Patent Description:
Very often in the past, the "hazard" of a landfill has been deemed to be proportional to its ability to percolate sewage (leachate) into the soil, with less importance being given to the effect of biogas emissions. More recently, biogas collection and treatment has been considered in response to different urges: on the one hand the hazards of biogas and on the other its energy potential.

This variety of urges has promoted interest in biogas collection issues, thereby leading to the development of regulations aimed at reducing and controlling biomass emissions. Thus, a new approach to landfill design has been developed, with a view to enhanced control of biogas production and maximized collection (Enrico Magnano (<NUM>). Biogas da discarica. EPC libri, Roma, p.

Environmental impacts of landfill management can be divided into small-scale and large-scale impacts.

The effects of the first type of impacts are felt in the vicinity of the landfill (up to a few kilometers away) and create the greatest problems of acceptance by the surrounding population due to the emission of malodorous compounds.

On the other hand, large-scale impacts are mainly linked to the decisive contribution of biogas to the greenhouse effect, due to the release of CO<NUM> and in particular CH<NUM> into the atmosphere. Leaving aside the issue of the greenhouse effect, in which several competing mechanisms are involved, biogas production at landfills causes a number of problems, including olfactory impact; the risks of fire and explosion,
the risks of asphyxiation, the risks of intoxication, phytotoxicity, and the synergy of all these effects (https://www. cloud/en/problems-represented-by-landfill-biogas-in-terms-of-environmental-impact/).

In view of the above, it will be apparent that a modern landfill site cannot ignore the problems of biogas collection and management, with a view to at least minimizing emissions; enabling recovery of a renewable energy source; ensuring safe landfill conditions by controlling flammability of the biogas mixture.

In addition to biogas, the operation of a landfill also requires implementation of appropriate underground drainage work to prevent the leachate percolation into groundwater.

Legislative Decree no. <NUM>/<NUM> consolidated on <NUM>/<NUM>/<NUM>, concerning the management of landfills, provides (section. <NUM>(m) the most recent definition of leachate as "any liquid mainly originating from water infiltration into the waste mass or from its decomposition, and emitted from or contained within a landfill".

The landfill may be somewhat deemed to be a biological reactor in which reactions occur and produce a gas mixture (biogas, composed of <NUM>% methane and <NUM>% carbon dioxide) and a liquid mixture (leachate, composed of a high load of elements that can be deemed to be nutrients such as nitrogen and phosphorus, but also salts, hydrocarbons and heavy metals) (Eva Micheli (<NUM>). Prove di fertirrigazione con percolato da discarica pretrattato con un sistema di bio-stabilizzazione aerobico. Facoltà di Scienze Matematiche, Fisiche e Naturali, Università degli studi di Pisa).

Biogas and leachate collection and management systems form an integral part of the design of the landfill. Referring to <FIG>, which schematically represents the section of a general facility, the following building blocks can be identified at any landfill site:.

The most widely used biogas collection systems in today's landfills include the so-called vertical collection wells. In most cases, wells are dry drilled once the landfill has been closed, with varying diameters (typically from a minimum of <NUM>,<NUM> up to a maximum of <NUM>). The well is filled with a draining material (typically gravel), while the upper end section is sealed with waterproofing material. A cracked collection tube configured for biogas collection is placed inside the well and biogas is collected without being released into the atmosphere due to the high percentage of CH<NUM> (high greenhouse gases). Due to its high heat value, it is usually sent to a CHP plant or combustion flare.

Another type of a collection net is a horizontal collection systems, which do not hinder daily waste disposal operations and are therefore suitable for biogas collection from the earliest life stages of a landfill.

Vertical collection wells often integrate two landfill requirements: biogas collection and leachate management, which also fall under the above class of leachate drainage systems (c): water from rainfall and waste moisture, once saturation in the waste has been reached, which is not eliminated by evapotranspiration or surface runoff, starts to produce leachate which must be disposed of.

Leachate drainage systems typically include the following:.

The collected leachate may be conveyed into a decanting tank and then sent for treatment to a sewage treatment plant, which may be internal or external to the landfill body.

