Recovery Of Valuable Products Research Articles

Demulsification of Pickering Emulsions by Chemical Dissolution of Stabilizers.

Demulsification of particle-stabilized oil-in-water emulsions is crucial in diverse fields such as treatment of produce water, recovery of valuable products of Pickering emulsion catalysis, and so on. In this work, we investigated a facile method for destabilizing emulsions by dissolving stabilizer particles by the introduction of acid or base. Nanoellipsoidal hematite-stabilized decane-in-water emulsions are destabilized by dissolving hematite with oxalic or hydrochloric acid in situ. Time required for complete demulsification decreased as the acid concentration is increased. The demulsification time is typically on the order of a few hours for the chosen protocol. Similarly, the silica-stabilized decane-water emulsion is demulsified by the addition of aqueous sodium hydroxide. Demulsification kinetics is presented as the temporal change of the emulsion volume with time. Emulsion volume decreases in two stages: an initial slow decrease followed by an exponential decrease. Scanning electron microscopy analysis shows that the stabilizing particles are completely dissolved and recrystallized as salts of respective kinds. An estimate of the desorption free energy suggests that particle size should be reduced to a few nanometers for inducing destabilization. This work describes a facile method to destabilize oil-in-water emulsion, and it can be generalized to any other particle-stabilized emulsions by choosing appropriate chemical reagent for dissolution.

Valorization of organic carbon in primary sludge via semi-continuous dark fermentation: First step to establish a wastewater biorefinery

In this study, lab-scale, bench-scale, and pilot-scale experiments were carried out to optimize short-chain fatty acids production from primary sludge. Batch tests showed the requirement of short retention times and semi-continuous operation mode showed a plateau of maximum daily productivity at 36-hours hydraulic retention time with minimal methanation. Optimization from pH 5 to pH 10 at 36 h-hydraulic retention time under long-term semi-continuous operating mode revealed that production of short-chain fatty acids was pH dependent and highest yields could be achieved at pH 7 by establishing optimum redox conditions for fermentation. Pilot-scale experiments at 32 °C showed that daily productivity (3.1 g∙Lreactor-1∙dHRT-1) and yields (150 mg∙gVS-1; OLR = 21 gVS∙Lreactor-1∙dHRT-1; pH 7) of short-chain fatty acids could be significantly improved, specifically for acetic and propionic acids. From these results, a robust dark fermentation step for recovery of valuable products from the solids treatment step in a biorefinery can be achieved.

Evolution and speciation transformation of chlorine during automobile shredder residue pyrolysis

Disposal of automobile shredder residue (ASR) via pyrolysis enables the recovery of valuable products; however, the production of hazardous pollutants and low-value products is inevitable due to its high chlorine content. In this work, chlorine evolution behavior and the conversion mechanism during ASR pyrolysis between 480 and 600 °C were systematically studied. The experimental results for organic chlorine (Org-Cl) showed that released chlorinated gases were complex, and HCl only accounted for 35% of the gas phase products, while short-chain hydrocarbons with carbon atoms between two and four accounted for 52%. Chlorine was predominantly retained in the char, and Org-Cl was the primary contributor to the residual chlorine, accounting for over 50% of the char. The content of inorganic chlorine (InO-Cl) was low in the raw sample but significantly increased in the char. Through the distinction between organic and inorganic chlorine content in char, it was confirmed that Org-Cl could be converted to InO-Cl due to complex secondary reactions with metallic compounds. The conversion was favored by increasing the Org-Cl content and the temperature. Our findings clarified the evolution mechanism of chlorine and the transformation from Org-Cl to InO-Cl, thus providing guidance for chlorine regulation and the efficient recycling of metal resources.

Advances in understanding kinetic mechanisms underlying waste ground tyre rubber pyrolysis

The depletion of natural resources and the need to reduce solid waste in urban areas have necessitated the incorporation of used materials such as waste ground tyre rubbers (WGTR), into manufacturing processes. As a result, techniques and recycling methods have been established to use tyres as feedstock for marketable products since tyres have a calorific value higher than coal and contain a significant amount of carbon black. Among several techniques, pyrolysis has emerged as the most appealing for treating WGTRs. This technique allows the recovery of valuable products like combustible gases, fuels and chemicals, and activated carbon. Studies have focused on understanding the mechanism underlying the WGTR pyrolysis through the establishment of mathematical models and reaction patterns to valorise WGTRs and efficiently produce marketable chemicals. This paper presents an overview of recent developments in understanding WGTR pyrolysis mechanisms. A general mechanism observed involves a first depolymerisation/condensation of the rubbers, then a degradation of the condensed products, and finally a devolatilisation of additives. Based on the limited information available on the chemicals' formation mechanism, it is assumed that limonene and isoprene are derived from natural rubber (NR), through a series of β-scission and depropagation reactions of polyisoprene and intramolecular cyclisation and scission of monomeric isoprene, respectively, with an equilibrium step of Diels-Alder reaction. The maximum yield of limonene and isoprene have been found to be 51% and 20.5% at temperature around 500°C respectively. The isoprene yield can be increased up to 37.57 % with the use of catalyst such as Calcium Oxide.

