Techno-economic assessment of biopolymer production from methane and volatile fatty acids: effect of the reactor size and biomass concentration on the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) selling price.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is a biobased and biodegradable polymer that could efficiently replace fossil-based plastics. However, its widespread deployment is slowed down by the high production cost. In this work, the techno-economic assessment of the process for producing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from low-cost substrates, such as methane and valeric acid derived from the anaerobic digestion of organic wastes, is proposed. Several strategies for cost abatement, such as the use of a mixed consortium and a line for reagent recycling during downstream, were adopted. Different scenarios in terms of production, from 100 to 100,000 t/y, were analysed, and, for each case, the effect of the reactor volume (small, medium and large size) on the selling price was assessed. In addition, the effect of biomass concentration was also considered. Results show that the selling price of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is minimum for a production plant with 100,000 t/y capacity, accounting for 18.4 €/kg, and highly influenced by the biomass concentration since it can be reduced up to 8.6 €/kg by increasing the total suspended solids from 5 to 30 g/L, This adjustment aligns the breakeven point of PHBV with the reported average commercial price.

Polyhydroxyalkanoate recovery overview: properties, characterizations, and extraction strategies.

Due to their excellent properties, polyhydroxyalkanoates are gaining increasing recognition in the biodegradable polymer market. These biogenic polyesters are characterized by high biodegradability in multiple environments, overcoming the limitation of composting plants only and their versatility in production. The most consolidated techniques in the literature or the reference legislation for the physical, chemical and mechanical characterisation of the final product are reported since its usability on the market is still linked to its quality, including the biodegradability certificate. This versatility makes polyhydroxyalkanoates a promising prospect with the potential to replace fossil-based thermoplastics sustainably. This review analyses and compares the physical, chemical and mechanical properties of poly-ß-hydroxybutyrate and poly-ß-hydroxybutyrate-co-ß-hydroxyvalerate, indicating their current limitations and strengths. In particular, the copolymer is characterised by better performance in terms of crystallinity, hardness and workability. However, the knowledge in this area is still in its infancy, and the selling prices are too high (9-18 $ kg-1). An analysis of the main extraction techniques, established and in development, is also included. Solvent extraction is currently the most widely used method due to its efficiency and final product quality. In this context, the extraction phase of the biopolymer production process remains a major challenge due to its high costs and the need to use non-halogenated toxic solvents to improve the production of good-quality bioplastics. The review also discusses all fundamental parameters for optimising the process, such as solubility and temperature.

Production of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from methane and volatile fatty acids: properties, metabolic routes and current trend.

Polyhydroxyalkanoates (PHAs) are biobased and biodegradable polymers that could effectively replace fossil-based and non-biodegradable plastics. However, their production is currently limited by the high production costs, mainly due to the costly carbon sources used, low productivity and quality of the materials produced. A potential solution lies in utilizing cheap and renewable carbon sources as the primary feedstock during the biological production of PHAs, paving the way for a completely sustainable and economically viable process. In this review, the opportunities and challenges related to the production of polyhydroxyalkanoates using methane and volatile fatty acids (VFAs) as substrates were explored, with a focus on poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate). The discussion reports the current knowledge about promising Type II methanotrophs, the impact of process parameters such as limiting nutrients, CH4:O2 ratio and temperature, the type of co-substrate and its concentration. Additionally, the strategies developed until now to enhance PHA production yields were also discussed.

Exploring New Strategies for Optimizing the Production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from Methane and VFAs in Synthetic Cocultures and Mixed Methanotrophic Consortia.

In this work, the potential of a synthetic coculture and a mixed methanotrophic consortium to synthesize poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) from renewable and waste-based feedstocks was assessed batchwise. Methylocystis parvuscocultivated with Rhodococcus opacus and a Methylocystis-enriched culture previously grown on methane were subjected to nutrient starvation in a medium enriched with valeric acid (30% w w-1 of Ctot) or with a VFAs mixture containing acetic, propionic, butyric, and valeric acids (15% w w-1 of Ctot) under a CH4:O2 or air atmosphere. For all test series, pH was adjusted to 7 after adding the cosubstrates, and a negligible substrate consumption or polymer production was considered the end point of the trial. Results showed that valeric acid promoted PHBV accumulation in both cultures regardless of the atmosphere. Interestingly, the mixture of VFAs supported PHBV accumulation only in the presence of methane. The highest PHBV contents for the coculture and the mixed consortium, equal to 73.7 ± 2.5% w w-1 and 49.6 ± 13% w w-1, respectively, were obtained with methane and the VFAs mixture. This study demonstrates the suitability of cocultures and biobased cosubstrates for the sustainable production of the biodegradable polymer PHBV.