It shall be understood from the information that have been given so far, gravel - as a drainage material - is a very important and widely used element in landfills. The most commonly used type of gravel is the so-called "quarry gravel", a virgin material that must have (for landfill purposes) a low percentage content of carbonates, limestones, dolomites, evaporites or vitriol stones.

D1 (<CIT>) describes a composition comprising a matrix of solid particles embedded in a binder, wherein the binder is present in an amount comprised between <NUM> and <NUM>% by weight of the total weight of the composition (w/w) and comprises at least one thermoplastic synthetic polymer. The solid particles are preferably a combination of aggregate (sized between <NUM>-<NUM>), filler (sized up to <NUM>) and sand (sized between <NUM> and <NUM>); the concentration of the solid particles exemplified in D1 is on average greater than <NUM>% by weight of the weight of the composition (w/w).

D2 (<CIT>) describes a thermoplastic polymer concrete building block comprising <NUM>% by weight acrylonitrile butadiene styrene (ABS), <NUM>% by weight LDPE, <NUM>% by weight HDPE, and <NUM>% by weight sand. According to an alternative embodiment, the building block comprises <NUM>% ABS, <NUM>% sand, <NUM>% polyethylene.

D3 (<CIT>) describes a moulded product containing at least <NUM>% by weight of a thermoplastic component, and at least <NUM>% by weight of a particulate filler material, which includes sand.

D4 (<CIT>) describes a <NUM>:<NUM> mixture by weight of granulated thermoplastic waste materials and sand superficially coated with sugar (sucrose) in an amount between <NUM>% and <NUM>% by weight.

D5 (<CIT>) discloses a sleeper for use in track superstructures, which is formed of a mixture of plastic granules, particularly polypropylene (PP) and polyethylene (PE, in particular HDPE), and sand in an amount of <NUM>% by weight.

D6 (<CIT>) discloses building products, in particular roofing tiles, concrete products, and floor tiles, comprising <NUM>-<NUM>% by mass of plastic waste material, in particular thermoplastic waste materials, granulated or shredded, and <NUM>-<NUM>% by mass of sand.

Gravel is an expensive material that has a significant economic impact on the overall landfill management it has to be extracted from quarries of silica aggregates and then carried to the facility, using significant resources by the operators.

The choice of a gravel suitable for landfill mining and management is not to be underestimated: the selection of an excessively calcareous material may lead to gravel cementation, resulting in loss of drainage capacity.

In addition, gravel is a virgin material that is naturally formed through a long process resulting from compact rock breaking; then the fragments formed thereby undergo a mechanical abrasive action by water and ice, resulting in rounding of corners and edges. Gravel is also a highly demanded material, and is also used in other industrial applications, such as asphalt and concrete construction; beach nourishment; porous asphalt; aggregates for prefabricated buildings; and aggregates for land remediation.

This is an obstacle to proper and smooth landfill management, as well as to the achievement of circular economy goals.

Now, the Applicant has identified a composition to form a composite material that can partially or totally replace the common quarry gravel as currently used in landfills.

Therefore, the present invention relates to a composite material used for drainage and filling at a landfill site, comprising:.

The invention further relates to a process for the manufacture of the composite material and the uses for which the composite material is intended.

Non-reusable or non-recyclable plastic materials may still be employed in landfill environments instead of "quarry gravel" raw material, which is now used for the drainage of biogas and leachate through the waste mass.

This solution is suggested as an equivalent alternative to currently used natural gravel, in terms of efficiency.

It should be noted that the composite material has a draining effect not because of the porosity of the material, but because of the gaps created by the disordered arrangement of the various pieces of the material at landfill sites.

The composite material of the invention provides the following benefits:.

<FIG>: section of a common landfill, showing the various functional layers of the landfill, as well as biogas and leachate collection systems.

The following definitions are useful for interpreting the text for the purposes of the invention.

A landfill or landfill site preferably refers to a landfill for special non-hazardous waste.

A composite material refers to a system composed of two or more heterogeneous phases, which may be identified as a continuous phase, or "matrix", and a discontinuous, dispersed phase.

