Life cycle assessment (LCA) applied to the process industry: a review

Purpose : Life cycle assessment (LCA) methodology is a well-established analytical method to quantify environmental impacts, which has been mainly applied to products. However, recent literature would suggest that it has also the potential as an analysis and design tool for processes, and stresses that one of the biggest challenges of this decade in the field of process systems engineering (PSE) is the development of tools for environmental considerations. Method : This article attempts to give an overview of the integration of LCA methodology in the context of industrial ecology, and focuses on the use of this methodology for environmental considerations concerning process design and optimization. Results : The review identifies that LCA is often used as a multi-objective optimization of processes: practitioners use LCA to obtain the inventory and inject the results into the optimization model. It also shows that most of the LCA studies undertaken on process analysis consider the unit processes as black boxes and build the inventory analysis on fixed operating conditions. Conclusions : The article highlights the interest to better assimilate PSE tools with LCA methodology, in order to produce a more detailed analysis. This will allow optimizing the influence of process operating conditions on environmental impacts and including detailed environmental results into process industry

Thermo-pressing of cake meal from sunflower whole plant, one only operation for two actions : expression of residual oil and molding of biodegradable agromaterials

The starting material used in this study was a cake generated during thermo-mechanical fractionation of sunflower (Helianthus annuus L.) whole plant in a Clextral BC 45 (France) twin-screw extruder. It was slightly deoiled (17.6% dry matter for residual oil content), leading to an oil extraction yield of 46.1% (yield based on the residual oil content in cake). As it was a mixture of fibers and proteins, it could be considered as a natural composite that was processed successfully into fiberboards by thermo-pressing. This study aimed to evaluate the influence of thermo-pressing conditions on oil expression yield during molding and on flexural properties of fiberboards manufactured from this cake. An experimental design with three variables was realized: from 250 to 500 kgf/cm² for pressure applied (in 5 levels), from 60 to 300 s for molding time (in 7 levels), and from 600 to 1200 mg/cm² for cake quantity (in 3 levels). Temperature of the aluminium mold positioned between the two plates of the heated hydraulic press (PEI, France) with 400 tons capacity was 200°C. All fiberboards were cohesive. As an internal binder, proteins ensured the agromaterial cohesion, and fibers entanglement also acted like reinforcement. Thermo-pressing was not only a molding operation. It also consisted in increasing the oil extraction efficiency. Oil expression yield during molding increased with the increase of pressure applied, and especially with the increase of molding time. At the same time, it was not so much influenced by the modification of cake quantity. Highest oil expression yield was 58.8% in proportion to the oil that the cake contained, leading to a total oil yield (oil extracted by water in twin-screw extruder, and oil expressed during molding) of 77.8% in proportion to the oil that the sunflower whole plant contained. It was associated with the next thermo-pressing conditions: 469 kgf/cm² for pressure applied, 300 s for molding time, and 697 mg/cm² for cake quantity. Flexural properties of the corresponding fiberboard were 8.1 MPa for flexural strength at break, and 1778 MPa for elastic modulus. Its thickness was 5.40 mm, leading to a mean apparent density of 1.25. Such flexural strength at break was a bit lower (-25%) than the one of the most resistant fiberboard (10.8 MPa), manufactured from the next thermo-pressing conditions: 250 kgf/cm² for pressure applied, 300 s for molding time, and 807 mg/cm² for cake quantity. For such conditions, oil expression yield was 48.0% in proportion to the oil that the cake contained, leading to a total oil yield close (-8%) to the highest yield obtained (71.9% in proportion to the oil that the sunflower whole plant contained instead of 77.8%). Thermo-pressing of cake from sunflower whole plant led to two actions in a single step: the expression of part of residual oil in cake that contributed to the improvement of the oil extraction efficiency, and the molding of biodegradable fiberboards. Their flexural properties were promising. Moreover, because residual oil content in fiberboards was at least 8.0% dry matter, they were not too water-sensitive (i.e. more durable than other thermo-pressed agromaterials). Such fiberboards were value-added agromaterials that may have direct industrial applications. Indeed, they would be potentially usable as inter-layer sheets for pallets, for the manufacturing of biodegradable containers (composters, crates for vegetable gardening), or for their heat insulation properties in building trade

