Multiscale mathematical models for simulation and scale-up of green processes in the perspective of industrial sustainability

The present work presents research studies aimed at developing tools useful to design engineering solutions moving in the direction of industrial sustainability. The investigations hereinafter discussed regard an extraction process of active compounds \u2013 polyphenols \u2013 from agro-food industry wastes (olive and grape pomaces) and a biorefinery exploiting waste frying oil, solid organic wastes and algal biomass to produce biofuels. In particular, for the former topic, a procedure aimed at the evaluation of the technological feasibility at pilot scale of said process is discussed. The proposed approach takes into consideration the extended kinetic route coupled with mathematical simulation. Detailed physically-based dynamic mathematical models, taking into account mass and energy balance equations, are adopted to describe both the lab-scale and the pilot-scale reactors. Chemical physical parameters appearing in the models are estimated from the experimental data at lab-scale or are partially taken from literature. Different heating systems are designed for the pilot scale reactor and their performance is tested by simulation. Characteristic times are evaluated also during start-ups and different control loops are analyzed in order to set-up the best process and operating variables. Average yields in polyphenols are finally evaluated for both the batch and the continuous operated pilot reactor, by considering feed variability and fluctuations of process parameters. For what concerns the biorefinery, special attention was devoted to the modeling of the airlift reactor, its most delicate and complex component. In fact, to optimize this interesting microalgae cultivation system, a precise description of the moving interfaces formed by the liquid and gas phase is critical. In this study, coupled front capturing methods (standard and conservative level set methods) and finite difference method are used to simulate gas bubbles dynamics in a pilot-scale external loop air-lift photobioreactor in which microalgae are used to capture CO2 from flue gas and to treat wastewater. Numerical simulations are carried out on rectangular domains representing different sections of the vertical axis of the riser. The data employed was either acquired from previous experimental campaigns carried out in the airlift reactor or found in the literature. The rise, shape dynamics and coalescence process of the bubbles of flue gas are studied. Moreover, for each analyzed applications, a procedure based on Buckingham \u3c0-theorem to perform a rigorous scale-up is proposed. In this way, scale-invariant dimensionless groups describing and summarizing the considered processes could be identified. For the research focused on the scale-up of photobioreactors used to cultivate Chlorella Vulgaris, an experimental campaign at three levels was designed and carried out to evaluate the characteristic dimensionless numbers individuated by the theoretical formulation. Since scale-up regards both geometrical dimensions and type of reactor, passing from lab-scale stirred tanks to pilot scale tubular and airlift, particular attention was devoted to define characteristic lengths inside the dimensionless numbers

A level set approach for computation of bubble dynamics in airlift reactors.

In this work, we employ the so-called level set approach to simulate the rising of gas bubbles in a pilot-scale external loop airlift photobioreactor in which microalgae are used to capture CO2from flue gas and to treat wastewater. A coupled level set and finite difference method is adopted in this work to track the moving gas-liquid interfaces in the ALR riser. Level set methods implicitly represent dynamic fronts by solving an Hamilton-Jacobi partial differential equation such as the normal flow equation, in turn dependent on a flow function that can be regarded as a speed vector field. This latter, for the case at hand, is obtained by solving the non-dimensional Navier-Stokes equations through a Chorin type projection technique on a staggered gri

A Low-Cost Monitoring System and Operating Database for Quality Control in Small Food Processing Industry

The use of completely automated systems for collecting sensor data with the aim of monitoring and controlling the quality of small-scale food processes is not widespread. Small and micro-enterprises usually do not carry out their own precompetitive research or prototype development as regards to automation technologies. This study proposes a web-based, low-cost monitoring and supervisory control and data acquisition (SCADA) system whose kernel is available for free, as a possible solution that could be adopted by these food producers. It is mainly based on open SW/HW so as its configuration is adaptable to the application and type of plant. It presents a modular architecture and its main functionalities encompass the acquisition, management, aggregation and visualization of process data, providing an operating database. It also provides food tracking and process quality control: The time series are browsable due to QR-Code generation and different early warning detection strategies are implemented. A tool for solving migration problems based on Fick\u2019s equation is offered as a packaging decision support system

Adhesion of sea-urchin living cells on nano-patterned anodic porous alumina

In this work we investigated the possibility of using living cells as stress sensing material in biosensors, in the light of the three Rs principle \u2013 Replacement, Reduction and Refinement . This approach requires the necessity to cultivate them on biocompatible electrical conducting substrate and to insert the circuit into a culture chamber that must assure both the transport of oxygen and the diffusion of the medium containing the potential stressor to the cells, without modifying their response and the structure of the culture. To this aim we fabricated nano-patterned substrates of anodic porous alumina to be used for enhancing cell adhesion, and culture chambers made in polylactic acid. Sea-urchin cells (coelomocytes) were cultured on these substrates at different times of 1, 3 and 5 days in vitro. Since these cells are progenitors of immune cells in vertebrate systems (blood cells), they carry out similar functions. For this reason, although they can differ considerably from vertebrates, they have been proved to be very promising sentinels of environmental water qualit

