In 2006 I warned about just how many trees a cellulosic ethanol plant could consume:
Let’s consider a typical mid-sized 50 million gallon per year ethanol plant. Using Iogen’s demonstrated yields, the biomass requirement would be 50 million/70 = 714,286 tons of biomass per year. According to Dr. Bruce Marcot, an ecologist at the USDA Forest Service the average Douglas fir yields about 1660 lbs of pulp (90% of the tree’s weight). So, to run a mid-sized cellulosic ethanol facility would require the equivalent of 714,286 tons * 2000 lbs/ton /(1660) or 860,585 Douglas firs PER YEAR. That’s a lot of biomass, and it puts into perspective the issue of a declining EROEI as biomass must be secured from farther afield.
Seems that people are starting to figure this out, as forestry experts are starting to wonder where Mascoma is going to get all of the trees to supply the cellulosic ethanol plant they plan to build in Michigan:
When Making Fuel From Wood, Be Sure You Have Wood
That’s the lesson Michigan is learning as forestry experts question whether the state can grow enough timber to support what could be the nation’s first cellulosic ethanol plant producing commercially viable biofuel from wood. Biofuel startup Mascoma plans to build the $225 million refinery near Sault Ste. Marie in Michigan’s beautiful upper peninsula. It is working with Longyear, a Michigan timber company that owns at least 100,000 acres of forest in the western part of the state.
The million refinery would consume 375,000 cords of timber — a cord measures 8 feet long, 4 feet wide and 4 feet tall – to make 40 million gallons of cellulosic ethanol annually. Therein lies the problem.
Of course if you saw my initial essay, you were aware of this problem a couple of years ago. Pretty soon they will figure out that while this may seem like an enormous amount of wood, at least it will go for a good cause. It will produce enough ethanol to replace 0.02% of our gasoline supply.