Growing Our Fuel
It is time to revisit the question of using biomass as the feedstock for our liquid fuels, as it is looking more and more like we will have few other choices.
While converting coal to liquid fuels is possible and obviously popular in coal producing states, there are limits on how far coal can go to replace oil as a source for liquid fuels. If coal consumption increases rapidly to meet the need for liquid fuels, then our estimated 250-year supply would quickly turn into a 50-year supply and we would be back where we started. Converting one fossil fuel into another may be a reasonable short-term transition strategy, but it is not going help our grandchildren.
Before going further, it needs to be pointed out that, at present, there seems to be no way growing fuel can make up for the 325 billion gallons of petroleum products the US uses each year.
Even if we take the most optimistic projections, that the US can produce 1.5 billion tons of biomass (plant and other organic material that can be converted into ethanol) per year, and assume we can process 100 gallons of ethanol out of each ton, we only come up with 150 billon gallons of liquid fuel per year.
Therefore, there is simply no alternative to massive conservation efforts both in the short and long run. The US can no longer be a consumer of 21+ million barrels of oil per day— especially with our natural gas supplies showing signs of running low.
Many are skeptical we can ever grow a significant portion of our fuel needs, as biomass currently is contributing only about three percent of US energy consumption. However, recent studies and research breakthroughs offer hope.
Last spring, a joint study prepared by the US Departments of Energy and Agriculture concluded the country could remove some 370 million dry tons of biomass from our forests each year and could grow an additional billion tons of biomass on agricultural land on a sustainable basis. If this proves to be the case, it appears the raw biomass would not be a problem.
How might a large scale biomass-to-fuels industry work? First, growing and processing biomass is going to be a local industry compared to the way our oil companies currently work. Hauling millions of tons of grass or tree branches across the country to large centralized processing plants will not work because you would use a large portion of the fuel you are trying to make hauling the raw material to a distant processing plant. Thus, growing and processing biomass into fuel is going to be a cottage industry with hundreds or thousands of small to medium sized processing plants scattered all over our rural areas.
Perceptive readers will start to see why the big oil companies, who are used to oil fields yielding millions or even billions of barrels, can't get too excited about building thousands of mini-refineries in rural counties and arranging for the biomass feedstock to be grown by thousands of farmers.
The product from processing biomass into fuel would be either biodiesel or ethanol. Neither of these products is new. They currently are widely sold in Midwestern states as a way of using up the oversupply of corn and soybeans the US has been producing in recent decades. Urban readers might not be aware that average corn yields in the US have gone up from 20 bushels per acre in the 1930s to over 160 bushels per acre today and are projected to increase to over 200— if our fertilizer production holds out in the face of natural gas shortages.
During the current era of cheap oil, converting surplus grains to fuel is primarily a way to help US agriculture by increasing the demand for its products even if it takes a government subsidy. The fact corn based ethanol is taking nearly as much energy to produce as it is yielding is not particularly relevant.
All that is about to change. As the price of conventional liquid fuels increases above the cost of producing biomass into fuel, the demand for ethanol made from crops quickly will surge to undreamed of proportions. The issue of "we have to eat too," of course, will put a limit on the portion of our food crops that can be turned into motor fuel
Without going too deeply into the chemistry of converting plants to fuel, biomass has edible components (starch, food oils, and protein) and non-edible components (lignin, hemicellulose, and cellulose). While there still appears to be some room for growth in converting edible biomass (soybeans, corn, rapeseed) to fuel, the real jackpot will come from the non-edible components, called lignocellulosic biomass.
There currently are four ways of converting lignocellulosic biomass into the ethanol that can be used in an internal combustion engine. They all work at laboratory scale and, as yet, it is too early to tell which technology will be the most cost effective when scaled to industrial quantities. The various conversion techniques are said to yield from 60 to 130 gallons of ethanol per ton of biomass feedstock. There is currently a pilot conversion plant working up in Canada .
One of the more promising sources of grown-for-fuel biomass is a native American plant called switchgrass. This grass, which can grow up to nine feet tall, is a perennial requiring low inputs of fertilizer, yet yields 5-8 tons per acre. At 65 gallons of ethanol per ton, each acre could produce about 425 gallons per year. Right now, the cost of growing and converting switchgrass to ethanol can't quite compete with gasoline even at $2.25 per gallon, but when the price of oil moves higher than locally produced ethanol, it will become very attractive.
For those concerned with global warming, it should be noted that biomass based fuels are "carbon neutral." That means the carbon released when ethanol or biodiesel are burned was recently absorbed from the air as the plant was growing. Thus, there is no net addition of carbon to the atmosphere as there is from burning fossil fuels whose carbon was absorbed from the atmosphere eons ago.
The last point to consider is how we can start producing and consuming biomass for fuel prior to the advent of very expensive gasoline. The trouble is it will take many years or decades to get a nationwide biomass-based ethanol industry going. Establishing a good stand of switchgrass can take three growing seasons and a lot of work.
One early step might be to require a small percentage of switchgrass be added to the fuel in coal-fired power plants. This would not only reduce emissions from the power plant but would establish a market for switchgrass prior to the construction of lignocellulosic processing plants.
The bright spot in all this is that American agriculture, which has been suffering from low agricultural prices wrought by 60 years of heavy fertilization and pesticides application, now has much better prospects. The arrival of peak oil, coupled with the developing shortages of natural gas and the consequent demand for coal, will leave biomass as the least costly source for transportation fuels. Farmers as well as the environment will certainly do better.
The sooner we can get started on this new paradigm, the better for us all.