Energy Accounting and Firewood

 I have a compact farm tractor that I use for chores around my property, like collecting firewood. It's great for that purpose. I can drive back into my woods and drag full sized logs out to my firewood chopping area in a few minutes. I can probably retrieve and chop up a cord of wood in about 1 hour--probably less. Without the tractor it'd be an all day project or maybe a 4 hour project if I built some specialty tools to move the logs.

It takes much less than a gallon of diesel to run the tractor to collect a log. However, the energy embodied in the tractor is significant. There's a few thousand pounds of steel there, huge tires, and many pounds of non-ferrous metals like aluminum and copper. Also, the tractor requires a pretty significant amount of maintenance and consumable items, like filters for oil and fuel and air. It probably costs about $2/hour to run the machine and properly maintain it. I wonder if I'll ever harvest enough firewood to balance out the energy embodied in the tractor.

The answer is almost certainly "no", which is pretty crazy if you think about it for a while. The overall industrial system created a product that is a net-loser of energy. Most of the people in my neighborhood, which is pretty rural, have some similar machine in their garage. I use mine much more than they do, typically, but still, there's a huge amount of energy sunk into the tractor fleet in my neighborhood.

It's only possible to build a machine like a tractor and have a big "energy debt", because energy is pretty close to free. There's a huge quantity of what's essentially stored solar energy in the form of fossil fuels underpinning economic activity and the production of products like my tractor.

If we had to rely solely on current-energy, e.g. from solar panels, it'd be insane to make things like my tractor or even electric cars. Some portion of current energy is needed for day to day activity, like heating and running water pumps or for necessary transportation. In theory, whatever surplus we had could go toward production of consumer goods, tools, etc... or to things like a tractor.

It would probably make way more sense to use horses and simple labor saving devices rather than high-energy-content equipment.