What is bio-derived polyethylene?

Bio-derived polyethylene (BPE) is polyethylene made from plant-based ethanol rather than from crude oil. Bio-derived polyethylene is chemically identical to oil-based polyethylene.

Outline the manufacture of bio-derived polyethylene from sugar cane.

Sugar cane juice is fermented by yeast to make ethanol, which is then distilled. The ethanol is dehydrated over a heated catalyst to give ethene, which is polymerised into polyethylene.

What happens in the dehydration step of bio-derived polyethylene manufacture?

Ethanol vapour is passed over a hot catalyst such as aluminium oxide. Each ethanol molecule loses a molecule of water to form ethene.

Why can bio-derived polyethylene be recycled in existing systems?

Bio-derived polyethylene has the same structure and properties as oil-based polyethylene. Bio-derived polyethylene can go into the same collection and reprocessing streams without contaminating them.

Why is bio-derived polyethylene not biodegradable?

Bio-derived polyethylene has the same long carbon chains as conventional polyethylene. Micro-organisms cannot break these chains down, so a plant origin does not make the plastic degradable.

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Plastics for the Future

Bio-derived polyethylene and a sustainable plastics future

3 things to know
AS 1

Overview

Making polyethylene from sugar cane ethanol, why it recycles but does not biodegrade, its carbon benefits and land drawbacks, Braskem in Brazil, polylactic acid, the circular economy, the 2022 UN plastics resolution and the Plastic Packaging Tax.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

How can bio-derived polyethylene lower greenhouse gas emissions?

Key term

What are the environmental drawbacks of growing crops for bio-derived plastics?

Key term

Assess how urgently the world needs to make and use plastics more sustainably.

Questions from this subtopic

Each one with the model answer underneath.

1
What is bio-derived polyethylene?
Model answer
Bio-derived polyethylene (BPE) is polyethylene made from plant-based ethanol rather than from crude oil. Bio-derived polyethylene is chemically identical to oil-based polyethylene.
2
Outline the manufacture of bio-derived polyethylene from sugar cane.
Model answer
Sugar cane juice is fermented by yeast to make ethanol, which is then distilled. The ethanol is dehydrated over a heated catalyst to give ethene, which is polymerised into polyethylene.
3
What happens in the dehydration step of bio-derived polyethylene manufacture?
Model answer
Ethanol vapour is passed over a hot catalyst such as aluminium oxide. Each ethanol molecule loses a molecule of water to form ethene.
4
Why can bio-derived polyethylene be recycled in existing systems?
Model answer
Bio-derived polyethylene has the same structure and properties as oil-based polyethylene. Bio-derived polyethylene can go into the same collection and reprocessing streams without contaminating them.
5
Why is bio-derived polyethylene not biodegradable?
Model answer
Bio-derived polyethylene has the same long carbon chains as conventional polyethylene. Micro-organisms cannot break these chains down, so a plant origin does not make the plastic degradable.
6
How can bio-derived polyethylene lower greenhouse gas emissions?
Model answer
Sugar cane absorbs carbon dioxide from the air as it grows. The plastic stores this plant carbon instead of fossil carbon. Sugar mills often burn bagasse, the crushed cane fibre, for process energy.

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Fossil Fuels

Global Action on Energy Conservation and Climate Change

Macrogeneration

Microgeneration

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