Challenges and opportunities in lactic acid bioprocess design—From economic to production aspects

Exergy analysis of a lignocellulosic-based biorefinery annexed to a sugarcane mill for simultaneous lactic acid and electricity production

Driven by a range of sustainability challenges, e.g. climate change, resource depletion and expanding populations, a circular bioeconomy is emerging and expected to evolve progressively in the coming decades. South Africa along with other BRICS countries (Brazil, Russia, India and China) represents the emerging bioeconomy and contributes significantly to global sugar market. In our research, South Africa is used as a case study to demonstrate the sustainable design for the future biorefineries annexed to existing sugar industry. Detailed techno-economic evaluation and Life Cycle Assessment (LCA) were applied to model alternative routes for converting sugarcane residues (bagasse and trash) to selected biofuel and/or biochemicals (ethanol, ethanol and lactic acid, ethanol and furfural, butanol, methanol and Fischer–Tropsch synthesis, with co-production of surplus electricity) in an energy self-sufficient biorefinery system. Economic assessment indicated that methanol synthesis with an internal rate of return (IRR) of 16.7% and ethanol–lactic acid co-production (20.5%) met the minimum investment criteria of 15%, while the latter had the lowest sensitivity to market price amongst all the scenarios. LCA results demonstrated that sugarcane cultivation was the most significant contributor to environmental impacts in all of the scenarios, other than the furfural production scenario in which a key step, a biphasic process with tetrahydrofuran solvent, had the most significant contribution. Overall, the thermochemical routes presented environmental advantages over biochemical pathways on most of the impact categories, except for acidification and eutrophication. Of the investigated scenarios, furfural production delivered the inferior environmental performance, while methanol production performed best due to its low reagent consumption. The combined techno-economic and environmental assessments identified the performance-limiting steps in the 2G biorefinery design for sugarcane industry and highlighted the technology development opportunities under circular bioeconomy context.

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Multi-product biorefineries from lignocelluloses: a pathway to revitalisation of the sugar industry?

Recently, lactic acid production from renewable materials has gained enormous attention due to the several functional properties it offers in different fields. The high yield productivity of lactic acid by utilizing economical and easily available substrates has received immense attraction in the petrochemical industry. Biomass or waste materials from various sources have become a significant concern because they cause severe environmental pollution if disposed of improperly. Hence, the employment of an integrated biorefinery platform for waste materials is an ideal option to produce high-value bio-products while remediating the waste. Optical pure lactic acid production through fermentation has gained interest due to its high potential applications in food, pharmaceutical, textiles, and cosmetic industries as well as highly promising packaging materials. The manufacturing of biodegradable bioplastic from polylactic acid materials is a green alternative to that derived from petrochemicals. However, high manufacturing costs have impeded the widespread application of polylactic acid due to the high cost of lactic acid production. This review paper summarizes the most recent advancements and challenges in pure lactic acid production from various substrates and conventional processes, including pretreatment and enzymes hydrolysis and fermentative technologies. Moreover, a detailed analysis of the techno-economic feasibility, downstream processing, and lactic acid purification techniques are also discussed.

A review on the lactic acid fermentation from low-cost renewable materials: Recent developments and challenges

Techno-economic analysis and environmental impact assessment of lignocellulosic lactic acid production

Process designs for the continuous recovery of lactic acid from fermentation broth by reactive distillation (esterification and hydrolysis with C1 to C4 alcohols) are developed and optimized to minimize cost. The best designs are qualitatively different for different alcohols because of the differing volatility ranking of reactants and products and the formation of a two-liquid phase zone in some cases. The results suggest that the methanol and butanol processes are the most attractive. The costs of these two processes are similar, and the ranking depends on the payback period. The ethanol and isopropyl alcohol processes are more expensive because an entrainer is required to break the alcohol/water azeotrope.

Plant-Wide Economic Comparison of Lactic Acid Recovery Processes by Reactive Distillation with Different Alcohols

Plantwide control of processes to purify lactic acid by esterification and subsequent hydrolysis are investigated. Two processes are considered and compared: one using methanol and the other using butanol. The alcohol liberated in the hydrolysis column is recycled to the esterification column, and the water liberated in the esterification column can be reused in the hydrolysis column, resulting in highly interconnected process flowsheets. For both processes, designs with one recycle stream (alcohol only) and two recycle streams (alcohol and water) are tested, and for each alcohol and each configuration, both temperature and composition control are tested for all columns (reactive and nonreactive). The results show that processes with only a single recycle stream are somewhat easier to control. For the butanol process, a temperature control structure with only a single composition controller is found to be adequate, while additional composition measurements with constraints on controller outputs are requir...

Chien-Yuan Su

Papers

Plant-Wide Economic Comparison of Lactic Acid Recovery Processes by Reactive Distillation with Different Alcohols

Control of Highly Interconnected Reactive Distillation Processes: Purification of Raw Lactic Acid by Esterification and Hydrolysis