Analysis regarding the use of earth's sustainable resources and regenerability indicate that society is currently on an unsustainable path. In fact, if everyone lived like Americans, people would require 5.2 earths to be sustainable. "The picture is not terribly pretty," McBride admits.
Currently, the transportation sector accounts for 27 percent of the United States' total energy consumption. In 2006, 11 percent of the American gross domestic product was made up of energy sector. Finding a cheap and sustainable source of biofuels is critical to the future of the United States.
So why hasn't the United States made the switch from petroleum fuels to biofuels?
Making biofuels is also a slow, inefficient process. Petroleum industries are currently 85% efficient, a rather large efficiency ratio in the petrochemical industry. Research is still being conducted to determine the efficiency of biofuel production.
The process to create biofuels involves multiple steps in which energy is lost. Biomass is first pretreated, biologically processed by bacteria and enzymes and then distilled. In addition, thermochemical processing can also be performed on the remnants of the biomass to obtain process heat and power for the plant that is producing the generating the biofuel. "Thermochemical processes go very well with the biological processes," McBride said.
Coal often provides the process heat needed for the biological processing steps, resulting in unnecessary greenhouse gas emissions.
As a result of the carbon released through the production of biofuels, wide opinions have emerged about the sustainability in biomass utilization.
"Land conversion issues are the center of biofuel conversion," McBride said. Each time land is converted to be used for biofuel production, the capacity to produce something else, often food, is reduced. Biofuels are commonly created from foods rich in starches (corn), sugar (sugar beets) and oil (soy beans).
Carbon debts accompanying the conversion of land can take several decades to repay.
Surprisingly, environmental impacts are not a big concern with the production of biofuels. Plants used to create biofuels actually reduce erosion and stabilize the soil nearby. Wildlife and biodiversity also increase as a result of the plants. Even better, net carbon displacement can actually be negative. Carbon is both absorbed by the plant and remains in the ground after a harvest.
Biomass productivity is also another highly debated subject. Surprisingly, switchgrass is more productive than soybeans in terms of biomass output and cost. Research has also begun on the effects of planting double crops to yield a greater throughput per acre.
Currently, the U.S. Department of Agriculture and Department of Energy estimates that there are 600 million tons of residual biomass not being collected or converted. Tapping into these untouched sources could help alleviate an energy crisis.
Satisfying the United States' current vehicle energy demand with biofuels will require 1030 million additional acres devoted to typical biomass production. With advanced processing techniques utilizing process heat, this number could be brought down to 410 million acres. If biomass crops were converted from soy to switchgrass, only 10 million additional acres would be required.
John McBride is a graduate of St. Olaf with majors in mathematics and biology. He is currently pursuing a Ph.D. in biochemical engineering from Dartmouth. McBride currently works for Mascoma Corp, a company commercializing sustainable energy from cellulosic biomass.