Tray for greening of surfaces and process for manufacturing a tray for greening of surfaces

Abstract

A tray for greening of surfaces, in particular for roofs of building structures, is provided comprising a base and upstanding walls forming an open-top receptacle having an inner surface and an outer surface, wherein the fibers comprise a thermoplastic polymer, wherein the base comprises a three-dimensional material layer comprising fibers and having a first main surface and a second main surface and at least a first liquid permeable separation layer oriented plane-parallel, and preferably adjacent, to the first main surface of the three-dimensional material layer of fibers comprised in the base, wherein the three-dimensional material layer comprising fibers comprised in the base has an open space of at least 50%, wherein the upstanding walls comprise a material layer comprising fibers and having a first main surface and a second main surface and at least a second separation layer oriented plane-parallel, and preferably adjacent, to the first main surface of the material layer of fibers comprised in the upstanding walls, wherein the first liquid permeable separation layer comprised in the base and the second separation layer comprised in the upstanding walls are oriented towards the inner surface of the open-top receptacle.

Description

[0001]CFN3264 Tray for Greening of Surfaces and Process for Manufacturing a Tray forGreening of Surfaces ___________ Description:The application pertains to trays for greening of surfaces and to processes formanufacturing trays for greening of surfaces, in particular for greening of roofs ofbuilding structures.There is a trend for greening of surfaces, for example greening of roofs of buildingstructures, in particular for flat roof. Greening of surfaces such as roofs may contribute to fight global warning by conversion of carbon dioxide into plants, and may help to locally reduce the temperature, for example in cities having a high density of concrete buildings and little green spaces such as for example parks. Some conventional systems for creating green roofs are constructed from a plurality of layers applied one after the other to a roof, for example a waterproofing layer to protect the roof structure against rain, a root barrier to prevent roots of plants to damage the waterproofing layer, a horizontal water drainage layer todrain off excess water, a substrate layer and in some cases a water retention layerto enable plants to grow, and plants.As plants, sedum plants are commonly used, which can be cultivated on anappropriate substrate layer already applied onto the roof. However, cultivation on the roof involves manual labor and associated high costs as cultivation on the roof cannot be automated, since every roof is constructed differently.The plants can also be pre-cultivated on mats in a greenery and then transportedto and positioned on the prepared roof. After pre-cultivating of sedum mats, themats can be rolled up, transported to the roof and rolled out onto the roof. Relatively long dry periods are harmful to the young plants in this phase. The plants may be damaged when the mats are being rolled up and placed on the roof.To cultivate the plants further on the roof, precise watering has to be ensuredduring the cultivation step, with associated high costs.Alternative, plants can be cultivated in a greenery in cassettes or trays havingdiscrete dimensions of for example 50 cm by 50 cm. Once the plants have been cultivated to a pre-determined level, e.g. regarding height of the plants and / or coverage of the cassette by the plants, the cassettes can be transported to and positioned on the prepared roof. The plants cultivated in the cassettes are not susceptible to damage by rolling and unrolling of mats. Trays can be provided from a continuous plastic sheet which is deep-drawn into the desired three-dimensional shape, or by injection molding. However, such plastic trays generally require a second processing step to provide openings at least in the bottom of the tray to allow excess water to be drained from the tray. Deep-drawn plastic trays have the disadvantage that cultivation of plants in suchplastic trays still involves a high level of manual labor and associated high costs ascultivation of plants in such plastic trays cannot be automated, since such plastic trays do not have the required compression resistance to allow equipment to rolled over or driven over the trays.US 10,076,084 B2 discloses a roof-greening cassette having walls and / or basesmade of a porous material having preferably open pores, wherein the porous material is water-retentive as well as water-permeable.An example of a green roof cassette according to US 10,076,084 B2 is branded asPlace ‘n Go® available from Sempergreen®, which comprises a bottom drainagelayer onto which a tray is placed having a bottom layer and side walls made from alightweight recycled polyurethane molded foam. The foam tray holds a soilsubstrate wherein plants can be cultivated. The foam tray is assembled in an elaborate process from several separate strips or panels forming the base and the walls of the tray, which strips or panels are made of flakes of recycled polyurethane foam having a selected density and / or a selected porosity. The foam tray is then placed on and preferably connected to a horizontal drainage layer. The use of polyurethane foam makes it difficult to process the foam trays at theend of life of for example a green roof. A tray comprising polyurethane foam canfor example not be biodegraded in an industrial bio-composting unit. A tray comprising polyurethane foam also does not allow for other mechanical recycling processing involving for example mechanically grinding the tray into small parts,melting the small parts, and forming new products by an extrusion process.There remains a need for improved trays for greening of surfaces, in particular forroofs of building structures, and for improved processes for manufacturing trays forgreening of surfaces overcoming, or at least reducing, the disadvantages of theprior art.The object of the invention is thus to provide a tray for greening of surfacesovercoming, or at least reducing, the disadvantages of the prior art. The object is solved by the process for manufacturing a tray for greening ofsurfaces according to claim 1 and by the tray for greening of surfaces according toclaim 7.Advantageous further improvements of the tray for greening of surfaces and of theprocess for manufacturing a tray for greening of surfaces are provided by the dependent claims.A process comprising the steps of providing a composite material comprising athree-dimensional material layer comprising fibers and having a first main surface and a second main surface, wherein the fibers comprise a thermoplastic polymer and at least a liquid permeable separation layer oriented plane-parallel, andpreferably adjacent, to the first main surface of the three-dimensional materiallayer of fibers, and shaping the composite material into a tray comprising a baseand upstanding walls forming an open-top receptacle having an inner surface andan outer surface, wherein the three-dimensional material layer comprising fibers comprised in the base has an open space of at least 50%, wherein the liquidpermeable separation layer comprised in the base is oriented towards the innersurface of the open-top receptacle, enables to provide a tray for greening ofsurfaces which does not require a process of assembling a tray from separatestrips or panels forming the base and the walls of the tray. The composite materialmay be shaped into a tray in a single process step. The process enables toprovide a tray for greening of surfaces as a unitary structure. Preferably, the fiberscomprise a synthetic thermoplastic polymer, The term unitary structure is understood to mean that the tray is not assembled from a separate base and one or more separate upstanding walls. The process for manufacturing a tray for greening of surfaces providing the tray as a unitarystructure enables to exclude an adhesive in the tray, as the tray is not assembledfrom a separate base and one or more separate upstanding walls connected toeach other by an adhesive. The process may provide a tray which preferablyexcludes an adhesive. The process may provide a tray which preferably excludes polyurethane foam, which improves the possibilities for processing of the tray at the end of life. In the process, the liquid permeable separation layer comprised in the compositematerial is, after the step of shaping the composite material into a tray comprisinga base and upstanding walls forming an open-top receptacle having an innersurface and an outer surface, oriented towards the inner surface of the open-topreceptacle of the tray, enables to retain a substrate within the open-top receptacleof the tray wherein plants can be cultivated, while allowing an excess of water tobe drained from the tray through the liquid permeable separation layer and throughthe three-dimensional material layer comprising fibers. An excess of waterretained within the tray could damage the plants being cultivated within the tray, for example due to rotting of roots of the plants.The composite material being provided in the process may have an open space ofat least 50%. Preferably, the composite material being provided in the processmay have an open space of at least 75%, or preferably of at least 85%, morepreferably of at least 90%, even more preferably of at least 95%, to improvedraining of excess water from the tray. The open space of the three-dimensionalmaterial layer comprising fibers, in this context, is defined as the total volumebetween two planes directly sandwiching the three-dimensional material layercomprising fibers over a given area, minus the volume occupied by the fibersthemselves of the three-dimensional material layer, as a percentage.The three-dimensional material layer comprising fibers may be any type of three-dimensional material layer comprising fibers, provided that it has an open space ofat least 50%, and may for example be selected from a three-dimensional knittedfabric, a three-dimensional woven fabric, or a three-dimensional mat of extrudedentangled filaments.The fibers comprised in the three-dimensional material layer may be thermallybonded to each other at contact points of the fibers, to provide improved resilienceand / or improved compression resistance.The fibers comprised in the three-dimensional material layer comprise athermoplastic polymer. In an embodiment, the fibers comprised in the three-dimensional material layer are composed for at least 50 wt.% of thermoplasticpolymer, preferably for at least 75 wt.%, more preferably for at least 90 wt.%, more preferably for at least 95 wt.% of thermoplastic polymer. The fibers comprised inthe three-dimensional material layer may consist of thermoplastic polymer.Preferably, the fibers comprise a synthetic thermoplastic polymer,The fibers comprised in the three-dimensional material layer may comprise, orconsists of, any suitable thermoplastic polymer or a blend of thermoplasticpolymers. Preferably, the fibers comprise a synthetic thermoplastic polymer or ablend of synthetic thermoplastic polymers, The fibers may comprise a polyolefin,such as for example polyethylene (PE) or polypropylene (PP), a halogenatedpolyolefin, such as for example polytetrafluorethylene (PTFE) or polyvinylidenedifluoride (PVDF), a polyester, such as for example polyethylene terephthalate(PET) (based either on DMT or PTA), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN) and / or polylactic acid (PLA), a polyamide, such as for example polyamide-6 (PA6), polyamide-6,6 (PA6,6) and / or polyamide-6,10 (PA6,10), polyimides (PI), polysulfides (PS) such as polyphenylenesulfide (PPS), polyethyleneimide (PEI), polyoxymethylene (POM), thermoplastic elastomers (TPE) such as thermoplastic polyurethanes (TPU), and / or any copolymer or any blend thereof.The fibers comprised in the three-dimensional material layer may preferablycomprise, or consists of, a polyolefin, more preferably a polypropylene (PP).In another embodiment, the fibers comprised in the three-dimensional materiallayer may comprise, or consists of, any suitable thermoplastic polymer or blend ofthermoplastic polymers, preferably any suitable synthetic thermoplastic polymer orblend of synthetic thermoplastic polymers, which is bio-compostable, in accordance with EN13432, at the end of the lifetime of the tray, preferably a polymer made by a polycondensation reaction of hydroxylcarboxylic acids or a ring opening polymerization of lactides. Preferred synthetic polymeric materialscomprise polymer(s) of α-, β-, γ-, δ-, or ε-hydroxylesters. Preferably, thepolymer(s) comprised in the fibers comprised in the three-dimensional materiallayer are selected from the group of polyhydroxyalkanoates (PHA’s), such as forexample polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), poly-(3- hydroxybutyrateco-3-hydroxyvalerate) PHVB or polyhydroxyhexanoate (PHH) as for example available from Metabolix under the Mirel brand name, polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), poly-β-butyrolactone (PBL), polybutylene succinate (PBS), cellulose derivates and / or blends thereof. In a preferred embodiment, the synthetic polymeric material comprised in the fiberscomprised in the three-dimensional material layer is a polylactic acid (PLA).The fibers comprised in the three-dimensional material layer may advantageouslybe macroscopic fibers having an apparent diameter of at least 0.1 mm, preferablyof at least 0.2 mm, or preferably of at least 0.3 mm, or preferably of at least 0.4mm, or preferably of at least 0.5 mm enabling to obtain large open spacesbetween the fibers of the three-dimensional material layer. The fibers comprised inthe three-dimensional material layer may have an apparent diameter of at most2.5 mm, preferably of at most 2.0 mm, or preferably of at most 1.5 mm, or preferably of at most 1.2 mm, or preferably of at most 1.0 mm, or preferably of at most 0.8 mm.In an embodiment, the three-dimensional material layer comprising fibers ispreferably a three-dimensional mat of extruded entangled filaments having anopen space of at least 50%, preferably of at least 75%, or preferably of at least 85%, or more preferably of at least 90%, or even more preferably of at least 95%.The three-dimensional mat of extruded entangled filaments can be easily cutenabling to cut a tray to smaller size to precisely fit the tray at the edges of the surface to be greened. Deep-drawn plastic trays of the prior art are difficult to cut precisely due to the breaking of the deep-drawn plastic trays. The three-dimensional mat of extruded entangled filaments may advantageouslybe made of extruded filaments that are irregularly looped and entangled into ahighly porous, three-dimensional structure having a large open space, wherein theextruded filaments are preferably bonded where they cross. Preferably, theextruded filaments are stretched only by gravity before being irregularly loopedand entangled into a highly porous, three-dimensional structure having a largeopen space.The extruded filaments may be irregularly looped and entangled into a highlyporous, three-dimensional structure having a large open space by extrudingfilaments and collecting the extruded filaments into a three-dimensional structureby allowing the filaments to bend, to entangle and to come into contact with eachother, preferably in a still molten state. The extruded filaments may be allowed tobend, to entangled and to come into contact with each other by allowing theextruded filaments to come into contact with a surface. The surface may be the surface of a cooling bath comprising a cooling liquid, in particular cooling water, to solidify the extruded filaments after being irregularlylooped and entangled into a highly porous, three-dimensional structure. Allowingthe extruded filaments to come into contact with a surface of a cooling bathcomprising a cooling liquid enables to form a three-dimensional mat of extrudedentangled filaments wherein the filaments have a random distribution within thethree-dimensional mat of extruded entangled filaments, which may have an essentially isotropic property distribution.The three-dimensional mat of extruded entangled filaments may be a three-dimensional structured mat of extruded entangled filaments, which may be provided by extruding filaments and collecting the extruded filaments into a three-dimensional structure by allowing the filaments to bend, to entangle and to comeinto contact with each other, preferably in a still molten state. Bending andentangling of the extruded filaments are preferably initiated by collecting thefilaments onto a profiled surface, which defines the structure of the three-dimensional structured mat of extruded entangled filaments. Preferably, thesurface on which the filaments are collected is profiled such that the three- dimensional structured mat of filaments is shaped into a three-dimensional form which comprises hills and valleys, hemispheres, positive and / or negative cuspates, cups and / or waffles, pyramids, U-grooves, V-grooves, cones and / or cylinders capped with a hemisphere.The filaments comprised in the three- three-dimensional mat of extrudedentangled filaments may be thermally bonded to each other at contact points ofthe filaments, to provide improved resilience and / or improved compressionresistance.The extruded filaments comprised in the three-dimensional mat of extrudedentangled filaments may advantageously have apparent diameter of at least 0.1mm, preferably of at least 0.2 mm, or preferably of at least 0.3 mm, or preferably ofat least 0.4 mm, or preferably of at least 0.5 mm for improving the resilience of thecomposite material. The fibers comprised in the three-dimensional material layer may have an apparent diameter of at most 2.5 mm, preferably of at most 2.0 mm, or preferably of at most 1.5 mm, or preferably of at most 1.2 mm, or preferably of at most 1.0 mm, or preferably of at most 0.8 mm.The three-dimensional material layer comprising fibers, preferably a three-dimensional mat of extruded entangled filaments, may have a weight of at most1500 g / m², preferably of at most 1200 g / m², or preferably of at most 1000 g / m², or preferably of at most 800 g / m², and the three-dimensional material layercomprising fibers, preferably a three-dimensional mat of extruded entangledfilaments, may have a weight of at least 100 g / m², preferably of at least 200 g / m²,or preferably of at least 300 g / m², or preferably of at least 400 g / m², to provide improved resilience.The three-dimensional material layer comprising fibers in the composite materialprovided in the process enables to provide a tray wherein cultivation of plants canbe automated, as the three-dimensional material layer may have sufficientresilience to allow equipment to rolled over or driven over the trays, without significantly reducing the thickness of tray. The composite material comprising thethree-dimensional material layer comprising fibers may have a resilience of atleast 75%, preferably at least 80%, or preferably at least 85%, or preferably atleast 90%, preferably at least 95%. The resilience of the composite material isdetermined on samples of 10 cm by 10 cm with an Instron tensile tester applying the following procedure. The sample is compressed between two horizontal plates until a pre-load of 1N is reached defining the initial thickness of the sample, after 2 seconds the load is increased to 0.5 kPa and then the load is 20 times cyclically increased to 32 kPa and decreased to 0.5 kPa, after which the remaining thickness of the sample is determined at a load of 1N. The resilience is then determined by the remaining thickness of the sample as a percentage of the initial thickness of the sample, for an average of three samples. The composite material comprising the three-dimensional material layer comprising fibers may have a resilience at increased load of 500 kPa of at least50%, of at least 75%, preferably at least 80%, or preferably at least 85%, orpreferably at least 90%, preferably at least 95%. The resilience at increased loadof 500 kPa of the composite material is determined similar to the resilience, with the difference that the load is 20 times cyclically increased to 500 kPa instead of 32 kPa. The extruded entangled filaments of the three-dimensional mat of extrudedentangled filaments comprised in the base of the tray may comprise athermoplastic polymer. Preferably, the extruded entangled filaments of the three-dimensional mat of extruded entangled filaments comprised in the base of the traycomprise a synthetic thermoplastic polymer or a blend of synthetic thermoplasticpolymers. In an embodiment, The extruded entangled filaments of the three-dimensional mat of extruded entangled filaments are composed for at least 50wt.% of thermoplastic polymer, preferably for at least 75 wt.%, more preferably forat least 90 wt.%, more preferably for at least 95 wt.% of thermoplastic polymer.The extruded entangled filaments of the three-dimensional mat of extruded entangled filaments may consist of thermoplastic polymer. The extruded entangled filaments of the three-dimensional mat of extruded entangled filaments comprised in the base of the tray may comprise, or consists of, any suitable thermoplastic polymer or blend of thermoplastic polymers. Theextruded entangled filaments may comprise a polyolefin, such as for example polyethylene (PE) or polypropylene (PP), a halogenated polyolefin, such as forexample polytetrafluorethylene (PTFE) or polyvinylidene difluoride (PVDF), apolyester, such as for example polyethylene terephthalate (PET) (based either on DMT or PTA), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN) and / or polylactic acid (PLA), a polyamide, such as for example polyamide-6 (PA6), polyamide-6,6 (PA6,6) and / or polyamide- 6,10 (PA6,10), polyimides (PI), polysulfides (PS) such as polyphenylenesulfide(PPS), polyethyleneimide (PEI), polyoxymethylene (POM), thermoplasticelastomers (TPE) such as thermoplastic polyurethanes (TPU), and / or any copolymer or any blend thereof. The extruded entangled filaments of the three-dimensional mat of extruded entangled filaments may preferably comprise, or consists of, a polyolefin, morepreferably a polypropylene (PP).The extruded entangled filaments of the three-dimensional mat of extrudedentangled filaments may comprise additives, such as for example spinningauxiliaries, fillers, flame retardant materials, UV inhibitors, crystallization retarders / accelerators, plasticizers, heat stabilizers, antimicrobial additives, antistatic agents, colouring agents or any combination thereof.In another embodiment, the extruded entangled filaments of the three-dimensionalmat of extruded entangled filaments may comprise, or consists of, any suitable thermoplastic polymer or blend of thermoplastic polymers, preferably any suitablesynthetic thermoplastic polymer or blend of synthetic thermoplasticpolymers,which is bio-compostable, in accordance with EN13432, at the end of thelifetime of the tray, preferably a polymer made by a polycondensation reaction of hydroxylcarboxylic acids or a ring opening polymerization of lactides. Preferred synthetic polymeric materials comprise polymer(s) of α-, β-, γ-, δ-, or ε-hydroxylesters. Preferably, the polymer(s) of which the three-dimensionalentangled mat of extruded filaments is made is selected from the group of polyhydroxyalkanoates (PHA’s), such as for example polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), poly-(3-hydroxybutyrateco-3-hydroxyvalerate) PHVB or polyhydroxyhexanoate (PHH) as for example available from Metabolix under the Mirel brand name, polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), poly-β-butyrolactone (PBL), polybutylene succinate (PBS), cellulose derivates and / or blends thereof. In a preferred embodiment, the synthetic polymeric material of which the three-dimensional entangled mat of extruded filaments is made is a polylactic acid (PLA). The extruded entangled filaments of the three-dimensional mat of extruded entangled filaments comprising a suitable thermoplastic polymer or blend ofthermoplastic polymers, preferably a suitable synthetic thermoplastic polymer or ablend of synthetic thermoplastic polymers, which is bio-compostable at the end ofthe lifetime of the tray may comprise additives, such as for example spinningauxiliaries, fillers, flame retardant materials, UV inhibitors, crystallization retarders / accelerators, plasticizers, heat stabilizers, antimicrobial additives,antistatic agents, colouring agents or any combination thereof. In a preferredembodiment, the extruded entangled filaments of the three-dimensional mat of extruded entangled filaments comprising a suitable thermoplastic polymer or blendof thermoplastic polymers, preferably a suitable synthetic thermoplastic polymer ora blend of synthetic thermoplastic polymers, which is bio-compostable at the endof the lifetime of the tray comprises a filler, in particular calcium carbonate.The liquid permeable separation layer comprised in the composite material andwhich is oriented plane-parallel, and preferably adjacent, to the first main surfaceof the three-dimensional material layer of fibers may also comprise, or consists of,any suitable thermoplastic polymer or blend of thermoplastic polymers, preferablya suitable synthetic thermoplastic polymer or a blend of synthetic thermoplasticpolymers, which is bio-compostable at the end of the lifetime of the tray, preferablya polymer made by a polycondensation reaction of hydroxylcarboxylic acids or a ring opening polymerization of lactides. Preferred synthetic polymeric materials comprise polymer(s) of α-, β-, γ-, δ-, or ε-hydroxylesters, allowing the tray to bebio-composted at the end of life. Preferably, the