Life cycle assessment and recycling

Welcome to Life Cycle Assessments and Recycling!

In this chapter, we are going to look at how chemists track the "footprint" of a product from the moment its raw materials are pulled out of the ground until the moment it is thrown away. We will also explore why reducing, reusing, and recycling are the best ways to protect our planet's limited resources. This is all part of the "Using Resources" section of your AQA syllabus.

Think of a Life Cycle Assessment as a "cradle-to-grave" biography for an object, like a plastic bottle or a paper bag.

1. Life Cycle Assessments (LCAs)

A Life Cycle Assessment (LCA) is a way of looking at the environmental impact of a product. To get the full picture, scientists look at four specific stages of a product's life.

The Four Stages of an LCA

1. Extracting and processing raw materials: Getting the "ingredients" ready. This includes mining metals (which uses lots of energy) or drilling for crude oil to make plastics. Processing these materials often creates waste and pollution.
2. Manufacturing and packaging: Turning those ingredients into the product. This stage uses energy and can release harmful chemicals into the environment.
3. Use and operation during its lifetime: How the product affects the environment while you are actually using it. For example, a car uses fuel and releases CO\(_2\) during this stage, while a paper bag doesn't do much at all.
4. Disposal at the end of its useful life: What happens when you're done? This includes transport to the landfill or recycling center, and whether the product decomposes or sits in a pile for 500 years.

Don't Forget Transport!

In an exam, remember that transport and distribution happen at every single stage. Moving raw materials to the factory uses fuel, and moving the product to your house uses fuel too!

Is an LCA Always Accurate?

Some parts of an LCA are easy to measure. We can use numerical values (numbers) to say exactly how much water, energy, or raw material was used. This is objective data.

However, other parts are harder to measure. How do you "score" the effect of a pollutant on a local ecosystem? This requires value judgements (opinions), so LCAs are not always 100% objective. This means different scientists might come up with slightly different results.

Quick Tip: Watch out for selective LCAs. Companies sometimes write an LCA that only shows the "good" parts of their product to help them with advertising. This can be misleading!

Key Takeaway:

An LCA looks at raw materials, manufacturing, use, and disposal. It uses a mix of hard numbers and expert opinions to judge environmental impact.

2. Comparing Products: Plastic vs. Paper Bags

This is a classic exam favorite! You might be asked to compare a plastic shopping bag and a paper shopping bag. Don't worry if it seems tricky; here is the breakdown:

Plastic Bags:
- Raw Material: Crude oil (a finite resource - it will run out).
- Manufacturing: Fractional distillation and cracking (uses energy but creates little waste).
- Use: Can be reused many times.
- Disposal: Don't biodegrade; they take up space in landfills and can harm wildlife.

Paper Bags:
- Raw Material: Timber/Trees (a renewable resource).
- Manufacturing: Turning wood to pulp uses massive amounts of water and energy.
- Use: Usually only used once or twice (they tear easily).
- Disposal: Biodegrade quickly and are non-toxic.

Which is better? It depends! Paper is renewable, but plastic uses less energy to make and lasts longer. This is why we use LCAs to compare them!

3. Reducing the Use of Resources

Our Earth has limited resources. To be sustainable (meaning we leave enough for future generations), we must reduce how much we use. This reduces waste, saves energy, and stops us from destroying habitats through mining and quarrying.

Reusing vs. Recycling

Reusing is the most efficient. Example: Glass bottles can be washed and refilled without needing any new materials.
Recycling involves changing the product into something new. This still uses energy, but much less than making it from scratch.

Recycling Specific Materials

1. Glass: Glass can be crushed, melted, and molded into new bottles or jars. Some glass that can't be reused for food is used for things like road surfacing.
2. Metals: We recycle metals by melting them and recasting them. This is much better than mining new ores.
Example: Scrap steel can be added to iron in a blast furnace. This reduces the amount of new iron ore we need to dig up!

Common Mistake to Avoid:

Students often forget that separation is a big part of recycling. We have to sort different types of metal (like aluminum vs. steel) before they can be melted, which takes time and effort.

Quick Review Box

- LCA Stages: Raw Materials → Manufacturing → Use → Disposal.
- Finite Resource: A resource that is being used up faster than it can be replaced (like oil).
- Renewable Resource: A resource that can be replaced at the same rate we use it (like timber).
- Benefits of Recycling: Saves energy, protects habitats, reduces pollution from mining.

Key Takeaway:

Reducing, reusing, and recycling help save finite resources and protect the environment. Melting scrap metal or glass uses much less energy than extracting new materials from the Earth.