Automotive Paint Sludge: A Review of Pretreatments and Recovery Options

Automotive paint sludge (PS) is the waste product generated in the painting process of vehicle bodies. Although automotive spray painting is an automated operation, its efficiency is still quite low, since approximately 40–50% of the employed paint does not reach the target and, after being mixed with the collecting water, becomes PS. PS is a very complex material that contains several organic and inorganic components, in addition to 90% water immediately after production. Italian automotive factories produce from 2.5 to 5.0 kg of PS per painted car. If that figure is related to the number of vehicles produced worldwide every year, in the order of 100 million, it determines an annual PS amount in the order of 200,000–500,000 t. Consequently, a proper final destination for PS must be found. The waste management hierarchy and the principles of the circular economy require that we privilege solutions that foresee the recovery of valuable products or energy. This paper first reviews the processes and the machines that have been recently developed to obtain an enhanced mechanical dewatering of PS. The pretreatment of PS dewatering is often crucial in order to obtain high efficiency in the subsequent recovery process. Afterwards, the paper presents and discusses the recovery options that have been proposed and tested, at different scales, by several authors in the last thirty years. The processes for PS management can be grouped as follows: (i) direct employment of physically/chemically treated PS in the production of primers and sealants; (ii) utilization of PS for the production of building materials, as supplementary components of cement concrete, mortar, or bituminous mixtures; (iii) extraction of valuable organic and inorganic products by using thermal processes (pyrolysis, gasification); (iv) biological processes for PS detoxification, metal recovery, and stabilization before landfilling.

Recovery of Cellulose, Extracellular Polymeric Substances and Microplastics from Sewage Sludge: A Review

Wastewater treatment plants are considered to be not only as treatment facilities, but also essential elements of the circular economy. Wastewater treatment plants can be essential chains of the circular economy cycle. Despite this, sewage sludge management and utilization are mostly limited to biodegradation and further agricultural uses or incineration. The recovery of valuable products is mainly limited to nitrogen and phosphorus compounds. Fewer analyses focus on generating, recovering, and removing various polymers from sewage sludge, such as cellulose or extracellular polymeric substances (EPS). On the other hand, sewage sludge also contains polymeric pollutants, such as microplastics. The recovery and use of biopolymers is significant considering the problems connected with the presence and effects of artificial polymers (microplastics) in the environment. Despite the technical possibilities, not many technical scale installations are operated. Law regulations should make some incentives to develop the technologies and sell the recovered polymers in the market not as waste material, but as a valuable product. This paper presents state-of-the-art technologies for selected polymers’ recovery from sludge, including technical parameters of the processes and possible applications of recovered products, but it also considers the possibility of microplastics’ removal from this waste material.

Progress and challenges in sustainable pyrolysis technology: Reactors, feedstocks and products

Pyrolysis is a thermo-chemical decomposition process that converts organic or inorganic materials into solid, liquid and gaseous products. The pyrolysis process involves multiple complex chemical reactions, and the derived products are highly dependent on the pyrolysis operating parameters and type of feedstock. In the present review, progress on the state-of-the-art pyrolysis technology, feedstock and properties of the end products are thoroughly reviewed. The potential application of the pyrolysis products in the industries is discussed: solid leftover can be upgraded and used as a bio-adsorbant, soil amendment, fertilizer or solid fuel; pyrolysis liquid can be used as a bio-chemical source or upgraded into liquid fuel; gaseous products can be used as recirculating gas for the pyrolysis environment or burnt as fuel for heat and power generation. Despite the potential of pyrolysis in processing agricultural or industrial wastes, studies regarding the economic feasibility and environment sustainability of scaled-up pyrolysis plant are scarce. A comprehensive overview on the type of pyrolysis reactor technology, potential feedstock and the properties of the derived products is presented. Further, the sustainability of the technology is assessed from the aspects of energy balance, environment and economics. In spite of the potential benefits to the environment and recovery of valuable products, there are several challenges that need to be addressed to ensure the sustainability and commercialibility of the pyrolysis technologies.

