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Low-Moisture A nhydrous A mmonia (LMAA) Pretreatment of Corn S tover

This study explores the effectiveness of LMAA pretreatment on corn stover for efficient ethanol production and long-term storage. Optimization experiments and storage experiments were conducted to evaluate the results.

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Low-Moisture A nhydrous A mmonia (LMAA) Pretreatment of Corn S tover

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  1. Low-Moisture Anhydrous Ammonia (LMAA) Pretreatment of Corn Stover Minliang Yang Ming-Hsun Cheng Xiong Cao Kurt A. Rosentrater Department of Agricultural and Biosystems Engineering Iowa State University

  2. Outline • Introduction • Overall Objectives • Optimization Experiments • Storage Experiments • Conclusions

  3. Introduction Procedure of ethanol production Pretreatment is required for efficient hydrolysis. Hydrolysis Glucose (Fermentable) Cellulose (Glucan, β-1,4-glucose)

  4. Introduction Pretreatment Pretreatment / Incubation Hydrolysis / Fermentation

  5. Overall Objectives • Can we do it? How well does LMAA work? • Will LMAA help storage? • How much will LMAA cost?

  6. Optimization Experiments

  7. Batch Reactors • Sealed batch reactor (690mL): • Optimized Conditions: • 0.1 g ammonia/g biomass, 80°C, 84h • Results: • 89% of the maximum theoretical ethanol yield • 24.9 g/L ethanol production in fermentation • Scaled-up reactor (3L): 4 x larger • Conditions: • 0.1 g ammonia/g biomass, 75°C, 72h • Results: • 71.6% of the maximum ethanol yield • $3.86 /gal of bioethanol

  8. Phase One – Results • Glucan Digestibility of treated vs. untreated corn stover *Note: Conditions for untreated treatment: 50% moisture content and medium size; Conditions for optimal treatment: 72h, 75°C, 50% moisture content and medium size. Compared with untreated corn stover, LMAA pretreatment method greatly improved enzymatic digestibility (% improvement=119) 8

  9. Phase Two – Results • Glucan Digestibility of treated vs. untreated corn stover 71.6 ° ° *Note: Conditions for untreated treatment: 50% moisture content and medium size; Conditions for optimal treatment: 72h, 75°C, 50% moisture content and medium size. Compared with untreated corn stover, LMAA pretreatment method greatly improved enzymatic digestibility (% improvement=213)

  10. Phase Two – Results 71.6 60.3 58.0 * Note: Conditions for 144h treatment: 144h, 120C, 80% moisture content and large size; Conditions for 24h treatment: 24h, 120C, 80% moisture content and large size. Longer incubation time may improve digestibility, but not very obvious. *Note: Conditions for 20C treatment: 24h, 20C, 80% moisture content and small size; Conditions for 120C treatment: 24h, 120C, 80% moisture content and small size. Lower incubation temperature may improve digestibility compared with higher.

  11. Original setup Modified setup Experimental Modifications Output Input Input Output Ammonia loading: 0.1 g/g biomass 0.18 g/g biomass • Optimization of LMAA conditions • Increase glucan digestibility • Ammonia diffusion • Hydrolysis conditions

  12. Ammoniation & Pretreatment Modifications Pretreatment Conditions • Ammonia pressure • Original setup: 0.1 g NH3/g biomass (db) • Increase NH3 loading: 0.18 gNH3/ g biomass (db) • Biomass moisture content • 50% (DM) • Ammoniation time • Original setup: 30 min • Increase to 80 min • Incubation • Temperature: 75 oC • Time: 72 to 144h

  13. Enzymatic Hydrolysis Modifications NREL LAP (NREL, Enzymatic saccharification of lignocellulosic biomass. Laboratory Analytical Procedure (LAP). 2008) • Enzyme loading • Original loading: 15 FPU Cellulase (GC220) • 30 CBU β-glucosidase (Novozyme 188) • Increase loading: 15 FPU Cellulase (GC220) • 60 CBU β-glucosidase (Novozyme 188) • Hydrolysis • Temperature: 75 oC • Time: 72 & 144 hr • RPM: 68

  14. Phase 3– Results Last year’s conditions • 0.1 g NH3 / g biomass (db) • 30 min ammoniation • 75 oC and 72 hr incubation • 15 FPU cellulose • 30 CBU β-glucosidase Results • Particle size smaller than 1mm • Digestibility: 46.8% • Particle size smaller than 0.5mm • Digestibility: 49.5%

