The growing consumption of petroleum products has made gasoline the major energy source that drives our economy, our lives and our industry in the US. Over 37% of total energy used in the US was in petroleum last year (more than any other single source), and 70% of petroleum was used in transportation. In fact, we consume more energy in transportation than any other sector of the economy. The transportation sector is also the most energy inefficient one – largely due to Carnot limits compounded with other auxiliary factors as well. As the US consumes about 1/5 of the world’s production of crude oil, our growing demand increases the world price of gasoline, increasing the costs of energy for our entire economy, and the rest of the world as well. The US consumption of petroleum and other fossil fuels currently is responsible for 20% of world CO2 emissions, despite the fact that the US contains less than 5% of world population. Potential effects of greenhouse gas driven climate change would prove damaging to our natural resources, industry, agriculture and even our way of life.There are alternatives, but because of the massive infrastructure we have built around transportation (over 117,000 gas stations, 250M cars in the US) that would need to be somehow transitioned onto a different fuel, there are limits to potential alternative technology. There are four major alternatives to gasoline as energy storage (or fuel): ethanol, hydrogen, electric batteries and synthetic fuels. Out of those, the only one that exists on a comparative scale to the gasoline economy currently is ethanol, and even that difference is huge (10% of gasoline). In the near future, ethanol seems to be the only feasible option, although there are multiple ways in which it can be produced. Batteries are much less energy dense, so for the same amount of fuel require both more space and weight in a car, and also take longer to recharge than it does to fuel a car (the Nissan Leaf batteries take 30 minutes for 80% charge). Hydrogen suffers from a complex storage mechanism, and like batteries, requires completely different transportation infrastructure than is currently available. Synthetic fuels have been developed for military and experimental purposes, but are currently deemed to expensive for production on the regular market on a large scale. Overall, the US fossil fuel economy is changing, and the increasing price of crude is making other options, both in terms of fossil fuels and alternatives seem more economical.

Cars Love Gasoline

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The consumption of petroleum reached 19 million barrels per day in 2009. That is equivalent to roughly 1.8 gallons per person per day spent on transportation (70% of total petroleum use). Just for comparison, that is almost 40 times the amount of milk per person per day consumed in the US (3/4 of a cup in 2006). Over 50% of that oil in 2009 was imported, and on net imports the US spent over $194 billion on importing crude oil in 2009, 50% of which goes into production of reformulated motor oil, or the gasoline that we regularly put into our car (The rest goes mostly into diesel and jet fuel, but there is also LPG, propylene and various other products.). Since President Nixon and the oil embargo of 1973, every president has had a plan to reduce the US dependence on foreign oil, and despite that the US dependence on foreign oil has grown from 20% in 1974 to over 57% in 2008. President Ford increased the fee on imported crude in order to cut imports, and proposed developing synthetic fuels. CAFE standards were also developed during his administration. President Carter set the federal speed limit to 65 (though he really wanted 55) MPH, effectively punishing people for driving inefficiently, as well as developed the Department of Energy. President Bush introduced subsidies for ethanol production and facilitating opening up new oil reserves for drilling, mostly in Alaska and the Gulf of Mexico.

The main cause of our dependence on petroleum is such a combination of transport ease (using pipelines) and compactness of fuel, which is measured through the concept of energy density, the amount of energy per weight or volume. The energy density of gasoline is 46.4 MJ/kg, which is very high compared to even the most efficient lithium battery, currently at 6 MJ/kg. Using hydrogen would be fantastic as it’s energy density is almost 3 times that of gasoline, but storage and transportation of the fuel is still an open question, since we are talking about a gas that binds through everything over time, making any container brittle. The most energy dense fuels are radioactive components, such as those use in nuclear fission which can reach 3.5 TJ/kg in a commercial reactor, but we still haven’t realized how to reasonably put one into a vehicle beyond the Ford Nucleon.

