Out of idle curiosity, I wanted to know how extensively wood gas technology could be deployed before it would result in serious deforestation. I did a back of the envelope calculation and arrived at the following numbers. You guys can check my assumptions on this.

There are about 136 million registered cars in the US.

The average car is driven about 12,000 miles per year.

A cord of wood will cary a car over 5,000 miles.

Therefore, it would require 136,000,000*12,000 / 5000 = 326,400,000 cords of wood to fuel all passenger cars with wood for a year.

One acre of average forest can supply 1.5 cords of wood on a perpetual basis.

Therefore, 217,600,000 acres of forest would be needed to fuel all US passenger cars.

There are about 747 million acres of forest in the US.

Therefore, 29% of US forests would be sufficient to supply perpetual energey for all passenger cars in the US.

This calculation does not include trucks and other commercial vehicles.

Hi Kyle, I have heard this question asked before but no one has actually attempted to break it down numerically for me.
I am probably not qualified to answer your concerns on this subject because I am so new to the subject myself, but I have picked up a few things that might shed some light onto the issue. Please, others chime in with your perspectives because this is a point that will come up as more people become acquainted with the woodgas movement.
I think that the largest misconception is that everyone, or even the majority, will get involved in woodgas. I really doubt this will be the case because of several factors. First, is the fact that all vehicles require lots of attention to use woodgas on a regular basis, some much more than others. With having to drain the condensate tanks every couple hundred miles, draining the tar every thousand miles, and cleaning out the bio-char buildup, not to mention the concerns of proper disposal of these byproducts we eliminate most housewives and those too busy or carefree to keep up with the necessary procedures. Next comes the issue that most cars are not designed for low maintenance use of woodgas. By this, I am referring to all vehicles with carburetors, throttle bodies, and air intakes that will need serious maintenance every thousand miles or so to remove baked on soot deposits and those with plastic intakes cannot be used at all. Let’s face it, the greater majority of drivers today just want to put gas in and go. Most of them are not even qualified to change the oil. Then we have to consider all of the vehicle owners who will not want or be able to carry numerous large barrels and cooling apparatus to generate and treat the smoke before introducing it into the engine. We also should point out that many people can’t or won’t want to give up the 25 - 30% horsepower that will result in the change-over to woodgas. But probably the most limiting of all factors is the point that Wayne Keith makes when he says that driving on woodgas is 25% machine and 75% operator knowledge and experience; simply put, most people don’t have what it takes to drive on woodgas. In addition, perhaps the final nail in the coffin of concerns about deforestation to drive us around is the fact that these units can drive on a much wider diet than just wood. Pretty much any sufficiently dried bio-mass will push these vehicles down the road. If we listen to and learn from Gary Gilmore, petroleum byproducts like recycled plastics and automobile tires can be used to supplement wood. Or just ask Mike Larosa about using tumbleweeds to drive on. Heck if worse comes to worse; we can recycle dried manure from all of God’s creatures, even ourselves. (Talk about puttering down the road…)
With all things considered, like Wayne has pointed out, probably only about 1% of the drivers will opt to go to woodgas. Even if things become dire on the petroleum horizon, I doubt if more than 10% ever change over.
So Kyle, I think you could reduce the wood demand by 90 – 99%. Heck we could probably fill that demand by simply diverting all wood that currently goes to landfills, not to mention all of the wood that is wasted in the act of clearing land for constructing buildings and roads.

hi, i have thought about this question before, and i think unless we have a very serious shortage of oil , there will never a great demand for bio-gas run vehicles, i agree with lou 99 + % of the people in the usa are spoiled , including myself, i went 45 years of my life without air conditining, now i just pay the higher electricity bill, and am happy to be cool in the summer time, lou is right i go to the landfills here sometimes 6 or 8 times per day, if 1/2 of the bio-waste was turned into gas it would run a million +++ trucks and a live tree would never need to be cut to run a gasifier. we have a waste disposal problem in this country especially around large cities, waste management is building a large plasma-gasification facility at thier eastern oregon landfill. it will generate electricity and reduce what has to be burried, there are several others built and bieng built around the country you do not hear much about it but they are building them. iF our country does not fall apart financially i think all landfills will be turned into gasification producers in 50 years ? it takes a un-common type of person to be willing to deal with a wood gas vehicle. a very independent motivated personality, most people would not do it even if it was easy and you gave them the wood chunks, they just want to turn the key, push on the gas and go. DAVID - O

HI Kyle and Lou, what concerns me is not the gifted amateur converting his truck to woodgas but what happens when industry wakes up to the possibilities of breaking down the gases and recombining them into synfuels on a global scale. That makes the resource a whole lot more convenient, shippable and tradable. It would probably always be expensive so that might slow down usage some. After watching over the last twenty years the reports on the tar sands development It is clear that mankind will go to any lengths to keep the lights on and the wheels turning. Good math by the way I had never seen the wood usage expressed that way. I think you are forgetting something though. If oil/natural gas become more pricey options the amount of wood used in heating would skyrocket. My area was bare of most of its tree cover 75 years ago and only heating oil allowed it to return. Then there is that during world war 2 the casual woodgasser ran on charcoal not wood so for every driver that wants an easier vehicle to operate he will be using 3 time more wood then a raw wood machine. I’m trying to incorporate heat recovery into my charcoal making but traditionally that was not the way charcoal is made. Just saying there are a lot of variables out there, just build cool machines and have fun.
best regards, David Baillie

Great topic. I did a little poking around and came up with an official study, here:

http://www.afandpa.org/temp/Forisk_Forest_Resource_Study_July_2010.pdf

From the report:

Nation-wide, 49.6 million dry tons of forest and wood-related residues are estimated to be “readily available” for bioenergy users. Logging residues represent the single largest source (57%); mill residues represent the smallest source (3%). This does not include ~5 million tons of unused, pulpwood-sized material.

“Readily available” includes wood residues that are (1) unused by other wood raw material consumers and (2) directly accessible with existing logging configurations without major capital reinvestments.

According to my back of the envelope calcs, if woodgassers all drove Dodge Dakotas and each drove at the same rate Wayne does (about 25k per year) then there’s only enough “readily available” wood for about 5 million woodgassers. The next 5 million will have to plant some trees.