ethanol production from corn was about 34% of the total corn crop.
Traditionally, the major consumers of our corn crop have
been livestock, and they still are the largest single consumer.
But you can see that this is now a much smaller proportion of the total.
This number has grown further, so by 2012, we're up to about 40%.
A very large proportion of our corn crop being used to make ethanol.
So, the thinking is that this is one of
the factors that's contributing to the increase in corn prices
that we've seen since 2005, which then puts pressure on
consumers who are buying products that have corn in them.
And especially putting a lot of pressure on livestock farmers who
now have to pay more for the, for their animal feed.
So, the thinking is, let's stop where we are now and not increase this any further.
So, the new re, renewable fuel standards still
have incentives to encourage the development of ethanol production
from other sources as well as other bio-fuels, but
leveling off the ethanol production where it is now.
So, how do we make ethanol from corn?
Well, corn kernels are packed full of starch, which is
a carbohydrate that can be easily broken down to, to glucose.
So, here is a diagram showing starch.
It's just a chain of glucose subunits, and on an industrial
scale you can break that down into glucose in one of
two ways, either through acid hydrolysis, or by adding an enzyme
called amylase, which just clips off these glucose units one by one.
So, to make ethanol from corn, the first step is to mash up the corn kernels.
And mix them amylase in these giant fermentors,
which are also have yeast added to them
and the yeast can then metabolize the, the
glucose that's released, to produce ethanol as shown here.
So, the, the glucose is going to metabolize
this, the yeast are going to metabolize the glucose in
the absence of oxygen producing ATP, which is a
form of energy that the yeast cells can use.
Breaking it down into these smaller or molecules and releasing,
in the process, two waste products, carbon dioxide and ethanol.
So, the yeast are not producing the ethanol because it's useful to them.
It's essentially a by-product of this metabolic
pathway that's actually toxic to the yeast.
So, this process can only go so far before the ethanol
builds up to a concentration that would kill off the yeast.
So, in practice, fermentation can only produce so much ethanol.
And, and in, in industrial ethanol production here we end up
with a sort of a beer-like liquid containing about 10% ethanol.
So, that's still mostly water, at that point.
And a lot more work is needed here to get this up
to a level of purity that makes it useful as a gasoline additive.
Basically, the next step is accomplished by a fermentation, okay?
So basically, you're taking this fermentation
slurry with a 10% or so ethanol.
Heat, and heating it up, taking advantage of the fact
that the boiling point for ethanol is lower than water.
So, you heat this up to the point
where the ethanol vaporizes but the water doesn't.
The ethanol vaporizes, and is collected here in this
tube, that's then cooled down so the ethanol returns
to a liquid state and is collected in a
separate compartment here, leaving most of the water behind.
Okay?
So that gets the ethanol up to 92
to 95% purity, and it's purified further by passing
it over these molecular sieves that mostly absorb
water, bringing this up to something like 99% purity.
So, an important thing to understand about, ethanol production from
corn then, is that this process requires a lot of energy.
This is the most energy intensive part of
corn ethanol production, is heating up this fermentation slurry
of enormous volume of liquid that's mostly water,
takes a lot of energy to heat that up.