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 Author: kenharrison [ Mon Oct 24, 2005 7:52 pm ] Post subject: Comparison of two alternatives with different costs I've read the Horvath and Hendrickson paper comparing the environmental impacts of two bridge designs. In that study, the bridges were functionally equivalent but the costs of the bridges were not. It appeared that the EIO-LCA model was used to estimate the LCI impacts of each bridge design given the amounts spent (delineated by sector). As the costs of the bridges are not equivalent, wouldn't it be important to investigate in what sectors the cost savings were applied? Suppose that the EIO-LCA mode were used in the same fashion of that paper for the comparison of the following two alternatives that are functionally equivalent (e.g., two bridges with same lifetime, designed to handle the same maximum loading). If alternative A costs \$1million with emissions of 10 mt PM10, and alternative B costs \$2 million with EIO-LCA model emissions of 10 mt PM10, in the spirit of the EIO-LCA model, wouldn't there be fewer emissions if B were adopted, since the savings from adoption of A (\$1 million) would be applied (of course with posssible economic benefit) to a sector(s) with associated emissions? Or have I lost my mind? It would seem important to factor in such emissions in an LCA comparison, or at least to note it.

 Author: Aurora [ Thu Oct 27, 2005 3:02 pm ] Post subject: Ken-- Not sure if this totally answers your question, but basically the EIO-LCA model operates linearly. As a result, if you spend \$1 million on two bridges, you would be modeling that as \$1 million spent twice in the "Highway, street, bridge, and tunnel construction" sector. The model cannot differentiate between different types of bridges or any other product in a given sector due to aggregation. Consequently, if you spend \$1 million each on two bridges, you will essentially be modeling the same thing in EIO-LCA. As a result, you will have the exact same environmental emissions for each (say 10 mt PM10) because you spent the same amount of money in the same sector to build each bridge. However, if you spend only \$100,000 on a bridge and the environmental value of PM10 emissions is, say, 0.00001 mt PM10/\$ in the bridge construction sector, you would only have 1 mt PM10 emissions for this much cheaper bridge (less money, fewer emissions) Thus, per EIO-LCA, as price reduction occurs, so do PM10 emissions and for a less expensive bridge (or any other type of product), you will have fewer emissions compared to a more expensive product from the same sector.

 Author: kenharrison [ Thu Oct 27, 2005 3:09 pm ] Post subject: Not really the question I was asking. In the paper I reference, the two bridges are made of different proportions of materials and the EIO-LCA modeling required the expenditures in different sectors corresponding to the material inputs. Aurora wrote:Ken--Not sure if this totally answers your question, but basically the EIO-LCA model operates linearly. As a result, if you spend \$1 million on two bridges, you would be modeling that as \$1 million spent twice in the "Highway, street, bridge, and tunnel construction" sector. The model cannot differentiate between different types of bridges or any other product in a given sector due to aggregation. Consequently, if you spend \$1 million each on two bridges, you will essentially be modeling the same thing in EIO-LCA. As a result, you will have the exact same environmental emissions for each (say 10 mt PM10) because you spent the same amount of money in the same sector to build each bridge. However, if you spend only \$100,000 on a bridge and the environmental value of PM10 emissions is, say, 0.00001 mt PM10/\$ in the bridge construction sector, you would only have 1 mt PM10 emissions for this much cheaper bridge (less money, fewer emissions)Thus, per EIO-LCA, as price reduction occurs, so do PM10 emissions and for a less expensive bridge (or any other type of product), you will have fewer emissions compared to a more expensive product from the same sector.