Imagine you want to do an LCA or sustainability assessment of a product and you feel like the development process may have a significant share of the impact in the overall life cycle. Or you want to include investments in your LCA, without knowing exactly how they relate to physical flows. That’s when input-output sustainability databases (IO databases) come in handy.
In economic sciences, an IO model represents the interdependencies between different branches of a national economy or of different regional economies. For example, the steel sector in a country is buying X million dollars of goods or services from the transportation sector in that same country, and Y million dollars from other countries.
IO databases for sustainability assessments and LCA couple this economic information with statistical impact data, for example on environmental emissions or social characteristics. For example, the production of X million dollars of steel is associated with Y tonnes of CO2 emissions and employment of Z low-skilled workers.
For LCA practitioners, the main advantage of using an IO database is that the entire economy is covered, which removes the need to limit your model’s system boundaries or substitute processes if you don’t have all the data. IO databases also provide consistent allocation and scope.
However, the drawback is a higher level of aggregation, which makes it difficult to model a specific product with only IO databases. IO databases are also very dependent on the timeframe of the assessment, since the volatility of prices can affect the robustness of the LCA result: the same amount of money may not buy you the same amount of raw material today than you would have got when the database was created. And in the end, it is not the money that causes the environmental impact, it is the material use.
Still, IO databases are a valuable weapon in the arsenal of any LCA practitioner. SimaPro includes several IO databases, such as the EU and DK Input Output library and the Swiss Input Output. Others are available, such as Exiobase or the Social Hotspots Database for social assessment.