MicroRNA 193b-3p as a predictive biomarker of chronic kidney disease in patients undergoing radical nephrectomy for renal cell carcinoma

Background: A significant proportion of patients undergoing radical nephrectomy (RN) for clear-cell renal cell carcinoma (RCC) develop chronic kidney disease (CKD) within a few years following surgery. Chronic kidney disease has important health, social and economic impact and no predictive biomarkers are currently available. MicroRNAs (miRs) are small non-coding RNAs implicated in several pathological processes. Methods: Primary objective of our study was to define miRs whose deregulation is predictive of CKD in patients treated with RN. Ribonucleic acid from formalin-fixed paraffin embedded renal parenchyma (cortex and medulla isolated separately) situated >3 cm from the matching RCC was tested for miR expression using nCounter NanoString technology in 71 consecutive patients treated with RN for RCC. Validation was performed by RT–PCR and in situ hybridisation. End point was post-RN CKD measured 12 months post-operatively. Multivariable logistic regression and decision curve analysis were used to test the statistical and clinical impact of predictors of CKD. Results: The overexpression of miR-193b-3p was associated with high risk of developing CKD in patients undergoing RN for RCC and emerged as an independent predictor of CKD. The addition of miR-193b-3p to a predictive model based on clinical variables (including sex and estimated glomerular filtration rate) increased the sensitivity of the predictive model from 81 to 88%. In situ hybridisation showed that miR-193b-3p overexpression was associated with tubule-interstitial inflammation and fibrosis in patients with no clinical or biochemical evidence of pre-RN nephropathy. Conclusions: miR-193b-3p might represent a useful biomarker to tailor and implement surveillance strategies for patients at high risk of developing CKD following RN

Sustainable Biodiesel Production by Transesterification of Waste Cooking Oil and Recycling of Wastewater Rich in Glycerol as a Feed to Microalgae

none2The amount of solid and liquid organic waste and wastewater is continuously increasing all over the world. The necessity of their reuse and recycling is, therefore, becoming more and more pressing. Furthermore, the limited fossil fuel resources, in conjunction with the need to reduce greenhouse gas emissions, advocate the production of renewable fuels. In this work, we analyze a sustainable second-generation process to produce biodiesel by transesterification of waste cooking oil, coupled with a third-generation process in cascade for recycling the incoming wastewater. Since this latter is rich in glycerol, it is used as a feed for microalgae, from which oil can be extracted and added to the waste cooking oil to further produce biodiesel and close the cycle. We studied the influence of different factors like temperature, catalyst load, and reactants ratio on the kinetics of transesterification of the waste oil and estimated the kinetic parameters by different kinetic schemes. The obtained values of activation energies and pre-exponential factors at chosen conditions of T = 60 °C and catalyst load of 0.6% w/w in methanol are: Ea,direct = 35,661 J mol−1, Ea,reverse = 72,989 J mol−1, k0,direct = 9.7708 [dm3 mol−1]3 min−1, and k0,reverse = 24,810 [dm3 mol−1]3 min−1 for the global fourth-order reversible reaction scheme and Ea = 67,348 J mol−1 and k0 = 2.157 × 109 min−1 for the simplified pseudo-first-order irreversible reaction scheme; both in strong agreement with literature data. Furthermore, we designed very efficient conditions for discontinuous and continuous operating mode, both at lab-scale and pilot-scale. The quality of the biodiesel produced from waste cooking sunflower oil is compared with that of biodiesel produced by different kinds of virgin vegetable oils, showing that the former possesses acceptable quality standards (Cetane number = 48 and LHV = 36,600 kJ kg−1). Finally, the recycling of wastewater rich in glycerol as a nutrient for mixotrophic microalgae nurturing is discussed, and microalgae growing kinetics are evaluated (k1 about 0.5 day−1), endorsing the possibility of algae extraction each 4–5 days in a semi-continuous operating mode. The experimental results at the pilot scale finally confirm the quality of biodiesel, and the obtained yields for a two-stage process prove the competitiveness of this sustainable process on the global market.nonePaladino, Ombretta; Neviani, MatteoPaladino, Ombretta; Neviani, Matte

Airlift photo-bioreactors for Chlorella vulgaris cultivation in closed-loop zero waste biorefineries