The co-conversion of methane and mixtures of volatile fatty acids into poly(3-hydroxybutyrate-co-3-hydroxyvalerate) expands the potential of an integrated biorefinery.

In this work, the potential of Methylocystis hirsuta to simultaneously use methane and volatile fatty acids mixtures for triggering PHBV accumulation was assessed for the first time batchwise. Biotic controls carried out with CH4 alone confirmed the inability of Methylocystis hirsuta to produce PHBV and achieved 71.2 ± 7 g m-3d-1 of PHB. Pure valeric acid and two synthetic mixtures simulating VFAs effluents from the anaerobic digestion of food waste at 35 °C (M1) and 55 °C (M2) were supplied to promote 3-HV inclusion. Results showed that pure valeric acid supported the highest polymer yields of 105.8 ± 9 g m-3d-1 (3-HB:3-HV=70:30). M1 mixtures led to a maximum of 103 ± 4 g m-3d-1 of PHBV (3-HB:3-HV=85:15), while M2 mixtures, which did not include valeric acid, showed no PHV synthesis. This suggested that the synthesis of PHBV from VFAs effluents depends on the composition of the mixtures, which can be tuned during the anaerobic digestion process.

Application of Electrochemical Oxidation for Water and Wastewater Treatment: An Overview.

In recent years, the discharge of various emerging pollutants, chemicals, and dyes in water and wastewater has represented one of the prominent human problems. Since water pollution is directly related to human health, highly resistant and emerging compounds in aquatic environments will pose many potential risks to the health of all living beings. Therefore, water pollution is a very acute problem that has constantly increased in recent years with the expansion of various industries. Consequently, choosing efficient and innovative wastewater treatment methods to remove contaminants is crucial. Among advanced oxidation processes, electrochemical oxidation (EO) is the most common and effective method for removing persistent pollutants from municipal and industrial wastewater. However, despite the great progress in using EO to treat real wastewater, there are still many gaps. This is due to the lack of comprehensive information on the operating parameters which affect the process and its operating costs. In this paper, among various scientific articles, the impact of operational parameters on the EO performances, a comparison between different electrochemical reactor configurations, and a report on general mechanisms of electrochemical oxidation of organic pollutants have been reported. Moreover, an evaluation of cost analysis and energy consumption requirements have also been discussed. Finally, the combination process between EO and photocatalysis (PC), called photoelectrocatalysis (PEC), has been discussed and reviewed briefly. This article shows that there is a direct relationship between important operating parameters with the amount of costs and the final removal efficiency of emerging pollutants. Optimal operating conditions can be achieved by paying special attention to reactor design, which can lead to higher efficiency and more efficient treatment. The rapid development of EO for removing emerging pollutants from impacted water and its combination with other green methods can result in more efficient approaches to face the pressing water pollution challenge. PEC proved to be a promising pollutants degradation technology, in which renewable energy sources can be adopted as a primer to perform an environmentally friendly water treatment.

Electrochemical Removal of Nitrogen Compounds from a Simulated Saline Wastewater.

In the last few years, many industrial sectors have generated and discharged large volumes of saline wastewater into the environment. In the present work, the electrochemical removal of nitrogen compounds from synthetic saline wastewater was investigated through a lab-scale experimental reactor. Experiments were carried out to examine the impacts of the operational parameters, such as electrolyte composition and concentration, applied current intensity, and initial ammoniacal nitrogen concentration, on the total nitrogen removal efficiency. Using NaCl as an electrolyte, the NTOT removal was higher than Na2SO4 and NaClO4; however, increasing the initial NaCl concentration over 250 mg·L-1 resulted in no benefits for the NTOT removal efficiency. A rise in the current intensity from 0.05 A to 0.15 A resulted in an improvement in NTOT removal. Nevertheless, a further increase to 0.25 A led to basically no enhancement of the efficiency. A lower initial ammoniacal nitrogen concentration resulted in higher removal efficiency. The highest NTOT removal (about 75%) was achieved after 90 min of treatment operating with a NaCl concentration of 250 mg·L-1 at an applied current intensity of 0.15 A and with an initial ammoniacal nitrogen concentration of 13 mg·L-1. The nitrogen degradation mechanism proposed assumes a series-parallel reaction system, with a first step in which NH4+ is in equilibrium with NH3. Moreover, the nitrogen molar balance showed that the main product of nitrogen oxidation was N2, but NO3- was also detected. Collectively, electrochemical treatment is a promising approach for the removal of nitrogen compounds from impacted saline wastewater.

