Traditional LCA databases contain environmental data per process, for instance the emissions associated with the production of one kilogram of steel. A simplified approach as compared to the latter is to use available data per industrial sector. In this case environmental load is collected per euro of sector output. This approach can be useful when dealing with a service where material flows are difficult to quantify.
To illustrate this, we can take the environmental load per euro output of the steel sector in a country. In the traditional LCA, the designer specifies the amount of steel needed to produce the product, in the second case, the designer needs to specify the purchasing value of the steel. Of course, the steel sector cannot produce steel in an isolated way. It needs energy, and transport, as well as mining activities for the cokes and ores that are not produced in the sector. This means we need to trace the purchases of each sector. In each modern economy, a table that specifies the flow of commodities through the sectors is available, and this table is usually referred to as the input output table.
The significant benefit for PSS, is that is relatively simple to use such data for services. Services often do not have a clear unit, such as “kg of steel”. Knowing how much is spend on a service sector is relatively easy to determine, and by knowing the purchasing from a service sector can give a good indication about the environmental load associated with the service.
Figure 1 IO matrix specifies trade between sectors, imports and delivery to consumers
In 2003, a US input output dataset was compiled with very detailed environmental data on over 500 main commodities (Sangwon Suh, CML Leiden University). So far this is the best table available. The European Union does not have a central input-output table, only member countries have it. Relatively well developed tables with environmental data are available in the Netherlands and Denmark.
The US dataset can be freely obtained by downloading the demo version of SimaPro 6 LCA software, from www.pre.nl/simapro6 (there are two versions, take the version with the largest file size). The demo allows you to perform some basic calculations.
To run an analysis the following steps should be carried out :
- Check which commodities are defined in the US economy, and select the ones that come close to the type of services and products you use in the PSS;
- Estimate the costs for the services and the products. The datasets in the tool are defined as environmental load per dollar of market value. Data was collected at different times, around year 2000. You will need to convert your currency into dollars, you can also add uncertainty ranges and run a Monte Carlo analysis on this;
- Define a so-called assembly (SimaPro terminology) and list the services and products, and enter the trade value, or in this case the estimated costs;
- Repeat the procedure for alternative systems and run a compare, se also the simple example below.
Beware that this approach has significant uncertainties such as conversion rates, differences in economic structures (energy prices, technological levels), uncertainty on financial and emission data on which the input/output database is constructed, etc… Please be aware of this when interpreting the data: this tool provides only rough estimates.
To illustrate the idea, we will just compare the environmental impacts of spending a dollar on a cinema or theater with spending a dollar at a restaurant. Go to Processes\Use\Input Output\USA and select Eating and drinking places. Next scroll to Motion Pictures and Theatres. Select this, while holding the CTRL key down. Now click the compare button, and see that, from a sustainable consumption point of view, it would be better if consumers shift spending from restaurants to theatres.
There are two results possible:
- You can compare alternative PSS designs
- You can analyse a PSS system, and find which products and services are dominant
Please observe some limitations:
- The environmental load per dollar may not be completely comparable in regions outside the USA, and will certainly not match with conditions in non OECD regions;
- Databases like these, have significant uncertainties;
- The commodities are combine many elements. For instance there is only one commodity called restaurants, so there is no difference between slowfood and fastfood, restaurants, only the price of the meal determines the environmental load.
LCA expertise, good communication with suppliers and stakeholders that have participation in the value chain (use, disposal, distribution, etc)., especially to get a good understanding of the costs.