Method for bleaching, drying and deodorizing algae or algae extracts

Abstract

The present invention relates to a method for bleaching, drying and deodorizing algae or algae extracts, for uses thereof in the manufacture of plastics or composites. The method according to the invention comprises the following steps: Bleaching, drying and deodorizing algae or algae extracts, outside of an aqueous medium, comprising the following steps: - (a) a step of obtaining an algal biomass or algae extracts, - (b) a step of preparing a bleaching and deodorizing solution comprising hydrogen peroxide and water, - (c) a step of spreading the algal biomass or algae extracts on a flat surface, - (d) a step of uniformly spraying said solution for bleaching and deodorizing the algal biomass or the algae extracts, it being possible for said step (d) to be carried out before the spreading step (c), - (e) a step of bleaching, deodorizing and drying the algal biomass or the algae extracts, under light exposure for at least 24h, - (f) a step of recovering bleached, deodorized and dried algae or algae extracts.

Description

[0001] DESCRIPTION

[0002] TITLE: PROCESS FOR BLEACHING, DRYING AND DEODORIZING ALGAE OR ALGAE EXTRACTS

[0003] The present invention relates to a process for bleaching, drying and deodorizing algae, or algae extracts. More specifically, the invention relates to a process for bleaching, drying and deodorizing algae, or algae extracts, for use in the manufacture of plastics or composites.

[0004] STATE OF THE ART

[0005] The increased demand for plastics imposed by modern society results in annual production levels reaching millions of tons. The production of plastic products relies on a limited stock of fossil raw materials (oil and gas), which constitute more than 90% of its raw material. It has experienced exponential growth, increasing from 2.3 million tons in 1950 to 359 million in 2018. Plastic is one of the most polluting and dangerous materials for the environment, humans, and animals. For example, of the 8.3 billion tons of plastics manufactured between 1950 and 2015, 6.3 billion tons became waste, of which approximately 79% accumulated in landfills or in nature. In addition, the manufacture of plastic itself is a source of pollution because it generates polluting by-products.

[0006] While imagining a world without plastic is almost impossible today, careful consideration of production methods is necessary to limit the impact of plastics on our environment. Therefore, solutions must now be found to:

[0007] Reduce our plastic consumption, particularly by banning single-use plastic packaging;

[0008] Eco-design, that is to say, thinking, before it becomes waste, about reducing the impact of a product when it has become waste; Promoting the reuse of a product;

[0009] Facilitate and develop plastic recycling;

[0010] Limit greenhouse gases and reduce production linked to non-renewable fossil fuels.

[0011] Thus, given the growing awareness of consumers and manufacturers, research has for several years focused on the use of renewable and ideally biodegradable plant-based materials to replace fossil raw materials in the manufacture of plastic. Such plastic is then called "bio-sourced." A large majority of bio-sourced plastics are made from plant materials derived from wheat, corn, beetroot, sugar cane, or potatoes. While this alternative offers more environmentally friendly plastics, it has the disadvantage of diverting part of the plant production initially intended for food consumption.

[0012] Thus, more recently, algae have been the subject of studies and research as raw materials or sources of raw materials in the manufacture of plastics. Indeed, algae synthesize a large quantity of compounds, in particular polysaccharides, which have interesting functional properties for the manufacture of plastic products and which can be extracted for this purpose. Examples include ulvans, agar, alginates, as well as lactic acid. In addition, the plastic products thus manufactured are biodegradable and compostable. Furthermore, the use of algae in the manufacture of plastics responds to another environmental problem: the proliferation of algae on the coasts and its dangerousness.

[0013] Green algae, for example, are present in the sea in their natural state, but their rapid proliferation is linked to environmental disruptions, such as soil pollution by nitrates and phosphates, global warming, etc. This imbalance represents a danger for humans and ecosystems. The excessive growth of algae can be the source of episodic or chronic phenomena of anoxia in the environment and the suffocation and death of many species. When stranded in large quantities and not collected, their decomposition is encouraged and causes the emission and accumulation of greenhouse gases, but also of hydrogen sulfide, a toxic gas that can be fatal in high concentrations. If left uncollected and unused, they represent a danger for humans and the environment.

[0014] Giving a value to this waste would help reduce the environmental impact associated with seaweed strandings.

[0015] The use of algae or algae extracts in the manufacture of plastics thus makes it possible to respond to a double problem: on the one hand, the increase in demand for plastic by limiting the use of petroleum-based materials and plant materials which compete with agricultural land and on the other, the pollution of algae which is dangerous for humans and the environment if they are not treated.

[0016] The production of plastics from algae is, for example, described in international application WO 2017 / 046356.

[0017] However, while algae or algae extracts are ideal for producing plastics and finished plastic products with mechanical properties at least identical to those of standard plastics, a drawback remains due to the color and odor characteristics they induce. However, manufacturers are waiting for finished products with little or no color and without the characteristic odor of algae.