Thermo-mechanical behaviour of the raffinate resulting from the aqueous extraction of sunflower whole plant in twin-screw extruder: manufacturing of biodegradable agromaterials by thermo-pressing

Biorefinery of sunflower whole plant can be realized using a twin-screw extruder. Thermo-mechanical fractionation and aqueous extraction are conducted simultaneously. A filter section is outfitted along the barrel to collect continuously an extract and a raffinate (cake meal). Oil yield obtained is 53%. Proteins are partly extracted at the same time, just as pectins and hemicelluloses. Protein yield is 46%. Cake meal is relatively moist (66% for the moisture content). It is first dried to make easier its conservation. It is largely composed of lignocellulosic fibres (59% of the dry matter) from depithed stalk. Lipid content is 13% of the dry matter or 35% of the oil in whole plant. Protein content is 7% of the dry matter or 45% of the proteins in whole plant. DSC measurements indicate that denaturation of proteins is almost complete in the cake meal. DMTA spectrum of its milled powder reveals a significant peak at high temperature (between 175 and 200°C). As already observed with industrial sunflower cake meal, it can be associated with the glass transition of proteins. As a mixture of fibres and proteins, the cake meal can be considered as a natural composite. It is successfully processed into biodegradable and value-added agromaterials by thermo-pressing. As for DMTA analysis, the glass transition of proteins in the cake meal is also observed with PVT analysis at around 180°C. It makes easier the choice of the best thermo-pressing conditions to produce panels with higher mechanical properties in bending. These properties increase simultaneously with temperature, pressure and time chosen for molding operation. The highest flexural strength at break (11.5 MPa) and the highest elastic modulus (2.22 GPa) are obtained for the next molding conditions: 200°C and 320 kgf/cm2 during 60 s. Drop angle measurements show that the corresponding panel is also the most resistant to water. No significant transition is observed inside this panel above 0°C and until 200°C with DMTA analysis. Proteins ensure the agromaterial cohesion without any phase change in this temperature range, and fibres entanglement also acts like reinforcement. This panel could be used as inter-layer sheets for pallets or for the manufacturing of biodegradable containers (composters, crates for vegetable gardening) by assembly of panels

The twin-screw extrusion technology, an original and powerful solution for the biorefinery of sunflower whole plant

The objective of this study was to evaluate the feasibility of an aqueous process for the biorefinery of sunflower whole plant using a twin-screw extruder. Aqueous extraction of oil was chosen as an environment-friendly alternative to the solvent extraction. The extruder was used to carry out three essential unit operations: grinding, liquid/solid extraction, and liquid/solid separation. Wringing out the mixing was effective. However, drying of the cake meal was not optimal. Lixiviation of cotyledon cells was also incomplete. Extraction efficiency depended on operating conditions: screw rotation speed, and input flow rates of whole plant and water. In the best conditions, oil yield was 57%. Residual oil content in the cake meal was 14%. These conditions leaded to the co-extraction of proteins, pectins, and hemicelluloses. The corresponding protein yield was 44%. Oil was extracted in the form of two oil-in-water emulsions. These hydrophobic phases were stabilized by phospholipids and proteins at interface. An aqueous extract containing part of the water-soluble constituents, mainly proteins and pectins, was also generated. As a mixture of fibers and proteins, the cake meal was molded by thermo-pressing. Panels produced had interesting mechanical properties in bending. The obtained fractions may have applications as bases for industrial products

New process for the biorefinery of sunflower whole plant by thermo-mechanical fractionation and aqueous extraction in a twin-screw extruder