Latest Advances in Waste Plastic Pyrolytic Catalysis

With the increase in demand for plastic use, waste plastic (WP) management remains a challenge in the contemporary world due to the lack of sustainable efforts to tackle it. The increment in WPs is proportional to man’s demand and use of plastics, and these come along with environmental challenges. This increase in WPs, and the resulting environmental consequences are mainly due to the characteristic biodegradation properties of plastics. Landfilling, pollution, groundwater contamination, incineration, and blockage of drainages are common environmental challenges associated with WPs. The bulk of these WPs constitutes polyethene (PE), polyethene terephthalate (PET) and polystyrene (PS). Pyrolysis is an eco-friendly thermo-chemical waste plastic treatment solution for valuable product recovery, preferred over landfilling and incineration solutions. In this extensive review, a critical investigation on waste plastic catalytic pyrolysis (WPCP) is performed, including catalyst and non-catalyst applications to sustainably tackle WP management. Current catalysis techniques are revealed, and some comparisons are made where necessary. Common pyrolytic products and common shortcomings and errors related to WP catalysis were also identified. The benefits of catalysts and their applications to augment and optimise thermal pyrolysis are emphasised. With all these findings, and more, this paper provides reassurance on the significance of catalysis to industrial-scale applications and products and supports related WPCP research work concerning the environment and other beneficiaries.

Expanding ASM models towards integrated processes for short-cut nitrogen removal and bioplastic recovery

In next-generation water resource recovery facilities (WRRFs), it is becoming increasingly important to save energy costs and promote resource recovery of valuable products. One way of reducing the substantial aeration energy costs at WRRFs is to employ shortcut N removal, while polyhydroxyalkanoate (PHA) production and recovery as bioplastic is a promising means of recovering a valuable product from biosolids. Both objectives can be achieved simultaneously through the Short-Cut Enhanced Phosphorus and PHA Recovery (SCEPPHAR) process. However, current mathematical models have not previously been employed to describe the behavior of such a process, which limits engineering design and optimisation of process operation. This work focusses on extending the ASM3 model towards the description of short-cut nitrogen removal and simultaneous PHA recovery in a sidestream treatment process. The calibrated and validated model described very well the nitritation process coupled with the aerobic feast/anoxic famine process for the selection of PHA producing organisms at a pilot-scale facility operated in Carbonera, Italy, where the normalised root mean squared error (NRMSE) was consistently <20%. Furthermore, the model applied to the PHA selection stage could effectively describe the PHA accumulation stage without recalibration. A simulation study was performed using the modified ASM3 model to assess the relative benefits of the SCEPPHAR process strategy as compared to the fully aerobic selection process for mixed culture PHA production. While the level of PHA production was found to be 34% lower with SCEPPHAR, a 43% savings in volatile fatty acids (VFAs) demand, a 15% decrease in Total suspended solids (TSS) production and a 28% decrease in oxygen demand were also achievable, which could lead to savings in operational costs. This study facilitates the design and optimisation of WRRFs that integrate short-cut N removal with PHA production, saving aeration energy costs while achieving resource recovery.

Biocontrol Potential of Chitin and Chitosan Extracted from Black Soldier Fly Pupal Exuviae against Bacterial Wilt of Tomato.

Globally, Ralstonia solanacearum (Smith) is ranked one of the most destructive bacterial pathogens inducing rapid and fatal wilting symptoms on tomatoes. Yield losses on tomatoes vary from 0 to 91% and most control measures are unaffordable to resource-poor farmers. This study investigated the antimicrobial activities of chitin and chitosan extracted from black soldier fly (BSF) pupal exuviae against R. solanacearum. Morphological, biochemical, and molecular techniques were used to isolate and characterize R. solanacearum for in vitro pathogenicity test using disc diffusion technique. Our results revealed that BSF chitosan significantly inhibited the growth of R. solanacearum when compared to treatments without chitosan. However, there was no significant difference in the antibacterial activities between BSF and commercial chitosan against R. solanacearum. Soil amended with BSF-chitin and chitosan demonstrated a reduction in bacterial wilt disease incidence by 30.31% and 34.95%, respectively. Whereas, disease severity was reduced by 22.57% and 23.66%, when inoculated tomato plants were subjected to soil amended with BSF chitin and chitosan, respectively. These findings have demonstrated that BSF pupal shells are an attractive renewable raw material for the recovery of valuable products (chitin and chitosan) with promising ability as a new type of eco-friendly control measure against bacterial wilt caused by R. solanacearum. Further studies should explore integrated pest management options that integrate multiple components including insect-based chitin and chitosan to manage bacterial wilt diseases, contributing significantly to increased tomato production worldwide.

