Life Cycle Assessment and Recycling

1. What is the purpose of a life cycle assessment?

Answer: To examine the impact of a product on the environment throughout its life.


2. How are metals recycled?

Answer: Metals are recycled by melting and recasting or reforming into new products.


3. How do we obtain raw materials from the Earth to make metals and building materials?

Answer: Raw materials for metals and building materials are obtained by quarrying or mining.


4. Shopping bags can be made from several different materials including plastic, paper and cotton.

a) State the finite raw material used to make plastic shopping bags.

Answer: Crude oil is the finite raw material used to make plastic shopping bags.


b) Give the raw material used to make paper shopping bags.

Answer: Wood is used to make paper shopping bags.


c) Explain how shopping bags can be made more sustainably.

Answer: There are three ways to use resources more sustainably: reduce, reuse and recycle. When we reduce, we use less material for products. This reduces the amount of material used and the cost of transport as it is lighter. If we reuse shopping bags rather than just using them once and then throwing them away landfill will be reduced. As we need to make fewer bags, the energy cost to make the product is reduced. Recycling products uses less energy and reduces use of resources from the Earth.


5. The figure below shows what happens to plastic shopping bags after they have been purchased.


a) Calculate the percentage of shopping bags that are recycled.

Answer: 100 - (59 + 5) = 36%


b) Calculate how many times more likely you are to reuse than put into landfill the shopping bag.

Answer: 59/5 ≈ 12


c) Explain how putting a plastic shopping bag into landfill can cause environmental damage.

Answer: Plastic is non-biodegradable and will not break down in theenvironment, but it may break into smaller pieces and be eaten by animals, which can kill them. We are using more land for landfill.


d) Explain how life cycle assessments may or may not be biased.

Answer: Use of water, resources, energy sources and production of some wastes can be quantified. So, this aspect of the LCA is an objective process without bias. Allocating numerical values to the impact of pollutant is less straightforward and requires value judgements (opinions), so LCAs can be biased as the process is not completely objective. Selective or abbreviated LCAs can be made which evaluate a product. These can be misused to support pre-determined conclusions, for example in support of claims for advertising purposes.


6. Glass is a type of ceramic and can be used to make bottles.

a) Describe how glass bottles can be reused.

Answer: Glass bottles can be collected, cleaned and sterilised and re-filled.


b) Describe how glass can be recycled.

Answer: Glass can be recycled by crushing, melting and reforming into a new shape.


c) State where most of the energy to make glass has come from.

Answer: Most of the energy to make glass comes from finite resources (fossil fuels).


d) The energy saved by producing a bottle from recycled glass rather than from raw materials is enough to power a computer for 25 minutes. A desktop computer uses 30 J/s. Calculate the energy saved.

Answer: 60 × 25 × 30 = 45000 J = 45 kJ