polymer(s) of which the liquid permeable separation layer comprised in the composite material and which isoriented plane-parallel, and preferably adjacent, to the first main surface of thethree-dimensional material layer of fibers, is made is selected from the group of polyhydroxyalkanoates (PHA’s), such as for example polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), poly-(3-hydroxybutyrateco-3-hydroxyvalerate) PHVB or polyhydroxyhexanoate (PHH) as for example available from Metabolix under the Mirel brand name, polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), poly-β-butyrolactone (PBL), polybutylene succinate (PBS), cellulose derivates and / or blends thereof. In a preferred embodiment, the synthetic polymeric material of which the liquid permeable separation layer comprised in the composite material is made is a polylactic acid (PLA). In the process, the liquid permeable separation layer comprised in the compositematerial and which is oriented plane-parallel, and preferably adjacent, to the firstmain surface of the three-dimensional material layer of fibers may be any type ofliquid permeable material, and may preferably be selected from a perforated film, awoven fabric or a nonwoven fabric. Preferably, the liquid permeable separationlayer comprised in the composite material and which is oriented plane-parallel,and preferably adjacent, to the first main surface of the three-dimensional materiallayer of fibers is a nonwoven fabric.The nonwoven fabric may in principle be any type of nonwoven, such as for example staple fiber nonwovens produced by well-known processes, such as carding processes, wet-laid processes or air-laid processes, or any combination thereof. The nonwoven fabric may also be a nonwoven composed of filaments produced by well-known spunbonding processes wherein filaments are extruded from a spinneret and subsequently laid down on a conveyor belt as a web of filaments and subsequently consolidated, also known as bonding, the web to form a nonwoven layer of fibers, or by a two-step process wherein filaments are spun and wound on bobbins, preferably in the form of multifilament yarns, followed by the step of unwinding the filaments or multifilament yarns and laying the filaments down on a conveyor belt as a web of filaments and consolidating the web to form a nonwoven layer of fibers. The nonwoven fabric may have been consolidated by any suitable known consolidation technology, including mechanical consolidation, for example by stitching, mechanical needling and / or hydrodynamic consolidation by fluid jets, in particular by hydroentanglement, by chemical consolidation, for example by applying a binder dispersion or a binder solution to the nonwoven layer of fibers, which is generally dried and optionally cured, and / or by thermal consolidation, for example by calendaring, ultrasonic bonding and / or hot air bonding. The nonwoven fabric may comprise a higher melting polymer and a lower meltingpolymer, facilitating thermal bonding of the nonwoven fabric. The lower meltingpolymer may have a melting temperature which is at least 10°C, preferably at least 20°C, or preferably at least 50°C, lower than the melting temperature of the higher melting polymer.The higher melting polymer may be comprised in a first type of mono-componentfibers the lower melting polymer may be comprised in a second type of mono- component fibers. The lower melting polymer comprised in the nonwoven fabric may be comprised in multicomponent fibers, preferably in bicomponent fibers. A basic distinction is being drawn between three types of bicomponent fibers: side-by-side types, core-sheath types and islands-in-the-sea types of bicomponent fibers. Preferably, theratio of low melting polymer and high melting polymer in the bicomponent fibers, preferably sheath / core bicomponent fibers lies between 95 / 5 vol.% and 5 / 95 vol.%. More preferably the ratio of low melting polymer and high melting polymer lies between 50 / 50 vol.% and 95 / 5 vol.%.The mono-component or multicomponent fibers comprised in the nonwoven fabricmay have any cross sectional shape, including round, trilobal, multilobal or rectangular. Preferably, the fibers in the nonwoven fabric are filaments in order to provide higher tensile strength and / or higher tear strength to the composite material. The liquid permeable separation layer comprised in the composite material andwhich is oriented plane-parallel, and preferably adjacent, to the first main surfaceof the three-dimensional material layer of fibers may preferably be a nonwovenfabric composed of bicomponent sheath / core filaments comprising a core of a polyester, preferably a polyethylene terephthalate (PET), and a sheath of a copolyester (coPET). The liquid permeable separation layer comprised in the composite material andwhich is oriented plane-parallel, and preferably adjacent, to the first main surfaceof the three-dimensional material layer of fibers may have a weight of at most 500g / m², preferably of at most 400 g / m², or preferably of at most 300 g / m², or preferably of at most 200 g / m², and the liquid permeable separation layer comprised in the composite material and which is oriented plane-parallel, andpreferably adjacent, to the first main surface of the three-dimensional materiallayer of fibers may have a weight of at least 25 g / m², preferably of at least 30 g / m²,or preferably of at least 50 g / m², preferably of at least 100 g / m², enabling to retaina substrate within the open-top receptacle of the tray wherein plants can becultivated, while allowing excess water to be drained from the tray. The liquid permeable separation layer comprised in the composite material and which is oriented plane-parallel, and preferably adjacent, to the first main surfaceof the three-dimensional material layer of fibers may have a characteristic size ofthe openings (O-90) in accordance with NEN-EN-ISO 12956:200 of 200 µm or less, preferably 175 µm or less, or preferably 150 µm or less, or preferably 125 µm or less, or preferably 100 µm or less, or preferably 75 µm or less, or most preferably 50 µm or less, enabling to retain a substrate within the open-topreceptacle of the tray wherein plants can be cultivated, while allowing an excess ofwater to be drained from the tray through the liquid permeable separation layerand through the three-dimensional material layer comprising fibers.The process for manufacturing a tray for greening of surfaces may comprise thestep of providing a second layer oriented plane-parallel, and preferably adjacent,to the second main surface of the three-dimensional material layer of fibers. Thesecond layer oriented plane-parallel, and preferably adjacent, to the second mainsurface of the three-dimensional material layer of fibers may be provided over thefull area of the second main surface of the three-dimensional material layer offibers.The second layer oriented plane-parallel, and preferably adjacent, to the secondmain surface of the three-dimensional material layer of fibers may alternatively beprovided only over the area of the second main surface of the three-dimensionalmaterial layer of fibers which is shaped into the base of the tray.The second layer oriented plane-parallel, and preferably adjacent, to the secondmain surface of the three-dimensional material layer of fibers may be liquidpermeable, in particular water permeable, enabling an excess of water to bedrained from the tray vertically through the three-dimensional material layer comprising fibers.The second layer oriented plane-parallel, and preferably adjacent, to the secondmain surface of the three-dimensional material layer of fibers may be liquidimpermeable, in particular water impermeable, to prevent that liquid, in particular water, being drained from the tray comes into contact with surface to be greened, which may be located below the tray, while the liquid, in particular water, can still be drained from the tray horizontally or under a slight angle of for example lessthan 5°, or less than 2°, to the horizontal. Additionally, the liquid impermeable, inparticular water impermeable, second layer enables to reduce the risk of root penetration through the base of the tray. The process for manufacturing a tray for greening of surfaces comprising the step of compression molding, preferably at elevated temperatures at which polymerscomprised in the composite are softened, the composite material into the tray forgreening of surfaces, preferably between an upper mold and a lower mold, wherein the upper mold and lower mold are shaped such that, when the mold isclosed, the composite material is shaped into a tray comprising a base andupstanding walls forming an open-top receptacle having an inner surface and anouter surface, wherein the three-dimensional material layer comprising fibers comprised in the base has an open space of at least 50%.In the process of shaping the composite material into a tray comprising a base andupstanding walls forming an open-top receptacle having an inner surface and anouter surface, preferably by compression molding, preferably at elevated temperatures at which polymers comprised in the composite are softened, thecomposite material forming the base of the tray may be compressed such that thethickness of the composite material is reduced by at most 50%, preferably by atmost 25%, or preferably by at most 20%, or preferably by at most 15%, orpreferably by at most 10%, or most preferably by at most 5%, thereby enablingthat the three-dimensional material layer comprising fibers comprised in the basehas an open space of at least 50%, preferably of at least 75%, or preferably of atleast 85%, more preferably of at least 90%, even more preferably of at least 95%, to ensure sufficient draining of excess water from the tray. In an embodiment, thecomposite material forming the base of the tray is not compressed in the processof shaping the composite material into a tray.The thickness of the three-dimensional material layer comprising fibers in thecomposite material provided in the process may be varied, for example in view ofthe amount of excess water which is expected to be required to be drained from the tray, for example to the expected amount of rainfall in a geographical area.The thickness of the three-dimensional material layer comprising fibers in thecomposite material may be at most 200 mm, or preferably at most 150 mm, orpreferably at most 100 mm, or preferably at most 75 mm, or preferably at most 50mm, or preferably at most 40 mm, or preferably at most 30 mm, or most preferablyat most 25 mm. The thickness of the three-dimensional material layer comprisingfibers in the composite material may be at least 5 mm, or preferably at least 10mm, or preferably at least 15 mm, or most preferably at least 20 mm.The thickness of the three-dimensional material layer comprising fibers in the baseof the tray may be at most 200 mm, or preferably at most 150 mm, or preferably atmost 100 mm, or preferably at most 75 mm, or preferably at most 50 mm, orpreferably at most 40 mm, or preferably at most 30 mm, or most preferably at most25 mm. The thickness of the three-dimensional material layer comprising fibers inthe base of the tray may advantageously be at least 3 mm, or preferably at least 4 mm, or preferably at least 5 mm, or preferably at least 10 mm, or preferably atleast 15 mm, or most preferably at least 20 mm.The three-dimensional material layer comprising fibers in the base of the traypreferably has a thickness of at least 15 mm, more preferably of at least 20 mm to prevent, or at least reduce, that plants, substrate and / or water retention layer come in contact with water puddling on a waterproofing layer located beneath the tray for a prolonged period of time, in particular when the tray is to be installed onan essentially flat surface, such as a roof, having an angle of inclination between0° and 2° to the horizontal.The three-dimensional material layer comprising fibers in the base of the traypreferably has a thickness of at least 3 mm, more preferably of at least 4 mm, or more preferably of at least 5 mm, in particular when the tray is to be installed on an slightly inclined surface, such as a roof, having an angle of inclination between 2° and 10° to the horizontal.The three-dimensional material layer comprising fibers in the base of the tray mayhave a thickness less than 3 mm, in particular when the tray is to be installed on an inclined surface, such as a roof, having an angle of inclination between 10° and45° to the horizontal. In the process of shaping the composite material into a traycomprising a base and upstanding walls forming an open-top receptacle having aninner surface and an outer surface, preferably by compression molding, preferably at elevated temperatures at which polymers comprised in the composite aresoftened, the composite material forming the upstanding walls of the tray may becompressed such that the thickness of