MIPS Categories

MIPS (Material Input per Service unit) is calculated for five categories of natural resources: abiotic raw materials, biotic raw materials, water, air and soil movements in agriculture and forestry. When calculating material inputs, these categories are calculated and presented separately. Sometimes abiotic and biotic resources are added up and expressed as one figure for reasons of simplicity.

As an example, we present the material inputs for the production, and use of one T-shirt in Germany according to Michael Ritthoff, Holger Rohn, Christa Liedtke and Thomas Merten 2002: Calculating MIPS - Resource productivity of products and services.

Abiotic raw materials: 2 kg in production + 117,5 kg during use.
Abiotic resources are unrenewable natural resources. In T-shirt production they include for example the fossil energy and electricity, including the ecological rucksacks for them, which is used during  manufacturing and use of the T-shirt. In other products they can be for example ores and gravel.

Biotic raw materials: 1,2 kg in production.
Biotic resources are renewable resources such as cotton in our T-shirt example. The mass of the T-shirt makes a part of this figure. In the case of meat for instance, the biotic material inputs include all the biomass consumed by the cattle.

Water: 1480 kg in production + 2720 kg during use.
The amount of  water consumption during product chains is usually high. Water is used for the irrigation of cotton. Water consumption should not be expressed in the same figure with the other materials because it would make the share of them insignificant. During the use of a T-shirt a large amount of water is consumed e.g for washing.

Air: 12,5 kg in production + 27,5 kg during use.
Air consumption in the production and use phases means the physical and chemical transformation and combustion of air and its components, such as oxygen. The output of carbon dioxide is thus often in indirect relation to the air consumption.

Soil movements in agriculture and forestry: production 223 kg.
The soil movements consist of erosion and the deepest mechanical soil movement (e.g. by ploughing) during the season. As data for mechanical soil movement is not always available, erosion and mechanical soil movement are commonly presented in seperate figures. So far, often only erosion figures are available. In the T-shirt case presented here, the figure represents both erosion and mechanical soil movement.

In order to calculate MIPS values for the use of the T-shirt, the benefit and the service unit have to be determined. In this case, it's assumed that the T-shirt is washed and ironed 100 times during its useful life. The service unit for the T-shirt is one wearing cycle, i.e. the use between washes, so that the MI figures in five categories presented above are divided by 100 wearing cycles.

The next phase makes the calculations MIPS calculations. The figures are changed into material consumption per service. So they are divided by 100 since the service unit was one wearing cycle of a T-shirt.

abiotic raw materials:         1,2 kg/ wearing cycle
biotic raw materials:           0,01 kg/ wearing cycle
water:                                   42,0 kg/ wearing cycle
air:                                        0,4 kg/ wearing cycle
erosion:                               2,2 kg/ wearing cycle

With these MIPS figures it is easy to compare different T-shirts to each other. For example, another T-shirt lasts only 20 wearing cycles instead of a 100, the MIPS values of the long-lasting T-shirt are smaller, i.e. the material input per wearing cycle is smaller, because the manufacturing phase is divided by more uses. 

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