Techno-Economic Analysis of Alternative Designs for Low-pH Lactic Acid Production

Abstract

Lactic acid production is highly affected by the fermentation pH. The need for neutralizing agents and the salts produced during fermentation have a significant impact on the overall process performance. Changing the neutralizing agent and allowing lower pH fermentation can improve the process profitability. This work investigates the impact of fermentation parameters and evaluates the process economics of alternative downstream processing designs to produce lactic acid. The results show that low-pH fermentation (pH = 3.86) was profitable (internal rate of return, IRR > 10%) at a fermentation yield of 0.97 g/g sucrose. Decomposing the salt subproduct to reduce the environmental burden associated with gypsum disposal has a significant impact on the economic performance, resulting in a lower IRR than the other designs. Although the salt decomposition process has a high energy demand, it is compensated by the savings obtained in the downstream processing, thus resulting in a similar overall energy demand when compared to conventional reactive distillation. A novel process configuration with ammonium sulfate subproduct shows potential for 3 p.p. higher IRR and up to 30% lower fuel demand in comparison with the conventional process. Therefore, alternative downstream processes could drive low-pH fermentation to outperform the conventional process without any neutralizing agent.

Lactic acid and biomethane production from bread waste: a techno-economic and profitability analysis using pinch technology

“…Therefore, one alternative is fermentation using acid-resistant microorganisms (Scenario II). 34 Engineered microorganisms are reported to tolerate low pH, and Cargill (for example) has produced LA commercially using acid-tolerant (pH ≤ 3.0) microorganisms. 34 Therefore, the economic performance of Scenario I was compared with low-pH fermentation using acid-resistant microorganisms (Scenario II).…”

“…34 Engineered microorganisms are reported to tolerate low pH, and Cargill (for example) has produced LA commercially using acid-tolerant (pH ≤ 3.0) microorganisms. 34 Therefore, the economic performance of Scenario I was compared with low-pH fermentation using acid-resistant microorganisms (Scenario II). The RStoic reactor model was used for both the saccharification reactor and fermenter.…”

“…25 Marchesan et al reported an economic analysis to produce LA from 212 MT sugarcane per h. They evaluated economic performance at different pH in the fermenter with a 24 h fermentation time, 130 g L −1 sugar, and LA yield of 0.97 g g −1 glucose. 34 The minimum LA selling price was estimated as $1.134 and $1.057 per kg for acid-neutral and low pH fermentation, respectively, considering thirty years of plant life and 10% IRR. The minimum 80% LA selling price was reported to be $0.943 per kg from 10 MT food waste per hour.…”

“…Fermentation using acid-resistant microorganisms is a possible alternative to circumvent process complexity and cost. 34 This approach also avoids the need for expensive chemicals and the disposal of calcium salt. The economic and profitability performance of traditional acid-neutral fermentation was further compared with low-pH equivalents for producing LA from BW.…”

Electrochemical membrane-assisted pH-swing extraction and back-extraction of lactic acid

“…Therefore, it is crucial to consider its impact in the design process and maintain a suitable pH during the operation to ensure satisfying extraction rates. This can either be done by employing the electrochemical pH shift prior to extraction or by developing acid tolerant strains of lactic acid producing microorganisms [44][45][46].…”