A thermoplastic material refers to a plastic material that reacts to heat by softening becoming malleable, which allows it to be modeled to form finished products. When cooled, the thermoplastic material becomes rigid again and, if pure, the softening and cooling process may be repeated several times without any change in material properties.

A virgin plastic or plastic material refers to a polymer directly obtained from a petrochemical raw material, such as natural gas or crude oil, which has never been used before.

A softening point or temperature refers to the thermodynamic state at which a material that does not have a defined melting point (such as a plastic material) begins to change its aggregation state from solid to fluid.

A multilayer laminated plastic material refers to a composite material comprising a plurality of overlapping layers, such layers being made of heteropolymer plastics such as polyolefins and polyesters or derivatives thereof. For example, polymers commonly used to make multilayer laminates are polyethylene (PE), ethyl vinyl alcohol (EVOH), polyethylene terephthalate (PET). Multilayer laminated plastic materials sometimes include intermediate layers with the function of adhesives or binders (such as ethylene vinyl acetate (EVA) layers); barriers (such as metallization or EVOH layers); dyes (such as TiO<NUM> -based layers). The intermediate layers only constitute a small part of the total weight of the composite material, typically < <NUM>% by weight. As such, multilayer coupled plastics are not easily recycled, due to the lack of easy-to-use technologies for post-industrial deconstruction of multilayer into "pure" separately recyclable polymers. A multilayer laminated plastic material generally has the form of a film of varying thickness (<NUM>-<NUM>). By way of example and without limitation, multilayer laminated plastic materials are typically used in the food industry to form packages or bags.

Sand refers to a loose clastic sedimentary rock, resulting from the erosion of other rocks, including sandstone (sedimentary rock).

Drainage refers to a multilayered element of a landfill site, comprising at least one drainage layer, which is used to channel leachate and biogas into the collectors (or end collection wells). The drainage layer is preferably above a waterproofing or protective layer, with the interposition of a separation layer; the purpose of the separation layer is to protect the protective layer from cutting and deformation of the drainage material itself (generally gravel).

Filling, at a landfill site, refers to a layer of inert material that is used to fill excavation voids, to raise the plane of an area of the soil, to equalize depressed areas, etc. In landfills, the filling may be used in the formation of biogas and leachate collection wells; in the formation of bottom and/or wall waterproofing layers; in the formation of drainage layers inside the landfill body.

Landfill mining refers to the deposition of successive waste and functional layers (such as drainage, cover or waterproofing layers).

A landfill capping refers to a multilayered element of a landfill, generally located at a surface level and used to isolate waste from the external environment; minimize water ingress; and stabilize the landfill to prevent erosion or settling.

In the composite material of this invention, the thermoplastic material represents the matrix or continuous phase of the system, whereas sand, and optionally, the multilayer laminated plastic material, constitute the dispersed phase.

Preferably, the composite material comprises or is made of a non-virgin thermoplastic material. In other words, the thermoplastic material comprises or consists of thermoplastic polymers otherwise intended for recycling (non-virgin), which have already been used or have been discarded by industries due to their being defective or not meeting the technical requirements for their production/use.

It shall be noted that the thermoplastic material includes or consists of one or more thermoplastic polymers, each being preferably a "pure" thermoplastic polymer, i.e. not contaminated by/ laminated with other materials (such as paper, aluminum or other plastic polymers). The reason for the purity of thermoplastic polymers is the need for these ingredients to maintain their physical properties (melting and re-solidification) at the time of use, which would otherwise be lost in case of contamination or lamination with other materials.

Preferably, the thermoplastic material comprises or consists of one or more thermoplastic polymers, preferably selected from polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET) or polypropylene (PP).

According to a preferred embodiment, the thermoplastic material comprises or consists of a mixture of PE and at least one additional thermoplastic polymer selected from PVC, PP and PET. Preferably, PE makes up from approximately <NUM>% to <NUM>% by weight based on the total weight of the thermoplastic material, preferably from approximately <NUM>% to <NUM>% by weight, preferably from approximately <NUM>% to <NUM>% by weight.

Preferably, the thermoplastic material comprises or consists of a mixture of PE + PET or PE + PP, with the PE in the amounts by weight as given above.

