Lesson Video: The Life-cycle and Recycling of Materials Chemistry

In this video, we will learn about all the factors that are important when describing the energy cost and environmental impact of the production, use, and disposal of everyday materials and products. Together, these assessments form a life cycle assessment. We’ll also examine the advantages and disadvantages of recycling.


Video Transcript

In this video, we will learn about some of the factors that are important when describing the energy cost and environmental impact of the production, use, and disposal of everyday materials and products. Together, these assessments form a life-cycle assessment. We’ll also examine the advantages and disadvantages of recycling. We’re going to explore life-cycle assessments and recycling using one of the most popular examples, the aluminum soda can.

When you use an aluminum soda can, you might not think about what happened on its journey to the store or what happens after you put it in the recycling bin. An aluminum can is a great product. It’s light, stackable, and gives the contents a very long shelf life. And when you’ve enjoyed your soda, you can even crush it. So it’s even more compact when you throw it away. But here we’re going to look at the whole life story of a can and the materials inside it.

Let’s start by listing the materials the can is made of. The body of the can is mostly made of aluminum, even the pull tab. Different alloys are involved, but we’ll leave that detail aside for this video. The outside of the can will be decorated with printed information. There are too many pigments to deal with here, so we’ll leave that aside as well.

The other significant part of the can is actually hidden in sight. Rather than being bare metal on the inside, an aluminum soda can will have a plastic coating that keeps the acidic soda away from the reactive aluminum. Without this coating, an aluminum can would be eaten away in just days by regular soda. Of course, a soda can isn’t complete without the soda. But for the sake of simplicity, we’ll ignore that as well and focus on the materials of the can.

So we have two parts to worry about: the body that we’ll assume is pure aluminum for now and the plastic liner. There are different types of plastic liner, but we’re going to focus on just one type, liners made of epoxy resin. Let’s take a closer look at their stories.

When doing a life-cycle assessment, we should adopt a cradle-to-grave approach. What this means is that we think about the whole picture from the beginning to the end. We look at where the raw materials came from; the creation of the item itself; how it might be used; and how it’s disposed of, reused, or recycled. Without the full picture, we can’t be sure what the real costs and the real impacts are.

A natural starting point on our journey is the production of the can. Various pieces of aluminum are shaped, connected together, and then the resin is added to the insides, where it sets into a very thin layer. They’re filled with soda, and the lid is attached. The lid has a protective coating as well. We can call this stage the manufacturing stage. However, this is only one step in the life cycle of a can. What comes into the manufacturing stage are the raw materials. The resin will need to be made from other chemicals, and the aluminum will need to be produced from its ore. Both of these processes will require energy and other raw materials.

We can already see this is going to get complicated, but I’ll stick with simple labels for now. Just bear in mind that each of these steps involve many, many steps of their own. Making aluminum requires a lot of energy. Aluminum has to be made through electrolysis of molten aluminum ores. So we need lots of heat and lots of electrical energy. Making epoxy resin is also quite expensive from an energy perspective. But as we don’t need a lot of it, it’s the aluminum that’s going to have the biggest impact.

Currently, a lot of the energy we use for aluminum production comes from nonrenewable sources. So CO2 emissions are also something we need to factor in. In fact, there’ll be an associated energy and emission cost associated with every single step of the process. So far, we have energy cost, emission, and manufacturing. But one of the most significant parts of a life cycle and its components is transportation. Every time we transport something, it costs energy and causes emissions. To make aluminum, we need to get ore to the aluminum plant. And to make the can, we need to get aluminum to the manufacturing plant. Also, there may be an entirely different plant that fills the empty cans with soda and puts on the lids.

This already looks quite busy, but I’m afraid we’re not done yet. The cans need to arrive at the store so that they can be sold, which means transporting them to shops. Even at this stage, there will be some energy costs and some emissions. The next stage might perhaps be the most important because we get to drink the soda. Once they’re on the shelf, we can buy them and enjoy them. You might be tempted to leave out the energy and emission costs of this step, but we should include them just in case.

Once we’re done with the can, there are a few different options. If we put the can in general waste, it will probably go to landfill. Or we can put it in the recycling bin, which means it goes through a recycling system. Or we could reuse the item in some way. While we aim to reduce energy cost and emissions, we may not be perfectly effective, so even these options may have a cost. If we recycle the can, we’ll likely be able to get the aluminum back, but not the plastic. If we reuse the can, we might turn it into a bit of art or another type of container. But if we put it to landfill, we can’t recover any of the materials, so it’s effectively a waste.

All these steps and relationships make up what we call a life-cycle assessment. A life-cycle assessment is an assessment of the resources used to make, use, and dispose of something and of the environmental impact involved. Even though we always call it a cycle, some products won’t ever be recycled. When we design something, it’s really important to know what impact it might have. We don’t just want to reduce the costs, but we should try to reduce the energy we use, the amount of materials we use, and the environmental impact as well.

