Cellulosic EthanolJonathan Boyd

Introduction

Ethanol is derived from a wide variety of plant materials

Two main sources today are corn starch and sugarcane

Cellulose is the material that gives the plant its structure

Cellulose can not be used for food or feed

Recent advances in technology make it a more viable option

What is Cellulose?

General term used to describe hemicellulose and cellulose

Comes from stalks, stems, and leaves of plants

Makes up 60-90% of terrestrial biomass

Can come from many sources including switch grass, prairie grass, woody

crops, and residential and forestry remains

Easiest material to make ethanol?

Sugarcane is the simplest where yeast digests simple sugars and converts

them into ethanol

In corn starch enzymes are needed to break down long glucose chains so that

the yeast can digest them

Cellulose needs even more work to break down tightly held glucose chains

which are packed quite differently

How is cellulosic ethanol made?

Two main steps: pretreatment and fermentation

Pretreatment is used to break down the cellulose and hemicellulose

Done with a physical step and chemical step and ending with hydrolysis

Fermentation is where the yeast digests the sugars and produces ethanol just

as you would with any other material

What makes cellulosic ethanol difficult?

Trying to take the structure of the plant strip it down and break it into small

glucose chains

The glucose chains are tightly packed to help protect from disease

Pretreatment is currently the most cost intensive part of production

Scientists are looking for ways to reduce cost and for enzymes that will work

more effectively

Advantages to cellulosic ethanol

Cellulose is very abundant

It is not used as food or feed

Significantly improves GHG emissions

Depends on the composition of ethanol

Berkely study estimates a 90% reduction in comparison to petroleum based

fuels

Project Liberty

First commercial production cellulosic ethanol plant located in Emmetsburg,

Iowa

Started production September 3, 2014

Uses corn stover as the cellulosic material (cobs, leaves, husks, upper stalks)

Estimate 20-25 million gallons of ethanol every year

Consolidated Bioprocessing (CBP)

Mascoma is the company leading the way in CBP

Developed specially formulated yeasts that also have necessary enzymes to

break down the sugars

Their yeasts can also break down xylose which means better yield

Using 11 enzymes allows them to achieve 90% hydrolysis yield

Cellic CTec3

Enzyme produced by Novozymes

Aids in the process of breaking down cellulose and hemicellulose

Works 1.5 times better than the previous CTec2

Allows you to use 1/5 the amount compared to competitors

Conclusion

These advances in technology have greatly helped make it a more viable

option

Ethanol is something people are already used to and something current

vehicles will run off of

Only time will tell which technology becomes most prevalent