Fractionation of sunflower whole plant is carried out with water in a twin-screw extruder. An extract and a raffinate are produced in a single step. Oil extraction yield is 55%. Lipids are extracted in the form of two oil-in-water emulsions: the higher hydrophobic phase and the lower one. Stability of both hydrophobic phases is ensured by the presence at interface of surface-active agents co-extracted: phospholipids and proteins. Pectins and non pectic sugars complete the dry matter of the lower hydrophobic phase. Hydrophobic phases may have applications for non food uses: biolubricants market, transport of active principles (odours, colours, bactericides, antifungals), and treatment of hydrophilic surfaces. They can be also used for oil production because their demulsification with ethanol is efficient. Oil recovery produces also a precipitate containing proteins with tensioactive properties. The extract contains also a hydrophilic phase (aqueous phase). This largest phase is an extract of the soluble constituents from whole plant: proteins from kernel, pectins from pith and head, and hemicelluloses from stalk. Valorization of hydrophilic phase is difficult because it is much diluted. Nevertheless, it would be potentially recyclable for aqueous extraction. It would be also possible to use it for the production of proteins with surface-active properties and pectins. The raffinate (cake meal) is rich in fibres and proteins with thermoplastic properties. It would be suitable for use in animal feeds and for energy production. It is also a natural composite, and it can be manufactured into biodegradable agromaterials by compression moulding. Panels can be used as inter-layer sheets for pallets or for the manufacturing of containers

Process for recovering carboxylic acids from sugar cane industry by-products

Food industry by-products such as molasses and vinasses may provide an important source of organic acids. The aim of this study is to compare three processes, precipitation, chromatography and liquid-liquid extraction, for the recovery of carboxylic acids from sugarcane molasses from Réunion Island. Precipitation was performed with different temperatures by addition of calcium chloride. The results revealed that precipitation can recover aconitic acid efficiently from molasses. Liquid-liquid extraction was carried out with TBP in n-dodecane. The results indicated that the selectivity depends on solution pH. Extraction with molasses is hindered by the appearance of a third phase. Chromatography was performed on ion exchange resin (Amberlite IRA 900 Cl) from Rohm & Haas. The extraction yields were low in the synthetic solutions and the recovery of carboxylic acids from molasses was impossible due to their high viscosity

The thermo-mechano-chemical fractionation of sunflower whole plant in twin-screw extruder, an opportunity for its biorefinery

Biorefinery of sunflower whole plant is conducted according to an aqueous process using a twin-screw extruder. Aqueous extraction of oil is looked upon as an environmentally cleaner alternative technology to solvent extraction. Twin-screw extruder carries out three unit operations continuously: conditioning and grinding of whole plant, liquid/solid extraction and liquid/solid separation. Extraction efficiency depends on screw speed, and input flow rates of whole plant and water. In best conditions, oil yield is 57%, and residual oil content in cake meal is 14%. These conditions lead to the co-extraction of proteins, pectins and hemicelluloses. Oil is extracted in the form of two oil-in-water emulsions stabilized by phospholipids and proteins at interface. They could be used as co-emulsifiers for creams production in cosmetic industry. An aqueous extract containing part of the water-soluble constituents from whole plant, mainly proteins and pectins, is also generated. It can be recycled to the process. As a mixture of fibers and proteins, the cake meal can be moulded by thermo-pressing. Denser fiberboards have promising mechanical properties in bending. They could be used in furniture industry. Fiberboards with the lowest densities are more fragile but they could be used for their heat insulation properties in building industry

Biorefinery of sunflower whole plant by thermo-mechano-chemical fractionation in twin-screw extruder: representation of liquid/solid transport inside the barrel

