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Our current industrial ammonia cycle is far from being sustainable – while intense energy is required to produce ammonia – almost half of it ends up in wastewater treatment plants (WWTPs) where is finally transformed and lost. This work shows the application of flat sheet membrane distillation (MD) commercial modules for the ammonia recovery from WWTPs. First, optimized operating conditions – in terms of ammonia flux, specific thermal energy (STEC) and chemical demand – were investigated in the laboratory with a 2.3 m2 MD module. Second, optimized conditions were demonstrated in a pilot installation on site operating a 14.5 m2 MD module continuously (24/7) for three months. Results showed that MD is a robust, low-maintenance technology that can be operated at low temperature and corresponding STEC (i.e. 38 °C and 13.6 kWhth per kg1 NH3, respectively) and low pH (i.e. 8.7) for the recovery of 90% of the water-bound ammonia as an ammonium sulphate (AS) solution. The AS product reached a concentration of 5 g l-1 N–NH4, lower than conventional fertilizers, however given its high quality and volume reduction factor, it constitutes a potential fertilizer solution for local needs. The maximum AS permeate concentration was limited by the increasing water vapour flux due to a higher osmotic distillation effect and a minor ammonia flux decrease with increasing permeate concentration. Further research will focus on optimizing the module configuration to minimize water flux and overall system operation for increased heat recovery and open-loop operation.

It is well known that the traditional synthetic polymers, such as Polyurethane foams, require raw materials that are not fully sustainable and are based on oil-feedstocks. For this reason, renewable resources such as biomass, polysaccharides and proteins are still recognized as one of the most promising approaches for substituting oil-based raw materials (mainly polyols). However, polyurethanes from renewable sources exhibit poor physical and functional performances. For this reason, the best technological solution is the production of polyurethane materials obtained through a partial replacement of the oil-based polyurethane precursors. This approach enables a good balance between the need to improve the sustainability of the polymer and the need to achieve suitable performances, to fulfill the technological requirements for specific applications. In this paper, a succinic-based polyol sample (obtained from biomass source) was synthesized, characterized and blended with cardanol-based polyol (Mannich-based polyol) to produce sustainable rigid polyurethane foams in which the oil-based polyol is totally replaced. A suitable amount of catalysts and surfactant, water as blowing reagent and poly-methylene diphenyl di-isocyanate as isocyanate source were used for the polyurethane synthesis. The resulting foams were characterized by means of infrared spectroscopy (FTIR) to control the cross-linking reactions, scanning electron microscopy (SEM) to evaluate the morphological structure and thermal gravimetric analysis (TGA) and thermal conductivity to evaluate thermal degradation behavior and thermal insulation properties.

Nowadays, the chemical industry is looking for sustainable chemicals to synthesize nanocomposite bio-based polyurethane foams, PUs, with the aim to replace the conventional petrochemical precursors. Some possibilities to increase the environmental sustainability in the synthesis of nanocomposite PUs include the use of chemicals and additives derived from renewable sources (such as vegetable oils or biomass wastes), which comprise increasingly wider base raw materials. Generally, sustainable PUs exhibit chemico-physical, mechanical and functional properties, which are not comparable with those of PUs produced from petrochemical precursors. In order to enhance the performances, as well as the bio-based aspect, the addition in the polyurethane formulation of renewable or natural fillers can be considered. Among these, walnut shells and cellulose are very popular wood-based waste, and due to their chemical composition, carbohydrate, protein and/or fatty acid, can be used as reactive fillers in the synthesis of Pus. Diatomite, as a natural inorganic nanoporous filler, can also be evaluated to improve mechanical and thermal insulation properties of rigid PUs. In this respect, sustainable nanocomposite rigid PU foams are synthesized by using a cardanol-based Mannich polyol, MDI (Methylene diphenyl isocyanate) as an isocyanate source, catalysts and surfactant to regulate the polymerization and blowing reactions, H2O as a sustainable blowing agent and a suitable amount (5 wt%) of ultramilled walnut shell, cellulose and diatomite as filler. The eect of these fillers on the chemico-physical, morphological, mechanical and functional performances on PU foams has been analyzed.