Team:Nevada/Project/Background

Consequences of our dependence on fossil fuels

The human race has become highly dependent on fossil fuels to meet its energy needs. In particular, global transportation infrastructures are built around vehicles that require petroleum derived liquid fuels. Unfortunately, because petroleum is a limiting resource and predicted to become scarce in the coming decades (Shafiee, S., and Topal, E. (2009). Policy 37, 181-189), our dependence on this resource is clearly not sustainable. The solutions to this problem are to either develop an alternative that can function as a direct replacement for petroleum as liquid fuel production or to invent modes of transportation that don’t require liquid fuel. While efforts for the latter alternative are emerging in the development of electric vehicles; efforts to address this problem in the near term will likely focus on the development of alternative liquid fuels. In addition to the economic consequences described above, the world is also experiencing drastic global climatic changes that can be traced back to our heavy consumption of fossil fuels. The increase in “greenhouse” gas emissions resulting from the combustion of fossil fuels has led to unprecedented increases in the Earth’s surface temperature (Mitchell, J.F.B. (1989).Rev Geophys 27, 115-139). Researchers forecast the occurrence of catastrophic events including rising sea levels, disease pandemics, crop failure and loss of biodiversity if these practices continue (Hughes, L. (2000) Trends in Ecology & Evolution 15, 56-61). World governments are prescribing policies to mitigate greenhouse gas emissions by curbing fossil fuel consumption. Unfortunately, without an alternative energy source such policies would cripple most industrialized nations.

Biofuels as Fossil Fuel Alternatives

The production of electricity from wind, solar, geothermal and nuclear sources will contribute greatly to replacing fossil fuels for residential and industrial energy needs. However, because we lack portable, high capacity means of storing electricity, it is currently not feasible to utilize electricity on a large enough scale to support long distance transportation systems. These systems include highly mobile forms of transport such as aircraft, automobiles, and trucks. Due to their high fuel density, liquid hydrocarbon based fuels remain the best option for these applications. Biofuels have several properties that make them ideal direct replacements to petroleum based transportation fuels. First, due to the high degree of synthetic diversity present in biology, naturally occurring or genetically engineered organisms are available that can produce chemically equivalent, or even superior compounds, as compared to current petroleum based fuels. Second, biofuels are ultimately photosynthetically derived from atmospheric carbon dioxide. As such the combustion of biofuels does not contribute to net increases in greenhouse gas levels.

Food vs. Fuel Controversy

Current first generation biofuels include biodiesel (vegetable oil) and bioethanol (fermented plant derived sugars). These fuel sources depend on available crop species which are primarily used as food sources for humans and livestock (Naylor et al. (2007)Environment 49, 30-43). For instance, corn, sugar cane and cassava, are the primary source of sugar for the fermentative production of ethanol. Biodiesel, on the other hand, is produced from edible oilseed crops including canola, soybean and palm. Using food crops as feedstocks for biofuel production is controversial because it can lead to an unbalanced situation in which the continuity of food distribution is disrupted. Early signs of such problems were seen in 2009 when ethanol subsidies by the U.S. government prompted biofuel producers to increase corn purchases (Gura (2009) Cell 138, 9-12), which lead to subsequent increases in corn prices. Corn represents a major component of livestock feed and as such a large spike in meat and dairy prices occurred (Hill et al.(2006) PNAS 103, 11206-11210; Pimentel et al. (2008) Energies 1, 41-78). The production of biofuels and biofuel fermentation feedstocks in non-food sources such as cyanobacteria and microalgae could be circumvent this problem.