By Jon Van Gerpen, Project Director, Biodiesel Education Program (Posted on October 18, 2010)
It has become popular lately to refer to biofuels as “first generation,” “second generation,” “third generation” and so on. First generation biofuels consist of ethanol from sugar or starch (such as from corn) and biodiesel from animal fats and vegetable oils. Second generation biofuels are those produced from ligno-cellulosic materials such as switchgrass or wood chips. At this point the definitions get a little less well defined, but third generation is usually defined as fuels from algae, and fourth generation status is claimed by every new technology seeking to promote itself as the next big thing.
The term “generation” carries a connotation of a sequence of time. It implies that higher generation fuels are superior to lower generation fuels and will replace them over time. First generation fuels are criticized for competing with food, for negative land use changes, for taking too much energy to produce, and for only being economically viable with government subsidies. Higher generation fuels are supposed to be free of these disadvantages and will provide greater supplies of low-cost fuel while helping to reduce climate-changing greenhouse gases.
Unfortunately, this understanding of the development of biofuels is based on false assumptions and leads to incorrect conclusions.
A better model for how the various biofuel options should be compared can be drawn from the petroleum industry and the manner in which petroleum is extracted. In a new oil field, about 5 to 15% of the petroleum rises to the surface under its own pressure and is known as primary recovery.
The amount of oil that can be produced by primary recovery is limited, so the desire for more petroleum leads to the implementation of more expensive and more technically sophisticated techniques such as water or CO2 injection to raise the pressure of the petroleum so it can be removed. These techniques are known as secondary recovery, and they allow extraction of an additional 30 to 50% of the oil.
The desire for even more extraction leads to tertiary recovery techniques such as steam injection that are based on lowering the viscosity of the petroleum so it can flow more easily toward the well.
The lesson to be learned from the petroleum model is that the desire to increase the supply of the product is met by introducing more expensive and more sophisticated technology.
In the same manner, biofuels should be categorized as primary, secondary, and tertiary. Primary biofuels are those which are least expensive and which require the least technology to produce. These are the low-hanging fruit, and include sugar and starch-based ethanol and biodiesel. Although requiring subsidies to compete with petroleum (which is itself subsidized, of course), these fuels have already achieved commercial status and market acceptance.
Ultimately, it should be expected that their success will cause the price of corn and soybean oil to increase to the point where additional production of the primary biofuel is not economically viable. To further displace petroleum with additional biofuel will require a move to secondary biofuels. These fuels will be more difficult to produce and more expensive. Cellulosic ethanol is likely to be the first fuel to enter the marketplace in serious volumes using straw or corn cobs/stover as feedstock. Although the feedstock is cheaper than corn, the processing is much more extensive, making cellulosic ethanol more expensive. If this were not the case, then this approach would already be the primary source for biofuel and corn would return to its traditional use as food for cattle, hogs and chickens.
Tertiary biofuels from algae will also be needed if we are to replace a major fraction of our current petroleum consumption. These fuels are even more expensive and involve even more difficult technical problems.
What we can learn from this model is that secondary and tertiary biofuels do not replace primary Biofuels—they supplement those fuels. Primary oil extraction is always preferred, but meeting the demand for petroleum requires supplemental oil from secondary and tertiary recovery. Primary biofuels will always be around and they will become increasingly profitable as higher fuel prices draw secondary and tertiary fuels into the market.
A criticism of primary biofuels is that the increase in demand for feedstocks causes an increase in food prices and land use changes. These impacts have been exaggerated in many cases or do not recognize positive benefits such as rural revitalization and higher income for farmers. It should be recognized that secondary and tertiary biofuels will be subject to these same criticisms if they achieve any level of success. Growing switchgrass to produce ethanol will be criticized for displacing food crops and requiring fertilizer. Gathering straw and stover will lower soil quality. Growing camelina on rangeland and algae in the desert will destroy delicate eco-systems. Biofuels do not come without drawbacks.
As a society, we have to make choices about how we want to allocate the costs of different fuel options. It seems clear we have opted to maintain our mobility. Now the question is whether the economic, environmental and societal costs of biofuels are sufficiently below those of petroleum to justify continued support.