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ARS Home » Plains Area » Las Cruces, New Mexico » Cotton Ginning Research » Research » Publications at this Location » Publication #418495
Research Project: Improving the Production and Processing of Western and Long-Staple Cotton and Companion Crops to Enhance Quality, Value, and Sustainability

Location: Cotton Ginning Research

Title: High throughput pretreatment of corn stover using compacted biomass with recycled ammonia (COBRA) process

Author
item ZHANG, JIAN - East China University Of Science And Technology
item MOHAMMEDI, MAEDEH - University Of Houston
item GONG, HENG - East China University Of Science And Technology
item HODGE, DAVID - Montana State University
item Tumuluru, Jaya Shankar
item SOUSA, LEONARDO - Michigan State University
item DALE, BRUCE - Michigan State University
item BALAN, VENKATESH - University Of Houston

Submitted to: Chemical Engineering Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2025
Publication Date: 2/1/2025
Citation: Zhang, J., Mohammedi, M., Gong, H., Hodge, D., Tumuluru, J., Sousa, L.D., Dale, B., Balan, V. 2025. High throughput pretreatment of corn stover using compacted biomass with recycled ammonia (COBRA) process. Chemical Engineering Journal. 505. Article 159731. https://doi.org/10.1016/j.cej.2025.159731.
DOI: https://doi.org/10.1016/j.cej.2025.159731

Interpretive Summary: This study focuses on utilizing the compacted biomass pretreated with recycled ammonia (COBRA). Ammonia pretreatment improves the digestibility of lignocellulosic biomass. The COBRA pretreatment is compared with other processes, such as ammonia fiber expansion (AFEX) and extractive ammonia (EA) for corn stovers. The results indicated that COBRA achieved higher conversion at lower temperatures and pressures. The x-ray diffraction studies showed the same results where the COBRA pretreatment effectively converted the recalcitrant crystalline cellulose I to more digestible cellulose III. COBRA produced 216.9 g ethanol per kg corn stover, surpassing AFEX (198.0 g) and approaching EA (235.9 g). The techno-economic analysis showed that integrating the biomass supply system from local depots and COBRA pretreatment is suitable for producing cellulosic ethanol economically on a large scale.

Technical Abstract: In this study, a Compacted Biomass with Recycled Ammonia (COBRA) pretreatment was used, utilizing densified corn stover and anhydrous liquid ammonia under mild conditions to increase pretreatment throughput. COBRA was then compared with established Ammonia Fiber Expansion (AFEX) and Extractive Ammonia (EA) pretreatments for sugar conversion and ethanol fermentation. The optimal pretreatment conditions for the COBRA process were determined to be 67 °C, with an NH3-to-biomass ratio of 0.8:1, and a duration of 5.5 h. X-ray diffraction analysis confirmed that COBRA effectively converted recalcitrant crystalline cellulose I to the more digestible cellulose III. Using an optimized enzyme cocktail (CTec2:HTec2:Pectinex; 0.6:0.2:0.2) of 15 mg/g glucan, COBRA-pretreated corn stover achieved high sugar yields. Separate hydrolysis and fermentation (SHF) at 6 % glucan loading, yielded 62 g/L glucose and 28 g/L xylose after 96 h of hydrolysis. Subsequent fermentation with S. cerevisiae 424A for 96 h, without nutrient supplementation or detoxification, produced 38.3 g/L ethanol with an 87.6 % metabolic yield. COBRA pretreatment followed by hydrolysis and fermentation produced 216.9 g of ethanol per kg of biomass, compared to AFEX (198.0 g) and EA (235.9 g). While COBRA’s ethanol yield was lower than EA, its advantages lie in improved reactor filling ratio (16.7 % vs 4.4 %), milder conditions (67 °C vs 120 °C, 400 psi vs 1300 psi), and lower ammonia usage (NH3:biomass 0.8:1 vs 6:1). A techno-economic analysis showed that integrating COBRA pretreatment with a localized biomass supply chain system is economically viable for large-scale cellulosic ethanol production.