The electrosorptive response of a carbon nanotube flow-through electrode in aqueous systems

The capture and recovery of valuable products from wastewater and/or bio-broths is one of today’s industrial challenges. Potential-controlled chromatography is a versatile solution to separate charged or polarized target species from aqueous systems. This capacitive flow-through technique combines the advantages of capacitive desalination and ion-exchange chromatography. The separation principle is controlled by system-dependent solid–liquid interaction mechanisms at the potential-controlled interface and characterized by the electrochemical double layer (EDL) formation. We conducted new experiments on the process- and environment-dependent surface effects in aqueous systems to better understand electrically driven processes inside a macroporous multi-walled carbon nanotube electrode. Here, the column and current response are investigated as a function of flow rate, as well as mobile phase pH-value, composition and concentration. Due to the strong water affinity of the material, water ions significantly co-define the EDL. The current response depends particularly on the ion properties and concentration. The use of electrolytes promotes capacitive and faradaic current and diminishes pH-deviation occurring at a negative potential. The effective range of the EDL decreases with increasing shear forces. Finally, a better performance for electrosorbing maleic acid is guaranteed at higher electrolyte concentration and low flow rate. This paper successfully addresses research gaps in potential-dependent effects that occur in multi-walled carbon nanotube electrodes.

Sequestration of light hydrocarbons in Ionic Liquids at high-pressures: Consistency and thermodynamic modeling

Ionic liquids are applicable in the recovery of valuable products, remotion of polluting agents, and used in many CO2-capture techniques. In this work, high-pressure vapor-liquid equilibria of twenty-one binary mixtures of light hydrocarbons + IL has been modelled with Peng-Robinson/Stryjek-Vera equation of state applying Wong-Sandler mixing rules and van Laar model for the gamma-phi approach and Perturbed Chain-Statistical Associating Fluid Theory equation of state for the phi-phi approach. Critical properties were determined using a group contribution method. Adjustable characteristic pure component parameters were obtained using predicted vapor pressures and saturated liquids densities values. Experimental data, obtained from literature, were subjected to thermodynamic consistency area test. For the thermodynamic modelling, adjustable parameters were fitted between predicted and experimental bubble pressure. Van Laar and interaction parameters were regarded as temperature-dependent. Results obtained for both models, in terms of the main deviations between experimental and calculated pressures, were reasonably satisfactory.

Multi-component separation of small molecular/ionic pollutants with smart pH-gating membranes

Precise molecular separation through a membrane is critical in sustainable water purification applications. Routine separation membranes with inflexible molecular transmission channels are effective for the separation of two substances, which cannot meet the practical treatment requirements of multicomponent complex wastewater. We report a pH-gating membrane (PGM) formed by cross-linking a polyaniline/polyimide substrate with polyethyleneimine. PGMs exhibit tunable and reversible molecular sieving architectures under pH stimuli, which are attributed to the contraction and extension of polyaniline (PANI) chains during the transition between protonation and deprotonation. Based on this smart pH gating property, precise separation of the three-component mixture of Alcian Blue 8 GX, Orange II, and NaCl can be achieved with a single membrane at pH 8 and 2. The dye molecule-to-NaCl selectivity of this membrane reaches 942.1. It outperforms most state-of-art membranes, demonstrating promising applications for the selective separation and recovery of valuable products instead of harmful discharge.

Effects of oxidising atmosphere on brewer’s yeast hydrothermal treatment and subsequent biopolymer recovery