the composite material is reduced by atleast 50%, preferably by at least 60%, or preferably by at least 70%, or preferablyby at least 80%, or most preferably by at least 90%.The upstanding walls of the tray may be liquid permeable, in particular waterpermeable, to some extent after the step of shaping the composite material into atray comprising a base and upstanding walls forming an open-top receptaclehaving an inner surface and an outer surface, allowing to distribute liquid, inparticular water, from the tray to another tray positioned adjacent to the tray. However, the upstanding walls of the tray may also be liquid impermeable, inparticular water impermeable, for example when the composite material formingthe upstanding walls of the tray may be compressed to a high percentage.The thickness of the three-dimensional material layer comprising fibers in theupstanding walls of the tray may be at most 20 mm or at most 10 mm. Preferably,the thickness of the three-dimensional material layer comprising fibers in theupstanding walls of the tray is at most 7.5 mm, or preferably at most 5 mm, orpreferably at most 3 mm, or preferably at most 2 mm, or preferably at most 1 mm,as determined at the top edge of the upstanding wall. The thickness of the three-dimensional material layer comprising fibers in the base of the tray may be at least0.5 mm, or preferably at least 0.75 mm, or preferably at least 1 mm, or preferablyat least 1.5 mm. Reducing the thickness of the upstanding walls of the trayenables to obtain a greened surface having a more uniform appearance, and enables improved cross fertilization of plants across multiple trays placed on thesurface to be greened as the plants are closer together. A cassette according tothe prior art which comprises a bottom drainage layer onto which a tray is placedhaving a bottom layer and side walls made from a lightweight recycledpolyurethane molded foam has a wall thickness of about 10 mm, which means thatwhen two cassettes are placed next to each other on the surface to be greened,the total thickness of the two walls combined is about 20 mm, on top of which noplants are cultivated resulting in a visible line in the greened surface.In the process of shaping the composite material into a tray comprising a base andupstanding walls forming an open-top receptacle having an inner surface and anouter surface, preferably by compression molding, preferably at elevated temperatures at which polymers comprised in the composite are softened, thecomposite material forming the upstanding walls of the tray may be shaped suchthat the upstanding walls may have a height of at least 20 mm, preferably at least30 mm, or preferably at least 50 mm, or preferably at least 75 mm, or preferably atleast 100 mm, or preferably at least 125 mm, or preferably at least 150 mm. The height of the upstanding walls comprised in the tray may be varied. The height of the upstanding walls comprised in the tray may be in the range of 30 mm to 50 mm, which is advantageous for cultivating plants whose roots grow particularly in a horizontal direction, such as for example sedum plants. Theamount of substrate within the open-top receptacle of the tray wherein plants canbe cultivated can then be kept to a minimum enabling to provide a particularly lightweight tray comprising cultivated plants. The height of the upstanding walls comprised in the tray may be in the range of 50 mm to 150 mm, which is advantageous for cultivating plants whose roots growparticularly in a vertical direction, such as for example herbs or wildflowers. Theheight of the upstanding walls comprised in the tray in the range of 50 mm to 150mm is also advantageous when the tray comprises a water retention layer in theopen-top receptacle of the tray, for example on the inner surface of the open-top receptacle. The process may comprise the step of providing a water retention layer in theopen-top receptacle of the tray, wherein the water retention layer may have athickness of 5 mm to 100 mm, preferably of 7.5 mm to 75 mm, or preferably of 10 mm to 40 mm, and wherein the water retention layer may be a layer of glass wool, a layer of mineral wool, a layer of shoddy recycled textile material, or a nonwoven fabric. The water retention layer reduces the required amount of substrate withinthe open-top receptacle of the tray enabling to provide a particularly light weight tray comprising cultivated plants, while providing retention of water to facilitate plant growth over a prolonged period of time.In the process of shaping the composite material into a tray comprising a base andupstanding walls forming an open-top receptacle having an inner surface and anouter surface, preferably by compression molding, preferably at elevated temperatures at which polymers comprised in the composite are softened, thecomposite material forming the upstanding walls of the tray may be compressedsuch that the upstanding walls the angle alfa between the base and theupstanding walls at the inner surface of the tray is larger than 90°. The angle alfa may be at least 92°, or preferably at least 94°, or preferably at least 95°, enablingto stack multiple trays into each other when the trays are not yet filled with asubstrate facilitating easy transport of the empty trays.In the process of shaping the composite material into a tray comprising a base andupstanding walls forming an open-top receptacle having an inner surface and anouter surface, preferably by compression molding, preferably at elevated temperatures at which polymers comprised in the composite are softened, thecomposite material forming the upstanding walls of the tray may be shaped suchthat the upstanding walls comprise a first part of a form fit connection configured toconnect to a second part of a form fit connection in another tray which can be placed adjacent to tray on the surface to be greened, thereby ensuring that a continuous layer of trays can be formed on the surface to be greened. Preferably,the composite material forming the upstanding walls of the tray may be shapedsuch that a first upstanding wall of the tray comprises a first part of a form fitconnection, and a second upstanding wall of the tray opposite to the firstupstanding wall comprises a second part of a form fit connection, enabling toconnect a series of trays, improving ease of installation and / or to improve wind- uplift resistance.In the process of shaping the composite material into a tray comprising a base andupstanding walls forming an open-top receptacle having an inner surface and an outer surface, preferably by compression molding, preferably at elevated temperatures at which polymers comprised in the composite are softened, thecomposite material forming the base of the tray may be shaped such that the basehas any desired shape. Preferably, in the process the composite material formingthe base of the tray is shaped such that the base has a shape such that multipletrays can be placed adjacent to each other such that a continuous layer is formed.The base of the tray may for example have a triangular shape, a parallelogramshape, a hexagon shape, a rectangular shape, or a square shape. The dimensionsof the base of the tray may be varied. The base of the tray preferably has dimensions selected such that the tray can be lifted and handled manually by a person installing the tray on the surface to be greened. The largest dimension of a side of the base of the tray (large side length) may be at most 120 cm, preferably at most 100 cm, or preferably at most 80 cm, or preferably at most 60 cm. The smallest dimension of a side of the base of the tray (short side length) may be of at most 60 cm, preferably at most 50 cm, or preferably at most 40 cm.The base of the tray may have a rectangular shape having a large side length of atmost 120 cm, preferably at most 100 cm, or preferably at most 80 cm, orpreferably at most 60 cm, and a short length of at most 60 cm, preferably at most 50 cm, or preferably at most 40 cm.The base of the tray may have a square shape having a side length of at most 100cm, preferably at most 80 cm, or preferably at most 60 cm, or preferably at most50 cm. However, in greening of surfaces also trays having different shape for the base of the trays may be provided, which preferably can form a continuous layer when multiple trays are placed adjacent to each other, for example trays having an octagon shape and trays having a rectangular shape wherein the side edges ofthe base octagon shaped base and the side edges of the base of the rectangularshaped base have the same length. Greening of surfaces with trays having a different shape for the base of the trays allows to create a specific pattern of plants on the surface to be greened when each type of tray comprises different types of plants.A tray for greening of surfaces is provided comprising a base and upstanding wallsforming an open-top receptacle having an inner surface and an outer surface,wherein the fibers comprise a thermoplastic polymer, preferably a syntheticthermoplastic polymer, wherein the base comprises a three-dimensional materiallayer comprising fibers and having a first main surface and a second main surface and at least a first liquid permeable separation layer oriented plane-parallel, and preferably adjacent, to the first main surface of the three-dimensional materiallayer of fibers comprised in the base, wherein the three-dimensional material layercomprising fibers comprised in the base has an open space of at least 50%,wherein the upstanding walls comprise a material layer comprising fibers andhaving a first main surface and a second main surface, and at least a second separation layer oriented plane-parallel, and preferably adjacent, to the first mainsurface of the material layer of fibers comprised in the upstanding walls, whereinthe first liquid permeable separation layer comprised in the base and the secondseparation layer comprised in the upstanding walls are oriented towards the innersurface of the open-top receptacle.The tray for greening of surfaces may advantageously be a unitary structure. Thetray as a unitary structure is not assembled from a separate base and one or more separate upstanding walls. The tray preferably excludes an adhesive. The tray preferably excludes polyurethane foam, which improves the possibilities for processing of the tray at the end of life. The three-dimensional material layer comprising fibers comprised in the base of the tray has an open space of at least 50%. The three-dimensional material layercomprising fibers comprised in the base of the tray may have an open space of atleast 75%, preferably of at least 85%, more preferably of at least 90%, even more preferably of at least 95%, to improve draining of excess water from the tray.The three-dimensional material layer comprising fibers comprised in the base ofthe tray may be any type of three-dimensional material layer comprising fibers,provided that it has an open space of at least 50%, and may for example beselected from a three-dimensional knitted fabric, a three-dimensional woven fabric,or a three-dimensional mat of extruded entangled filaments.The fibers comprised in the three-dimensional material layer may be thermallybonded to each other at contact points of the fibers, to provide improved resilienceand / or improved compression resistance.The fibers comprised in the three-dimensional material layer comprise athermoplastic polymer, preferably a synthetic thermoplastic polymer. In anembodiment, the fibers comprised in the three-dimensional material layer arecomposed for at least 50 wt.% of thermoplastic polymer, preferably for at least 75wt.%, more preferably for at least 90 wt.%, more preferably for at least 95 wt.