Process for reducing carbon footprint of waste wood

Abstract

The invention relates to processes for forming useful products in an environmentally-friendly manner from wood powder created from wood waste, thereby reducing the amount of wood waste being disposed

Description

The environmental credentials of a real Christmas tree versus an artificial tree have been extensively debated. One downside associated with a real or natural tree is that they tend to end up in landfill sites. The emissions from a real tree disposed in landfill are significantly lower than those of an artificial Christmas tree. The Carbon Trust estimates that a two-meter-tall artificial tree produces about 40 kg of carbon dioxide equivalent (CO2e), while a similar sized real Christmas tree disposed of in landfill creates 16 kg CO2e. However, if a real Christmas tree is disposed of by burning it or shredding it and using it in the garden, the emissions drop dramatically to an estimated 3.5 kg CO2e. Approximately 7 million real Christmas trees are dumped in landfill in the UK every year, releasing an estimated 100,000 tonnes of harmful greenhouse gases into the atmosphere, including methane gas (CH4), which is 25 times more potent than carbon dioxide (CO2). Having real Christmas trees ending up in landfill is costly to both the environment and to the taxpayer, with local authorities required to pay increasing fees and landfill taxes per tree left on landfill. The carbon footprint of a Christmas tree could be dramatically reduced by recycling the tree once it is no longer wanted. Ideally, the recycling results in items that have their own intrinsic value, whilst being cheap and easy to manufacture in a sustainable and environmentally-friendly manner. The invention is not limited in its application to Christmas trees. Other wood waste could be similarly processed. However, Christmas trees are unusual in that they have a very short period of usefulness before they are discarded. Summary According to a first aspect of the invention, there is provided a process comprising: cutting wood waste to produce a wood powder; mixing the wood powder with a binder composition; shaping the mixture of wood powder and binder composition into a desired shape; and drying the shaped mixture to provide a dried product. In some embodiments, the listed steps are preceded by a step of collecting the wood waste. In some embodiments, the wood powder has an average particle size of about 0.5 to about 10 mm. In some embodiments, cutting the wood waste comprises two steps, wherein the wood waste is first cut to form wood chips and then the wood chips are cut to form the wood powder. In some embodiments, the process comprises cooking the cut wood by exposure to heat and water before the step of mixing the wood powder with the binder. In some embodiments, the cut wood is cooked at a temperature of from about 90°C to about 200°C. In some embodiments, the cut wood powder is cooked for a period of from about 30 to about 180 minutes. In some embodiments, the cooked cut wood is strained and / or pressed after cooking to remove the water. In some embodiments, the binder composition comprises one or more binders selected from the group consisting of: starches, polysaccharides, pectins, celluloses, cellulose derivatives and alginates. In some embodiments, the binder composition comprises potato starch. In some embodiments, the mixture of wood powder and binder composition comprises from about 10% to about 95% by weight of wood powder. In some embodiments, the mixture of wood powder and binder composition comprises: about 20 to about 60 wt% wood powder; about 2 to about 10 wt% binder; and about 40 to about 70 wt% water. In some embodiments, the mixture of wood powder and binder composition is processed to have a dough-like consistency such that the mixture retains its form once shaped. In some embodiments, the mixture of wood powder and binder composition is shaped by being pressed into a mould. In some embodiments, the shaped mixture is removed from the mould before the drying step. In some embodiments, the mould is treated to prevent the mixture of wood powder and binder adhering to the surface of the mould. In some embodiments, the surface of the mould is dusted with wood shavings. In some embodiments, the shaped mixture is dried to have a water content of no more that 20 wt%. In some embodiments, the process further comprises applying one or more coatings to the dried product. In some embodiments, the coating is a protective coating, such as a water-proofing coating and / or a decorative coating. In some embodiments, the coating comprises a biodegradable material, such as a wax. According to a second aspect of the invention there is provided a product comprising a dried mixture of wood powder formed from wood waste and binder. In some embodiments, the product is a decorative or ornamental item. In some embodiments, the product is a Christmas decoration, such as a three-dimensional bauble. In some embodiments, the product is a shaped packaging or building material. Brief Description of the Drawings Figure 1 is a flow chart showing the key steps in the process of processing wood waste to form useful finished items. Figure 2 is a flow chart showing the steps in a process comprising further steps. Figure 3 is a schematic representation of the possible life cycle of a Christmas tree using the process described herein. Detailed Description Moulded pulp products (MPPs), also