Ten fundamentals about bioenergy: Part 2
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Fundamental #2: Autotrophically derived carbon-hydrogen (C-H) bonds are the “currency” of renewable bioenergy fuels.
This is the second in a series of brief articles regarding ten fundamental components of bioenergy. Last week
we introduced the concept of autotropically derived energy, which
simply means the energy was created from organisms using inorganic CO2
and sunlight in the process we call photosynthesis. We may recall from
our middle school biology class that the chemical formula for the
photosynthetic process is:
Photosynthesis (Ps): 6CO2 + 6H2O + (light energy) → C6H12O6 + 6O2
The “light energy” which of course comes from the sun, is effectively stored as chemical energy in the C-H bond of the autotrophically derived six carbon sugar molecule we call “glucose.” The same C-H bond is the primary currency for energy in gasoline, ethanol, diesel, biodiesel, and interestingly in the bagel you had for breakfast this morning. When the C-H bond from fuel is burned in your engine, or for that matter from the bagel in your stomach, the H bonded to the C is replaced by oxygen (O).
The cleaving of the H bond actually takes a little bit of energy (the spark or compression in your engine), but the formation of the C-O bond in CO2 gives off energy. In your engine this process is called combustion, and the resulting energy from the formation of the CO2 is converted from chemical energy to mechanical energy when the oxidative explosion forces the piston down thus providing torque to the crankshaft. The somewhat similar though much less violent process going on inside your body from ingesting your morning bagel is called respiration. Like your engine, the body oxidizes the C-H bond, but unlike your engine, your body transfers the chemical energy to a storage molecule known as ATP.
You = Respiration:
C6H12O6 + 6O2 → 6CO2 + 6H2O + (energy)
Your E-85 car = Combustion:
2C2H6O + 7O2 → 4CO2 + 6H2O + (energy)
Next issue’s discussion: “The finite supply of fossil fuel.”