© J. Dirk Nies, Ph.D.
Energy on demand, that’s what fuels provide. Logs lie dark and quiet upon the hearth, candles stand stoically upon the mantle, gasoline waits patiently in the tank, until we call upon their energy. But have you ever stopped to consider why these organic materials (logs, candles, fuel) do not spontaneously ignite and burst into flames? Why is a match or a spark needed to set them ablaze? Why don’t flammable materials catch fire of their own accord?
In a macabre way, Charles Dickens explored this idea. In his 1853 novel Bleak House, Mr. Krook, the malevolent, unctuous landlord and shopkeeper, dies of spontaneous human combustion. His living body was consumed by fire that started without the aid of an external source of ignition. Dickens relied upon documented cases as source material for Mr. Krook’s demise, such as the personal and deadly conflagration in 1725 of Nicole Millet, an innkeeper of Rheims, France. The Italian Countess Cornelia Di Bandi suffered a similar fate a few years later. Lest you think spontaneous human combustion is a passé superstition rooted in ignorance, Irish coroner Dr. Ciaran McLoughlin and his team of well-respected pathologists, scientists and fire officials certified this cause of death as the only plausible explanation for the fiery demise of Michael Faherty on the night of December 22, 2010.
I bring up these dramatic examples for two reasons, to jar us into questioning our assumptions and to highlight the necessity to our economy, and to life itself, of being able to store energy in stable forms and to release this energy in controlled and directed ways. Understanding these thermodynamic and kinetic processes leads to a deeper understanding of the dynamic balance and interplay between life and energy.
Consider this analogy. Imagine a pane of glass leaning at an angle against the wall. Now envision placing a marble on its tilted surface. As soon as you let go, the marble will begin rolling till it strikes the floor. This behavior reveals what energy wants to do. Energy wants to move downhill. Like water, energy seeks its lowest level. No outside effort is needed to roll a marble down an incline, to transport water from the mountains to the sea, or in the case of spontaneous combustion, to start organic materials burning. They all happen naturally.
If, however, this were the only force at play, it would be impossible to store energy. Without some sort of barrier, marbles will not stay put on the surface of an inclined pane of glass, water will move downstream, and energy will not maintain its perch. Without barriers at the atomic level, all organic compounds that contain carbon and hydrogen (sugars, carbohydrates, proteins, fats and fossil fuels) would instantaneously burst into flame when exposed to air. In the presence of atmospheric oxygen, the most stable, lowest energy forms of carbon and hydrogen are carbon dioxide and water. These two combustion products are what the carbon and hydrogen in foods and fuels naturally wish to be, and what they instantly would become, in the absence of any constraints.
On the other hand, if the barriers were insurmountably high, there would be no way to release stored energy and it could not be harnessed to do work. Fortunately, natural barriers exist that are of just the right magnitude to allow energy to be stored in chemical bonds, while permitting these bonds to be broken and energy released under the right conditions.
To help understand the effect of these natural barriers, imagine organic molecules as marbles sitting in a row on a glass shelf affixed to a pane of glass. Where the shelf and the pane meet, they form a “V.” All the organic marbles are held in the trough of the “V” keeping the marbles in place. Now imagine jiggling the glass. The harder the glass is shaken to and fro, the more marbles fall off the shelf and unto the floor.
Heat is like jiggling. Heat provides organic molecules with sufficient motion and vibrational energy to bounce out of these invisible but real energy barriers. Unlike marbles, however, as these organic molecules jump over and react with oxygen, they give off heat, thereby sustaining and perpetuating the process as long as there are fuel and oxygen in the proper proportions.
Turning now to a practical application in our lives, the most energy-intensive activity we do in our homes is to generate heat. In fact, two-thirds of all the energy we use in our residences is directed toward producing heat. We use this heat to warm our homes, provide hot water, and cook our food. According to the U. S. Energy Information Administration, Americans annually expend 45 percent of all residential energy to heat air. This is followed by our expenditures to heat water (18 percent) and to cook food (4 percent).
Most residential heat is derived from natural gas. Let’s take a look at how the chemical energy stored in methane, the principal hydrocarbon component of natural gas, is converted into heat.
In a gas-fired furnace, methane from the gas company comes in contact with oxygen from the air. In the presence of a flame, sufficient energy is available to overcome the natural barriers to allow reactions to occur. The carbon-hydrogen bonds of methane (CH4) and the oxygen-oxygen bonds of molecular oxygen (O2) are broken. The carbon-oxygen bonds of carbon dioxide (CO2) and the hydrogen-oxygen bonds of water (H2O) are formed. Specifically, each time one methane molecule and two oxygen molecules react, they are transformed into one carbon dioxide molecule and two water molecules. This reaction is repeated myriad times as methane flows through the burner and combines with oxygen. Excess energy, derived from the difference between the initial, higher energy arrangement and the final, lower energy arrangement of the atoms within these molecules, is released primarily as heat. With the use of heat exchangers, cold outside air is heated and this warmed air is delivered throughout the house.
Living organisms have another, more elegant, and more finely calibrated way for overcoming natural barriers and directing energy to perform useful work. Instead of crudely adding heat and allowing energetic molecules to react as they will, organisms selectively lower energy barriers using enzymes! These remarkable biomaterials are catalysts that facilitate reactions, select desired reaction pathways over others, and permit all this to happen at temperatures compatible with life.
At a fundamental level, life can be defined as the continuous process of obtaining, storing and releasing energy in directed, controlled ways. This concept holds true for our economy as well. We imitate life’s energy processes with our technologies. Hydroelectric power plants mimic photosynthetic plants in that they both continuously gather and store renewable energy from an outside source and transform this energy into useful forms. Automobiles and battery-powered electronics are like carnivores in that they consume energy obtained from an outside source to perform work.
In summary, our lives and livelihoods are not only dependent upon energy, but upon appropriate energy barriers as well. I will be mindful of this the next time I experience trouble lighting charcoal briquettes or starting my chain saw. I will chuckle at myself and be thankful that releasing energy in a measured way is as hard as it is. Firefighters and EMTs already have enough to do.