Sustainable Process for the Production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from Renewable Resources: A Simulation Study.

Bacterially produced polyhydroxyalkanoates are valuable substitutes for petrochemical plastics, but their current production capacities are very scarce. Producing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-co-HV) from methane and odd-chain carbon fatty acids could make the production of this biodegradable polymer cost-effective. This study analyzes the main factors affecting methanotrophic growth and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) accumulation, simulating a pilot-scale process based on a double-stage approach. The effects of the nitrogen source and the oxygen partial pressure during a 20 day growth phase were studied; the cosubstrate concentration, the culture selected, and the methane partial pressure were investigated during the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production stage performed within 15 days under nutrient starvation. Methylocystis parvus OBBP and Methylosinus thricosporum OB3b reached the maximum growth productivities with ammonium as the nitrogen source and oxygen at high partial pressure. The simulation of the PHB-co-HV accumulation revealed that methanotrophs could better accumulate the polymer with low valeric acid concentrations. A methane-abundant gas stream (0.5 atm of methane) could increase process yields up to 0.32 kg m-3 d-1.

Poly(3-hydroxybutyrate) production from methane in bubble column bioreactors: Process simulation and design optimization.

The pressing problem posed by plastic pollution has led to other, environmentally friendly alternatives, such as polyhydroxyalkanoates. This work proposes an innovative process to produce poly(3-hydroxybutyrate) by replacing expensive substrates, such as sugars, with methane. A two-step process was simulated: a first fermentation is performed in a continuous mode for 20 days to grow a strain belonging to the genus Methylocystis, while a second semi-continuous and nitrogen-limited fermentation is employed to induce the poly(3-hydroxybutyrate) accumulation within 12 days. The effects of the superficial gas velocity on the mass transfer and the poly(3-hydroxybutyrate) production yields were evaluated. Several scenarios were analyzed to optimize the geometry of the reactors and the methane utilization. The working volume of the reactors, as well as the presence of gas recycling stream, were shown to affect the global yields positively, while improving the aspect ratio from 8 to 19, with equal volume, lowered the fraction of poly(3-hydroxybutyrate) into the biomass by up to 37.5%.

Modelling of autogenerative high-pressure anaerobic digestion in a batch reactor for the production of pressurised biogas.

BACKGROUND: Pressurised anaerobic digestion allows the production of biogas with a high content of methane and, at the same time, avoid the energy costs for the biogas upgrading and injection into the distribution grid. The technology carries potential, but the research faces practical constraints by a.o. the capital investment needed in high-pressure reactors and sensors and associated sampling limitations. In this work, the kinetic model of an autogenerative high-pressure anaerobic digestion of acetate, as the representative compound of the aceticlastic methanogenesis route, in batch configuration, is proposed to predict the dynamic performance of pressurised digesters and support future experimental work. The modelling of autogenerative high-pressure anaerobic digestion in batch configuration, which is not extensively studied and simulated in the present literature, was developed, calibrated, and validated by using experimental results available from the literature. RESULTS: Under high-pressure conditions, the assessment of the Monod maximum specific uptake rate, the half-saturation constant and the first-order decay rate was carried out, and the values of 5.9 kg COD kg COD-1 d-1, 0.05 kg COD m-3 and 0.02 d-1 were determined, respectively. By using the predicted values, excellent fittings of the final pressure, the CH4 molar fraction and the specific methanogenic yield calculation were obtained. Likewise, the variation in the gas-liquid mass transfer coefficient by several orders of magnitude showed negligible effects on the model predictive values in terms of methane molar fraction of the produced biogas, while the final pressure seemed to be slightly influenced. CONCLUSIONS: The proposed model allowed to estimate the Monod maximum specific uptake rate for acetate, the half-saturation rate for acetate and the first-order decay rate constant, which were comparable with literature values reported for well-studied methanogens under anaerobic digestion at atmospheric pressure. The methane molar fraction and the final pressure predicted by the model showed different responses towards the variation of the gas-liquid mass transfer coefficient since the former seemed not to be affected by the variation of the gas-liquid mass transfer coefficient; in contrast, the final pressure seemed to be slightly influenced. The proposed approach may also allow to potentially identify the methanogens species able to be predominant at high pressure.

