Ways of reducing the use of resources

What you'll learn

• Why many everyday materials depend on limited raw materials and limited energy sources.
• How reduction, reuse and recycling reduce waste and environmental impacts.
• Why different materials, such as glass and metals, are recycled in different ways.
• How to evaluate resource-saving options using evidence, not just vague phrases like “better for the environment”.

The big idea: products have a resource cost

Every product has to come from somewhere. A glass bottle, metal can, plastic tray or brick starts with raw materials taken from the Earth. Energy is then used to process those materials, make the product, transport it, use it and dispose of it.

This diagram shows the main choice: keep following a “take → make → waste” route, or reduce the need for new resources by reducing, reusing and recycling.

Why extraction causes problems

Many useful materials are produced from limited raw materials:

• Metals are extracted from ores. An ore is a rock containing enough metal compound for extraction to be worthwhile.
• Glass is made from raw materials such as sand and limestone, which must be heated strongly.
• Building materials such as concrete, cement and bricks use quarried rocks, limestone, clay and aggregates.
• Clay ceramics, such as tiles and pottery, are made from clay minerals and fired in kilns.
• Most plastics are made from chemicals obtained from crude oil or natural gas.

Getting these materials often involves mining or quarrying.

Mining usually means digging underground or using large open pits to obtain ores or fuels. Quarrying usually means removing rock from the surface in an open site.

Both can cause environmental impacts, including:

• destruction of habitats
• scars in the landscape
• noise, dust and traffic
• pollution from waste rock or processing
• large energy use, often producing carbon dioxide

The three main ways to reduce resource use

At GCSE, you need to know three main approaches used by end users: reduce, reuse and recycle.

1. Reduce

To reduce means to use less material in the first place.

Examples include:

• buying only what you need
• choosing products with less packaging
• using a product for longer before replacing it
• designing lighter containers that use less plastic, glass or metal

Reduction is powerful because it can avoid several stages of the life cycle: less raw material extraction, less manufacturing, less transport and less waste.

2. Reuse

To reuse means to use the same product again, usually for the same purpose, with little processing.

A classic example is a glass milk bottle or drinks bottle. It can be collected, washed, checked and refilled. This avoids making a completely new bottle each time.

Reuse still has impacts. Bottles may need transport, hot water, detergents and inspection. However, if the bottle is reused many times, the resource saving can be large.

3. Recycle

To recycle means to process a waste material so that it can be made into a useful material or product again.

Recycling usually involves stages such as:

• collecting the waste
• sorting and separating materials
• cleaning or removing labels
• melting, crushing or reforming the material
• making a new product

Recycling different materials

Glass

Glass bottles can often be reused first. If they cannot be reused, they can be crushed and melted to make new glass products.

Recycling glass reduces the need for new raw materials and can reduce waste sent to landfill. However, glass may need to be separated by colour or type, because different glass products need different properties.

Metals

Metals are very useful to recycle because extracting metals from ores can use large amounts of energy.

Metals can be recycled by:

• melting and recasting them into new shapes
• reforming them into different products
• adding suitable scrap metal to new metal during manufacture

For example, some scrap steel can be added to iron from a blast furnace. This reduces the amount of iron that must be extracted from iron ore.

Building materials, clay ceramics and plastics

Some products cannot easily be reused in their original form. Instead, they may be recycled for a different purpose.

Examples include:

• crushed concrete or brick used as aggregate for roads
• broken ceramics used as hardcore or filler
• plastics melted and remoulded, if they can be separated properly

Plastics are often harder to recycle than metals or glass because different polymers have different properties. A mixture of plastics may melt unevenly or produce a weaker final material.

Why separation matters

The amount of separation needed depends on the material and the quality needed in the final product.

If the final product can tolerate some impurities, less separation may be needed. If the final product needs very specific properties, the recycling process must be much more carefully controlled.

For example:

• electrical copper needs high purity because impurities reduce conductivity
• steel for a particular use needs the correct mixture of iron, carbon and other elements
• plastics often need sorting by polymer type before being melted

How to evaluate ways of reducing resources

This topic often appears as an evaluation question. That means you should weigh up advantages and disadvantages using the information provided.

A strong answer compares:

• raw materials used
• energy used
• waste produced
• pollution or greenhouse gas emissions
• transport distance
• cost, if given
• whether the final product has the required properties

If you are given numbers, use them. For example, a percentage reduction can be calculated using:

$$percentage\; reduction=\frac{original\; value-new\; value}{original\; value}\times 100$$

The key takeaway

Reducing, reusing and recycling all help to conserve limited resources. They reduce the need for mining and quarrying, reduce energy use, reduce waste, and lower environmental impacts.

However, the best option depends on the material, the product, and the evidence given. In Chemistry exams, your job is to make a justified judgement from the data.