2.3.4. Lactic acid, lactide and PLA production stage
Glucose is converted to lactic acid by fermentation, followed by
purification. The fermentation process requires energy use (steam
and electricity) and contributes substantially to the fossil energy
demand of PLA. Sulfuric acid, calcium carbonate, and auxiliary
chemicals are required as operating supplies. The PLA
manufacturing from lactic acid occurs in two steps. The first step is
the conversion of lactic acid into the lactide, and then purification
by distillation. In the second step the polymerization of lactide to
polylactide takes place in the presence of a tin catalyst. Inventory
data on the energy use and process chemical demand for the lactic
acid, lactide, and polylactide production were extracted from Groot
and Borén (2010). Based on 1 kg of PLA, the production requires
0.97 kWh of electricity and 12.74MJ of steam. This study considered
two different scenarios as described below