Let us start with some facts (Source: Sierra Club, 2014):
- Every day, the U.S. uses ~400 million gallons of oil to move people, goods, and vehicles.
- There are ~230 million gasoline-fueled vehicles in the U.S. that travel average 12,000 miles per year.
- About 70% of all oil used in the U.S. is used for transportation.
- About 70% of all oil used in the U.S. is imported from the countries at "high risk" of instability.
- Every day, the U.S. sends about $1 billion abroad for oil expenses.
While the demand for transportation fuels is increasing, the continuing dependency of the U.S. economy on the foreign oil has put the country in extremely vulnerable position with respect to meeting its transportation energy needs. This vulnerability is the critical motivator in searching for alternative fuels for vehicles and looking for alternative types of transportation as well. Sustainability of transportation basically means the flexibility and ability to provide for your own needs using the resources that are local, widely available, or renewable. What are the options there?
A number of alternatives (including both liquid and gaseous transportation fuels) have been a subject of research and implementation for the last few decades. Let us review the background behind those options. Click on the following links to read about the various classes of alternative fuels considered for transportation purposes:
All of the alternative fuels have their current advantages and disadvantages, which are briefly summarized in US DOE Data Table (U.S. DOE, 2007).
Please note, the second row of this table shows an important metric used to characterize fuels (not only transportation fuels) - energy content or energy density. It is measured in energy units per unit volume or unit mass of the fuel. For example, from the data in the table we can see that diesel and biodiesel fuels provide the highest amount of energy compared to other liquid fuels.
Alternative fuel supply chain and distribution
Viability of certain types of transportation fuels is closely related to the processing, supply, and distribution infrastructure. This is especially critical in the U.S. society and economy, which are heavily reliant on the usage of road vehicles for personal and industrial needs.
The following reading will introduce you to the strategies and facts associated to the transportation liquid fuel supply chains. This covers both existing renewable and non-renewable fuel infrastructures:
Report: Boutwell, M., Hackett, D.J., Soares, M.L., Petroleum and Renewable Fuel Supply Chain, Stillwater Associates, 2014.
While reading, try to find answers to the following self-study questions:
- What are the main types of liquid alternative fuels intended for transportation?
- What are the main feedstocks to produce those alternative fuels at the national scale?
- What are the main fuel delivery systems used to distribute petroleum and alternative fuels from the source of treatment to the consumers? Are those systems similar or must be different?
- Can you understand the nomenclature of ethanol blends? For example, what are E85 or B20 fuels by composition?