[0018] PURPOSE OF THE INVENTION

[0019] The aim of the present invention is to propose a simple, effective and environmentally friendly process for bleaching, drying and deodorizing algae or algae extracts, in particular with a view to their use in the manufacture of plastic or composite materials for the production of colorless and odorless finished products.

[0020] OBJECTS OF THE INVENTION To this end, the invention relates to a process for bleaching, drying and deodorizing algae or algae extracts, outside an aqueous medium, comprising the following steps:

[0021] (a) a step of obtaining an algae biomass or algae extracts,

[0022] (b) a step of preparing a bleaching and deodorizing solution comprising hydrogen peroxide and water,

[0023] (c) a step of spreading the algal biomass or algal extracts on a flat surface,

[0024] (d) a step of watering the algae biomass or algae extracts with said bleaching and deodorizing solution, in a homogeneous manner, said step (d) being able to be carried out before the spreading step (c),

[0025] (e) a step of bleaching, deodorizing and drying the algae biomass or algae extracts, under light exposure for at least 24 hours, preferably in the open air,

[0026] (f) a step of recovering the algae or algae extracts, bleached, deodorized and dried.

[0027] In the process according to the invention, it is the combined action of hydrogen peroxide and light that allows the bleaching and deodorization of algae or algae extracts. Drying under exposure to natural or artificial light makes it possible to quickly obtain bleached, dried and deodorized algae or algae extracts.

[0028] Implementing the process outside an aqueous medium, that is to say, on a spread material and with controlled watering of the bleaching and deodorizing solution allows significant savings in water and solution compared to treatment in a basin.

[0029] Bleaching, deodorization and drying of the biomass take place simultaneously, during the same step, saving time.

[0030] The progress of the bleaching process can be monitored visually using a color chart or by spectrometry. Thus, at the end of the process according to the invention, the algae or algae extracts are suitable for use in the manufacture of colorless, bleached and odorless plastics or composites. The process can be carried out using all species of algae, filamentary or in the form of leaves, green, brown or red algae, etc., on whole or crushed, fresh or dry algae, or on algae extracts.

[0031] Furthermore, since hydrogen peroxide is non-persistent and decomposes quickly into oxygen, the process according to the invention is perfectly environmentally friendly.

[0032] In the context of the invention, the term "algal extract" means any compound, or mixture of compounds, obtained after the implementation of any extraction process known to those skilled in the art. These will in particular be extracts of polysaccharides or fibers. Polysaccharides and fibers derived from algae are known and their algal origin is identifiable.

[0033] The term "natural light" also refers to all the different forms of light emitted by the sun or the moon.

[0034] “Artificial light” also means all the different forms of light produced artificially and diffused by a lamp or any other artificial light source.

[0035] "Bleaching" also means the loss of the natural color of the material, by neutralization, elimination or destruction of the compounds responsible for the color, in particular pigments. The term "discoloration" can be used alternatively.

[0036] Deodorization also means the loss of the natural odor of the material, by neutralizing, eliminating or destroying the compounds responsible for the odor.

[0037] According to a characteristic of the invention, during step (b), the bleaching and deodorizing solution is prepared with sea water, fresh water or brackish water, preferably sea water. Indeed, unexpectedly, the combined action of hydrogen peroxide and sea water makes it possible to obtain bleaching and deodorizing more quickly and more effectively.

[0038] Preferably, the bleaching solution is prepared at a volume concentration of 0.01 to 15% hydrogen peroxide.

[0039] Preferably again, step (b) of preparing a bleaching and deodorizing solution comprises adjusting the pH of said solution to a value between 7 and 11.5, more preferably 7.

[0040] The pH of fresh or sea water around 7 is suitable, but a modification of the pH between 11 and 11.5, for example by adding sodium hydroxide, can be considered.

[0041] According to one embodiment, the method comprises the addition, during step (b), of at least one compound chosen from iron sulfate, alkali metal silicate, an alkaline earth metal, an alkaline earth ion complexing agent, or one of their mixtures in the bleaching and deodorizing solution.

[0042] The addition of such components helps accelerate the rate of bleaching and deodorizing reactions by promoting the oxidation of hydrogen peroxide. However, such additions remain completely optional.

[0043] Preferably, step (c) of spreading the algal biomass or algal extracts comprises spreading at a density of 1 to 5 kg DM / m 2 .

[0044] Such a spreading density allows the consumption of a quantity of hydrogen peroxide of 0.35kg / kgMS for a 35% solution or 0.125kg / kgMS for a pure solution.

[0045] Advantageously, step (c) of spreading the algae biomass or algae extracts is carried out on a mobile conveyor.

