Alkaline pretreatment of wheat straw “Analytical methods for non-wood raw materials and their products and processes” COST FP0901 meeting, 19-21 August 2010, Hamburg Richard Gosselink, Hans van der Kolk, Paulien Harmsen, Robert Bakker Outline presentation (cid:1) Wheat straw biorefinery (cid:1) Alkaline pretreatment (cid:1) Analytical tools (cid:1) Highlights results (cid:1) Available samples for Round Robin COST PF0901 2 Wheat straw biorefinery concept S L Clark et al. 2006 3 Pretreatment (cid:1) Goal (cid:2) Fractionation of lignocellulosic to cellulose, hemicellulose and lignin (cid:2) Make cellulose and hemicellulose fractions more accessible for enzymatic hydrolysis (cid:2) Make lignin available for higher-valued products (cid:1) Numerous processes (cid:2) Mechanical, chemical, enzymatic (cid:2) Acids, alkaline, organic solvents (cid:2) Combinations thereof 4 Alkaline pretreatment (high pH) (cid:1) Alkali induces swelling of biomass, leading to increase of internal surface area (cid:1) Disruption of lignin structure (lignin removal) (cid:1) Reduction of cellulose crystallinity (cid:1) Results in improved accessibility of cellulose and hemicellulose towards enzymatic hydrolysis 5 Alkaline pretreatment (cid:1) Common alkaline pretreatment route (cid:2) Base as catalyst (NaOH, Ca(OH) , ammonia); T<120 °C 2 (cid:2) Carried out under (close to) atmospheric conditions (cid:2) Long reaction times (hours) (cid:2) Need for chemical recycling (cid:1) Improve alkaline pretreatment (cid:2) Apply milder process conditions • Less formation of degradation products (e.g. inhibitors) • Lower operational costs (cid:2) Improve accessibility of sugars to enzymes (cid:2) Obtain lignin of high purity 6 From wheat straw to fermentable sugars Wheat Enzymatic Pretreatment Polymeric sugars straw hydrolysis Monomeric Lignin sugars (cid:1) Enzymatic hydrolysis Fermentation (cid:1) Pretreatment efficiency (cid:2) Conversion of solid fraction (cid:2) Properties of solid fraction (cellulose-rich) • Glucan to glucose Ethanol or • Biochemical composition • Xylan to xylose (cid:2) Properties of liquid fraction (cid:2) Standard procedure ABE • Sugars, organic acids and lignins in • 50 °C, 120h solution • Excess of enzyme • Recovery of lignin (GC220) 7 Experimental setup Base case: 4h alkaline pretreatment in stirred reactor (cid:1) Preliminary experiments (2 L, 70 °C) (cid:2) Base case (cid:2) Effect NaOH-concentration (cid:1) Main experiments (200 L, 90 °C) (cid:2) Base case (cid:2) Extrusion (cid:2) Refining 8 Analytical tools (selection) (cid:1) Biochemical composition untreated & pretreated straw (solids) 500RnCG070918 #27 [modified by User, 5 peaks manually assigned] ECD_1 (cid:2) Extraction (ASE) 400 300 (cid:2) Carbohydrates (HPAEC-PAD) 5 - Glucose - 19.733 200 (cid:2) Lignin (AIL by weight, ASL by UV) 100 (cid:2) Ash (TGA, ignition) 0 1 - fucose - 5.221 73- R- hAarmabnion4so -es G e- a1- l21a.2c0.t08o00s0e - 61 7- .X07y3 -l3 oMsaen -n 2o4s.e0 5- 0285 -. 6935 2-0 .3648.3033 (cid:2) Proteins (N by Kjehldahl or Dumas, AA by UPLC) -100 min 0.0 10.0 20.0 30.0 40.0 50.0 (cid:2) Morphology (SEM) 0.70 0.60 3934 - 20.121 (cid:2) Cellulose cristallinity (WAXS) 0.50 0.40 AU (cid:1) Liquids 0.30 0.20 (cid:2) Carbohydrates (monomers, oligomers) 0.10 0.00 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00Minu1te8s.00 20.00 22.00 24.00 26.00 28.00 30.00 32.00 34.00 (cid:2) Lignin SSaammpplleeNNaammee:: OOrrggaannoossoollvv lliiggnniinn AARRDD 12 (cid:2) Fermentation inhibitors (phenolics, organic acids by LC) AliphaticOH Internal std SyringylOH GuaiacylOH (cid:1) Isolated lignin p-CoumarylOH (cid:2) FT-IR (cid:2) Impurities (carbohydrates, proteins, ash) COOH (cid:2) MWD (alkaline SEC)1 (cid:2) Functional groups (31P NMR)1 Cond. Arom.OH 1Gosselink, R.J.A. et al.Holzforschung 2010 9 Pretreatment efficiency Solid fraction 100 Other Ash (TGA) %) 80 14 Lignin 17 wt 23 18 Hemicelluloses ( n Cellulose o 20 i it 60 30 s o 27 p 26 m 24 o 22 c 40 l a c i m e h oc 20 36 38 44 41 i 33 B 0 Wheat 0% NaOH 6% NaOH 9% NaOH 12% NaOH straw NaOH-conc as wt% dry biomass 10