Inconsistent application of energy proxy data. After these three preparatory steps, the proxy data for chemicals production processes from the Gendorf and Ludwigshafen sites are applied to all datasets with gaps in their exchange data. Examples of using the proxy data for the electricity, heat or water requirements of basic chemicals in the ecoinvent datasets are visualized in figure . From this overview, it can be seen that the proxy data has been frequently applied, even for some very common chemicals whose synthesis steps and conditions are well covered in the literature in comparison to more specialized chemicals. This suggests that sometimes proxy data use was not necessary, contributing to the uncertainty of results. In some cases, the proxy data is used for several sequential synthesis steps, e.g. from cumene production to the epoxy resins production. Under such circumstances, the proxy data may prominently determine the environmental impacts of the final product.