% ofthermoplastic polymer. The fibers comprised in the three-dimensional materiallayer may consist of thermoplastic polymer.The fibers comprised in the three-dimensional material layer may comprise, orconsists of, any suitable thermoplastic polymer or blend of thermoplastic polymers,preferably any suitable synthetic thermoplastic polymer or blend of syntheticthermoplastic polymers. The fibers may comprise a polyolefin, such as forexample polyethylene (PE) or polypropylene (PP), a halogenated polyolefin, suchas for example polytetrafluorethylene (PTFE) or polyvinylidene difluoride (PVDF),a polyester, such as for example polyethylene terephthalate (PET) (based either on DMT or PTA), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN) and / or polylactic acid (PLA), a polyamide, such as for example polyamide-6 (PA6), polyamide-6,6 (PA6,6) and / or polyamide- 6,10 (PA6,10), polyimides (PI), polysulfides (PS) such as polyphenylenesulfide(PPS), polyethyleneimide (PEI), polyoxymethylene (POM), thermoplasticelastomers (TPE) such as thermoplastic polyurethanes (TPU), and / or any copolymer or any blend thereof.The fibers comprised in the three-dimensional material layer may preferablycomprise, or consists of, a polyolefin, more preferably a polypropylene (PP).In another embodiment, the fibers comprised in the three-dimensional materiallayer may comprise, or consists of, any suitable thermoplastic polymer or blend ofthermoplastic polymers, preferably a suitable synthetic thermoplastic polymer or ablend of synthetic thermoplastic polymers, which is bio-compostable, inaccordance with EN13432, at the end of the lifetime of the tray, preferably a polymer made by a polycondensation reaction of hydroxylcarboxylic acids or a ring opening polymerization of lactides. Preferred synthetic polymeric materialscomprise polymer(s) of α-, β-, γ-, δ-, or ε-hydroxylesters. Preferably, thepolymer(s) comprised in the fibers comprised in the three-dimensional materiallayer are selected from the group of polyhydroxyalkanoates (PHA’s), such as forexample polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), poly-(3- hydroxybutyrateco-3-hydroxyvalerate) PHVB or polyhydroxyhexanoate (PHH) as for example available from Metabolix under the Mirel brand name, polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), poly-β-butyrolactone (PBL), polybutylene succinate (PBS), cellulose derivates and / or blends thereof. In a preferred embodiment, the synthetic polymeric material comprised in the fiberscomprised in the three-dimensional material layer is a polylactic acid (PLA).In an embodiment, the three-dimensional material layer comprising fiberscomprised in the base of the tray is preferably a three-dimensional mat of extrudedentangled filaments having an open space of at least 50%, preferably of at least75%, or preferably of at least 85%, or more preferably of at least 90%, or even more preferably of at least 95%.The three-dimensional mat of extruded entangled filaments comprised in the baseof the tray can be easily cut enabling to cut the tray to smaller size to precisely fit the tray at the edges of the surface to be greened. Deep-drawn plastic trays or injection molded trays of the prior art are difficult to cut precisely due to the breaking of hard and relatively brittle plastic shape in combination with a substrate such as soil within such deep-drawn or injection molded plastic trays. The three-dimensional mat of extruded entangled filaments comprised in the baseof the tray may advantageously be made of extruded filaments that are irregularlylooped and entangled into a highly porous, three-dimensional structure having alarge open space of at least 50%, wherein the extruded filaments are preferablybonded where they cross. Preferably, the extruded filaments are stretched only bygravity before being irregularly looped and entangled into a highly porous, three-dimensional structure having an open space of at least 50%.The extruded filaments may be irregularly looped and entangled into a highlyporous, three-dimensional structure having an open space of at least 50% byextruding filaments and collecting the extruded filaments into a three-dimensionalstructure by allowing the filaments to bend, to entangle and to come into contactwith each other, preferably in a still molten state. The extruded filaments may beallowed to bend, to entangled and to come into contact with each other by allowingthe extruded filaments to come into contact with a surface. The surface may be the surface of a cooling bath comprising a cooling liquid, in particular cooling water, to solidify the extruded filaments after being irregularlylooped and entangled into a highly porous, three-dimensional structure. Allowingthe extruded filaments to come into contact with a surface of a cooling bathcomprising a cooling liquid enables to form a three-dimensional mat of extrudedentangled filaments wherein the filaments have a random distribution within thethree-dimensional mat of extruded entangled filaments, which may have an essentially isotropic property distribution. The three-dimensional mat of extruded entangled filaments comprised in the baseof the tray may be a three-dimensional structured mat of extruded entangledfilaments, which may be provided by extruding filaments and collecting the extruded filaments into a three-dimensional structure by allowing the filaments tobend, to entangle and to come into contact with each other, preferably in a stillmolten state. Bending and entangling of the extruded filaments are preferablyinitiated by collecting the filaments onto a profiled surface, which defines the structure of the three-dimensional structured mat of extruded entangled filaments. Preferably, the surface on which the filaments are collected is profiled such that the three-dimensional structured mat of filaments is shaped into a three- dimensional form which comprises hills and valleys, hemispheres, positive and / or negative cuspates, cups and / or waffles, pyramids, U-grooves, V-grooves, cones and / or cylinders capped with a hemisphere.The filaments comprised in the three- three-dimensional mat of extrudedentangled filaments may be thermally bonded to each other at contact points ofthe filaments, to provide improved resilience and / or improved compressionresistance.The three-dimensional material layer comprising fibers, preferably a three-dimensional mat of extruded entangled filaments, comprised in the base of the traymay have a weight of at most 1500 g / m², preferably of at most 1200 g / m², or preferably of at most 1000 g / m², or preferably of at most 800 g / m², and the three-dimensional material layer comprising fibers, preferably a three-dimensional mat ofextruded entangled filaments, comprised in the base of the tray may have a weightof at least 100 g / m², preferably of at least 200 g / m², or preferably of at least 300 g / m², or preferably of at least 400 g / m², to provide improved resilience.The three-dimensional material layer comprising fibers, preferably a three-dimensional mat of extruded entangled filaments, comprised in the base of the traymay have a desired thickness. The three-dimensional material layer comprisingfibers, preferably a three-dimensional mat of extruded entangled filaments,comprised in the base of the tray may have a desired thickness of at most 200mm, or preferably at most 150 mm, or preferably at most 100 mm, or preferably atmost 75 mm, or preferably at most 50 mm, or preferably at most 40 mm, orpreferably at most 30 mm, or most preferably at most 25 mm. The three-dimensional material layer comprising fibers, preferably a three-dimensional mat ofextruded entangled filaments, comprised in the base of the tray mayadvantageously have a thickness of at least 3 mm, or preferably at least 4 mm, orpreferably at least 5 mm, or preferably at least 10 mm, or preferably at least 15mm, or most preferably at least 20 mm.The three-dimensional material layer comprising fibers in the base of the traypreferably has a thickness of at least 15 mm, more preferably of at least 20 mm to prevent, or at least reduce, that plants, substrate and / or water retention layer come in contact with water puddling on a waterproofing layer located beneath the tray for a prolonged period of time, in particular when the tray is to be installed on an essentially flat surface, such as a roof, having an angle of inclination between 0° and 2° to the horizontal.The three-dimensional material layer comprising fibers in the base of the traypreferably has a thickness of at least 3 mm, more preferably of at least 4 mm, or more preferably of at least 5 mm, in particular when the tray is to be installed on an slightly inclined surface, such as a roof, having an angle of inclination between 2° and 10° to the horizontal.The three-dimensional material layer comprising fibers in the base of the tray mayhave a thickness less than 3 mm, in particular when the tray is to be installed on an inclined surface, such as a roof, having an angle of inclination between 10° and 45° to the horizontal.The three-dimensional material layer comprising fibers, preferably a three-dimensional mat of extruded entangled filaments, comprised in the base of the traymay have sufficient resilience to allow equipment to rolled over or driven over the trays, without significantly reducing the thickness of tray. The three-dimensionalmaterial layer comprising fibers, preferably a three-dimensional mat of extrudedentangled filaments, comprised in the base of the tray may have resilience of atleast 75%, preferably at least 80%, or preferably at least 85%, or preferably atleast 90%, preferably at least 95%. The extruded entangled filaments of the three-dimensional mat of extrudedentangled filaments may comprise a thermoplastic polymer, preferably a syntheticthermoplastic polymer. In an embodiment, The extruded entangled filaments of thethree-dimensional mat of extruded entangled filaments are composed for at least50 wt.% of thermoplastic polymer, preferably for at least 75 wt.%, more preferablyfor at least 90 wt.%, more preferably for at least 95 wt.% of thermoplastic polymer.The extruded entangled filaments of the three-dimensional mat of extruded entangled filaments may consist of thermoplastic polymer. The extruded entangled filaments of the three-dimensional mat of extruded entangled filaments comprised in the base of the tray may comprise, or consists of, any suitable thermoplastic polymer or blend of thermoplastic polymers. Theextruded entangled filaments may comprise a polyolefin, such as for examplepolyethylene (PE) or polypropylene (PP), a halogenated polyolefin, such as forexample polytetrafluorethylene (PTFE) or polyvinylidene difluoride (PVDF), apolyester, such as for example polyethylene terephthalate (PET) (based either on DMT or PTA), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN) and / or polylactic acid (PLA), a polyamide, such as for example polyamide-6 (PA6), polyamide-6,6 (PA6,6) and / or polyamide- 6,10 (PA6,10), polyimides (PI), polysulfides (PS) such as polyphenylenesulfide(PPS), polyethyleneimide (PEI), polyoxymethylene (POM), thermoplasticelastomers (TPE) such as thermoplastic polyurethanes (TPU), and / or any copolymer or any blend thereof. The extruded entangled filaments of the three-dimensional mat of extruded entangled filaments comprised in the base of the tray may preferably comprise, orconsists of, a polyolefin, more preferably a polypropylene (PP).In another embodiment, the extruded entangled filaments of the three-dimensional mat of extruded entangled filaments comprised in the base of the tray may comprise, or consists of, any suitable thermoplastic polymer or blend ofthermoplastic polymers, preferably a suitable synthetic thermoplastic polymer or ablend of synthetic thermoplastic polymers, which is bio-compostable, inaccordance with EN13432, at the end of the lifetime of the tray, preferably a polymer made by a polycondensation reaction of hydroxylcarboxylic acids or a ring opening polymerization of lactides. Preferred synthetic polymeric materialscomprise polymer(s) of α-, β-, γ-, δ-, or ε-hydroxylesters. Preferably, the polymer ofwhich the three-dimensional entangled mat of extruded filaments is made is selected to comprise polymer(s) from the group of polyhydroxyalkanoates (PHA’s), such as for example polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), poly- (3-hydroxybutyrateco-3-hydroxyvalerate) PHVB or polyhydroxyhexanoate (PHH) as for example available from Metabolix under the Mirel brand name, polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), poly-β-butyrolactone (PBL), polybutylene succinate (PBS), cellulose derivates and / or blends thereof. In a preferred embodiment, the synthetic polymeric material of which the three- dimensional entangled mat of extruded filaments is made is a polylactic acid (PLA). The first liquid permeable separation layer oriented plane-parallel, and preferablyadjacent, to the first main surface of the three-dimensional material layer of fiberscomprised in the base of the tray and / or the second separation layer orientedplane-parallel, and preferably adjacent, to the first main surface of the materiallayer of fibers comprised in the upstanding walls of the tray may independentlyfrom each other comprise, or consists of, any suitable thermoplastic polymer orblend of thermoplastic polymers, preferably any suitable synthetic thermoplasticpolymer or a blend of synthetic thermoplastic polymers, which is bio-compostableat the end of the lifetime of the tray, preferably a polymer made by a polycondensation reaction of hydroxylcarboxylic acids or a ring opening polymerization of lactides. Preferred synthetic polymeric materials comprise polymer(s) of α-, β-, γ-, δ-, or ε-hydroxylesters, allowing the tray to be bio-composted at the end of life. Preferably, the polymer of which the first liquidpermeable separation layer oriented plane-parallel, and preferably adjacent, to thefirst main surface of the three-dimensional material layer of fibers comprised in thebase of the tray and / or the second separation layer oriented plane-parallel, andpreferably adjacent, to the first main surface of the material layer of fiberscomprised