This study aims to set up the operating conditions of a battery of airlift photo-bioreactors (AL-PBRs) for Chlorella vulgaris cultivation integrated into a pilot-scale Biowaste-to-Biofuels (BtB) production plant, producing both biodiesel by transesterification of waste frying oils and syngas by wood chips gasification. Microalgae are fed with both wastewater rich in glycerol and flue gas. Mixing, mass transport, kinetics, and light conditions inside the AL-PBRs are chosen by keeping some dimensionless numbers (Re, Sh, Da, and A) fixed around the values found at lab-scale (11000, 1550, 23, 35, respectively). pH, T, nutrient-related ratios, and light intensity are adjusted inside the optimal ranges found at indoor conditions. The number of AL-PBRs, feeding/extraction time intervals, and flowrates are designed by mass balancing the entire pilot-plant in order to operate in continuous quasi-zero waste. Outdoor tests confirmed that 12\u201315 AL-PBRs with a total volume of 125\u2013155 L reuse 28.8 L d 121 of wastewater by-produced from the biodiesel units providing 228 L d 121 of biodiesel and reuse the total of about 90 m3 h 121 of flue gas in exit from the syngas combustion unit with power generation of 9\u20139.5 kW. The battery works at an initial concentration for each cycle of around 0.5 g L 121 and concentration at extraction of around 1.05 g L 121

Scale-up of photo-bioreactors for microalgae cultivation by \u3c0-theorem

Robust microalgae cultivation at industrial scale needs complex scale-up of photobioreactors since the same yields obtained at lab-scale are hardly reached during pilot or industrial production. In this paper we propose a procedure based on Buckingham \u3c0-theorem to perform the scale-up of photobioreactors used to cultivate Chlorella Vulgaris fed by CO2 and wastewater rich in glycerol. This theoretical approach is usually overlooked in favor of the synergy of modeling tailored on the process and piloting, but it grants excellent generalizability. An experimental campaign at three levels was designed and carried out to evaluate the characteristic dimensionless numbers individuated by the theoretical formulation. Since scale-up regards both geometrical dimensions and type of reactor, passing from lab-scale stirred tanks (STRs) to pilot scale tubular and airlift, particular attention was devoted to defining characteristic lengths inside the dimensionless numbers. Moreover, since scale-up also regards the operating mode, scaling from discontinuous to semi-continuous to continuous, some interesting dimensionless numbers arise other than Re, Sh ,Da. They are mainly related to the type of biological process and its operating mode and are the ratios O2/CO2 and T/Topt, the ratio between the incident light intensity and the saturation constant, the absorbance, the ratio between the final and the initial concentration c/c0, the ratio between the maximum increase in cell population and its initial concentration, the ratio between the estimated specific kinetic constant and a variable representing the characteristic time of mixing inside the chosen reactor. Preliminary outdoor tests confirmed the operability of the scaled-up airlift reactors reaching c/c0\u2009=\u20095.3 \u2013 7.5, with c\u2009=\u20091.15\u2009g L-1 at extraction intervals of 5 days. They were operated under optimal light conditions of incident light greater than Chlorella v. saturation constant and absorbance A\u2009=\u200940 and at incipient churn flow (Re\u2009=\u200910000 - 11000) with dimension of fluegas bubbles around 5\u2009mm, apt to guarantee Sh\u2009=\u20091500-2500; and with a calculated Da around 25

Feasibility study of a pilot scale integrated biowaste to biofuel system fed with waste frying oil, organic waste and algal biomass

Nowadays, the importance of recycle and energy savings is increasing due to the current economic and environmental situation. A lot of different technologies were developed in order to utilize biowaste to produce biofuels but they are not always easily available and economically advantageous, especially at small scale. A possible solution could be to couple them in a synergic cooperation. In this paper we discuss the best layout of a pilot plant producing biofuels from waste frying oil, solid organic wastes and algal biomass. The crucial point of this work is to the find best layout and operative conditions in order to use organic wastes and by-products in a closed-loop process. The study is carried out through a complete experimental campaign on the integrated pilot process, consisting of three parts, so defined: i) biodiesel and glycerol production by transesterification of waste frying oil added with oil extracted from algal biomass; ii) syngas production by gasification of biowaste, added with glycerol to increase the total LCV; iii) algal biomass production in airlift photo-bioreactors, fed by the recycled process wastewater rich in glycerol, and capable to capture carbon dioxide from flue gases and to produce valuable material to be reintroduced in the process cycle. Waste oil and organic waste were provided by the University Campus canteen and wood pellets were collected in the Campus park. Quality levels of biodiesel cetane number ranged from 47.7 to 58.4 and LHVs ranged from about 36080 kJ/kg to 36992 kJ/kg. A better syngas quality was found by adding glycerol, and flue gas composition was suitable to partially feed the airlift reactors. On the basis of this first step of experimentation, the technological feasibility of the proposed closed loop integrated system is verified