Challenge: How can we re-use more polymers?

Teachers’ notes

Using this challenge

Learning outcomes

See Science at Work teachers’ notes.

Preparation

Prompt students to monitor their plastic waste at home for a week.

Props:

bin bag to help students visually estimate quantities, or picture of a wheelie bin if appropriate (find out its volume)

Optional:

bring in some shampoo bottles and find their average weight Starter Use the

Polymers for life?

case study to review how polymers are made from feedstocks produced from oil and gas, which are finite resources. Get the class to brainstorm all the plastics products they have used recently.

Main activity

Work through the slides. Answers are provided on Teacher slide 3. At Student slide 2, discuss any nearby landfills or incinerators, and how students feel about them. You could also measure the class waste as a number of bin bags, then inflate enough bags to represent the total (please re-use or recycle them!).

Plenary

Reflect that recycling reduces use of resources (including energy for manufacturing), but it relies on people taking action. How could students recycle more at home or at school?

Teacher slide 1

Using this challenge

Differentiation – Easier

Student slide 1: Provide a sample calculation for students to follow. Help students to visualise a cubic metre by asking them to construct a cube from 12 metre rules taped together.

Student slides 6 and 7: Omit.

Differentiation – Harder

Student slide 6: Challenge students to explain the concepts of life cycles for materials, and of ‘cradle to grave’ and ‘cradle to cradle’.

Teacher slide 2

Answers

1. Sample calculation: A student estimates that 1 bin bag of waste is thrown away each week in their home, and 50% of this is plastic. This gives a volume of 52 weeks x 0.5 x 0.15m

3 = 3.9m

3 in a year. Add total for all students.

5. 20 million x 2 x 0.04kg = 1.6 million kg or 1,600 tonnes.

6. Approximately 4 x 684,000 = 2,736,000 tonnes.

2. Fumes from incinerators and leakage (inc. methane, which is a greenhouse gas and is far more potent than CO eyesores.

2 ) from landfills; both incinerators and landfill sites can be visual 7. Since none of the high density polyethene (HDPE) is saved for re-use in the life cycle shown, more crude oil is required.

8. The last arrow is thinner because less HDPE becomes waste. The first arrow is thinner because recycling means that less crude oil is needed to make the same amount of HDPE.

3. Plastics are made from a finite resource. Since their raw material (oil) will run out one day, it is important to find ways to re-use them. Otherwise, we will not be able to use plastics in the future.

4. Use sample calculation for Question 1 as a guide for the method.

9. As reserves diminish, the most important uses for oil will be those for which there are few or no substitutes. Recycling will be an important way to reduce one source of demand because re using polymers removes the need for oil. This will allow remaining oil stocks to be used in applications where they are most needed.

Teacher slide 3 © BP International Ltd 2008

Challenge: How can we re-use more polymers?

Challenge presentation

How much plastic do you use?

1. How much plastic does your class THROW AWAY (not recycle) in a year?

Estimate: – how many bin bags your family fills each week – what percentage of this is plastic.

Calculate: – your family’s total plastic waste each year – the total for your class.

1 full bin bag = approx. 0.15m

3 Student slide 1

Where does waste plastic end up?

Recycling plastic keeps it from landfill or incineration.

2. What are some issues with these disposal methods?

Plastic is made from hydrocarbons that companies like BP refine from oil and gas.

3. Why might allowing plastic to go to waste cause problems in the future?

Student slide 2

What about recycling?

Many of you probably recycle some or all of your plastic.

4. Estimate the volume of plastic that you recycle each year.

Use the same method as before. This time, think about how much you put in your recycling bin. What sort of items do you recycle?

Student slide 3

What difference can recycling make?

Shampoo bottles are made from high density polyethene (HDPE).

It takes about 1.75kg crude oil to make 1kg HDPE.

An average shampoo bottle weighs around 40g. There are about 20 million homes in the UK.

5. If every home recycled two shampoo bottles each year, how much crude oil would be saved?

Student slide 4

It all adds up

Recycling can also help reduce CO 2 emissions.

The British Plastics Federation estimates that in the UK in 2006: – about 19% of waste plastic was recycled – this recycling saved 684,000 tonnes of CO 2 .

6. How much CO 2 might be saved if 80% of plastic waste was recycled?

Student slide 5

The plastic life cycle

The ‘life’ of an HDPE shampoo bottle might start with extracted crude oil, and end in landfill or incineration.

7. What is needed to produce more HDPE?

Student slide 6

A new life cycle for plastics

When HDPE is recycled, this adds a closed loop to the life cycle.

8. Why do you think the first and last arrows in the life cycle are now thinner?

Student slide 7

Better choices for a limited resource

Crude oil has many uses, but demand for it is increasing and one day it will run out.

Scientists are developing new technologies to provide long-term replacements for crude oil, including alternative energy technologies.

9. Why will recycling become more important as oil reserves near the end of their production?

Student slide 8