in the upstanding walls of the tray, is made is selected to comprisepolymer(s) from the group of polyhydroxyalkanoates (PHA’s), such as for example polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), poly-(3- hydroxybutyrateco-3-hydroxyvalerate) PHVB or polyhydroxyhexanoate (PHH) as for example available from Metabolix under the Mirel brand name, polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), poly-β-butyrolactone (PBL), polybutylene succinate (PBS), cellulose derivates and / or blends thereof. In a preferred embodiment, the synthetic polymeric material of which the first liquidpermeable separation layer and / or the second separation layer is made is apolylactic acid (PLA). The first liquid permeable separation layer oriented plane-parallel, and preferablyadjacent, to the first main surface of the three-dimensional material layer of fiberscomprised in the base of the tray may be any type of liquid permeable material,and may preferably be selected from a perforated film, a woven fabric or anonwoven fabric. Preferably, the first liquid permeable separation layer orientedplane-parallel, and preferably adjacent, to the first main surface of the three-dimensional material layer of fibers comprised in the base of the tray is anonwoven fabric. The nonwoven fabric may in principle be any type of nonwoven, such as for example staple fiber nonwovens produced by well-known processes, such as carding processes, wet-laid processes or air-laid processes, or any combination thereof. The nonwoven fabric may also be a nonwoven composed of filaments produced by well-known spunbonding processes wherein filaments are extruded from a spinneret and subsequently laid down on a conveyor belt as a web of filaments and subsequently consolidated, also known as bonding, the web to form a nonwoven layer of fibers, or by a two-step process wherein filaments are spunand wound on bobbins, preferably in the form of multifilament yarns, followed bythe step of unwinding the filaments or multifilament yarns and laying the filaments down on a conveyor belt as a web of filaments and consolidating the web to form a nonwoven layer of fibers. The nonwoven fabric may have been consolidated by any suitable known consolidation technology, including mechanical consolidation, for example by stitching, mechanical needling and / or hydrodynamic consolidation by fluid jets, in particular by hydroentanglement, by chemical consolidation, for example by applying a binder dispersion or a binder solution to the nonwoven layer of fibers, which is generally dried and optionally cured, and / or by thermal consolidation, for example by calendaring, ultrasonic bonding and / or hot air bonding. The nonwoven fabric may comprise a higher melting polymer and a lower meltingpolymer, facilitating thermal bonding of the nonwoven fabric. The lower meltingpolymer may have a melting temperature which is at least 10°C, preferably at least 20°C, or preferably at least 50°C, lower than the melting temperature of the higher melting polymer.The higher melting polymer may be comprised in a first type of mono-componentfibers the lower melting polymer may be comprised in a second type of mono- component fibers. The lower melting polymer comprised in the nonwoven fabric may be comprised in multicomponent fibers, preferably in bicomponent fibers. A basic distinction is being drawn between three types of bicomponent fibers: side-by-side types, core-sheath types and islands-in-the-sea types of bicomponent fibers. Preferably, theratio of low melting polymer and high melting polymer in the bicomponent fibers, preferably sheath / core bicomponent fibers lies between 95 / 5 vol.% and 5 / 95 vol.%. More preferably the ratio of low melting polymer and high melting polymer lies between 50 / 50 vol.% and 95 / 5 vol.%. The mono-component or multicomponent fibers comprised in the nonwoven fabric may have any cross sectional shape, including round, trilobal, multilobal or rectangular. Preferably, the fibers in the nonwoven fabric are filaments in order to provide higher tensile strength and / or higher tear strength to the composite material. The first liquid permeable separation layer oriented plane-parallel, and preferablyadjacent, to the first main surface of the three-dimensional material layer of fiberscomprised in the base of the tray may preferably be a nonwoven fabric composedof bicomponent sheath / core filaments comprising a core of a polyester, preferably a polyethylene terephthalate (PET), and a sheath of a copolyester (coPET). The first liquid permeable separation layer oriented plane-parallel, and preferablyadjacent, to the first main surface of the three-dimensional material layer of fiberscomprised in the base of the tray may have a weight of at most 500 g / m²,preferably of at most 400 g / m², or preferably of at most 300 g / m², or preferably of at most 200 g / m², and the first liquid permeable separation layer comprised in the composite material and which is oriented plane-parallel, and preferably adjacent,to the first main surface of the three-dimensional material layer of fibers may havea weight of at least 25 g / m², preferably of at least 30 g / m², or preferably of at least 50 g / m², preferably of at least 100 g / m², enabling to retain a substrate within theopen-top receptacle of the tray wherein plants can be cultivated, while allowingexcess water to be drained from the tray. The first liquid permeable separation layer oriented plane-parallel, and preferablyadjacent, to the first main surface of the three-dimensional material layer of fiberscomprised in the base of the tray may have a characteristic size of the openings(O-90) in accordance with NEN-EN-ISO 12956:200 of 200 µm or less, preferably 175 µm or less, or preferably 150 µm or less, or preferably 125 µm or less, or preferably 100 µm or less, or preferably 75 µm or less, or most preferably 50 µmor less, enabling to retain a substrate within the open-top receptacle of the traywherein plants can be cultivated, while allowing an excess of water to be drained from the tray through the first liquid permeable separation layer and through thethree-dimensional material layer comprising fibers comprised in the base of thetray. The first liquid permeable separation layer oriented plane-parallel, and preferablyadjacent, to the first main surface of the three-dimensional material layer of fiberscomprised in the base of the tray may, however, have a characteristic size of theopenings (O-90) in accordance with NEN-EN-ISO 12956:200 higher than 200 µm, for example when the tray comprises a water retention layer in the open-top receptacle of the tray, for example on the inner surface of the open-top receptacle. The first liquid permeable separation layer comprised in the tray comprising a baseand upstanding walls forming an open-top receptacle having an inner surface andan outer surface, is oriented towards the inner surface of the open-top receptacleof the tray, which enables to retain a substrate within the open-top receptacle ofthe tray wherein plants can be cultivated, while allowing an excess of water to be drained from the tray through the first liquid permeable separation layer andthrough the three-dimensional material layer comprising fibers. An excess of waterretained within the tray could damage the plants being cultivated within the tray, for example due to rotting of roots of the plants. The second separation layer oriented plane-parallel, and preferably adjacent, to the first main surface of the material layer of fibers comprised in the upstandingwalls of the tray may be any type of liquid permeable material which has thecapability to retain a substrate within the open-top receptacle of the tray whereinplants can be cultivated, and may preferably be selected from a continuous closedfilm, a perforated film, a woven fabric or a nonwoven fabric, and may more preferably be selected from a perforated film, a woven fabric or a nonwoven fabric.The second separation layer may be liquid impermeable, in particular waterimpermeable, and may preferably be a continuous closed film.The second separation layer may be liquid permeable, in particular waterpermeable, and may preferably be selected from a perforated film, a woven fabricor a nonwoven fabric. More preferably, the second separation layer orientedplane-parallel, and preferably adjacent, to the first main surface of the three-dimensional material layer of fibers comprised in the base of the tray is anonwoven fabric. The tray may comprise a second layer oriented plane-parallel, and preferablyadjacent, to the second main surface of the three-dimensional material layer offibers comprised in the base of the tray.The second layer oriented plane-parallel, and preferably adjacent, to the secondmain surface of the three-dimensional material layer of fibers comprised in thebase of the tray may comprise, or may consist of, a knitted fabric, a woven fabricor a nonwoven fabric configured as the loop side of a hook and loop connection. The hook side of the hook and loop connection can be fixedly connected to the surface to be greened, for example the hook side of the hook and loop connection can be fixedly connected to a waterproofing layer, to improve wind-uplift resistance or to prevent, or at least reduce, sliding of the tray when installed on an inclined surface, for example at angle of more than 2°, or more than 5°, or more than 10° to the horizontal. The second layer oriented plane-parallel, and preferably adjacent, to the second main surface of the three-dimensional material layer of fibers comprised in the base of the tray preferably is a nonwoven fabric configured as the loop side of a hook and loop connection. The tray may comprise a second layer oriented plane-parallel, and preferablyadjacent, to the second main surface of the material layer of fibers comprised inthe upstanding walls of the tray. The second layer comprised in the tray may be provided as a single continuouslayer oriented plane-parallel, and preferably adjacent, to the second main surfaceof the three-dimensional material layer of fibers comprised in the base of the trayand oriented plane-parallel, and preferably adjacent, to the second main surface ofthe material layer of fibers comprised in the upstanding walls of the tray.The second layer comprised in the tray may be provided only oriented plane-parallel, and preferably adjacent, to the second main surface of the three-dimensional material layer of fibers comprised in the base of the tray.The second layer comprised in the tray oriented plane-parallel, and preferablyadjacent, to the second main surface of the three-dimensional material layer offibers and / or oriented plane-parallel, and preferably adjacent, to the second mainsurface of the material layer of fibers comprised in the upstanding walls of the traymay be liquid permeable, in particular water permeable, enabling an excess of water to be drained from the tray vertically through the three-dimensional materiallayer comprising fibers and / or horizontally through the upstanding walls of the tray.The second layer comprised in the tray oriented plane-parallel, and preferablyadjacent, to the second main surface of the three-dimensional material layer offibers and / or oriented plane-parallel, and preferably adjacent, to the second mainsurface of the material layer of fibers comprised in the upstanding walls of the traymay be liquid impermeable, in particular water impermeable, to prevent that liquid, in particular water, being drained from the tray comes into contact with surface to be greened, which may be located below the tray, while the liquid, in particular water, can still be drained from the tray horizontally or under a slight angle of for example less than 5°, or less than 2°, to the horizontal. Additionally, the liquid impermeable, in particular water impermeable, second layer enables to reduce the risk of root penetration through the base of the tray and / or through the upstanding walls of the tray. The tray may comprise upstanding walls which are liquid permeable, in particular water permeable, allowing to distribute liquid, in particular water, from the tray to another tray positioned adjacent to the tray on the surface to be greened. The tray may also comprise upstanding walls which are liquid impermeable, in particular water impermeable, to prevent root penetration through the upstanding walls.The tray may comprise upstanding walls having a thickness of the material layercomprising fibers the upstanding walls of the tray of at most 20 mm or at most 10mm. The tray may comprise upstanding walls having a thickness of the materiallayer comprising fibers in the upstanding walls of the tray of at most 7.5 mm,preferably at most 5 mm, or preferably at most 3 mm, or preferably at most 2 mm,or preferably at most 1 mm, as determined at the top edge of the upstanding wall.The tray may comprise upstanding walls having a thickness of the material