referred to as moulded fibre products, have in the past been primarily used as packaging, such as food containers and serving trays. These items are often relatively unrefined and have an unfinished appearance. They are also designed to be single-use, being discarded (and hopefully recycled) after use. Other MPPs may be more refined, with thinner walls and smoother surfaces. Nonetheless, these items are generally disposable, single-use items, such as trays or bottles for use in medical or hospital settings. According to the present invention, products are formed from wood waste. As used herein, the term "wood waste" refers to wood that no longer serves its primary purpose. The Wood Recyclers Associate (WRA) categorises wood waste in four main grades: Grade A wood waste includes solid softwood and hardwood, packaging waste, scrap pallets, packing cases, and cable drums and process off-cuts from joinery / manufacturing. Grade A wood waste may include nails and metal fixings, minor amounts of paint, and / or surface coatings. Discarded real Christmas trees will be Grade A wood waste. Grade B wood waste may contain up to 60 Grade A material, plus building and demolition materials, and domestic furniture made from solid wood. Grade B wood waste may include nails and metal fixings, and / or some paints, plastics, glass, grit, coatings, binders and glues. Grade C wood waste included Grade A and B wood, fencing products, flat pack furniture made from board products and DIY materials. It may also include a high content of products such as chipboard, MDF, plywood, OSB and fibreboard. Grade C wood waste may additionally include paints, coatings and glues, as well as paper, plastics, rubber, glass and / or grit. Grade C wood waste may also include coated and treated timber. Grade D wood waste is classified as hazardous and generally requires disposal at special facilities due to the presence of hazardous treatments. In some embodiments, the wood waste suitable for use in the processes described herein is Grade A, Grade B and / or Grade C wood waste. In some embodiments, the wood waste is only Grade A and / or Grade B. In some embodiments, the wood waste used is Grade A wood waste. The products of the present invention provide the wood waste with a new purpose. In some embodiments, the products are additionally biodegradable and are readily disposed of in an environmentally-friendly manner. In some embodiments, the products made from the wood waste have an aesthetically pleasing, finished appearance and / or are articles that may be kept and reused (as opposed to being designed to be disposed of after a single use). In some embodiments, the products are formed from a mixture of wood powder and binder. The inclusion of the binder enhances the stability of the product. Further, in some embodiments, the products have a coating, optionally a waterproof coating, to further enhance their stability. In some embodiments, the products are ornaments, decorative items or the like. According to the present invention, a process is provided for converting wood waste into a shaped product, such as an ornament or decorative item. In some embodiments, the products are sufficiently stable to be repeatedly reused. Further, the composition of the products means that they are sustainable, biodegradable and readily recyclable. In an embodiment that may be particularly preferred, the wood waste comprises discarded Christmas trees. This has the advantage of preventing the used Christmas trees from ending up in landfill sites and the CO2 that is generated when they then decompose. As such, this recycling of the Christmas trees makes the choice of a natural tree more environmentally-friendly. The products formed according to this invention may be Christmas decorations, such as baubles for decorating Christmas trees. Not only are such decorative items sustainable, but they can be disposed of in a more environmentally-friendly manner than conventional baubles and other decorative items. The process comprises the following steps, preferably, but not necessarily, in the sequence set out below: (i) cutting wood waste to produce a wood powder; (ii) mixing or blending the wood powder with a binder composition; (Hi) shaping the mixture of wood powder and binder composition into a desired shape; and (iv) drying the shaped mixture to provide a dried product. In some embodiments, the process includes an additional step in which the cut wood waste is cooked by exposing the cut wood to water and heat. This sequence of steps is illustrated in the flow chart shown in Figure 1. In some embodiments, step (i) is preceded by a step of collecting the wood waste. Alternatively, the wood waste may be separately collected and may be provided for processing according to the invention described herein. The wood waste may be provided in a variety of sizes and forms. For example, the wood waste may be provided in the form of whole discarded Christmas trees. Alternatively, the wood waste may be in cut form, in larger pieces or smaller chips. The wood waste may first be processed to remove unwanted non-wood content, such as nails or metal fixings, or surface coatings. In the case of whole discarded trees, these may first be processed to remove associated materials such as plastics in the form of tinsel and adhesive tape. According to the process, the wood is cut, for example by chipping and / or grinding to provide wood particles of the desired size. Herein, the wood subsequently