[0046] The use of a mobile conveyor allows for frequent turning of the material during the process to achieve a homogeneous distribution of the bleaching solution. In addition, it facilitates the recovery of algae or algae extracts during the final stage (f) of the process.

[0047] According to a preferred embodiment, step (d) is carried out before spreading step (c).

[0048] This facilitates the homogenization of the material during spreading.

[0049] Advantageously, step (e) of bleaching, deodorizing and drying the algae or algae extracts takes place for at least 24 hours, preferably at least 48 hours, more preferably at least 72 hours.

[0050] Advantageously, step (e) of bleaching, deodorizing and drying the algae or algae extracts takes place in the open air.

[0051] According to this embodiment, the bleaching, deodorization and drying of the biomass take place simultaneously, during the same step and outdoors, therefore in the open air. This embodiment is very advantageous in terms of saving or reducing energy consumption.

[0052] It is noted that drying takes place on average between 2 and 5 days.

[0053] Optionally, the method may comprise a step (g) of hot air drying following step (e) of bleaching, deodorizing and drying.

[0054] This step is necessary in case the drying of step (e) is not sufficient or if the desired humidity values ​​are not reached.

[0055] Preferably, at least steps (c) to (e) take place in a greenhouse.

[0056] Thus, advantageously, step (e) of bleaching, deodorizing and drying comprises the regular turning and mixing of the algae biomass or algae extracts.

[0057] According to a preferred embodiment of the invention, step (e) of bleaching, drying and deodorizing takes place under natural or artificial light, said light being chosen from natural daylight, artificial light produced by LEDs, or artificial light combining LED and UV-C.

[0058] The LEDs, light emitting diodes, or electroluminescent diodes preferably used are those which emit wavelengths between 400 nm and 700 nm.

[0059] The invention also relates to bleached, dried and deodorized algae or algae extracts, obtained or capable of being obtained by a process as described above.

[0060] The invention also relates to a plastic or composite material comprising algae or algae extracts, bleached, dried and deodorized, obtained or capable of being obtained by a process as described above.

[0061] The invention also relates to a method for manufacturing finished plastic or composite products comprising a method as described above.

[0062] The invention finally relates to a finished plastic or composite product comprising algae or algae extracts, bleached, dried and deodorized, obtained or capable of being obtained by a process as described above.

[0063] A finished plastic or composite product here means any object made from plastic or composite materials, such as a container, a bag, a film, etc.

[0064] The above-mentioned and other features of the invention will become more apparent from the following detailed description.

[0065] DETAILED DESCRIPTION

[0066] Preparing the bleaching and deodorizing solution

[0067] One volume of hydrogen peroxide (33% or 35% active oxygen) can be mixed with fresh water, brackish water or sea water. The ratio of hydrogen peroxide to water is between 1 to 2 and 1 to 19. The pH of fresh water or sea water, which is around 7, is sufficient, but a modification of the pH between 11 and 11.5 by adding sodium hydroxide can be considered.

[0068] The Fenton reaction is an advanced redox reaction that involves initiating hydrogen peroxide decomposition reactions with metal salts to generate radical species (HO», HO»2, etc.), chemically highly reactive species due to the presence of unpaired valence electrons. Additions of iron sulfate can thus be considered to promote the bleaching and deodorization reaction.

[0069] Similarly, alkali metal silicate, alkaline earth elements (magnesium, calcium) and alkaline earth ion complexing agents can be added in small quantities (less than 1% by weight).

[0070] If such additions are made, it will then be preferable to solubilize these elements before adding hydrogen peroxide and before modifying the pH if necessary.

[0071] Contacting the bleaching and deodorizing solution with the bleaching matrix

[0072] The addition of hydrogen peroxide can be carried out on different matrices: algae (before or after grinding), extracts of fibers or polysaccharides recovered after any suitable extraction process known to those skilled in the art.

[0073] Contact of the solution with the material is achieved by watering or injection.

[0074] When it comes to spraying or injecting, the finer the jets, the more evenly the bleaching and deodorizing solution is distributed. Spraying or injecting can be done before spreading the material on a flat surface, or after.

[0075] The material is spread evenly on a flat surface, whether moving or not, preferably on a conveyor belt. The spreading is done in such a way as to have a precise density of material to be bleached, that is, knowing the mass of material used and the surface area used.

[0076] There is indeed a correlation between the quantity of algae and the quantity of hydrogen peroxide: the more algae there are, the longer the bleaching times will be at a fixed concentration of hydrogen peroxide. Similarly, the more algae there are, the lower the bleaching level will be. An algae density of 1 to 5 kg DM / m is recommended. 2 , and consume a quantity of hydrogen peroxide of 0.35kg / kgMS for a 35% solution or 0.125kg / kgMS for a pure solution.

[0077] To ensure uniform bleaching and drying throughout the material, it is important to turn and mix it frequently, for example once every 5 hours. This agitation can be carried out manually or using conveyor mixing systems.

