Design and Testing of a Pilot-Scale Aqueous Ammonia Soaking Biomass Pretreatment System

Thumbnail Image
Himmelsbach, Jennifer
Isci, Asli
Anex, Robert
Major Professor
Committee Member
Journal Title
Journal ISSN
Volume Title
Raman, D. Raj
Morrill Professor
Research Projects
Organizational Units
Organizational Unit
Agricultural and Biosystems Engineering

Since 1905, the Department of Agricultural Engineering, now the Department of Agricultural and Biosystems Engineering (ABE), has been a leader in providing engineering solutions to agricultural problems in the United States and the world. The department’s original mission was to mechanize agriculture. That mission has evolved to encompass a global view of the entire food production system–the wise management of natural resources in the production, processing, storage, handling, and use of food fiber and other biological products.

In 1905 Agricultural Engineering was recognized as a subdivision of the Department of Agronomy, and in 1907 it was recognized as a unique department. It was renamed the Department of Agricultural and Biosystems Engineering in 1990. The department merged with the Department of Industrial Education and Technology in 2004.

Dates of Existence

Historical Names

  • Department of Agricultural Engineering (1907–1990)

Related Units

Journal Issue
Is Version Of

Scale-up of the aqueous ammonia soaking (AAS) biomass pretreatment method to 75-L soaking vessel size was accomplished in this work. A novel, pilot-scale AAS system capable of pretreating 4 kg of switchgrass per cycle was designed, fabricated, and tested. The pretreatment process involved soaking biomass in 29.5% aqueous ammonium hydroxide at a liquid: solid ratio of 5 L/kg. Major vessel design criteria included (1) allowing thorough washing of the soaked biomass in the pretreatment reactor; (2) simple, low-cost fabrication; and (3) limiting safety hazards by minimizing ammonia fumes from the system. Based on these constraints, commercially available 75-L HDPE tanks were selected as the primary vessels for pretreatment. The pretreatments were conducted outside, without agitation during the summer months in Iowa, with ambient temperatures ranging from 15°C to 33°C. During the first experimental cycle, clogging of the outlet resulted in leakage from the vessel during rinsing, and led to redesign of the washout prevention system. The redesigned system used a "teabag" approach in which dry biomass was preloaded into a cylindrical mesh bag, and the filled bag was placed into the soaking vessel. This modification eliminated outlet clogging, simplified biomass loading and unloading, but slightly reduced washing efficiency. Through five soaking cycles, an average of 22% to 25% delignification was achieved (Klason lignin basis) compared to the 35% removal seen at the bench-scale as reported by our group. Approximately 50% to 60% of the pretreated switchgrass was recovered, dry basis, compared to 75% previously achieved at the bench-scale. Overall, the system successfully generated moderate quantities (10 kg/wk) of pretreated biomass for pilot-scale fermentation experiments while illustrating some of the materials handling challenges that must be addressed as pretreatment methods are scaled-up.


This article is from Applied Engineering in Agriculture, 25, no. 6 (2009): 953–959.

Thu Jan 01 00:00:00 UTC 2009