used in the process is referred to as wood powder and this powder comprises particles of wood with an average particle size of from about 0.1 mm to about 10 mm, depending on the final use and detail required in the form being produced. In some embodiments, the average particle size may be from about 0.1 mm to about 5 mm, or from about 0.1 mm to about 1 mm. The average particle size may refer to the weight mean. The particle size may refer to the largest dimension of a particle and can be determined, for example, by sieving. In some embodiments, an industrial shedder may be used to reduce the wood waste to a particle size small enough to be used in the process (referred to herein as "wood powder"). As illustrated in the alternative process of Figure 2, processing of the wood waste to form the wood powder may involve multiple processing steps that successively reduce the size of the wood particles. For example, the wood may first be roughly chopped, followed by chipping to form smaller chips or particles of wood, before being ground to produce the relatively fine wood powder that is to be combined with the binder. In some embodiments, the two or more steps used to reduce the wood waste to wood powder may be carried out consecutively. Alternatively, the so-called cooking step may be carried out between the size reduction steps. For example, the wood waste could be chipped to produce coarse particles (e.g., with a particle size of 20 to 50 mm), then cooked and then the cooked coarse wood particles could be treated to further reduce the particle size to the desired range of the wood powder. The consistency of the mixture of wood powder and binder will be influenced by the size of the wood particles, with smaller particles resulting in a smoother mixture and smoother, more refined products. In some embodiments, the process includes a step of treating the cut wood by exposure to heat and water. This step, referred to herein as "cooking", is preferably carried out after the wood waste has been cut, chopped and / or ground to the desired particle size, that is, after step (i). However, in some embodiments, some (for example, additional) particle size reduction may take place after the cooking step. In some embodiments, the cooking step involves adding the cut wood to water and heating this mixture. In some embodiments, the water does not include any other additives or chemicals. The purpose of the cooking step is to soften the wood so it is easier on the machines and can be consistently reduced to a finer powder once dried. The softer wood can also produce a softer and smoother dough once combined with the binder. In some embodiments, the wood powder and water mixture is heated to and / or maintained at a temperature of from about 90°C to about 300°C. In some embodiments, the temperature of the cooking step is from about 90 to about 200°C, or from about 100 to about 120°C. In some embodiments, the cooking step involves heating the mixture of water and wood powder for a period of from about 30 to about 180 minutes. In some embodiments, the period of cooking is from about 60 to about 120 minutes, minutes. In some embodiments, the cooking step is carried out by heating the water before being combined with the wood. The water may be held and heated in a vat into which the cut wood (such as wood chips or wood powder) is added. The amounts of water and wood are selected to ensure that all of the cut wood is covered by the water. Once the cut wood has been cooked for the desired length of time, it is removed from the vat, leaving as much of the water in the vat as possible. This means that the vat can then be refilled with more cut wood without requiring fresh water or waiting for the water to reheat. In some embodiments, the vat will be heated throughout the process to maintain the desired elevated temperature and to carry out the cooking within the desired temperature range. Commercial heated water or cooking vats are available that are suitable for this purpose. In some embodiments, the cut wood Is strained after cooking to remove the wood from the cooking water and to remove the excess water. Additionally, the wet wood removed from the cooking vat may be pressed to remove further water. Such steps will reduce the drying time. The wood powder does not have to be dried before the binder is added. However, It may be preferable to drying the cooked cut wood before combining it with the binder, as this will decrease the amount of shrinkage and reduce drying time of the shaped mixture later in the process. In some embodiments, the water content of the wood powder is no greater than 20 wt%, no greater than 15 wt% or no greater than 10 wt% when it is mixed with the binder. In some embodiments, the cooked cut wood is dried in a heated and well-ventilated room. Following any optional cooking step, the wood powder Is mixed with one or more binders. The binder is included to help hold the particles of the wood powder together when moulded into the desired shape and dried. Suitable binder materials include, for example, starches, polysaccharides, waxes, pectins, celluloses, cellulose derivatives and alginates. It may be preferable to use a sustainable and biodegradable binder material. In some embodiments, in addition to its binding properties, the binder may be selected to provide final dried product with desirable physical or chemical properties. For example, a hydrophobic binder may afford water-proofing properties to the