Leaving no hydrocarbons unburned

By Alan Linda | The Daily Journal

Published Tuesday, February 5, 2008

Folks often come up to me and ask: “What about burning wood? What about burning corn? Even: (once) What about wheat?” They wanted to know the cost comparisons between these fuels and oil, gas and electricity.

So here’s another trip down mathematics lane. Before summarizing the various amounts of BTUs that you can get for a penny from various other fuels, first we need to define one BTU (British Thermal Unit). If you burn one wooden kitchen match from head to toe, and it takes one hour, it will give off one BTU .

One BTU will warm one pound of water one degree. Water is always the substance against which all other energy-absorbing materials are compared. For example, air is much less dense, and because it is, it warms up four times faster than water. It also holds heat one-fourth as well as water.

Briefly, you can get about 1,000 BTU s of off-peak electrical heat for a penny, 400 BTUs of liquid propane for a penny, 450 BTUs of oil heat for a penny, and 700 BTUs of natural gas, or methane, heat for a penny. That’s today. Tomorrow, except for electricity, who knows.

Electricity is stable for a couple of reasons: First, we get ours made with western coal, and there’s a lot of that; second, electrical rates are subject to oversight by various government agencies, and, unlike oil and gas, cannot whimsically fluctuate at the slightest wish of the market.

Third, we’re talking about off-peak electricity — power companies are trading you cheap power for their ability to shut you off and level off the loads on their generating facilities.

First, let’s consider wood heat. Wood is normally purchased by the cord, which is a neatly arranged stack of wood four-feet-by-four-feet-by-eight-feet. A cord is not all the wood you can throw helter skelter into the back of a pickup truck. It has to be stacked neatly. How much heat you get depends upon the pounds of wood that you are burning, not the kind of wood. Apple, oak, and birch top the charts for weight per cord, and hence, BTUs. (More weight, more hydrocarbons, a hydrocarbon being anything that will burn.) A cord of oak at 20 percent moisture will weigh in the neighborhood of two tons.

At this point, no matter what you paid, if you just bought 20-percent moisture wood, you just bought 800 pounds of water. (20 percent of 4,000 pounds.) Dry fuel is important. Remember, all dry fuel gives off approximately 6,000 BTUs per pound — paper, oats, corn, wood, switchgrass, straw, etc. Oh yeah, and wheat.

Electricity is 100 percent efficient, gas burns at up to 92 percent efficiency, oil 80 percent. Depending upon how wet it is, wood may easily fall below 50 percent. The type and condition of the stove in which you burn it also severely affects its burning rate.

Nonetheless, let’s attempt some BTU comparison here. Say for example that you have a cord of dry oak delivered to your home for, oh, $150. Wood, like other various hydrocarbons, has about 6,000 BTUs of heat energy per pound. 6,000 BTUs per pound times 4,000 pounds divided by 15,000 pennies (what you paid for it, in cents) times 50 percent efficiency gives you 800 BTUs for your penny.

Dry it some more, burn it in a good furnace, the efficiency goes up, maybe to as much as 1,200-1,300 BTUs for your penny.

Now for corn, which also has about 6,000 BTUs per pound available for burning. Corn is normally stored at around 13 percent moisture content, and is currently selling for $4 per bushel, which is 56 pounds. Take 56 times 6,000, divide that product by 400 pennies, multiply that result by some efficiency, (let’s use 70 percent, because the exact figure again depends upon the dryness of the corn) and you have approximately 600 BTUs per penny.

For what it’s worth, burning wheat or oats can also be calculated, as can nearly anything, once one knows how much it costs and weighs, because all dry fuels give off around 6,000 BTUs per pound.

Obviously, burning corn, since its price went up, is no longer hugely advantageous. There’s no chimney with these kernel burners, so that increases their natural efficiency somewhat. They vent directly out the side of the house.

Some folks have removed their indoor corn burners because they emit particles of soot and ash inside the house, which, although invisible, do become a problem over time. If your corn is a little bit damper than 12 to 13 percent, it will build troublesome clinkers inside, and won’t work well.

If you plan on burning field-run corn, and the moisture content is high, your costs also will be high, because your efficiencies will plummet. However, if you’re a farmer and raise corn, this method of heating your home becomes a pre-tax scenario, and leaves the rest of us wishing we could deduct heating expenses from our IRS form, too.

There. I’ve left no bridges — or hydrocarbons — unburned.

Alan Linda writes from his home in New York Mills.