Example – combined transport of spare parts

Generic product activity or name
Freight transport, by container ship.

Combined transport of lightweight and heavy goods.

Context and background
Bicycles collected as lost property in Denmark are sent by container to Mozambique where they are made ready for sale and sold locally. In this particular example we look at the service of transport of spare parts that are habitually transported together with the bicycles in a container to Mozambique.

Presentation of example
The bicycles and some spare parts to maintain the bikes are transported together in the same containers. When the same container transports several items the transport service is a combined production. We therefore need to figure out how to allocate the environmental exchanges of this service to each by-product.

The effect of adding another item to be transported depends on what physical parameter is limiting the transport capacity. The container can carry a maximum load of 25000kg and a volume of 75 m3 giving a capacity limit of 330 kg/m3. For a heavy freight mixture (weighing more that 330 kg/m3) the weight would be the limiting factor, while for a light freight mixture (weighing less that 330 kg/m3) the volume would be the limiting factor.
In the actual case we know that the client fills the container with bikes (that are already assembled and thus very bulky but light) – but that they attempt to fill some of the empty spaces between the bikes with spare parts without ever reaching the weight maximum.

Their freight mixture is thus volume limited and the determining product could also be described as “transport of volume”. An additional demand for transport of weight alone (provided it does not add to the overall volume, as in this case where the bicycle parts can be fitted in into the empty spaces within the lightweight bikes!) can be satisfied without changes in the co-producing transport process, that is, the transport can be fully ascribed to the bicycles. If the co-transport would substitute another transport (i.e., a separate transport of a heavy-weight product), it is the transport of this heavy-weight product (the spare parts) that benefits from shifting to co-transport, because the unutilised weight in the co-transport would else have been wasted. Thus all exchanges from the transport are attributed to the volume demanding by-product, namely the bicycles, leaving the co-transported spare parts to be transported with no extra burden.
If the spare parts could not be fitted in into the empty spaces, in this situation where the transport is volume-limited, the burden would be determined by the volume of the spare parts, even though they are heavier than the capacity limit (330 kg/m3)

Notice that to reach this conclusion we did not need to know the actual weight or volume of the bicycles per m3, since the client has empirical evidence from actual transports showing that their containers never reaches weight maximum with the amount of spare parts they habitually need to transport.
In other hypothetical cases one would have to calculate the actual weight/volume ratios. To give you an idea of weights here are some averages: Air: 1.2 kg/m3, Styrofoam: 75 kg/m3, Cork 240 kg/m3, Wood 700kg/m3, Aluminum: 2700 kg/m3, Iron: 7870 kg/m3.

The above situation with co-products that are a transport services is sometimes regarded as “difficult” in terms of allocation. But, as demonstrated, the same method is used for service products as for material products (goods). And most importantly the allocation is simple because we are dealing with co-products were the “production” (in this case transport) can be varied independently.

Information sources used
To make this example we used the theories presented by the EDIP project reports (Weidema 2003, 2004). The data are from an actual LCA (climate footprint) made to assess CO2 savings by recycling bikes in Mozambique relative to re-melt them in Europe (Weidema 2013).

Weidema B P (2003). Market information in life cycle assessment. Copenhagen: Danish Environmental Protection Agency. (Environmental Project no. 863) http://lca-net.com/p/1078

Weidema B P (2004). Geographical, technological and temporal delimitation in LCA. UMIP 2003 method. København: Miljøstyrelsen. (Environmental News 74) http://lca-net.com/p/1046

Weidema B P (2013). Klima-fodaftryk for genbrug af hittegodscykler – Carbon footprint for Baisikeli’s genbrugsprojekt i Mozambique. 2.-0 LCA consultants, Aalborg, Denmark. http://www.lca-net.com/files/baisikeli_report.pdf

Author of this example
Bo Weidema


How to reference this
Weidema B P (2014), Example –combined transport of spare parts. Version: 2015-03-13 www.consequential-lca.org