy for Ammonium Sulfate Recovery from Anaerobic Digestate of Different Origin

Digestate represents the semi-liquid byproduct of the anaerobic digestion process. It was estimated that 56 Mtonnes of digestate are annually produced only in Europe. Digestate composition depends on the initial total solids (TS) mixture fed to the digester and by its origin (manure, food wastes, agricultural residues, wastewater sludge). Typical values for the different components include a stabilized organic matter content between 20 and 50 g/L, a good content of nitrogen compounds (2–8 g/kg) and of phosphorous compounds (up to 3 g/kg). In particular, ammonia presence in digestate is interesting for ammonium sulfate production, a fertilizer which favors plants' growth. Traditional ammonium sulfate synthesis is conducted by stripping followed by sulfuric acid absorption, a process which requires high energy and chemicals consumptions. This work investigates the exploitation of solar energy to evaporate the liquid phase of digestate in a lab-scale greenhouse. Digestate vapors, rich in ammonia, are sent in a Drechsler trap, filled with 38% w/w sulfuric acid solution, through three solar air fans. The process has been tested on digestates differing for TS content and origin. It emerged that the process is favored by digestates with high ammonia content, as those originated from manure, and a TS content of about 10% w/w, which allowed to obtain an ammonium sulfate concentration of about 2 M in the final solution

Thermalization with a multibath: an investigation in simple models

We study analytically and numerically a couple of paradigmatic spin models, each described in terms of two sets of variables attached to two different thermal baths with characteristic timescales $T$ and $\tau$ and inverse temperatures $B$ and $\beta$. In the limit in which one bath becomes extremely slow ($\tau \to \infty$), such models amount to a paramagnet and to a one-dimensional ferromagnet, in contact with a single bath. We show that these systems reach a stationary state in a finite time for any choice of $B$ and $\beta$. We determine the non-equilibrium fluctuation-dissipation relation between the autocorrelation and the response function in such state and, from that, we discuss if and how thermalization with the two baths occurs and the emergence of a non-trivial fluctuation-dissipation ratio.Comment: 15 pages, 6 figure

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

Electroporation and Cell Killing by Milli- to Nanosecond Pulses and Avoiding Neuromuscular Stimulation in Cancer Ablation

Ablation therapies aim at eradication of tumors with minimal impact on surrounding healthy tissues. Conventional pulsed electric field (PEF) treatments cause pain and muscle contractions far beyond the ablation area. The ongoing quest is to identify PEF parameters efficient at ablation but not at stimulation. We measured electroporation and cell killing thresholds for 150 ns–1 ms PEF, uni- and bipolar, delivered in 10- to 300-pulse trains at up to 1 MHz rates. Monolayers of murine colon carcinoma cells exposed to PEF were stained with YO-PRO-1 dye to detect electroporation. In 2–4 h, dead cells were labeled with propidium. Electroporation and cell death thresholds determined by matching the stained areas to the electric field intensity were compared to nerve excitation thresholds (Kim et al. in Int J Mol Sci 22(13):7051, 2021). The minimum fourfold ratio of cell killing and stimulation thresholds was achieved with bipolar nanosecond PEF (nsPEF), a sheer benefit over a 500-fold ratio for conventional 100-µs PEF. Increasing the bipolar nsPEF frequency up to 100 kHz within 10-pulse bursts increased ablation thresholds by \u3c 20%. Restricting such bursts to the refractory period after nerve excitation will minimize the number of neuromuscular reactions while maintaining the ablation efficiency and avoiding heating

Acoustic Emission and fracture energy dissipation in notched concrete beams subjected to three-point bending tests

In this study, three-point bending (TPB) tests on notched concrete beams having different size, have been carried out to evaluate the influence of propagation distance on the AE parameters. The most representative AE parameters have been measured by sensors at different distances from the source, in order to obtain detailed information on the type of cracks as well as on the source localization. The waves frequency and the rise angle are used to discriminate the prevailing cracking mode from pure opening or sliding [1]. The cumulated number of AE events and their amplitude are used to compute the signal energy. Each signal recorded during the bending test by the first sensor has been compared with the same signal captured by the other one. For all concrete beams, an average value of the AE parameters for each sensor has been made. The AE parameters average value indicates how important the propagation distance between the two sensors is for the AE analysis. However, AE waveform parameters are effected by strong attenuation and distortion due to propagation through an inhomogeneous medium, which should not be neglected in laboratory and, in particular way, on real structures. The AE results obtained from the three-point bending tests prove that the variation of the AE parameters during the loading process strictly depends on the specimen damage. A decrease in frequency may be provoked by large cracks progress both during tensile and sharing process, while an increase in AE signal energy content is detected approaching the final failure. A distinct element numerical model of the beam is described and used to model the energy dissipation during the three point bending test. The model accounts for the mesostructure of plain concrete in the region closed to the central notch. Each aggregate is modeled together with the bonding of the matrix. In this way it is possible to simulate numerically the concrete crushing, as well as the tensile cracking at the aggregate interface or through the matrix and, eventually, through the inclusions [2-4]. The model is able to simulate the Acoustic Emission localization and statistics, in addition to the fracture energy dissipation, allowing for a better understanding of the ongoing phenomen

The importance of hematocrit for oxygen delivery and hemodynamics

Anemia is common in elderly patients undergoing surgery and in critical patients. A 72-year-old man submitted to a revision of hip replacement implant was diagnosed with tuberculosis, followed by pulmonary fibrosis, pulmonary heart disease and compensatory erythrocytosis. In the postoperative period, he got anemia which improved his clinical status. Anemia reduces viscosity, i.e. one of the components of vascular resistance to laminar (according to the law of Hagen-Poiseuille) and turbulent flows. In conditions of decreased hematocrit, shear thinning occurs more easily and in larger caliber vessels. Hemodiluition reduces both right and left cardiac afterloads, thus provoking an improvement of the blood flow. As the hematocrit decreases, oxygen delivery increases, because the increase in the cardiac output is greater than the decrease in the concentration of hemoglobin. Further studies are needed to confirm this physical model and to establish the variable and degree of the transfusion trigger

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

Polyhydroxyalkanoated-Rich Microbial Cells from Bio-Based Volatile Fatty Acids as Potential Ingredient for Aquaculture Feed

In this study, the production of polyhydroxyalkanoated PHA-rich microbial biomass as a novel feed additive in aquaculture was investigated at a lab-scale. Bio-based volatile fatty acids (VFAs), obtained from the acidogenic fermentation of agricultural residues in existing anaerobic digestion plants, were used as carbon and energy to cultivate the PHA-rich microbial biomass. The experimental activities were carried out using Thauera sp. Sel9 as pure strain, which was grown in a continuous stirred-tank reactor (CSTR) operated at three different hydraulic retention times (HRT). The highest productivity obtained of biomass cells was 0.69 g/L day, operating at one day HRT while the observed PHAs production yield was 0.14 gPHA/g soluble COD removed. At these conditions, the PHA concentration in the microbial cells was 41%. Although the sulfur amino acids were available at high concentrations and above the typical concentration found in fishmeal, the amino acids profile of the obtained biomass revealed a lack of histidine and threonine. A preliminary economic analysis showed that the production of a novel source of feed additive from the conversion of agro-residues could give higher benefits in terms of revenues compared to the production of biogas production through anaerobic digestion