Burning wood wasteful

Warning: The following contains science and if you don't like science, you might want to stop reading now.

Okay, with the disclaimer out of the way, I thought that I would try to talk about some of the issues associated with energy production and consumption.

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Simplistically, energy is found in three forms. The first is electricity, the second is chemical, and the third is the direct use of geothermal (which is really a combination of a number of things including nuclear energy). The first two, though, are the important ones accounting for some 99 per cent of our energy use.

Electricity is the cleanest. It is simply the movement of electrons. No direct byproducts are produced. It can be turned on and off when needed.

And it has the potential for unlimited power.

That's the good news. The bad news is that electricity isn't readily available. It is rendered by the use of some other form of energy - the band gap in solar cells, the gravitational force of water in a hydro dam, or the combustion of methane and coal in a fossil fuel burning power plant which results in greenhouse gas emissions.

Electricity also has the disadvantage that it is very hard to store.

Secondary batteries - rechargeable batteries - are heavy and can only hold a limited capacity. (This is an area where I used to do research.) Electricity is simply not portable. We can use it to heat our houses, run our businesses, and light our cities but it doesn't work very well when it comes to powering our cars and other forms of transportation. Yes,

there are electric cars but their performance doesn't match up to that delivered by a chemical burning engine.

And from a "greenhouse gas" point of view, since 85 per cent of North American electricity is produced by burning fossil fuels, electricity is not really saving us anything.

That leaves that other form of fuel - carbon. Well, not really "carbon".

Carbon, by itself, is not a particularly good fuel.

The reason is that energy is not held within "chemical compounds" but obtained from the difference in energy between the starting materials and the final product.

At one end of the carbon-based fuel scale is a fully reduced molecule, methane. Methane is a central carbon surrounded by four hydrogen atoms each of which is bonded to the carbon. At the other end of the carbon-based fuel scale is a fully oxidized molecule, carbon dioxide. Carbon dioxide is a central carbon bonded to two oxygen atoms through

double bonds.

Energy is obtained from the differences in the strengths of the bonds holding the atoms together. That is, burning methane results in the loss of four carbon-hydrogen bonds and the creation of two carbon-oxygen double bonds. The difference is what we see and use as heat.

It is actually a little more complicated than that because oxygen molecules are involved as reactants and water molecules are generated as products, plus there are intermediaries along the way, but the essentially idea is that we can take hydrocarbons - molecules made

entirely of hydrogen and carbon - and convert them to carbon dioxide, resulting in the release of energy.

Anything that is partially along the scale will result in less energy being produced. That is, as the advertisements say, methane is the cleanest burning fuel giving the most energy per molecule of carbon dioxide formed.

Alcohols, such as methanol and ethanol, result in less energy because they are not hydrocarbons. They already have some oxygen incorporated.

They are partially oxidized and hence, have less energy per molecule of carbon dioxide produced.

Cellulose, the stuff that makes up trees, is also partially oxidized carbon. On a carbon dioxide molecule produced basis, burning wood is only 30 per cent and 50 per cent as efficient as methane.

The inefficiency of wood as fuel is not likely to be a major topic of discussion at the International Bio-Energy Conference that is taking place in Prince George this week but it should be.

The basic premise that wood based fuels operate under is that any carbon dioxide produced will be recycled into trees. But there is a word missing from that sentence and it is "eventually". It takes some 80 years or so for the carbon dioxide released today to be fully captured.

And with twice as much carbon dioxide being produced for the same amount of energy, that is a lot of additional greenhouse gases being introduced into the atmosphere in the short run.

This is a bit of a simplistic overview, but there are many more issues associated with bioenergy that need to be discussed - such as the "rebound effect". Hopefully, the conference will be addressing all of the issues with bioenergy and not just how to grow the industry, because we need to find the energy needed for economic growth without destroying the environment.

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