The Material Input per Service-Unit (MIPS)

(Source:  Hertwich et al., Evaluating the environmental impact of products and production processes: a comparison of six methods. Science of the Total Environment, 1996 Vol. 196, Issue 1, 13-29.)

The MIPS method estimates the mass of all the material input required to provide a product or service. The MIPS represents the total mass flow caused by the consumption of a service unit. The material input includes any material that is moved by the material extraction, production, packaging, distribution and use processes. The MIPS implies that each material input to production carries with it an ‘ecological rucksack’, the amount of material that had to be used for its production, e.g. coal for steel production. The total mass is aggregated in kilograms over the life-cycle of a product and related to the service provided by the product.

MIPS should promote long service-lives, remanufacturing and recycling, and a careful use of materials. It is concerned mainly with large-volume inputs. There is no explicit inclusion of effects like toxicity, global warming, or stratospheric ozone loss; the analysis is extremely shallow, but it is broad in including inputs to the entire lifecycle. MIPS is the direct translation of the insight that the current level of material throughput is unsustainable into a yardstick. It strengths are the simplicity of the conversion of the inventory to a final score and the strong image of an unsustainable mass flow. It is a good tool for illustration and education and has been used for that purpose.

If MIPS is a measure of environmental impact, it implicitly assumes that each mass throughput is equally undesirable, whether it is the natural gas that fuels a power plant or the river water that cools it. If used for design or management optimization, MIPS would invariable lead to perverse outcomes, such as the replacement of a non-toxic high-volume input with highly-toxic low-volume input, thereby increasing the burden on the environment.