Hello!
I am wondering how to measure the error of the emission factor in the LCA software database.
For example, I found the emission factor of cement in a LCA software, but the details indicated that the emission factor did not include the transportation process. So how do I quantify that part of the error into my research?
Best Regards,
Ning Zhang
I think you could calculate an additional process by yourself in the LCA, using relevant hypotheses on possible parameters (e.g. distance, transport mode, fuel intensity). Of course it will not be easy and straightforward. From my experience, the impact of transport is usually negligible, especially in energy-intensive processes such as cement production. Still, it depends if you are considering carbon emissions or other pollutants and which is the main goal of your model. A literature review on this aspect may be much quicker if you manage to find some relevant information.
In the US, as a general rule Portland cement manufacturing plants tend to be located fairly near the raw material source and so I would agree with Michel Noussan's statement that in most cases the pre-manufacturing transportation of raw materials contribution is very small in comparison to the manufacturing. That said, for a fair comparison to other materials it should be included. The post-manufacturing contribution is another matter. In some cases dry Portland cement is transported ridiculous distances to its point of being mixed. And for fair comparisons, the transportation after being mixed should also be included.
All that said, there will be large variations in the distances transported for various projects. In a given city, the cement used in one project may have been shipped only 100 miles while for another project, the cement used may have been shipped 1000 miles or more. For example, in 2019 the US imported $286 million worth of cement from Turkey. Over $10 billion (US$) in cement is shipped internationally every year.
Dear Ning, in most LCA software types (depending on whether you are using a free open source or commercial version), the "freight transport sector" is generally modeled separately in order to account for the impacts of transportation. If you are assessing cement or other product or industry, you could estimate alternative scenarios depending on the transportation mode "linked" to that product/industry. The same applies for the "building and construction materials" module of various types of projects.
Best regards.
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