Value judgement

Assigning one numerical score to these different effects involves deciding how much importance to give each of them. That requires value judgements, so an LCA is not a purely objective process.

Other comparisons require a value judgement. There is no purely scientific conversion that proves whether using a finite resource is more or less serious than producing a particular quantity of waste.

Giving these impacts different importance involves a value judgement. Local circumstances can affect that judgement: water use may be especially important where water is scarce, while energy use may matter greatly if the energy supply causes substantial pollution.