product. Inclusion of a large enough amount of binder may provide the product with at least a partial coating of the binder material on the surface of the product, and this coating may contribute to the protection or decoration of the product. In one particular embodiment, the binder comprises potato starch. The one or more binder may be added to the cooked wood powder by first forming a binder composition or glue. For example, the binder may be available in solid, powdered form. To form the binder composition, the binder may be added to a liquid component, such as an aqueous liquid. The binder may be soluble in the liquid component. In some embodiments, a dry binder may be combined with a liquid component such as water, and optionally heat, to form a viscous and sticky binder composition that it then mixed with the wood powder. In some embodiments, the liquid component of the binder composition is selected to evaporate and thereby allow the binder to bind the wood powder particles to one another. The ratio of liquid component to binder may, for example, be from about 30:1 to about 10:1 by weight, or from about 25:1 to about 20:1 by weight. In some embodiments, the binder used is a dry, powdered form of potato starch. This is used to form a binder composition or glue. The starch powder is mixed with water in a ratio of approximately 22:1 water to starch by weight. This mixture is then heated to around 70°C until it starts to thicken, for example for a period of approximately 30 seconds, although the time period will depend on starting temperature of the mixture. The binder composition or glue and the wood powder are mixed to form a dough. In some embodiments, the dough comprises wood powder, binder and water. In some embodiments, the dough comprises from about 10% to about 95% by weight of wood powder, from about 20% to about 60% by weight of wood powder, or about 25 to about 50% by weight of wood powder. In some embodiments, the dough comprises: 20 to 60 wt% wood powder 2 to 10 wt% binder and 40 to 70 wt% water . The dough may be a semi-solid mixture that can be mixed, kneaded and / or extruded. The dough formed from the mixture of wood powder and binder composition is preferably malleable, thick and elastic, allowing the mixture to be worked and pressed into a shape using a mould. In some embodiments, the shaped mixture can be removed from the mould prior art drying without any significant loss of shape. The mixture of wood powder and binder is shaped by being pressed into a mould. In some embodiments, the shaped mixture is removed from the mould before the drying step. In alternative embodiments, the shaped mixture is dried whilst in the mould. In some embodiments, the mixture of wood powder and binder is inherently sticky and so it may be necessary to take steps to ensure that the mixture does not adhere to the mould. For example, the surface of the mould may be dusted with fine wood shavings or sawdust to encourage the shaped mixture to separate from the surface of the mould without deforming or sticking. Additionally or alternatively, the surface of the portion of dough may be dusted with fine wood shavings or sawdust before being pressed into the mould. In embodiments where the product is a three-dimensional item, such as a decorative item like a bauble, the item may be solid or hollow. Once shaped, the shaped mixture is dried to solidify the material and fix its shape. In some embodiments, the mixture is removed from the mould to be dried. This option may be preferred as it allows a batch of multiple shaped items to be formed and dried together using just a single mould. Alternatively or additionally, the mixture may be at least partially dried whilst still in the mould. This may have the benefit of fixing the shape in which the mixture is dried, and therefore provide dried products of more consistent shape and appearance. Once again, drying may take place in a heated and well-ventilated room. The step of drying the shaped dough is variable and depends on the nature of product being formed, including the wall thickness of the product and the composition of the dough. For example, the drying step needs to be selected to ensure that the product is dried as quickly as possible without causing cracking or breaking. In an optional step, the dried product is to be completely or partially coated. The coating may have a structural or protective purpose, or a decorative purpose. A single coating may have multiple purposes or multiple coatings may be applied. Thus, the process may include one or more further steps in which a coating is applied to the surface of the product. In some embodiments, the coating is a water-proofing coating. In such embodiments, the coating material may be hydrophobic, repelling water and thereby protecting the agglomerated wood structure which may be hydrophilic and may absorb water which can lead to softening and damage. It may be preferable to use sustainable and biodegradable materials in the coating. In some embodiments, the coating may comprise a binder, such as one or more of the binders that may be included in the binder composition as discussed above. In some embodiments, the coating composition is applied as a liquid and then solidified, for example by drying or cooling. Where the coating composition dries, the liquid composition preferably comprises a solvent that readily evaporates. Where the coating solidifies on cooling, the composition is preferably solid at a temperature