OPINION: The environmental superiority of recycling is something we’re taught to appreciate from an early age. The waste hierarchy suggests we reduce, reuse, repair and recycle first, and only dispose of something if there are no other options left. These are good guidelines to live by.
There are many examples where recycling is environmentally superior to manufacturing the same material from virgin resources. Aluminium, steel – pretty much all metals – are great examples of this. Remelting something is much less energy intensive than mining and refining it. A similar logic applies for plastics and container glass. In some cases (for example, for aluminium), the recycled material can have an environmental footprint more than 10 times smaller than the virgin material.
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So if that’s the general rule, what are the exceptions?
Recycled crushed concrete
Recycled crushed concrete is often touted as an important way to make material flows more circular. This is largely because concrete contributes a large share of total waste flow by mass. While it is an important way of keeping large amounts of material out of landfill (and cleanfill), it doesn’t add toxins to landfill and is not so different from the rock that was initially dug up to make it.
Recycled concrete can have environmental benefits, but only if transported short distances (less than 100km). If the concrete is crushed on-site to use on-site or at a nearby construction project, then this is positive. However, if transportation involves a 100 km journey, it may well be better to produce virgin aggregate.
The reason for this is that recycled concrete doesn’t offset concrete – it offsets aggregate (gravel and sand). While aggregate makes up the bulk of the mass of concrete, it makes up only around 20 per cent of its carbon footprint – with the other 80 per cent or so coming from cement. You still need to mix new cement with recycled crushed concrete to create new concrete, just as you would with primary aggregate.
As a result, recycled crushed concrete is an example of downcycling, or turning a higher-value material (concrete) into a lower-value material (aggregate). Using recycled crushed concrete is still a very good solution, particularly in dense urban areas. The key point is simply that you need to have a use for the material near to the point where it is being taken out.
Recycling bottles into jumpers
Recycling PET bottles into fleece jumpers seems a good idea at first sight, but these fibres can shed when the jumper is washed, leading to microplastics in our waterways and oceans. This involves a loss of resource as well as pollution and could therefore could also be regarded as downcycling.
Recycling clear PET bottles back into PET bottles maintains the resource at a similar quality (albeit sometimes with a haze or tint) and within the same system.
Things get a bit more complicated when we turn to paper. It is generally true that recycled paper uses less energy than virgin paper. For example, the European Federation of Corrugated Board Manufacturers (FEFCO) calculate that producing recycled paper uses about 5 per cent less thermal energy and 35 per cent less electricity per tonne than virgin paper. So far, so good for recycling.
The challenge for paper recyclers comes in the source of thermal energy used. FEFCO’s database shows that recyclers used only around 4 per cent renewable thermal energy on average, with over 95 per cent from fossil sources. This compares with 63 per cent renewable thermal energy on average for manufacturers of virgin paper.
So why the disparity? The reason is partly the difference in manufacturing process and partly a difference in location of the paper mill.
In simple terms, papermaking involves breaking up plant fibres and mixing them with water so that they can be formed into long continuous sheets and then dried to create paper. It is this drying step that contributes a large share of the environmental impact. Given this, the source of thermal energy used for drying is highly important to the environmental impact of the finished paper.
Paper mills tend to be sited next to their feedstock to reduce transport costs. For virgin paper mills, this is a forest. For recycled paper mills, this is either a large city that produces enough scrap paper, or a port where scrap paper is shipped.
This means that virgin paper manufacturers can opt to burn wood waste from forestry to produce thermal energy to dry their paper. They also burn a by-product of the virgin paper manufacturing process called black liquor. This combination makes for a significant share of renewable energy – energy that is effectively carbon neutral because of the carbon absorbed by the trees as they grew, and that is re-sequestered from the atmosphere as new trees grow in the forest.
The data referred to above from FEFCO includes all stages that occur on-site at pulp and paper mills, but not the indirect stages such as forestry and extraction of natural gas. What happens if we include these? The carbon footprint of recycled paper works out to be around 40 per cent higher than that of virgin paper [the in-house calculations using GaBi software counts all emissions from the forest to the paper mill gate but excludes carbon sequestration in the paper].
In New Zealand, we have two other natural advantages that can change the picture even further. Our electricity grid is more than 80 per cent renewable, and our naturally occurring geothermal steam can be used to dry paper. In fact, three pulp and paper mills in New Zealand make use of the world’s largest industrial geothermal steamfield at Kawerau to help keep their pulp and paper dryers running.
And here’s the crux for recycled paper in New Zealand: we don’t make print or tissue paper from recycled paper here. All paper for recycling goes into producing packaging like cardboard boxes.
This means that all other paper featuring recycled content is imported, and often from countries with a high share of fossil-fuelled electricity. And if you don’t have wood waste, black liquor, or geothermal steam for pulp/paper drying, what do you use? The answer is usually natural gas, coal, or fuel oils – all fossil fuels which have a carbon footprint many times that of renewable energy sources.
The verdict for recycling
We saved paper until last because it is the most complicated case. In some instances, recycled paper will win the day from an environmental perspective. In others, it won’t. While each paper must be assessed on its own merits and own production processes, virgin paper made in New Zealand stands a good chance of beating imported recycled papers.
What we hope to demonstrate here is that having the right data is crucial to making an informed comparison. This data needs to take a life cycle perspective, factoring in not just the final stages of manufacture, but looking at the entire supply chain in a balanced way.
This means factoring in the materials and energy that go into every process step, and the emissions from those processes. Some manufacturers are now starting to publish verified data that does exactly this, either in the form of a product carbon footprint, Life Cycle Assessment, or Environmental Product Declaration. Only by having this kind of data can the customer truly make an informed choice.
Jeff Vickers is a technical director and Tim Worth is a communications advisor at Thinkstep Australia-New Zealand, a family business specialising in sustainability solutions, such as life cycle assessment studies.