All us Atkins guys understand why it’s easy to make fuel out of corn kernels and sugar and hard to make it out of the rest of the corn stalk, sawgrass, sawdust, and other fibers. When we drive our spouses crazy by reading the label of every can and box to check for poisonous carbs, we’re allowed to disregard all carb grams for fiber. We can’t digest the carbs out of the fiber so they do us no harm; trouble is that current ethanol plants can’t digest them either.
Moonshiners know how to make alcohol from anything with sugar or starch in it; today’s ethanol plants are just stills on a large scale. Because so much energy has to go into growing an acre of corn, transporting it, and then distilling it, the net gain in either energy independence or reduction of co2 emissions from substituting ethanol for gasoline is small; some people even dispute whether there is any gain at all although evidence seems to be that there is. There is also a cost in higher food prices as kernels that might have become high fructose corn starch become motor fuel instead.
The problem is one that an article in Science Magazine calls by the wonderful name of “biological intransigence”. Seems that plants have stubbornly evolved in a way that makes their key parts indigestible by most other species and most enzymes. The plants are willing to give up the fruit around the seed to get the seed dispersed. They have to pack some starch somewhere both for seeds and for themselves. But they don’t want their fiber to be a tempting snack so they’ve locked it in tight chemical bonds. Currently it costs us more energy to break these bonds than we get back out – sort of like pistachios with a completely closed shell.
Some animals have evolved to digest fiber. Cows are a good example although it takes them four stomachs in a row to make the process work. Every dairy or beef farmer knows that cows are marvelous machines for converting grass into methane – trouble is most of that methane ends up in the atmosphere as a greenhouse gas much more potent than co2. There are beginning to be manure powered electrical plants, however.
I’m optimistic that the chemical crackers for fiber’ll be found. This is just an engineering problem and engineering problems get solved. At that point most of the agricultural waste stream becomes a source of transport fuel – less net carbon emissions and less need to import Mideast oil. All goodness. Note that using the inedible byproducts of farming for energy production helps decrease pressure on food prices and involves little incremental expenditure of energy since the food crops are being planted, fertilized, and harvested anyway.
In the short-term until biological intransigence is overcome, I have a suggestion from an Atkins POV: make all the high fructose corn syrup into ethanol instead of adding it every conceivable product and rendering those products inedible for us carb-shunners.