  15. Phase 3 – Results New ammoniation and hydrolysis conditions • 0.1 g NH3 / g biomass (db) • 60 min ammoniation • 75 oC and 72 hr incubation • 15 FPU cellulose • 60 CBU β-glucosidase Results • No NH3 remained increased digestibility • Digestibility increased at least 20%

  16. Phase 3 – Results Ammoniation of corn stover with particle size smaller than 0.5 mm • 0.18 g NH3/ g biomass (DM) • 80 min ammoniation • 75 oC incubation • 72 and 144 hr incubation • 15 FPU cellulose • 60 CBU β-glucosidase Results • 3 days incubation • Digestibility: 85.19% • 6 days incubation • Digestibility: 85.57%

  17. Cost Impacts Unit cost of bioethanol based on optimized conditions: For the 85% digestibility results, we increased the ammonia loading from 0.1g ammonia / 1g biomass (db) to 0.18g ammonia /1g biomass (db), which increased 80% ammonia loading. Increased from $3.86/gal to $4.14/gal

  18. Impact of LMAA on Long-Term Storage

  19. Background • Why worry about storage? • Seasonal harvest • Stover not used immediately after the harvest • Among all base reagents, ammonia has been found to be very effective for preservation Source: http://www.ccur.iastate.edu/news/newsletters/2012/sep_oct/stoverproject.html

  20. Objectives • To evaluate the effect of the LMAA pretreatment on biomass quality, specifically, changes in carbohydrates, lignin, and ash content; • To optimize the storage time, and monitor the growth of fungi; • To compare the effects of sealed vs. open storage conditions • Help guide scale-up

  21. Methods • Grind corn stover to 2mm • Adjust moisture content to 20 wt.%, 40 wt.%, 60 wt.% • Ammoniated corn stover with ammonia loadings of 0, 0.1, 0.2 g NH3/g DM biomass • Transfer the ammoniated corn stover into various plastic containers and open bottles

  22. Methods • Place the pretreated corn stover for 6h, 1d, 5d, 12d, 30d, 60d, and 90d at ambient temperature (~21°C) • Conduct composition analysis, mass loss and visible mold observation for the pretreated corn stover over time • Mold determined using an OCCULAR test • All experiments were run in duplicate Sealed bag Open bottle

  23. Results - Visible Mold Growth

  24. Results - Visible Mold Growth Sealed containers Mold observed in sealed bags after 16 days in Treatment 3 (60 wt.% M.C., no LMAA); 1 day later, Treatment 2 (40 wt.% M.C., no LMAA) also appeared; No other mold growth observed in 20% wt % , no LMAA until 90 days Open containers No mold growth observed for any treatments – due to moisture loss LMAA treatments resulted in no mold growth for all storage times or conditions

  25. Results - Mass Loss • Mass loss (g) in sealed bags Relationship between mass changes (wet basis) and time in sealed containers.

  26. Results - Mass Loss • Mass loss (g) in open bottles • Under the same moisture content, the higher ammonia loading (TRT 8，9) resulted in higher mass loss • 60 wt.% moisture content resulted in highest mass loss • Highly dependent on ambient temperature and humidity 20 wt.% corn stover 40 wt.% corn stover 60 wt.% corn stover

  27. Results - Glucan • No significant reduction was observed between open and sealed conditions

  28. Results - Xylan • No significant reduction was observed between open and sealed conditions. • Higher ammonia loading tended to retain more xylan

  29. Conclusions • LMAA pretreated corn stover could be well preserved up to 90 days without mold growth nor reduction in carbohydrates • Lignin removal was more obvious in sealed bags • Mass loss in 0.2- was higher than 0.1 g/g biomass

  30. Impacts • 3 MS Students • 1 PhD Student • 2013-2014 • 5 conference papers at ASABE • 2015 • 2 conference papers at ASABE

  31. Thank you!Any questions?

  32. Optimization Conditions Suggested optimize conditions (Incubation conditions): Time: 79hr; Temperature: 67°C Ammoniation: 0.1 g NH3/g biomass

  33. Regression analysis of the mass loss of the seal containers.

  34. Methods

  35. Results --- Mass Loss • Mass loss (g) in open bottles • Highly dependent on ambient temperature and humidity • Under the same moisture content, mass loss remained almost the same amongst the ammonia loadings • The higher the moisture content, the higher the mass loss 60 wt.% corn stover 20 wt.% corn stover 40 wt.% corn stover

  36. Results --- Ash • General trend • Higher M.C. led to higher ash content • With increasing time, the difference in ash content tended to decrease.

  37. Results --- Lignin • Anhydrous ammonia has the potential to remove lignin.

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