This data set provides extensive description of one classic and one alternative (low-heat) processing routes for the manufacture of infant formula milk powders at a semi-industrial scale, the corresponding life cycle inventories using measurements, calculations of the material and energy balances, expert say information, or proxies collected at UMR STLO in the period 2020-2024, and the potential environmental impacts of 1 kg of the classic or alternative infant milk powder, using the Life Cycle Assessment (LCA) ISO 14 040 standard method, the CML-IA, ReCiPe 2016, Impact World+, LC-Impact or EF3.0 characterization methods and a dry matter allocation rule for the skimming operation. The dataset further provides variations of the inventories and environmental impact assessments to evaluate the sensitivity of the results to the formula’s dry matter prior to spray-drying or to the liquid versus dry state of the whey ingredient involved in the formula. The dataset participates in providing LCI of industrial food processes to the public. Infant formulas are industrial substitutes to human milk, used when breastfeeding is neither possible nor desirable. The classic processing route uses successive additions of dry ingredients and oils to skimmed bovine milk, blending, pasteurization, homogenization, concentration and spray-drying. However, successive heat loads are detrimental to the proteins' nutritional quality of the final product. An alternative processing route is evaluated that replaces the main pasteurization step at 85°C by microfiltration at 50°C i.e. below the heat-denaturation temperature of milk proteins.