[0078] To ensure bleaching and deodorization, the presence of light is essential. Exposure can be done under natural light (sun, moon) or under artificial light produced by LEDs or a combination of LED and UV-C.

[0079] Preferably, the bleaching and deodorization stage takes place in a greenhouse, particularly during periods of bad weather.

[0080] The contact time between the matrix and the bleaching and deodorizing solution can vary, particularly depending on the light source and temperature. Greenhouse bleaching can be carried out in 2 to 5 days. Greenhouse drying can be completed in 4 to 10 days. Temperature can be combined with light for more efficient, faster bleaching and / or to achieve higher levels of whiteness. Therefore, an additional heating step, for example, with hot air at 70°C, may be necessary.

[0081] It is noted that the dryness rate reached after the bleaching and drying stage in the greenhouse can reach 85% after 6 days without energy input (dehumidifier, heating, etc.). This allows a significant saving in energy consumption compared to a wet bleaching process with which the dryness of the biomass would not exceed 20%. Similarly, outside the wet process, drying the biomass allows an energy saving of more than 90% to be obtained.

[0082] Recovery of bleached matrix

[0083] After contact with the bleaching and deodorizing solution, the algae or algae extracts can be recovered.

[0084] Depending on the desired dry matter content, the matrices can undergo a further drying step.

[0085] Since hydrogen peroxide is non-persistent and decomposes rapidly in the presence of oxygen, there is little chance that an aqueous solution will still be present on the spreading surface. If this is the case, the recovered effluent can be sent to a lagoon area without specific treatment before recycling or release into the environment.

Claims

CLAIMS 1) Process for bleaching, drying and deodorizing algae or algae extracts, outside an aqueous medium, comprising the following steps: (a) a step of obtaining an algae biomass or algae extracts, (b) a step of preparing a bleaching and deodorizing solution comprising hydrogen peroxide and water, (c) a step of spreading the algal biomass or algal extracts on a flat surface, (d) a step of watering or injecting the algae biomass or algae extracts with said bleaching and deodorizing solution, in a homogeneous manner, said step (d) being able to be carried out before the spreading step (c), (e) a step of bleaching, deodorizing and drying the algae biomass or algae extracts, under light exposure for at least 24 hours, preferably in the open air, (f) a step of recovering the algae or algae extracts, bleached, deodorized and dried. 2) Method according to claim 1, characterized in that during step (b), the bleaching and deodorizing solution is prepared with sea water, fresh water or brackish water, preferably sea water. 3) Method according to claim 1 or 2, characterized in that the bleaching solution is prepared at a volume concentration of 0.01 to 15% of hydrogen peroxide. 4) Method according to one of the preceding claims, characterized in that step (b) of preparing a bleaching and deodorizing solution comprises adjusting the pH of said solution to a value between 7 and 11.5, more preferably 7. 5) Method according to one of the preceding claims, characterized in that it comprises the addition, during step (b), of at least one compound chosen from iron sulfate, alkali metal silicate, an alkaline earth, an alkaline earth ion complexing agent, or a mixture thereof in the bleaching and deodorizing solution. 6) Method according to one of the preceding claims, characterized in that step (e) of bleaching, deodorizing and drying the algae or algae extracts takes place for at least 24 hours, preferably at least 48 hours, more preferably at least 72 hours. 7) Method according to one of the preceding claims, characterized in that it comprises a step (g) of drying by hot air following step (e). 8) Method according to one of the preceding claims, characterized in that step (c) of spreading the algae biomass or algae extracts comprises spreading at a density of 1 to 5 kgMS / m 2 . 9) Method according to one of the preceding claims, characterized in that at least steps (c) to (e) take place in a greenhouse. 10) Method according to one of the preceding claims, characterized in that step (c) of spreading the algae biomass or algae extracts is carried out on a mobile conveyor. 11) Method according to one of the preceding claims, characterized in that the bleaching, deodorizing and drying step comprises the regular turning and mixing of the algae biomass or algae extracts. 12) Method according to one of the preceding claims, characterized in that step (e) of bleaching, drying and deodorizing takes place under natural or artificial light, said light being chosen from natural daylight, under artificial light produced by LEDs, or under artificial light combining LED and UV-C. 13) Bleached, dried and deodorized algae or algae extracts, obtained or capable of being obtained by a process as described in one of claims 1 to 12. 14) Plastic or composite materials comprising algae or algae extracts, bleached, dried and deodorized, obtained or capable of being obtained by a process as described in one of claims 1 to 12. 15) Method for manufacturing finished plastic or composite products comprising a method as described in one of claims 1 to 12. 16) Finished plastic or composite products comprising algae or algae extracts, bleached, dried and deodorized, obtained or capable of being obtained by a process as described in one of claims 1 to 12.