Biorefinery of sunflower whole plant can be conducted with water by thermo-mechano-chemical fractionation in a Clextral BC 45 (France) co-penetrating and co-rotating twin-screw extruder. An extract and a raffinate are produced separately and in a single continuous step. The arrangement of screw profile makes possible to define three successive zones along the barrel, in which the three unit operations of the aqueous extraction process are taking place. (I) The grinding zone consists of a succession of 10 monolobes paddles, and 5 bilobe paddles. It ensures the conditioning and the grinding of solid matter. (II) The extracting zone begins with water injection. It is composed of a second series of 5 bilobe paddles to mix liquid and solid. (III) The pressing zone is the place where liquid/solid separation is realized. Screw configuration is then arranged with reversed pitch screws used to place pressure on the liquid/solid mixture, and positioned immediately downstream from a filter section. Representation of liquid/solid transport inside the barrel is performed thanks to (i) the measuring of the filling of each screw element after visual observation, (ii) the characteristics of the corresponding solid, and (iii) the modelling of the contribution of each screw element to the residence time distribution of solid and liquid phases. Consequently, twin-screw extruder can be represented as the association of a grinder, a liquid/solid extractor, and a liquid/solid separator, in which material exchanges are intensified. Thus, it is possible to predict the evolution of mean residence times of liquid and solid in the three zones of twin-screw extruder with the main operating variables: screw rotation speed, and inlet flow rates of whole plant and water. The decrease of both screw rotation speed and inlet flow rate of whole plant, simultaneously with the increase of inlet flow rate of water, causes the increase of liquid to solid ratio in the extracting zone, and the increase of residence time of solid in the pressing zone. These operating conditions (60 rpm for screw rotation speed, 5.0 kg/h and 20.3 kg/h for inlet flow rates of whole plant and water, respectively) are favourable to an efficient contact between liquid and solid (8.2 for liquid to solid ratio), and to the liquid/solid separation (156 sec for residence time of solid inside the separator). Oil yield is then around 55%, and residual oil content of the cake meal is only 13% of dry weight. The oil is extracted in the form of oil-in-water emulsions. The emulsion stability is ensured at interface by surface-active agents: phospholipids, proteins, and pectins. Extracts are also made up of a hydrophilic phase. This major fraction contains water-soluble components: proteins, and pectins. Raffinates are rich in fibres, and they have also a significant content of proteins with thermoplastic properties. They can be manufactured into biodegradable agromaterials by compression moulding

The aqueous extraction of sunflower oil from whole plant in twin-screw extruder, a first step for the manufacturing of biodegradable agromaterials by thermo-pressing

Twin-screw extrusion is an original solution for the biorefinery of sunflower whole plant according to an aqueous extraction process. In best operating conditions, oil yield is 57% and residual oil content in the cake meal is 14%. Oil is extracted in the form of two oil-in-water emulsions stabilized by phospholipids and proteins at interface. The cake meal would be suitable for use in animal feeds and for energy production in pellets burning furnaces. As a mixture of fibers and proteins, it is also considered as a natural composite. It can be processed into biodegradable agromaterials by thermo-pressing. During molding, part of residual oil is expressed (until 41% of oil from whole plant), leading to the increase of the total oil extraction yield (aqueous extraction in twin-screw extruder and expression during thermo-pressing): until 81% of oil from whole plant. Panels have promising mechanical properties in bending (until 12 MPa for stress at break). They are usable as inter-layer sheets for pallets, for their sound and heat insulation properties or for the manufacturing of containers by assembly of panels. Their hydrophobic character (8% for residual oil content in the panels) makes them resistant to water

The twin-screw extrusion technology, an original solution for the extraction of proteins from sunflower and alfalfa

Twin-screw extrusion has been used for the protein extraction from sunflower and alfalfa. Thermo-mechanical fractionation and aqueous extraction are conducted simultaneously to collect separately a liquid extract and a solid raffinate. From sunflower whole plant, squeezing in the reversed screws is favored by the fibers abundance in the stalk, and it enables L/S separation. Protein yield is 44%, in the best conditions, and lipids are partly co-extracted. Water-soluble proteins are in an aqueous extract and in two O/W emulsions due to their surface-active properties. Hence, the oil is co-extracted in the form of emulsions stabilized by proteins at interface. Proteins can be collected in the aqueous extract by isoelectric precipitation. Emulsions are usable for oil production. Their demulsification with ethanol produces a precipitate rich in proteins with low denaturation level. From alfalfa whole plant, the highest protein yield in the aqueous extract (called green juice) is 25% when water is added in the extruder. Water-soluble and water-insoluble green juice proteins can be fractionated thanks to L/L extraction in sunflower oil and ammonium sulfate precipitation. Some other molecules are co-extracted (polysaccharides, phenolic compounds). They can be purified with ultrafiltration or chromatography