layercomprising fibers in the upstanding walls of the tray of at least 0.5 mm, preferablyat least 0.75 mm, or preferably at least 1 mm, or preferably at least 1.5 mm. Alower thickness of the upstanding walls of the tray enables to obtain a greenedsurface having a more uniform appearance, and enables improved cross fertilization of plants across multiple trays placed on the surface to be greened as the plants are closer together. A cassette according to the prior art whichcomprises a bottom drainage layer onto which a tray is placed having a bottomlayer and side walls made from a lightweight recycled polyurethane molded foamhas a wall thickness of about 10 mm, which means that when two cassettes are placed next to each other on the surface to be greened, the total thickness of the two walls combined is about 20 mm, on top of which no plants are cultivated resulting in a visible line in the greened surface. The height of the upstanding walls comprised in the tray may be varied. The tray may comprise upstanding walls having a height of at least 20 mm, preferably atleast 30 mm, or preferably at least 50 mm, or preferably at least 75 mm, orpreferably at least 100 mm, or preferably at least 125 mm, or preferably at least 150 mm. The tray may comprise upstanding walls having a height in the range of 30 mm to 50 mm, which is advantageous for cultivating plants whose roots grow particularly in a horizontal direction, such as for example sedum plants. The amount ofsubstrate within the open-top receptacle of the tray wherein plants can becultivated can then be kept to a minimum enabling to provide a particularly lightweight tray comprising cultivated plants. The tray may comprise upstanding walls having a height in the range of 50 mm to 150 mm, which is advantageous for cultivating plants whose roots growparticularly in a vertical direction, such as for example herbs or wildflowers. Theheight of the upstanding walls comprised in the tray in the range of 50 mm to 150 mm is also advantageous when the tray comprises a water retention layer in the open-top receptacle of the tray, for example on the inner surface of the open-top receptacle. The tray may comprise a water retention layer in the open-top receptacle of the tray, wherein the water retention layer may have a thickness of 5 mm to 100 mm, preferably of 7.5 mm to 75 mm, or preferably of 10 mm to 40 mm, and wherein the water retention layer may be a layer of glass wool, a layer of mineral wool, a layer of shoddy recycled textile material, or a nonwoven fabric. The water retention layerreduces the required amount of substrate within the open-top receptacle of thetray enabling to provide a particularly light weight tray comprising cultivated plants, while providing retention of water to facilitate plant growth over a prolonged period of time, or to temporarily store water in times of heavy rainfall for storm water management purposes. The tray may comprise the upstanding walls at an angle alfa to the base of tray larger than 90°. The angle alfa may be at least 92°, or preferably at least 94°, or preferably at least 95°, enabling to stack multiple trays into each other when the trays are not yet filled with a substrate facilitating easy transport of the empty trays.The tray may comprise one or more upstanding walls comprising a first part of aform fit connection configured to connect to a second part of a form fit connection in another tray which can be placed adjacent to tray on the surface to be greened, thereby ensuring that a continuous layer of trays can be formed on the surface tobe greened. Preferably, the tray comprises a first upstanding wall of the traycomprising a first part of a form fit connection, and a second upstanding wallopposite to the first upstanding wall comprising a second part of a form fitconnection, enabling to connect a series of trays.The tray may comprise a base having any desired shape. Preferably, the traycomprises a base having a shape configured for forming a continuous layer oftrays when multiple trays are placed adjacent to each other on the surface to begreened. The tray may comprise a base having for example a triangular shape, aparallelogram shape, a hexagon shape, a rectangular shape, or a square shape. The dimensions of the base of the tray may be varied. The base of the tray preferably has dimensions selected such that the tray can be lifted and handled manually by a person installing the tray on the surface to be greened. The largest dimension of a side of the base of the tray (large side length) may be at most 120 cm, preferably at most 100 cm, or preferably at most 80 cm, or preferably at most 60 cm. The smallest dimension of a side of the base of thetray (short side length) may be of at most 60 cm, preferably at most 50 cm, orpreferably at most 40 cm.The tray may comprise a base having a rectangular shape having a large sidelength of at most 100 cm, preferably at most 80 cm, or preferably at most 60 cm, and having a short length of at most 60 cm, preferably at most 50 cm, or preferably at most 40 cm.The tray may comprise a base having a square shape having a side length of atmost 100 cm, preferably at most 80 cm, or preferably at most 60 cm, or preferablyat most 50 cm. However, in greening of surfaces also trays having different shape for the base of the trays may be provided, which preferably can form a continuous layer when multiple trays are placed adjacent to each other, for example trays having an octagon shape and trays having a rectangular shape wherein the side edges ofthe base octagon shaped base and side edges of the base of the rectangularshaped base have the same length. Greening of surfaces with trays having different shape for the base of the trays allows to create a specific pattern of plants on the surface to be greened when each type of tray comprises different types of plants. The tray may comprise a substrate within the open-top receptacle of the tray. Thesubstrate may comprise soil, fertilizer and / or inorganic substances, such as forexample, lava, lightweight lava, natural pumice, expanded clay and / or expanded shale. The tray may comprise mycelium, for example in combination with gardening waste such as pruning waste, enabling to form a substrate in-situ within the tray.Figure 1 schematically depicts a side view of a composite material (100)comprising a three-dimensional material layer comprising fibers (110) and a liquidpermeable separation layer (101) oriented plane-parallel, and adjacent, to the firstmain surface of the three-dimensional material layer of fibers (110), which may beprovided into the process for manufacturing a tray.Figure 2 schematically depicts a side view cross-section of a tray (200) shapedfrom the composite material of Figure 1, the tray comprising a base andupstanding walls forming an open-top receptacle having an inner surface (211)and an outer surface (212). The base of the tray comprises a three-dimensionalmaterial layer comprising fibers (210) having an open space of at least 50%. Theliquid permeable separation layer (201) comprised in the base is oriented towardsthe inner surface (211) of the open-top receptacle. The tray of Figure 2 comprisesupstanding walls comprising a material layer comprising fibers (214), which maybe formed by compressing the three-dimensional material layer comprising fibers(110) of Figure 1. The separation layer (201) comprised in the upstanding walls isoriented towards the inner surface (211) of the open-top receptacle. Figure 3 schematically depicts a side view of another composite material (300)comprising a three-dimensional material layer comprising fibers (310) and a firstliquid permeable separation layer (301) oriented plane-parallel, and adjacent, tothe first main surface of the three-dimensional material layer of fibers (310), whichmay be provided into the process for manufacturing a tray. The composite material(300) also comprises a second layer (302) oriented plane-parallel, and adjacent, tothe second main surface of the three-dimensional material layer of fibers (310).Figure 4 schematically depicts a side view cross-section of a tray (400) shapedfrom the composite material of Figure 3, the tray comprising a base andupstanding walls forming an open-top receptacle having an inner surface (411)and an outer surface (412). The base of the tray comprises a three-dimensionalmaterial layer comprising fibers (410) having an open space of at least 50%. Theliquid permeable separation layer (401) comprised in the base is oriented towardsthe inner surface (411) of the open-top receptacle. The second layer (402)comprised in the base is oriented towards the outer surface (412) of the open-topreceptacle. The tray of Figure 4 comprises upstanding walls comprising a materiallayer comprising fibers (414), which may be formed by compressing the three-dimensional material layer comprising fibers (310) of Figure 3. The separationlayer (401) comprised in the upstanding walls is oriented towards the inner surface(411) of the open-top receptacle. The second layer (402) comprised in theupstanding walls is oriented towards the outer surface (412) of the open-topreceptacle. Figure 5 schematically depicts a side view of yet another composite material (500)comprising a three-dimensional material layer comprising fibers (510) and a firstliquid permeable separation layer (501) oriented plane-parallel, and adjacent, tothe first main surface of the three-dimensional material layer of fibers (510), whichmay be provided into the process for manufacturing a tray. The composite material(500) also comprises a second layer (502) oriented plane-parallel, and adjacent, tothe second main surface of the three-dimensional material layer of fibers (510).The second layer (502) is provided only over the area of the second main surfaceof the three-dimensional material layer of fibers (510) which is shaped into thebase of the tray.Figure 6 schematically depicts a side view cross-section of a tray (600) shapedfrom the composite material of Figure 5, the tray comprising a base andupstanding walls forming an open-top receptacle having an inner surface (611)and an outer surface (612). The base of the tray comprises a three-dimensionalmaterial layer comprising fibers (610) having an open space of at least 50%. Theliquid permeable separation layer (601) comprised in the base is oriented towardsthe inner surface (611) of the open-top receptacle. The second layer (602)comprised only in the base is oriented towards the outer surface (612) of the open-top receptacle. The tray of Figure 6 comprises upstanding walls comprising amaterial layer comprising fibers (614), which may be formed by compressing thethree-dimensional material layer comprising fibers (510) of Figure 5. Theseparation layer (601) comprised in the upstanding walls is oriented towards theinner surface (611) of the open-top receptacle. There is no second layercomprised in the upstanding walls of the open-top receptacle of the tray (600).Figure 7 schematically depicts a side view of another composite material (700)comprising a three-dimensional material layer comprising fibers (710) and a firstliquid permeable separation layer (701) oriented plane-parallel, and adjacent, tothe first main surface of the three-dimensional material layer of fibers (710), whichmay be provided into the process for manufacturing a tray. The composite material(700) also comprises a second layer (702) oriented plane-parallel, and adjacent, tothe second main surface of the three-dimensional material layer of fibers (710).Figure 8 schematically depicts a side view cross-section of a tray (800) shapedfrom the composite material of Figure 7, the tray comprising a base andupstanding walls forming an open-top receptacle having an inner surface (811)and an outer surface (812). The base of the tray comprises a three-dimensionalmaterial layer comprising fibers (810) having an open space of at least 50%. Theliquid permeable separation layer (801) comprised in the base is oriented towardsthe inner surface (811) of the open-top receptacle. The second layer (802)comprised in the base is oriented towards the outer surface (812) of the open-topreceptacle. The tray of Figure 8 comprises upstanding walls comprising a materiallayer comprising fibers (814), which may be formed by compressing the three-dimensional material layer comprising fibers (710) of Figure 7. The separationlayer (801) comprised in the upstanding walls is oriented towards the inner surface(811) of the open-top receptacle. The second layer (802) comprised in theupstanding walls is oriented towards the outer surface (812) of the open-topreceptacle. The tray (800) is shaped such that the angle alfa, between the baseand the upstanding walls at the inner surface of the tray is larger than 90°, indicated by the curved arrow in Figure 8, enabling to stack multiple trays into each other when the trays are not yet filled with a substrate facilitating easy transport of the empty trays.

