Mikrobiell förbehandling

Guido Zacchi, LTH

Develop and optimise pretreatment of lignocellulosic agricultural raw materials and rest products

1. Pre-pretreatment to facilitate storage and to facilitate the pretreatment

2. Perform pretreatment at milder conditions with a high yield of carbohydrates and minimal degradation of sugars

3. Improve the production of biogas from the stillage after SSF of pretreated material

Overall aim

Should result in better utilisation of the agricultural residuesi.e with higher energy efficiency and lower production cost

The influence of impregnation with lactic acid on sugar yields from steam pretreatment

Organic acids (Lactic acid) :

Weak acids (Less corrosive, lower degree of neutralization)

Biodegradable to produce biogas

Ensilage (crop preservation method)

WWT

Fermentation

Biomass

Pretreatment EnzymaticHydrolysis

Distillation

Sep

CHP

Biogas

Lignin

Stillage

SSF

Yeastcultivation

Dehydration Ethanol

Heat & Power

AD

Sludge

Liquid

Pretreatment influences all other process steps!

Schematic process

Pretreatment conditions OM-S OM+S TM-S TM+S Ref Ref.L

Storage with lactic acid (months) 1 1 2 2 - -

Concentration of. Lactic acid (wt%) 0.5 0.5 0.5 0.5 0 0.5

Impregnation with SO2 (wt%) 0 2.5 0 2.5 2.5 0

Temperature (C) 210 200 210 200 200 210

Residence time (min) 5 5 5 5 5 5

Pretreatment conditions

0

10

20

30

40

50

60

70

80

90

100

Glu

cose

Xyl

ose

Glu

cose

Xyl

ose

Glu

cose

Xyl

ose

Glu

cose

Xyl

ose

Glu

cose

Xyl

ose

Glu

cose

Xyl

ose

OM-S OM+S TM-S TM+S Ref. Ref.L

Enzymatic hydrolysis

Pretreatment

The influence of impregnation with lactic acid on sugar yields from steam pretreatment

Sugarcane bagasse

Suga

r yie

ld (%

of t

heor

etica

l in

the

raw

mat

eria

l) OM: One month storage with Lac

TM: Two months storage with Lac

Ref.: Impregnation with SO2 only

Ref.L: Impregnation with Lac only

-S: Only storage with Lac

+S: Storage with Lac and impregnation with SO2

Sugar degradation products(g/100 g raw material)

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

OMB-SO2 OM+SO2 TM-SO2 TM+SO2 Ref Ref.L.acid

HMFFurfuralSum

Conc

entr

ation

(g/1

00 g

raw

mat

eria

l)

OM-S OM+S TM-S TM+S Ref. Ref.L

Straw

Pretreatment SSF Distillation

SepBiogas

Solid

Stillage

Ethanol

ADLiquid

Slurry

Straw

Pretreatment SSF DistillationSep

Biogas

Solid

Stillage

Ethanol

AD

Liquid

Scenario 1

Scenario 2

Steam pretreatment of wheat strawThe influence of impregnation with acetic acid

Steam pretreatment of wheat strawThe influence of impregnation with acetic acid

Acetic acid concentration

Ene

rgy

effic

ienc

y (%

)

Lignin assumed to be used for process heat + electricty

Ensiling – for storageOleskowicz-Popiel et al, Biomass and Bioenergy 35, p2087 (2011)

CropsFresh maize (whole crop)

Fresh rye (whole crop)

Fresh clover (whole crop)

Enzymatic hydrolysis and SSF tested forFresh material

Ensiled material

Pretreated ensiled material (190 C, 10 min at 6% DM)

Ensiling – for storage (2)Enzymatic Hydrolysis

Yiel

d (g

glu

cose

per

100

gra

m c

ellu

lose

)

Maize Rye Clover

Fresh material 29.9 39.0 41.8

Ensiled material 29.0 28.1 34.5

Ensiled + pretreated material 72.0 80.7 75.7

Ensiling – for storage (3)SSF (with S.cerevisae)

Overall ethanol yield % of theoretical based on available C6 sugars in raw material

OBS The materials contain also some starch! Some of the sugars are converted to acids during ensiling

The use of an organic acid (or silage) for storage has improved the pretreatment.

Biogas production after pretreatment with an organic acid works well (data not shown).

Next step is to consider also pentose fermentation as an option and investigate more crops/residues

Perform real ensilage on selected residues

Conclusions

Acknowledgements

Swedish Energy Agency

PhD students: Sanam Monavari, Elisabeth Joelsson and Pia-Maria Bondesson