Also preferably, the thermoplastic material is not a residue resulting from multilayer laminated plastic materials.

The thermoplastic material is contained in the composite material at concentrations from <NUM>% to <NUM>% (w/w), preferably from <NUM>% to <NUM>% (w/w), preferably from <NUM>% to <NUM>% (w/w/w), preferably from <NUM>% to <NUM>% (w/w), preferably of <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% (w/w).

The composite material comprises sand at concentrations from <NUM>% to <NUM>% by weight based on the total weight of the composite material. The Applicant believes that sand, from the above minimum concentration onwards, imparts rigidity and strength to the thermoplastic matrix of the inventive composite material.

Sand is preferably contained at concentrations of <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% (w/w).

It should be noted that the sand suitable for the purposes of the invention has an average diameter from <NUM> to <NUM>, preferably from <NUM> to <NUM>, preferably from <NUM> to <NUM>, preferably from <NUM> to <NUM>, preferably from <NUM> to <NUM>.

The composite material also comprises a multilayer laminated plastic material. As mentioned above, this multilayer laminated plastic material is, like sand, an element dispersed in the thermoplastic matrix.

In particular, the Applicant believes that the multilayer laminated plastic material, by remaining partially or totally immiscible with the plastic matrix, acquires the role of a reinforcing fiber, and contributes to the overall strength of the composite material.

It should be noted that the composition of the invention does not preferably comprise reinforcing agents such as metals or alloys, for example steel fibers; silica or silicates (such as mica); glass; carbon, such as carbon fibers or flakes.

When preparing the composite material, the multilayer laminated plastic material should be shredded to a larger size than that of the thermoplastic material, preferably not more than <NUM>, so that the former will impart fibrous strength to the latter.

Preferably, the composite material comprises the multilayer laminated plastic material concentrations from <NUM>% to <NUM>% by weight, based on the total weight of the composite material (w/w), preferably from <NUM>% to <NUM>% (w/w), preferably from <NUM>% to <NUM>% (w/w), preferably of <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% (w/w).

Preferably, the composite material shall include additional additives, which are useful to impart additional properties to the composite material of the invention.

The additives are preferably contained in the composite material of the invention at concentrations from <NUM>,<NUM> % to <NUM> % by weight based on the total weight of the composite material (w/w), preferably from <NUM> % to <NUM> % (w/w), preferably of <NUM>, <NUM>, <NUM> % (w/w).

Suitable additives for the purposes of the invention include those known to the skilled person, such as flame retardants; antioxidants; anti-UV; compatibilizers.

It should be noted that the composite material has a softening temperature (at atmospheric pressure) above <NUM> and preferably below <NUM>; preferably from <NUM> to <NUM>.

In view of the average temperatures commonly reached at a landfill site (ranging from <NUM> to <NUM>), the composite material will thus have suitable chemico-physical properties for use in drainage and filling at a landfill site, for the purposes of biogas and leachate collection.

In a first embodiment, which is not part of the present invention, the composite material preferably comprises.

The first embodiment is preferably characterized by a softening temperature from <NUM> to <NUM>, preferably from <NUM> to <NUM>, preferably from <NUM> to <NUM>, preferably of <NUM>°, <NUM>°, <NUM>°, <NUM>°, <NUM>°, <NUM>.

In a second embodiment, which is not part of the present invention, the composite material preferably comprises.

The second embodiment is preferably characterized by a softening temperature from <NUM> to <NUM>, preferably from <NUM> to <NUM>, preferably of <NUM>°, <NUM>°, <NUM>°, <NUM>°, <NUM>°, <NUM>.

According to a third preferred embodiment, the composite material according to the present invention comprises:.

Still preferably, the composite material of the third embodiment of the invention preferably comprises:.

Preferably, the PE at the concentrations as stated under (a) of the third embodiment is combined with PP or PET to form <NUM>% of the thermoplastic material.

Preferably, the polyethylene is preferably selected from high-density polyethylene (HDPE), low-density polyethylene (LDPE) and mixtures thereof. Preferably, polyethylene consists of a <NUM>/<NUM> mixture of LDPE and HDPE.

