Published June 1998
Lactic acid (2-hydroxypropionic acid) is a naturally occurring, chiral, alpha-hydroxy acid that can be produced synthetically or by fermentation. A potential growth market for the acid is its use as a "green" raw material for biodegradable polymers. Furthermore, the ethyl and butyl esters of lactic acid are biodegradable cleaning agents that offer an environmentally acceptable alternative to conventional cleaning solvents in the metalworking and semiconductor industries.
The world's largest producer of lactic acid by fermentation, PURAC biochem, has entered into partnership with Cargill to manufacture lactic acid at Cargill's corn wet-milling site in Blair, Nebraska.
The focus of this review is a 1996 Cargill patent for the recovery of lactic acid from fermentation broth by CO2-assisted trialkylamine extraction. Cargill's patent claims a significant reduction in raw material use and waste generation. We examine the economics and technical issues for a new grass-roots 75 million lb/yr (34,000 t/yr) lactic acid facility based on this recovery technology.
Our economic evaluation, based on PEP's concept of the process and the claims outlined in the patent, indicates that the process is viable and will be competitive with existing technologies. The advantage of reduced waste generation relative to the historical process for lactic acid production is that Cargill's technology offers a better potential for large-scale production than current industry practice. Important technical issues that influence process economics, such as waste treatment, are discussed in the review.