Pump-and-treat configurations with vertical and horizontal wells to remediate an aquifer contaminated by hexavalent chromium.

Pump-and-treat technology is among the most used technologies for groundwater remediation. While conventional, vertical wells (VRWs) are well-known and used from long time, horizontal wells (HRWs) have been explored for remediation technologies only in last few decades. HRWs have shown to outperform vertical wells in terms of versatility, productivity and clean-up times under certain conditions. In this paper, the efficacy of an innovative pump-and-treat (P&T) configuration for groundwater remediation obtained by adopting either VRWs or HRWs technology is comparatively tested. A 3D transient finite element model of an unconfined aquifer containing a hexavalent chromium (Cr(VI)) contamination plume is considered to compare a single horizontal well configuration vs a range of spatially-optimised arrays containing vertical wells. A sensitivity analysis aimed at finding the best configuration to minimise the remediation time and the related cost is carried out by comparing different well diameters, D, pumping rates, Q, and position of wells. A comparative cost analysis demonstrates that, for the examined case-study, a single HRW achieves the clean-up goals in the same time span as for a greater number of vertical wells, but at higher price due to the excavation costs.

Enhancing Biomass and Lutein Production From Scenedesmus almeriensis: Effect of Carbon Dioxide Concentration and Culture Medium Reuse.

The main purpose of this study is to investigate the effects of operative parameters and bioprocess strategies on the photo-autotrophic cultivation of the microalgae Scenedesmus almeriensis for lutein production. S. almeriensis was cultivated in a vertical bubble column photobioreactor (VBC-PBR) in batch mode and the bioactive compounds were extracted by accelerated solvent extraction with ethanol at 67°C and 10 MPa. The cultivation with a volume fraction of CO2 in the range 0-3.0%v/v showed that the highest biomass and lutein concentrations - 3.7 g/L and 5.71 mg/g, respectively - were measured at the highest CO2 concentration and using fresh growth medium. Recycling the cultivation medium from harvested microalgae resulted in decreased biomass and lutein content. The nutrient chemical composition analysis showed the highest consumption rates for nitrogen and phosphorus, with values higher than 80%, while sulfate and chloride were less consumed.

Sorption of Organic Pollutants by Humic Acids: A Review.

Humic acids (HA) are promising green materials for water and wastewater treatment. They show a strong ability to sorb cationic and hydrophobic organic pollutants. Cationic compounds interact mainly by electrostatic interaction with the deprotonated carboxylic groups of HA. Other functional groups of HA such as quinones, may form covalent bonds with aromatic ammines or similar organic compounds. Computational and experimental works show that the interaction of HA with hydrophobic organics is mainly due to π-π interactions, hydrophobic effect and hydrogen bonding. Several works report that sorbing efficiency is related to the hydrophobicity of the sorbate. Papers about the interaction between organic pollutants and humic acids dissolved in solution, in the solid state and adsorbed onto solid particles, like aluminosilicates and magnetic materials, are reviewed and discussed. A short discussion of the thermodynamics and kinetics of the sorption process, with indication of the main mistakes reported in literature, is also given.

Selective Extraction of ω-3 Fatty Acids from Nannochloropsis sp. Using Supercritical CO2 Extraction.

