Plywood is a strong and versatile man-made wood.
It’s uses are far reaching. From roofing and walls to household interiors, stylish furniture and office fitouts.
With the material being so prevalent and affordable, a big question to ask is how sustainable is plywood?
How is plywood made?
Plywood is an engineered wood product made from thinner sheets of wood that are glued together. These thin layers are known as ‘plies’, hence the name plywood.
The sheets are glued together at right angles, which is known cross lamination. Once you have 3 or 5 cross laminated sheets glued together, you have an extremely strong product with a reduced chance of warping and high impact resistance.
It’s for these reasons why plywood has grown as a popular design material.
The cross laminated plywood sheets are also very flexible and can be manufactured in a variety of different thicknesses. The thickness will depend on the intended use, but the most common range is between 5mm and 20mm.
Plywood is often made from trees that generally, but not always, have a smaller diameter than those used for solid timber. You can see the most common trees used for plywood in the next section.
It’s said that a maximum of 75% of the usable wood is converted into plywood. To be more sustainable, you’d like to see this figure closer to 100% and ensure any waste by-product reused.
Plywood is made by the following process:
- Trees are selected to be cut down from the forest or managed woodland
- The trees are trimmed of their branches and the logs are loaded on trucks to go to the mill or processing plant
- The bark is removed from the outside of the logs using industrial machinery
- The logs are chopped into more manageable sections, usually between 2m and 3m in length
- The blocks of wood are heated and soaked in water to make them softer
- The wood blocks are then taken to the peeler lathe – this rotates the block onto a sharp cutting blade where a continuous sheet is peeled off. This is known as a veneer. Eventually, just a small wooden core is left.
- The long sheet of veneer can then be cut to size depending on its intended use, sorted and stacked
- The veneers are put into a dryer to reduce their moisture content
- Once dry the veneers can then be assembled and glued together. They are usually glued in three or five-ply sheets where each layer is rotated at 90o to the layer underneath
- Finally the sheets are loaded into a hot press to fully cure the adhesive. The sheets can then be trimmed to their final size and stamped with their grade marking.
What tree is plywood made from?
Plywood can be made using softwood or hardwood. With this in mind, plywood can be made from a number of different tree sources. The most popular trees for plywood include:
- Douglas Fir
Almost any tree that is often used in design and furniture making can be used to make plywood.
Birch-made plywood is one of the most popular woods to use. This is because birch is a fast-growing, widespread northern European tree.
The fact that birch is close by and often grown in the UK makes it one of the more sustainable choices for plywood.
Is plywood environmentally friendly?
When considering if plywood is environmentally friendly, we need to look at the two main components of this manufactured material: wood and glue.
Like all wood, the raw materials needed for plywood comes from trees.
Whereas some wood products can be very sustainable, such as cork that can be coppiced from trees without the need to cut the tree down, plywood requires some form of tree cutting.
Naturally, this is a form of deforestation and destruction of habitat.
If the wood source is from a well-managed woodland, this can all be done sustainably without the need for long-lasting environmental damage and habitat degradation.
This danger of severe environmental damage comes when the trees are logged illegally or with unsustainable practices that don’t consider the future.
A good tip here is to make sure your wood comes from FSC certified forests.
I’ve written previously about FSC certification and it’s not quite as rosy as it seems. That being said, unless you use a local wood source or know the exact location and management practices of the wood sourced, FSC is a good indicator.
Just make sure you get 100% FSC wood and not FSC Mix, which still contains a quantity of non-certified wood.
That’s the wood, let’s now take a look at the glue.
Is plywood glue environmentally friendly?
The other main ingredient in plywood is glue. This is used to bind the thin veneers together to form a solid end-product.
On the whole, glue is not the most environmentally friendly product.
The type of glue used for plywood is a chemical-heavy synthetic resin. Many plywood gleus are based around formaldehyde, although this is slowly being phased out. Manufacturing industrial chemicals as a whole is a dirty process that often results in air pollution.
Due to the chemicals involved, they usually have a high level of Volatile Organic Compounds (VOCs), which slowly emit gases into the air. This is known as off-gassing.
Many chemical-based household products will off-gas VOCs, including carpets and paints.
It is possible to get plywood glued together with a more eco-based adhesive that doesn’t contain formaldehyde and has much lower VOC emissions.
For example, some ply companies are now using a soy-based technology. However, soy-based glues are still not 100% natural and will contain some form of chemicals to provide a firm binding for all conditions.
Is plywood toxic free?
This fully depends on the type of synthetic glue used to bind the ply veneers together.
With plywood there are two main types of product created: plywood for exterior use and that for interior.
Because of the different elements these woods will be exposed to in the future, two different adhesives are used:
- Phenol-formaldehyde – for exterior use plywood. The use of phenol-formaldehyde was first popularised to make mouldable plastic products, but has since been used as a wood adhesive. This is because of the strong chemical bonds they create with the lignin component of the wood and their good levels of moisture resistance.
- Urea-formaldehyde – for interior use plywood. Made in a similar way to phenol-formaldehyde, the urea adhesive is lighter in colour and less weather resistance, which is why they are more suitable to interior plywood use.
The main toxic element of these resins is formaldehyde. Plywood adhesive can also be made from polyvinyl acetate and other phenol glues.
None of these glues are eco-friendly and will contain varying levels of toxicity.
On its own, formaldehyde is toxic to humans and poses a number of health risks. Numerous studies have associated formaldehyde with increased skin, eye and respiratory irritation, headaches and increased cancer risk.
On the flip side, once the glue is set and cured, there should be little off-gas release. Despite this, some VOCs will be released into the environment over time.
Is plywood biodegradable?
The presence of a chemical-based adhesive means plywood isn’t 100% natural and plant based.
This means that plywood is not biodegradable.
Even the soy-based adhesives that don’t use formaldehyde are not biodegradable as the resin will contain other chemicals.
Is plywood recyclable at the end of its life?
Ok plywood isn’t biodegradable but is it recyclable?
Yes, plywood can be recycled at the end of its life.
There are a couple of caveats to this though.
Plywood is a class B form of wood. This means it has been treated and is no longer a fully natural product.
To recycle plywood effectively, it needs to be separated from other forms of wood. Once separated it can then be shredded and repackaged to be used again.
However, plywood’s secondary uses are limited due to strength issues and a less efficient recycling process. This often means that unwanted plywood is burned for energy or dumped in landfill.
If you have plywood at home that you want to recycle you will have to take it to your local recycling centre and deposit it in the wood waste section. It is not possible to put the plywood in with your other green waste as your local council will not collect it.
It’s also not possible to compost your plywood.
How to make plywood more sustainable and environmentally friendly?
There are a few main ways in which plywood can be made a more sustainable product.
- FSC Certified – ensure that the wood source for the plywood is 100% FSC Certified. Don’t be tricked by the FSC Mix label as this contains sustainably sourced and uncertified wood.
- Low VOC emissions – if possible, source plywood that is made with formaldehyde-free adhesive. This will lower the toxicity and volatile organic compound emissions into the environment.
- Local wood – it’s always better if you can source local wood. This will save massively on the carbon emissions associated with transportation across the world.
So, is plywood a sustainable resource?
To wrap up, plywood is not a very sustainable type of wood.
This is due to the fact that it’s a man-made product that contains a chemical heavy glue and is difficult to recycle.
There can also be waste associated with the manufacturing process, although this will depend on whether the company making the plywood reuse the wood by-products and timber core.
As always with the sustainable option, it’s best to choose good local, well-made products from companies who have transparent policies and working methods.
Plywood can be sustainable, but you’ll have to go a long way to ensure there isn’t an environmental impact.