An Ecological Rucksack is the total quantity (in kg) of materials moved from nature to create a product or service, minus the actual weight of the product. That is, ecological rucksacks look at hidden material flows. Ecological rucksacks take a life cycle approach and signify the environmental strain or resource efficiency of the product or service.
B. Main Features
Ecological rucksacks measure the amount of materials not directly used in the product, but displaced because of the product. That is, ecological rucksacks represent the materials necessary for production, use, recycling and disposal of a product, but not the materials used in the product.
Ecological rucksacks are calculated by subtracting the weight of the product from the material intensity (MI) of the product or service:
ER = W - MI
where ER is the ecological rucksack, W is the weight of the product and MI is the material intensity. The material intensity is found using:
MI = SUM (Mi x Ri)
where Mi is weight of a material in kgs and Ri is the rucksack factor. The material input is calculated from five main categories: (1) abiotic raw materials, (2) biotic raw materials, (3) moved soil (agriculture and forestry), (4) water and (5) air. The rucksack factor is the quantity (in kgs) of materials moved from nature to create 1 kg of the resource. For example, the rucksack factor for aluminum is 85:1 (85 kg materials moved for every 1 kg of aluminum obtained), for recycled aluminum it is 3.5:1 and for diamond the rucksack factor is 53,000,000:1. Each material used in the production of the good or service is multiplied by its rucksack factor and then each normalized value is summed to produce the material intensity of that product or service. As far as possible, all materials used for the production, use and disposal, whether directly or indirectly, are included in the calculation.
The ecological rucksack of some materials will change over time as they become rarer or as technology makes extraction or processing more efficient. For example, copper has moved from an ecological rucksack of 1:1 when copper nuggets were easy to find to 500:1 where copper is being extracted from sulphide ores.
Ecological rucksacks direct attention to the whole life cycle of products and services and the environmental and resource impacts of that product.
C. Organizational Proponent
Friedrich Schmidt-Bleek from the Wuppertal Institute for Climate, Environment and Energy (Germany) first proposed the ecological rucksack concept.
D. Case Studies and Examples
1. Ecological Rucksack Values
The Association of Cities and Regions for Recycling provides some rucksack values for various products. A 5 gram gold ring for example, was found to have an ecological rucksack of 2,000 kg. An aluminum drink can was found to have an ecological rucksack of 1.2 kg. And a 20 kg computer was found to have an ecological rucksack of 1,500 kg.
2. Reducing the Ecological Rucksack of a Watch
By conducting a Material Intensity Per unit Service (MIPS) Analysis for the production phase of a new watch, opportunities to reduce the ecological rucksack of the watch were revealed. By changing the some materials used in the watch, the rucksack decreased.
E. Target Sectors / Stakeholders
Ecological rucksacks use a cradle to grave approach. Therefore, the stakeholders represent those responsible for extraction, through to manufacture through to disassembly and disposal.
F. Scale of Operation
The ecological rucksack is best applied at a product or service level.