In this article, microalgae Nannochloropsis sp. was used for fatty acid (FA) extraction, using a supercritical fluid-carbon dioxide (SF-CO2) extraction method. This study investigated the influence of different pre-treatment conditions by varying the grinding speed (200-600 rpm), pre-treatment time (2.5-10 min), and mixing ratio of diatomaceous earth (DE) and Nannochloropsis sp. biomass (0.5-2.0 DE/biomass) on FAs extraction. In addition, the effect of different operating conditions, such as pressure (100-550 bar), temperature (50-75 °C), and CO2 flow rate (7.24 and 14.48 g/min) on eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) recovery, was analyzed. Experimental data evidenced that, keeping constant the extraction conditions, the pre-treatment step enhanced the FAs extraction yield up to 3.4 fold, thereby the maximum extracted amount of FAs (61.19 mg/g) was attained with the pre-treatment with a ratio of DE/biomass of 1 at 600 rpm for 5 min. Moreover, by increasing both SF-CO2 pressure and temperature, the selectivity towards EPA was enhanced, while intermediate pressure and lower pressure promoted DHA recovery. The highest amount of extracted EPA, i.e., 5.69 mg/g, corresponding to 15.59%, was obtained at 75 °C and 550 bar with a CO2 flow rate of 14.48 g/min, while the maximum amount of extracted DHA, i.e., ~0.12 mg/g, equal to 79.63%, was registered at 50 °C and 400 bar with a CO2 flow rate of 14.48 g/min. Moreover, the increased CO2 flow rate from 7.24 to 14.48 g/min enhanced both EPA and DHA recovery.

Odorous emission reduction from a waste landfill with an optimal protection system based on fuzzy logic.

Effective landfill management and operation require an accurate evaluation of the occurrence and extent of odour emission events, which are among the main causes of resident complaints and concerns, in particular in densely urbanised areas. This paper proposes a fuzzy optimal protection system (FOPS) based on fuzzy logic to manage odour production from a municipal solid waste (MSW) landfill. The case study is a MSW landfill in an old quarry site located 6 km north-west of Naples city centre (Italy). The aim is to reduce the odour nuisance in the area surrounding the landfill where there are several sensitive receptors. FOPS is based on logical relationships between local atmospheric dynamics, number and intensity of odour pollution events detected by certain fixed receptors and odour emission rate via an optimal fuzzy approach. Such system allows to start, in real time, established mitigation actions required to further reduce the odorous emissions from the landfill itself (e.g. spraying of perfumed substances and activation of extraction wells), especially when weather conditions might not be favourable and cause by causing a higher odour perception. The fuzzy system was coupled with the air pollutant transport software CALPUFF to simulate the odour dispersion in the considered area taking into account both different odour emission rates and local weather conditions. FOPS results show that this approach can be very useful as, by measuring the odour concentrations, a significant reduction of the odour exceedances over the thresholds fixed, to minimise the olfactory harassment, was observed in the whole area studied.

Microalgae Characterization for Consolidated and New Application in Human Food, Animal Feed and Nutraceuticals.

The exploration of new food sources and natural products is the result of the increase in world population as well as the need for a healthier diet; in this context, microalgae are undoubtedly an interesting solution. With the intent to enhance their value in new commercial applications, this paper aims to characterize microalgae that have already been recognized as safe or authorized as additives for humans and animals (Chlorella vulgaris, Arthrospira platensis, Haematococcus pluvialis, Dunaliella salina) as well as those that have not yet been marketed (Scenedesmus almeriensis and Nannocholoropsis sp.). In this scope, the content of proteins, carbohydrates, lipids, total dietary fiber, humidity, ash, and carotenoids has been measured via standard methods. In addition, individual carotenoids (beta-carotene, astaxanthin, and lutein) as well as individual saturated, monounsaturated, and polyunsaturated fatty acids have been identified and quantified chromatographically. The results confirm the prerogative of some species to produce certain products such as carotenoids, polyunsaturated fatty acids, and proteins, but also show how their cellular content is rich and diverse. H. pluvialis green and red phases, and Nannochloropsis sp., in addition to producing astaxanthin and omega-3, contain about 25⁻33% w/w proteins on a dry basis. D. salina is rich in beta-carotene (3.45% w/w on a dry basis), S. Almeriensis is a source of lutein (0.30% w/w on a dry basis), and the C. vulgaris species is a protein-based microalgae (45% w/w on a dry basis). All, however, can also produce important fatty acids such as palmitic acid, γ-linolenic acid, and oleic acid. Considering their varied composition, these microalgae can find applications in multiple sectors. This is true for microalgae already on the market as well as for promising new sources of bioproducts such as S. almeriensis and Nannochloropsis sp.