• The presence of oxygen enhanced yeast disintegration. • Soluble proteins abated at long times when oxygen was present. • Oxygen caused a convergency in the different protein isoelectric points to 3. • Oxygen decreased protein hydrophobicity, worsening saline precipitation. • Oxygen reduced protein recovery but enhanced selectivity in IMAC. Spent brewer’s yeast is an underused by-product, whose current management offers low returns. This article studies, for the first time ever, the hydrothermal treatment of spent brewer’s yeast, paying special attention to the effect of the presence of oxygen on the physical properties, composition and potential recovery of valuable products from the hydrolysed yeast, as previous step towards the employment of these recovered proteins as renewable chemical feedstock for green industrial uses. Results showed a higher VSS disintegration employing an oxidising atmosphere, as well as a better solubilisation in terms of solid COD reduction, although it also lowered soluble COD but without significantly reducing soluble TOC. Both treatments led to an almost complete solubilisation of protein and carbohydrates from yeast, which were subsequently degraded in presence of oxygen if reaction times were lengthened. Looking at biopolymer recovery, protein precipitation by pH adjustment worked better in hydrolysates obtained in presence of oxygen, with almost 90% of protein precipitation and good selectivities at pH 2.5 and 3. Salting out was more effective, in terms of selectivity, for samples obtained in absence of oxygen and low concentrations of ammonium sulphate. The application of IMAC showed better results on yeast hydrolysates obtained under an inert atmosphere, reaching maximum sorption capacities of almost 100 mg protein/g dry resin, three times higher than those observed using the hydrolysate produced in presence of oxygen. A new perspective in yeast management during beer production is open as renewable chemical feedstock for protein, although further studies are required to optimise protein recovery and purification with respect to its applications.

Evaluation of Reverse Osmosis Membranes in Concentration of Beetroot Peel Extract

Recovery of valuable products from organic wastes with conventional extraction method plus modern separation technology is becoming popular in solid waste management. The major attention of this project was to test the efficiencies of two different types of reverse osmosis membranes (RO99 and X20) on juice concentration extracted from peel of beetroot which is "waste". The extractions of beetroot peel were completed using water and ethanol-water (15 v/v%) solvents at 22 °C for 60 minutes. The applied transmembrane pressure, temperature, and recirculation flow rate of membrane separation process were 40 bars, 30 °C, and 400 L/h, respectively. Quantifications of valuable compounds were detected using spectrophotometer. The permeate flux profiles were investigated and lower permeate flux was experienced with RO99 compared to X20 in both methods. Additionally, from the aspect of efficiency, RO99 outstripped X20 membrane on concentration of some compounds such as betalains, and phenolic components. Betaxanthin, betacyanin, antioxidant and TPC contents in final retentates of RO99 membrane concentration were as follow: 292.47±1.93 mg/L, 499.03±1.3 mg/L, 1133.15±25.74 mg/L,1243.96±106.56 mg/L (water solvent) and 337.26±4.31 mg/L, 585.2±5.83 mg/L, 698.55±22.53 mg/L, 1268.87±48.69 mg/L (ethanol-water solvent), respectively. From this experiment, expectation can be made that membrane technology can widen its applications in food and pharmaceutical industries.

Biopolymers recovery: dynamics and characterization of alginate-like exopolymers in an aerobic granular sludge system treating municipal wastewater without sludge inoculum

Alginate-like exopolymers (ALE) are present in the extracellular polymeric substances (EPS) of biological sludge such as aerobic granular sludge (AGS). The recovery of ALE from excess sludge produced by wastewater treatment plants (WWTP) is a relevant approach for the recovery of valuable products of industrial interest. However, little is known about dynamics of ALE content in sludge and associated factors. Thus, this study aimed at assessing the dynamics of EPS and ALE in terms of content, some chemical properties and influencing environmental factors along granulation in a sequencing batch reactor treating municipal wastewater. Results indicated that the EPS content was not correlated with the development of AGS, while the ALE content was higher, more stable and steadily increased after granulation achievement. Overall, 236 ± 27 mg VSALE/g VSsludge was recovered from AGS and 187 ± 94 mg VSALE/g VSsludge from flocs. However, the lower ALE content in flocs may be compensated by the higher sludge production rate in activated sludge systems. Principal component analysis (PCA) revealed that ALE content positively correlates with the nutrient and organic substrate conversion, and with the fraction of large AGS. Microbial analyses indicated that a stable microbial community composition was associated with a higher and more stable ALE content. ALE recovered from both flocs and AGS was endowed with hydrogel property, and no clear difference in their elemental composition and functional groups was observed. Therefore, our study provides insights about quantitative and qualitative aspects of ALE which are helpful for the improvement of waste biological sludge valorization.