It should be noted that, the multilayer laminated plastic material preferably comprises the following layers: paper, polyethylene, aluminum, joined together by a polyethylene film. Preferably, the multilayer comprises the above-mentioned materials in the following amounts by weight: about <NUM>% paper, about <NUM>% polyethylene, and about <NUM>% aluminum.

The third embodiment is preferably characterized by a softening temperature from <NUM> to <NUM>, preferably from <NUM> to <NUM> preferably of <NUM>°, <NUM>°, <NUM>°, <NUM>°, <NUM>°, <NUM>.

Preferably, the composite material is in the form of polyhedra measuring from <NUM> to <NUM> per side, preferably <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. <NUM>, <NUM> each side, regardless of the other sides.

The composite material may be made of synthetic gravel, which is also covered by the present invention.

The present invention also relates to the use of the composite material for drainage and filling at landfill sites, for the purpose of biogas and leachate collection.

Such drainage and filling, comprising or consisting of the composite material, are also (as such) covered by the scope of the present patent application.

Preferably, the drainage (or drainage layer) comprises at least one layer made of the composite material. According to a different embodiment, the drainage comprises a layer consisting of a mixture of composite material and common gravel.

Preferably, the drainage shall further comprise a waterproofing or protective layer, such as a geomembrane; and a separation layer, such as a geotextile (GTX). Preferably the separation layer is interposed between the composite layer and the geomembrane layer.

According to a preferred embodiment, the composite material is used for.

It should be noted that the composite material acts as a filling/filler and at the same time as a drainage material in all three above-listed cases.

Optionally, the composite material is used as a filler in the formation of barrier layers for waterproofing the bottom and sides of the landfill.

Preferably, a barrier layer for waterproofing the bottom and sides of a landfill shall comprise the following layers, in the direction from the outside to the inside:.

In this configuration, the waste layer is placed above the waterproofing barrier layer, in contact with the drainage layer.

Preferably, the landfill capping may be a temporary or permanent cover.

Preferably, the capping shall comprise, in the direction from the outside to the inside, the following layers:.

In this configuration, the capping layer is laid above the waste, with the leveling layer is contacting the mass of waste.

The above-described capping layer may also be covered as such by the present invention.

The process for manufacturing the composite material is described below. It shall be noted that the preferred embodiments as discussed in the previous sections also apply as such to the manufacturing process as described in this section.

The process for manufacturing the composite material for drainage and filling at a landfill site comprises the steps of:.

The shredding step should be carried out separately on each material involved in the manufacturing process. In other words, the thermoplastic material and any multilayer laminated plastic materials must be shredded separately from each other.

Preferably, the plastic granulate has a particle size of ≤ <NUM>,<NUM>, preferably from <NUM>,<NUM> to <NUM>.

Preferably, the plastic sheet has a side dimension of ≤ <NUM>, preferably from <NUM> to <NUM>.

Preferably, the step of introducing of the composite mixture into the molds (v) is carried out using polyhedral molds adapted to produce synthetic polyhedra preferably having a side from <NUM> to <NUM>, preferably <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

Preferably, the step of heating (iv) the composite mixture includes heating to a temperature below <NUM>, and preferably above <NUM>. The step of heating (iv) is preferably conducted at a temperature from <NUM> to <NUM>.

Preferably, the step of cooling (vi) is conducted by placing the composite material in water cooling tanks, to achieve the necessary hardening effect. Cooling is important for the material to maintain stability performance.

Preferably, when the temperature of the composite material is below <NUM>, it should be removed from the tanks and placed in a storage place.

The cooled composite material can be handled by means of loaders or power shovels and stored in areas specially intended for storage and subsequent loaded on means of transport.

The following are illustrative and non-limiting examples of the composite material of the invention.

The composite material is obtained in the form of an irregular polyhedral granulate, with a size of approximately <NUM>-<NUM> per side.

Claim 1:
A composite material for drainage and filling at a landfill site, comprising:
a) a thermoplastic material at a concentration from <NUM>% to <NUM>%;
b) a multilayer laminated plastic material at a concentration from <NUM>% to <NUM>%;
c) sand at a concentration from <NUM>% to <NUM>% by weight based on the total weight of the composite material.