Why We Will Still Have Good-Ol' Oil Decades From Now

USS Clueless has an excellent analysis of why biomass will never replace petroleum as a major fuel source.

One of the biggest advantages of coal and oil is that they are high-energy, but also extremely concentrated. A relatively small capital investment in a single area can harvest a great deal of useful end-product. A big open-pit coal mine can justify hundreds of millions of dollars spent on big shovels and huge dump trucks, because the shovel can dig more than a ton of coal on each bite, and each dump truck can carry several tons of coal out of the mine. The coal can be carried by rail point-to-point from the mine to a big power plant to be burned, or to a nearby harbor where it will be loaded on barges or ocean-going bulk carriers. All of this can be done big because huge amounts of coal come from one place, and go to a small number of destinations. Since petroleum is liquid, it is even easier to transport via pipelines or ships.

Coal would be a lot less valuable if it was found as a layer one centimeter thick spread over an area the size of the states of Iowa and Nebraska; the collection process would defeat the purpose. How difficult would it be to gather it all? How much equipment would be needed? Would it make sense economically to buy it all, given that each piece of equipment could only collect a relatively small amount of coal? Unfortunately, it wouldn't.

But that's exactly what the situation is when you're talking about any kind of biomass as a source of fuel; it grows on the ground, and though you may get a lot of it, it's spread over an immense area and you can't do anything until you pick it all up first and collect it.

Also, sugars and alcohols are already partly oxygenated, which means they don't yield as much energy in combustion per unit mass. Effectively, they're already partially burned. For example, methanol is methane which is one quarter burned. Each molecule of methanol weighs almost twice as much as a molecule of methane, but contains much less energy. In general the oxygen in biomass increases the weight and decreases the energy yield compared to hydrocarbons in oil or the almost-pure carbon of coal.

It takes two tons of dried biomass to yield as much energy as one ton of anthracite, but biomass isn't dry to begin with. There are huge amounts of water mixed into it, which isn't combustible but is exceedingly heavy and interferes with or outright prevents combustion. Drying the biomass takes a lot of energy in its own right, and even then all you're doing is reducing the quantity of water. Of course, you can dry it by leaving it out in the sun, which works fine as long as it doesn't rain. Or you can collect it while still full of water and bring it to some sort of drying facility, but that means you're expending a lot of energy hauling water around. But even if you leave it to dry in the sun, you'll still be hauling a lot of water (just not as much).

In one hour, one of the huge dumptrucks in an open pit coal mine hauls far more than its own weight in coal, and all of that coal can be burnt. But that's because it only has to haul that coal maybe a mile or two, from inside the pit up to some sort of big conveyer belt or a rail facility. And that dumptruck keeps doing that, 24 hours per day over the entire year (stopping only for maintenance and repair). It only stops when the coal runs out, but the coal deposits are immense. (The majority of the world's coal is in North America.)

The equipment which would be used to collect and haul biomass would only be used for a couple of months per year, and would haul the biomass a much greater distance, with the biomass itself yielding far less energy per ton transported. The energy used for collection and transport becomes a significant percentage of the energy being harvested, and the capital investment isn't efficient because most of the equipment sits idle most of the year.

This analysis is based on the overall characteristics of biomass versus coal and oil, and please notice that I didn't even talk about how the biomass would be used. Details about how the energy present in biomass might be utilized don't change this big picture. A new catalyst for releasing hydrogen from cellulose doesn't change the fact that the cellulose can only be used with that catalyst after it's been picked up off of fields or collected from forests where logging has been going on and hauled to where the energy is required.

That reported metal catalyst is a breakthrough in conversion process. "Biodiesel" is a different kind of conversion process for biomass. So is ethanol as a fuel. But none of them alter the fundamental characteristics of the source material, which is not really acceptable for purposes of producing energy at the scale we need at a price we're willing to pay. (In fact, ethanol is a total loser: it costs more energy to produce it than it yields when burned as a fuel.) As a practical matter, some of these technologies end up being more useful as a way of helping specific factories and processing facilities turn what is now seen as waste into a useful product, and for that reason they're quite valuable, but only in specific places where the economic conditions are right. They make sense because the source material is already concentrated and because you used to have to pay to have it hauled away. But they don't scale up.