Lactic acid (LA) is one of the few biobased chemicals that can be used for different applications and is expected to grow to a $10 billion industry by 2025. Currently, commercial facility producing LA using first-generation feedstock (corn grain) and non-existent for second-generation feedstocks (corn stover and miscanthus). Thus, the objective of this study was to evaluate the techno-economic feasibility and environmental impacts of commercial-scale LA production from corn grain, corn stover and miscanthus for three fermentation pathways using LA-producing 1) bacteria, 2) fungi, and 3) yeast, and compare it with petroleum-based pathway. A biorefinery with an annual LA production capacity of 100,000 metric tons (t) was considered. The study estimated resources requirements for feedstock production, delivery and conversion to LA, production costs, minimum selling price (MSP), and environmental impacts in terms of global warming potential (GWP) and eutrophication potential (EP). The data used for the analysis were obtained from lab experiments, field data, literature, different database and process models developed for TEA. LA production costs and MSP were in the range of $0.84-1.28/kg and $0.84-1.40/kg, respectively, with the lowest costs for LA produced from corn grain. Compared to petroleum-based LA, GWP and EP reductions for biobased LA were 65-87% and 65-72% , respectively. LA production pathway (yeast-based), which do not require LA neutralization during fermentation had lower costs and environmental impacts. Optimizing feedstock logistics and identifying microorganism strains with high LA yield under harsh fermentation conditions can further improve LA production costs and emissions.