Evaluation of low-moisture anhydrous ammonia (LMAA) pretreatment method of lignocellulosic biomass for bioethanol production

Yang, Minliang
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The major objective of this project was to evaluate the low-moisture anhydrous ammonia (LMAA) pretreatment process of corn stover for bioethanol production. In order to fully evaluate this pretreatment method, three sub-objectives were developed: the optimization of the conditions for the LMAA pretreatment process; the influence of the LMAA pretreatment process during long-term storage of corn stover; and the techno-economic analysis (TEA) of this LMAA pretreatment process in bioethanol production.

In optimization experiments, several influencing factors were being investigated. As a result, the LMAA process increased the glucose yield by nearly 3 times compared with un-pretreated corn stover. And the optimal conditions determined by the experiments were 50 wt % moisture content, 72h of pretreatment time, 75°C of pretreatment temperature and 0.1 g NH3/g DM biomass.

In storage experiments, two sealing conditions were being explored equipped with two independent variables for each scenario. The results showed that no significant reduction in carbohydrates was found in either sealed or open treatments, but lignin reduction was observed in sealed treatments. In terms of mass loss, it increased with time in sealed treatments, but in open treatments, the mass loss was affected by the environment.

As for the techno-economic analysis of the LMAA pretreatment process, the detailed cost analysis was conducted and the unit cost of the bio-ethanol was compared among three various scales. The results indicated that the minimum ethanol selling price corresponding to ethanol production of 50 MM gal/y was $3.86/ gal. However, this was still high compared with the current gasoline price.

Agricultural and Biosystems Engineering, anhydrous ammonia, lignocellulosic biomass, pretreatment, storage, techno-economic analysis