THERMAL CHARACTERISATION STUDY OF TWO DISPOSABLE DIAPER BRANDS

Disposable diapers have become a prominent feature of solid waste dumped in landfills. It is estimated that disposable diapers take anywhere between 300 to 500 years to decompose. Despite the associated environmental challenges, a plethora of studies show that disposable diapers have become a popular choice for parents when compared with cloth diapers. Disposable diapers are argued to be more convenient for parents because of their once-off use and super-absorbent ability, of which they are able to absorb 200-300 times the weight as compared to the cloth diapers. This study investigates thermal devolatilisation profiles of disposable diapers as well as their iso-conventional kinetic parameters, elemental and fractional composition. In this study, the two most dominant disposable diaper brands were sampled and analysed qualitatively and quantitatively. It was observed that the exterior fraction of both diapers showed a single peak devolatilisation at a temperature of around 500°C, while the interior fraction showed two distinctive devolatilisation peaks observed below 400°C and above 500°C. However, the pyrolysis heating rate produced no effect on the pyro-char fraction. Furthermore, the devolatilisation pathways of different types of disposable diaper fractions showed that there is a potential for conducting stepwise pyrolysis to promote fractional recovery of valuable products. Disposable diapers waste conversion can be better handled by separating the outer fraction (mainly fossil-based plastics and rubbery materials) from the inner fraction (mainly bio-based fibers and absorbents). It is further illustrated that the kinetic parameters, Ea and k0 are different for each disposable diaper fraction.

Green extraction processes, biorefineries and sustainability: Recovery of high added-value products from natural sources

The role of compressed fluids-based extraction techniques for the sustainable recovery of valuable products from natural sources is described and discussed. Important aspects for green process design including the use of new solvents with novel properties, the development of integrated and intensified multi-unit operation processes as well as scale-up and techno-economic and environmental assessment are emphasized. Within this important research field, some key aspects are identified for the future development of more efficient, environmentally friendly and sustainable processes for bioactives recovery from natural sources. The use of biorefinery platforms based on the use of supercritical and/or pressurized fluids will have a critical importance in the near future.

The gypsum reduction process and its validation using the Mintek Pyrosim model

ABSTRACTWaste gypsum is produced as a by-product from the fertilizer, mining industries, and acid mine water neutralization using calcium carbonate and/or lime and desalination processes using reverse osmosis and ion-exchange processes, resulting in environmental and storage problems. The purpose of the study was to establish optimum operating conditions for the recovery of valuable products, e.g., sulfur and precipitated calcium carbonate, from waste gypsum, hence, offer an attractive solution to the gypsum waste problem. The paper presents results on thermal studies of waste gypsum in a tube furnace and its validation using the Mintek Pyrosim model. Gypsum was homogeneously mixed with coal and the reduction experiments conducted. The following findings were made: (i) reduction of waste gypsum is an endothermic reaction since, ΔH values were greater than 0 (ΔH > 0) when the reduction temperature was increased from 25 to 1200°C, (ii) energy requirement is dependent on temperature and gypsum to coal ratio. Gypsum to calcium sulfide conversion of 83.5 and 83.8% was obtained at the optimum temperature range of 1100–1200°C and gypsum to calcium sulfide conversion of 85.4% was obtained at the optimum coal to gypsum mole ratio of 2.1:1, (iii) excess coal gave a lower conversion, and (iv) the predicted data using Mintek Pyrosim were found to be similar to the experimental data.

Protein recovery from solubilized sludge by hydrothermal treatments

New alternatives for sludge management have been developed in recent years, with hydrothermal treatments being one of the most attractive ones. Even though many studies have been made on the application of hydrothermal treatments as pre-treatment or end-line technologies for sludge stabilisation and/or minimization, there is a lack of knowledge about the products generated during the process and its characteristics. This information is a crucial step for the assessment of the recovery of valuable products of the sludge, mainly proteins, humic acids and carbohydrates, which can considerably improve the economic balance of the hydrothermal treatment.This work assesses, for the first time, the potential of hydrothermally hydrolysed sludge as renewable source for proteins recovery. For this purpose, firstly, the concentrations and properties of the main soluble biopolymers generated during the hydrothermal treatment, either in presence (wet oxidation, WO) or absence (thermal hydrolysis, TH) of oxygen, were measured, determining the reaction time necessary for a maximum solubilisation. Peak concentrations of 7.7g/l (0.291g/gVSSo) of proteins for WO and 7.2g/l (0.272g/gVSSo) for TH, were achieved at 87min of experiment.Afterwards, different separation methods, usually applied at industrial scale, were assessed for the separation of protein from the hydrolysed sludge, in terms of protein recovery and selectivity. Ammonium sulphate addition was found to be the best separation method, achieving 87% and 86% of protein recovery for TH and WO samples respectively, and the highest selectivity. Although further studies are required in order to achieve complete protein purification, a new perspective in sludge management is now open, by recovering valuable compounds.