Extraction of Astaxanthin and Lutein from Microalga Haematococcus pluvialis in the Red Phase Using CO2 Supercritical Fluid Extraction Technology with Ethanol as Co-Solvent.

Astaxanthin and lutein, antioxidants used in nutraceutics and cosmetics, can be extracted from several microalgal species. In this work, investigations on astaxanthin and lutein extraction from Haematococcus pluvialis (H. pluvialis) in the red phase were carried out by means of the supercritical fluid extraction (SFE) technique, in which CO2 supercritical fluid was used as the extracting solvent with ethanol as the co-solvent. The experimental activity was performed using a bench-scale reactor in semi-batch configuration with varying extraction times (20, 40, 60, and 80 min), temperatures (50, 65, and 80 °C) and pressures (100, 400, and 550 bar). Moreover, the performance of CO2 SFE with ethanol was compared to that without ethanol. The results show that the highest astaxanthin and lutein recoveries were found at 65 °C and 550 bar, with ~18.5 mg/g dry weight (~92%) astaxanthin and ~7.15 mg/g dry weight (~93%) lutein. The highest astaxanthin purity and the highest lutein purity were found at 80 °C and 400 bar, and at 65 °C and 550 bar, respectively.

Supercritical Carbon Dioxide Extraction of Astaxanthin, Lutein, and Fatty Acids from Haematococcus pluvialis Microalgae.

Haematococcus pluvialis microalgae in the red phase can produce significant amounts of astaxanthin, lutein, and fatty acids (FAs), which are valuable antioxidants in nutraceutics and cosmetics. Extraction of astaxanthin, lutein, and FAs from disrupted biomass of the H. pluvialis red phase using carbon dioxide (CO2) in supercritical fluid extraction (SFE) conditions was investigated using a bench-scale reactor in a semi-batch configuration. In particular, the effect of extraction time (20, 40, 60, 80, and 120 min), CO2 flow rate (3.62 and 14.48 g/min) temperature (50, 65, and 80 °C), and pressure (100, 400, and 550 bar.) was explored. The results show the maximum recovery of astaxanthin and lutein achieved were 98.6% and 52.3%, respectively, at 50 °C and 550 bars, while the maximum recovery of FAs attained was 93.2% at 65 °C and 550 bars.

Extraction of astaxanthin from microalga Haematococcus pluvialis in red phase by using generally recognized as safe solvents and accelerated extraction.

Solvent Extraction was tested to extract astaxanthin from Haematococcus pluvialis in red phase (HPR), by investigating effects of solvents, extraction pressure and temperature. Astaxanthin isomers were identified and quantified in the extract. The performances of acetone and ethanol, Generally Recognized As Safe (GRAS) solvents, were explored. Negligible effect of pressure was found, while with increasing extraction temperature astaxanthin recovery increased till a maximum value, beyond which thermal degradation seemed to be greater than the positive effect of temperature on extraction. Furthermore, to maximize the extraction yield of astaxanthin, mechanical pre-treatment of HPR biomass was carried out and several extraction runs were consecutively performed. Experimental results showed that after the mechanical pre-treatment the astaxanthin recovery strongly increased while a single extraction run of 20 min was sufficient to extract more than 99% of total astaxanthin extracted. After pre-treatment, maximum recovery of about 87% was found for acetone (pressure = 100 bar; temperature = 40 °C; total time = 60 min).

Development and Characterization of High Performance Shape Memory Alloy Coatings for Structural Aerospace Applications.

This paper presents an innovative approach, which enables control of the mechanical properties of metallic components by external stimuli to improve the mechanical behavior of aluminum structures in aeronautical applications. The approach is based on the exploitation of the shape memory effect of novel Shape Memory Alloy (SMA) coatings deposited on metallic structural components, for the purpose of relaxing the stress of underlying structures by simple heating at field-feasible temperatures, therefore enhancing their structural integrity and increasing their stiffness and rigidity while allowing them to withstand expected loading conditions safely. Numerical analysis provided an insight in the expected response of the SMA coating and of the SMA-coated element, while the dependence of alloy composition and heat treatment on the experienced shape memory effect were investigated experimentally. A two-phase process is proposed for deposition of the SMA coating in an order that induces beneficial stress relaxation to the underlying structure through the shape memory effect.