Wind turbine

What goes into an LCA?

A life cycle assessment allows the environmental impact of a product to be measured. It allows specific values to be put to the raw materials used, energy required and also the wastes produced.

It is difficult to measure things like the economic and social sustainability using an LCA.

Life cycle assessment

Comparison of paper and plastic shopping bags

Life cycle assessments can be used to compare the sustainability of different products. Look at the table which summarises an assessment of plastic and paper disposable shopping bags.

Which do you think will be more environmetally-friendly? Paper or plastic?

	Paper bag	Plastic bag
Raw materials	Wood (renewable)	Oil / gas (non-renewable)
Energy to make	1.7 megaJoules	1.5 megaJoules
Solid waste	50 grammes	14 grammes
Total emissions to air	2.6 kg	1.1 kg
Global warming (CO₂ equivalents)	0.23 kg	0.53 kg

Figures are obtained by comparing one paper bag with two plastic bags. This gives a comparable carrying capacity for both materials. They also assume current recycling rates. Source of data: Institute for Lifecycle Energy Analysis.

Paper or plastic?

Looking at the table, the plastic bags seem to be more sustainable. However, both paper and plastic bags use up resources and produce wastes. Looking at sustainability using the Natural Step Framework tells us that neither are sustainable in the long term.

Life Cycle Assessment appears to give clear answers but there are limitations as to how they can be interpreted.