Claims

Tray for Greening of Surfaces and Process for Manufacturing a Tray forGreening of Surfaces ___________ Claims:

1. A process for manufacturing a tray for greening of surfaces comprising thesteps of providing a composite material (100, 300, 500, 700) comprising athree-dimensional material layer comprising fibers (110, 310, 510, 710) andhaving a first main surface and a second main surface, wherein the fibers (110,310, 510, 710) comprise a thermoplastic polymer, and at least a first liquid permeable separation layer (101, 301, 501, 701) oriented plane-parallel, and preferably adjacent, to the first main surface of the three-dimensional materiallayer of fibers, and shaping the composite material (100, 300, 500, 700) into atray (200, 400, 600, 800) comprising a base and upstanding walls forming an open-top receptacle having an inner surface (211, 411, 611, 811) and an outersurface (212, 412, 612, 812), wherein the three-dimensional material layercomprising fibers comprised in the base (210, 410, 610, 810) has an open space of at least 50%, wherein the liquid permeable separation layer (201, 401,601, 801) comprised in the base is oriented towards the inner surface of theopen-top receptacle.

2. The process for manufacturing a tray for greening of surfaces according toclaim 1 comprising the step of providing a second layer (302, 502, 702)oriented plane-parallel, and preferably adjacent, to the second main surface ofthe three-dimensional material layer of fibers (310, 510, 710).

3. The process for manufacturing a tray for greening of surfaces according toclaim 2, wherein the second layer (302, 502, 702) is liquid permeable.

4. The process for manufacturing a tray for greening of surfaces according toclaim 2, wherein the second layer (302, 502, 702) is liquid impermeable.

5. The process for manufacturing a tray for greening of surfaces according to anyone or more of claims 1 to 4 comprising the step of compression molding thecomposite material into a tray (200, 400, 600, 800) for greening of surfaces.

6. The process for manufacturing a tray for greening of surfaces according to anyone or more of claims 1 to 5 wherein the tray (200, 400, 600, 800) for greeningof surfaces is a unitary structure.

7. A tray (200, 400, 600, 800) for greening of surfaces, in particular for roofs ofbuilding structures, comprising a base and upstanding walls forming an open-top receptacle having an inner surface and an outer surface, wherein the fibers(110, 310, 510, 710) comprise a thermoplastic polymer, wherein the base comprises a three-dimensional material layer comprising fibers (210, 410, 610,810) and having a first main surface and a second main surface and at least a first liquid permeable separation layer (201, 401, 601, 801) oriented plane- parallel, and preferably adjacent, to the first main surface of the three- dimensional material layer of fibers comprised in the base, wherein the three-dimensional material layer comprising fibers comprised in the base has an open space of at least 50%, wherein the upstanding walls comprise a material layer comprising fibers (214, 414, 614, 818) and having a first main surface and a second main surface and at least a second separation layer orientedplane-parallel, and preferably adjacent, to the first main surface of the material layer of fibers comprised in the upstanding walls, wherein the first liquid permeable separation layer comprised in the base and the second separationlayer comprised in the upstanding walls are oriented towards the inner surfaceof the open-top receptacle.

8. The tray for greening of surfaces according to claim 7 wherein the basecomprises a second layer (402, 602, 802) oriented plane-parallel, andpreferably adjacent, to the second main surface of the three-dimensionalmaterial layer of fibers (410, 610, 810).

9. The tray for greening of surfaces according to any one or more of claims 7 to 8,wherein the upstanding walls comprise a second layer oriented plane-parallel,and preferably adjacent, to the second main surface of the material layer offibers (414, 814).10.The tray for greening of surfaces according to any one or more of claims 7 to 9,wherein the second layer (402, 602, 802) is water permeable.11.The tray for greening of surfaces according to any one or more of claims 7 to 9,wherein the second layer (402, 602, 802) is water impermeable.12.The tray for greening of surfaces according to any one or more of claims 7 to11 wherein the upstanding walls have a thickness of at most 7.5 mm.13.The tray for greening of surfaces according to any one or more of claims 7 to12 wherein the tray comprises the upstanding walls at an angle alfa to the baseof tray larger than 90°, preferably at least 92°, or preferably at least 94°, or preferably at least 95°.14.The tray for greening of surfaces according to any one or more of claims 7 to13 wherein the tray comprises a water retention layer.15.The tray for greening of surfaces according to any one or more of claims 7 to14wherein the tray is a unitary structure.