Sustainable production of L-lactic acid from lignocellulosic biomass using an alternative buffer system: Process development and techno-economic and environmental analysis

L-lactic acid (L-LA), a key monomer in biodegradable plastics, is a sustainable alternative that can be derived from LCB. The L-LA production process typically involves various technologies such as fermentation, filtration, and distillation. In the L-LA production process, large amounts of buffers are used to maintain proper pH during fermentation, so conventional buffers (e.g., CaCO3) are often selected because of their low cost. However, these buffers cannot be recycled efficiently, and the potential for alternative buffers remains uncertain. In this work, we aim to develop and evaluate novel processes for sustainable L-LA production using the alternative buffer (i.e., KOH). The processes involve a series of different unit operations such as pretreatment, fermentation, extraction, and electrolysis. An efficient buffer regeneration process using membrane electrolysis is implemented to recycle the buffer with minimal energy input. Then, we evaluated the viability of the proposed processes compared to the conventional process based on minimum selling price (MSP), and global warming potential (GWP). The MSP for L-LA was evaluated to be 0.83 USD /kg L-LA, and the GWP was assessed to be 2.93 kg CO2-eq/kg L-LA. These results represent a 25% reduction in MSP and a 32% reduction in GWP compared to the conventional process. Additionally, a sensitivity analysis was performed to identify the major cost drivers of MSP, such as interest rate, and the price of biomass. The proposed process, as a cost-effective and eco-friendly process, promotes biotechnology practices for sustainable production of L-LA.