Woody Biomass

by Matthew Hall

The search for biofuels continues, and woody biomass is back in the spotlight. Seneca Sawmills is planning to build a wood fired generator to produce electricity. They are planning to haul slash piles from their clear cuts and burn them to run a steam turbine. Of course there are many environmental concerns with the city of Eugene in regards to the particulate and smoke pollution this will create. These slash piles would under normal conditions be burned on site after a logging operation. So in this sense, burning them and producing electricity is a better option. However, one has to ask how much fossil fuel will be required to transport these slash piles to the steam turbine. I am interested in seeing the ration of diesel consumed by transportation and preparation to the Kilowatts of energy produced.

The forest service is currently examining as old process with a new twist. On August 30th, the Register Guard ran an article on fast pyrolysis, which is a way of creating wood oil from wood chips. Again it requires energy to run the machinery, although a mix of gases are also produced which could be used to at least contribute to fueling the process. The article goas on to say that there are 11.6 million dry tons / year of woody biomass that could be produced from forest service land. This is enough to make about 40 million barrels of bio-oil. Here is the real shocker, 40 million barrels of bio-oil is equivalent to 8 days of U.S. oil production (not consumption).

The sobering fact is that the U.S. consumes 20.68 million barrels of oil per day. The conversion of 11.6 million tons of dry woody biomass to wood oil would provide us with approximately two days worth of our oil consumption. If you include fuels for transportation, thinning and other energy expenditures, the real return of energy will be reduced to 60 – 65% of the total (based on information from Dr. Mark Harmon of O.S.U.). That will reduce our production to barely more than 1 days worth of nation oil consumption*.

The focus on biofuels is, of course, the production of liquid fuels that can be substituted for petroleum products. There are more simple, old-fashioned methods that use the biomass as is, without converting it to a liquid fuel. For instance, the Hull-Oakes sawmill (west of Alpine) runs its main saw and some of the resaws on 60% of the sawdust generated by the mill. Originally this sawmill was completely powered by steam, as were many sawmills at the turn of the century and up into the 40’s. Similarly, the early steam donkeys, which were used at the same time, were logging winches powered by steam generated by burning wood from the logging operation.

In World War II Germany, civilians ran their cars on wood smoke created by burning logs (slowly smoldering) in a firebox attached to the side of the car. Of course, they probably cut their logs with a bowsaw or an axe, therefore not expending any fossil fuels in the preparation of their wood fuel (there weren’t any fossil fuels for them to use anyway).

At Aprovecho we use woody biomass in a direct way. All of our heating, cooking, and some of our hot water is fueled by firewood; simple, straightforward, and requiring a minimum amount of petroleum to process and haul. In addition, the amount used every year is roughly equivalent to one-tenth of the annual forest increment (growth) of the entire 40-acre site. Our firewood consumption is also equivalent to about one-tenth of the annual carbon sequestration of the 35-acres that we have in 54 year-old production forest.

Consider that much of the forest service and other federal and state lands that need to be thinned to reduce hazardous fuels are in remote areas. Haulage costs are high, and the expense of petroleum fuels is correspondingly high, which will subtract from gains made by creating bio-oil from these forest products.

I think that using wood as a biofuel makes a lot of sense in a local situation. For instance, it would make sense for Aprovecho to generate electricity from its own forest products as they are already on site. Individual forest-based communities could reduce their own dependence on foreign oil using simple low-tech methods of deriving energy from wood. Regardless of what energy source is used to generate the power we need, it’s obvious that we all need to use less of it. Even though wood is a renewable resource, Aprovecho’s forest can only produce so much of it per year. If we exceed those levels of annual increment, our use will be unsustainable.

* The use of woody biofuels are linked to the perceived need to reduce hazardous fuel buildup on 652 million acres of federal, state, and private lands nationwide. Onsite production of wood oil is seen as a potential way of adding value to the low-value, expensive to haul, products that would come out of thinning these lands.


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