Biofuels in Transportation

Kitty Kwan
November 26, 2016

Submitted as coursework for PH240, Stanford University, Fall 2016


Fig. 1: Biofuels are created from natural products such as plants. In particular, bioethanol is made from corn. (Source: Wikimedia Commons)

Transportation plays an integral role in our every day lives, in the form of commercial and personal vehicles of all uses. The energy usage that goes into transportation is significant and many of these sources come from finite resources, raising the issue over sustainability and environmental impact. As a result, how our society produces, stores, and uses energy for transportation years from now will be very different owing to changing energy technologies and infrastructure. One alternative to fossil fuels is biofuels, which provide a carbon-free and sustainable liquid fuel that can be used for transportation.

Transportation Energy Now

According to data from 2015, the United States consumes 17.3% of the world's energy. [1] Of this energy, American transportation consumes 28% of total energy use in 2014. [2] Petroleum represents the source for a vast majority of the oil energy, comprising 92% of total US transportation energy use. [2] These values are staggering considering the finite resources that we consume yearly and the low efficiency at which we use our energy.

Opportunities for Change

American use of energy for transportation is a topic with strong implications for technological advancement in energy usage and development as well as economic trade. The issue of oil prices is prevalent and demonstrates the impact of transportation energy in our daily lives. In particular, one issue related to the imbalance between the use and demand of petroleum within the United States. So much of our oil energy is refined from petroleum, yet in 2014 the US's net import as a share of US consumption for petroleum was 26.5%. [2] As a result, the US has been dependent on other countries in the past for oil supply. This situation is changing though; the United States has greatly spurred its domestic oil production through the use of hydraulic fracking. While it reduces the United States dependence on other countries, this form of expedited resource removal is not sustainable given that it is a finite resource.

Increasing the lifetime of the energy resources will require that countries and the United States reduce its consumption. There are several opportunities that are supported by technological advancements.

Biofuel Alternative

One promising form of emerging technology is the use of biofuels as a replacement to petroleum. Biofuels are a source of renewable energy that can target the issues over sustainability and environmental impact (Fig. 1). Its main appeal is its potential for carbon neutral liquid fuel. While it could be an ideal substitute to petroleum, researchers and scientists are still working on issues such as increasing energy density and lowering cost of development. Despite these issues, biofuels are already gaining prominence within the energy space. One study predicts that biofuels could substitute 37% of US transport fuel in the next 25 years. [3]

In particular, two types of biofuels are important: bioethanol and biodiesel. Bioethanol is a sustainable source of energy produced from corn. It can currently used in low concentrations in gasoline cars and higher concentrations (85%) in special vehicles called Flex Fuel vehicles. [4] Bioethanol presents a unique way to ease away from gasoline, without cutting it out completely as vehicles are developed in the future that can run on higher concentrations of bioethanol. In the future, bioethanol cost can be reduced, its energy density can be increased, and infrastructure can be updated to making bioethanol a more viable alternative.

© Kitty Kwan. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] "BP Statistical Review of World Energy," British Petroleum, June 2016.

[2] S. C. Davis, S. W. Diegel, and R. G. Boundy, "Transportation Energy Databook, Ed. 34," Oak Ridge National Laboraqtory, ORNL-6991, August 2015.

[3] S. C. Hunt, "Biofuels for Transportation," Worldwatch Institute, June 2006.

[4] S. Pietsch, "Flex Fuel Vehicles in the U.S.: Why Are We Lagging Behind Brazil?" Bioenergy Connection 3, No. 1, 33 (2014).