below about 40°C. In some embodiments, the coating comprises a wax. As waxes are insoluble in water and so would form a water barrier when used as a coating. They melt at elevated temperatures so that they can be readily liquified for easy application to the dried items. A further advantage associated with the use of a wax-based coating is that the wax may be melted to remove it from the product. This allows the coating to be separated from the wood and binder for separate disposal or recycling. Suitable waxes include, for example, animal waxes such as beeswax, lanolin and shellac wax; vegetable waxes such as soy wax, candelilla wax, carnauba wax and castor wax; mineral waxes such as peat waxes; and petroleum waxes such as paraffin wax. In some embodiments, the coating may further comprise one or more additive, such as a colourant or a fragrance. In some embodiments, the coating is applied by spraying a liquid coating composition on to one or more surfaces of the dried item. In other embodiments, the liquid coating may be painted on the surface(s) of the item or the item may be dipped into a bath of the liquid coating composition. In some embodiments, the coating comprises soy wax which is heated to a temperature in the region of 40 to 80°C, or from about 50 to 60°C. The molten wax may be provided in a bath into which the dried product is dipped. In some embodiments, the coating may comprise multiple layers. The layers may comprise the same of different coating compositions. Different coating compositions may be selected to provide a coating with different physical and / or chemical properties. In some embodiments, the final product of the process may comprise multiple parts, such as multiple dried shaped parts. Therefore, the process may include a further step of assembling said multiple parts and, optionally, adhering them to one another, for example with a binder composition. This assembly of parts may occur either before or after the application of any coating to the dried items. Further, the articles may also undergo some further treatment, for instance the application of decoration or the incorporation of additional parts. An embodiment of the process described herein is illustrated in the form of a flow diagram in Figure 1. The illustration includes optional steps that are not necessarily a part of the claimed process and could be carried out separately. The steps are shown in the preferred sequence, but some of these steps may be carried out in a different order, as discussed above. For example, the cutting wood, for example by chopping and / or grinding, to form the wood powder to be mixed with the binder may (additionally) be carried out after the cooking step. Further intermediate steps may also be included, such as the optional drying of the cooked cut wood before addition of the binder. Some of these additional steps are included in the flow diagram of Figure 2. For example, the illustrated process includes a two-step reduction of the wood waste to a wood powder. A further separate step may involve the preparation of the binder composition by combining a (solid) binder material with water and heat, ready for mixing with the wood powder. A further separate step may involve the preparation of the coating composition ready for application to the dried items. Figure 3 shows the possible life cycle of a Christmas tree using the process described herein. Starting with the harvesting of the growing tree 10 and use as a Christmas tree 11, the used tree is subsequently discarded and collected as wood waste 12 for processing according to the process described herein. The wood waste 12 is chopped and / or ground to produce a wood powder 13 that is cooked and then mixed with a binder to form a slurry 14. The slurry is mixed, kneaded and extruded, forming a dough 15 which can be split into portions 16 and pressed into a mould 17 to produce shaped dough items 18 that are then dried and assembled, coated and decorated to form the final product 19, in this case baubles for decorating a Christmas tree. The present invention also relates to products comprising a dried mixture of wood powder formed from wood waste and binder. In some embodiments, these products are produced from sustainable materials and are biodegradable within a reasonable timeframe. In some embodiments, the products may be compostable. Products such as shaped Christmas decorations, like baubles, have been discussed above. Other types of products include, for example, packaging materials and building materials, such as insulation materials. Bespoke, shaped packaging may be readily produced using the processes described herein. For example, shaped packaging similar to a conventional egg carton may be produced. Such packaging could be used to transport and store fragile items. Shaped building materials such as sheets or blocks could also be produced. The items could, for example, have interlocking shapes to allow them to be readily connected. The materials would have sound and heat insulating properties. Products may not only have shaped external surfaces. Items with hollow internal channels or chambers are also readily formed using the processes described herein. The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only and are not exhaustive and / or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and / or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist 5 essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future. 10