Sometimes these all involve doing the same things. But sometimes we need to spend a little bit more money to do the right thing. A lot of the things that we can do to improve a product like a can are down to the design and the manufacturing processes. But as those who drink soda from aluminum cans, we can still help out. When the energy comes from nonrenewable sources, making one kilogram of aluminum involves the emission of about 10 kilograms of carbon dioxide. Even more carbon dioxide will be emitted when we turn aluminum into a can and transport it around. If we recycle the can, we don’t need to make as much aluminum from scratch when we make the next can. Meanwhile, sending a can to a landfill is pretty much always going to be a waste.

Reusing a can can be very useful, as it means we don’t have to make other materials to do that job. By crushing a can and using it as a coaster, we don’t need to make a coaster from scratch. In the case of an aluminum can, it might be better to recycle, because the difference in energy spent from producing aluminum from ore and producing aluminum from recycled cans is 95 percent.

Reusing and recycling are not the same thing. To reuse something means to use for the same or different application without significantly changing it. Generally speaking, reusing something will have little to no energy cost and little to no emissions. However, if we recycle something, that means we’re breaking down the item to its raw materials. Once we’ve done that, we can either use those raw materials to make the same kind of thing, like melting a can to make new cans, or we can use it for something else, like making an aluminum saucepan.

Recycling requires some energy and, therefore, may involve further emissions. Sometimes it’s better to reuse rather than recycle. Recycling is far more crucial for single-use items, high-value finite resources, or materials that take much more energy to produce from scratch than when we recycle them. For example, we don’t need to recycle iron that often, it’s very cheap and readily available, whereas aluminum is expensive and relatively scarce. When we recycle something, there are still costs involved. It’s not an automatic saving.

Sorting one type of material from another takes time and effort. Processing a mixture of substances can cause problems. If we melt an aluminum can, the printing and the plastic liner have to be removed, perhaps burnt off, which is something we need to deal with. And sometimes recycling is only partly effective. We may get raw material back, but because of things that got mixed in, it’s not quite the same as the stuff that’s made from scratch. For example, if we recycle a plastic bottle, we may not be able to get the same quality of plastic back. It may not be as strong or it may have turned the wrong color. In these cases, we can recycle the plastic for other applications, like making pencil cases.

When we want to figure out which option is best for a particular material, we need their life-cycle assessment. If it’s worse to recycle than to make something from scratch, we shouldn’t recycle. When there’s not much difference, we may need to look in more detail to find an answer. But if it’s clearly better, then we clearly should recycle.

Now let’s have a look at an example.

An entertainment company has a big order for plates for a party. And they have a choice between cardboard or plastic plates. For this example, we’re going to assume that the cost is about the same. What we’re gonna focus on are all the other factors that might be important when making the decision to use one type of plate over the other.

One of the obvious differences between cardboard and plastic is that plastic is generally stronger. We can use less plastic to make a decent plate. So the plastic plate is going to be lighter than the cardboard plate. This means that we can pack more into the same space and transport more plates per truck. So the transport costs and emissions are going to be lower.

The next thing to look at is the material itself. We have to make plates from either cardboard or plastic. So we should bear in mind where the cardboard or plastic comes from. Cardboard is made from trees, which if grown properly can be renewable, whereas the plastic in this example ultimately comes from crude oil, which is a finite resource. There are sustainable plastics, but in this example, I’m going to assume that this plastic comes from nonrenewable resources.

Something else we can consider is that cardboard plates will pretty much always be thrown away, whereas there’s a small chance that a plastic plate might be reused. So this is a clear disadvantage to the cardboard plate, but it’s a debatable advantage for the plastic one. On the whole, they’re likely to be single use as well.

After thinking about how a plate is used, we need to think about what’s going to happen afterwards. A cardboard plate made of cardboard and a little bit of wax perhaps will biodegrade. So we don’t have to really worry about its long-term damage to the environment. However, a plastic plate likely mixed in with food might not be cleaned and put in the recycling bin. There’s a good chance it’s going to end up at landfill. So the disadvantage of the plastic plate is that it might not be recycled.

We’re looking at this example not to make the decision, but simply to understand how complex the decision will be. Balancing all these factors in an actual scenario takes a lot of work. We just need to be able to identify what’s a pro and what’s a con and why one thing makes one material better than another. Some factors may or may not be a disadvantage or an advantage. For instance, cardboard uses more water to make than making plastic. But we can make plastic plates with different colors without doing any printing. Our job is to apply our understanding of what’s going on and appreciate how that applies as a benefit or disadvantage for a particular material.

Now let’s have a look at the key points. A life-cycle assessment is an assessment of the resources used to make, use, and dispose of something and the environmental impact involved. A life-cycle assessment should adopt a cradle-to-grave approach, where we think about the origins of the materials and the nature of the product after it’s used, whether it’s disposed of, reused, or recycled.

Reusing something is generally going to be less costly and cause less emissions than recycling. But recycling is still much better than sending stuff to landfill. Recycling will always have some form of cost. And for some material, that’s higher than others. For instance, plastics tend to degrade every time they’re recycled.

And finally, when we compare one product to another and try and pick which is best, we need to have the whole picture. It may look like something is a clear advantage, but when we look at the details, we may see things that we didn’t see before. Overall, the cost of something is its impact at every stage of the process, not just the one you’re looking at.

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