Biomass → Ethanol Pathway

biomass

organic material used as feedstock

lignocellulosic biomass

plant material made of cellulose hemicellulose and lignin

pretreatment

first step to open biomass structure

steam explosion

high-pressure steam then rapid release

dilute acid pretreatment

low acid breaks hemicellulose

alkaline pretreatment

base removes lignin

delignification

removal of lignin

lignin

rigid polymer in plant cell walls

cellulose

structural carbohydrate in plants

hemicellulose

polymer surrounding cellulose

recalcitrance

resistance of biomass to breakdown

hydrolysis

breaking polymers into sugars

enzymatic hydrolysis

enzymes break cellulose

acid hydrolysis

acid breaks biomass chains

saccharification

conversion to simple sugars

cellulase

enzyme breaking cellulose

hemicellulase

enzyme breaking hemicellulose

glucose

six-carbon sugar

xylose

five-carbon sugar

fermentable sugar

sugar usable by microbes

fermentation

microbes convert sugars to products

yeast

microbe that produces ethanol

ethanol

two-carbon alcohol fuel

distillation

separates ethanol

dehydration

removes water from ethanol