Claims

1. A process comprising:cutting wood waste to produce a wood powder;mixing the wood powder with a binder composition;shaping the mixture of wood powder and binder composition into a desired shape; anddrying the shaped mixture to provide a dried product.

2. A process as claimed in claim 1, preceded by a step of collecting the wood waste.

3. A process as claimed in claim 1 or claim 2, wherein the wood powder has an average particle size of about 0.5 to about 10 mm.

4. A process as claimed in any one of the preceding claims, wherein cutting the wood waste comprises two steps, wherein the wood waste is first cut to form wood chips and then the wood chips are cut to form the wood powder.

5. A process as claimed in any one of the preceding claims, further comprising cooking the cut wood by exposure to heat and water before the step of mixing the wood powder with the binder.

6. A process as claimed in claim 5, wherein the cut wood is cooked at a temperature of from about 90°C to about 200°C.

7. A process as claimed in claim 5 or claim 6, wherein the cut wood powder is cooked for a period of from about 30 to about 180 minutes.

8. A process as claimed in any one of claims 5 to 7, wherein the cooked cut wood is strained and / or pressed after cooking to remove the water.

9. A process as claimed in any one of the preceding claims, wherein the binder composition comprises one or more binders selected from the group consisting of: starches, polysaccharides, pectins, celluloses, cellulose derivatives and alginates.

10. A process as claimed in claim 9, wherein the binder composition comprises potato starch.

11. A process as claimed in any one of the preceding claims, wherein the mixture of wood powder and binder composition comprises from about 10% to about 95% by weight of wood powder.

12. A process as claimed in any one of the preceding claims, wherein the mixture of wood powder and binder composition comprises: about 20 to about 60 wt% wood powder; about 2 to about 10 wt% binder; and about 40 to about 70 wt% water.

13. A process as claimed in any one of the preceding claims, wherein the mixture of wood powder and binder composition is processed to have a dough-like consistency such that the mixture retains its form once shaped.

14. A process as claimed in any one of the preceding claims, wherein the mixture of wood powder and binder composition is shaped by being pressed into a mould.

15. A process as claimed in claim 14, wherein the shaped mixture is removed from the mould before the drying step.

16. A process as claimed in claim 14 or claim 15, wherein the mould is treated to prevent the mixture of wood powder and binder adhering to the surface of the mould.

17. A process as claimed in claim 16, wherein the surface of the mould is dusted with wood shavings.

18. A process as claimed in any one of the preceding claims, wherein the shaped mixture is dried to have a water content of no more that 20 wt%.

19. A process as claimed in any one of the preceding claims, further comprising applying one or more coatings to the dried product.

20. A process as claimed in claim 19, wherein the coating is a protective coating, such as a water-proofing coating and / or a decorative coating.

21. A process as claimed in claim 19 or 20, wherein the coating comprises a biodegradable material, such as a wax.

22. A product comprising a dried mixture of wood powder formed from wood waste and binder.

23. A product as claimed in claim 22, wherein the product is a decorative or5 ornamental item.

24. A product as claimed in claim 23, wherein the product is a Christmas decoration, such as a three-dimensional bauble.10 25. A product as claimed in claim 22, wherein the product is a shaped packaging orbuilding material.

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