During the latter part of industrial revolution, when most our energy systems were set up, for some of the US crude oil was cheaper than clean water, gallon to gallon. Originally, gasoline was an unwanted byproduct of production of kerosene, which replaced whale oil in the 19th century as the chief source of energy for lighting. The car was invented to take use of this cheap and plentiful fuel. The massive expansion of the gasoline power transportation that occurred in the 120 years since the Otto engine had been invented is a testament to the power of cheap energy. But our production hasn’t kept in step with consumption, and  has been shrinking since the 60s, due to production limitations and dwindling reserves.
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Efficiency: Further on Less

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In order to decrease use of gasoline, or attempt to level it off, various initiatives focused on energy efficiency have been developed since the 70s. Cars have been designed with lighter materials, with more energy efficient engines and components and with aerodynamics in mind, aided by government mandates in the form of the Corporate Average Fuel Economy (CAFE) standards, all of which resulted in the average fuel efficiency rose from around 18MPG before 1970 to over 27MPG today, with plans for going up to 35.5MPG by 2016. Other US government mandates include the Gas Guzzler tax and mandating fuel economy be stated on every new car being sold, verified through the EPA. So, while our cars today are about twice as efficient as 40 years ago, this has not kept up with demand for gasoline (or demand for large cars), and while it has certainly slowed the rate of expansion, it has left us with growing demand for gasoline, and need to consider potential alternatives.
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Replacing gasoline

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The development of gasoline as such a major part of our energy economy makes replacing it with anything hard. We require a similarly energy dense fuel, also liquid with similar chemical properties, but hopefully less polluting and available for domestic production. The only substance today that comes close is ethanol. But ethanol has a major drawback – it is a simpler chemical compound, with energy density of 24 MJ/L compared to gasoline’s 34.2 MJ/L. The practical application is while once car run most cars on 85% ethanol with some modification (which is currently all but impossible given the costs of aftermarket re-certification through the EPA), but if you filled up your tank with pure ethanol, you could only get 70% of the energy from ethanol that you would from gasoline. Meaning, on average, people would need to pump gasoline more often and use more of it for the same level of driving. However, ethanol can be made out of almost any carbohydrate or cellulose rich biomass, and as such has great appeal to a country with great amounts of arable land, such as the US.

Currently, almost all gasoline in the US is actually gasohol – 90% gasoline, 10% ethanol. That 10% of current use means that we produce around 13 billion barrels a year of ethanol currently. 95% of that ethanol is currently produced from corn, as corn is one the most abundant and cheapest sources of carbohydrates currently available. The US currently produces two fifths of the worlds corn, over 333 million tons every year. Yet, at 10% of our gasoline needs we are consuming over 30% of the US corn crop. The current area in the US under production of corn is 88 Million acres. Ignoring slight differences between kinds of corn crop, that means that about 26 Million acres of US land are used to grow 10% of our need for gasoline. That is roughly an area of the size of Ohio that we are currently using to grow corn for ethanol. Corn ethanol, by itself, is not enough to substitute gasoline as transportation fuel. We would need to triple the current US yield of corn (effectively producing more than the entire world does now) which would require an area one and half times the size of Texas (and only slightly smaller than Alaska) to have enough corn to produce on the level we are producing gasoline. Demand for ethanol from corn has also raised fuel prices and is partially to blame for the rise in food prices (especially meat) over the last decade. Thus, other sources of ethanol need to be considered beyond corn.

On an economic note, the refinement of crude oil into gasoline results in a myriad of by-products, some of which are crucial petrochemical feedstocks, integral components of lubricants, plastics, fertilizers, and others. These products not only make refinement more economically attractive, but allow for diversification of income and insulation against demand shocks of single products. Until industries such as biofuel refining can produce similarly useful and marketable by-products, they will remain to be less economically attractive than gasoline.
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The gaseous BOOM

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Natural gas has been considered as vehicle fuel in two forms – compressed and liquefied – since at least the 90s in the US. Natural gas has 40% less greenhouse gas emissions and even fewer pollutants for the same energy gain when compared to conventional gasoline. However, concerns about the coupled nature of the prices of gas and oil seemed to forecast the same future for natural gas as for gasoline. Recent innovation in hydraulic fracturing (know colloquially as “fracking”), horizontal drilling and new shale gas fields in the US have increased domestic production, reducing need for imports and served to decouple the price of gas from the price of petroleum. This has served to increase interest in natural gas as an alternative to other fossil fuels. Stable prices are causing natural gas to gain incremental competitive advantage over coal as fuel for the next generation of power plants. Natural gas does suffer from the same disadvantage as many other alternatives – it is mostly incompatible with the current infrastructure for vehicle fuel, requiring different fuel pumps, different standards and changes to the design of the vehicle. Currently there is only one vehicle on the market made in 2011 that can use natural gas. While the new discoveries will make natural gas more attractive, it remains to be seen how wide spread the adoption will be. “Fracking” also has potential environmental drawbacks in the form of chemicals used to fracture the rock, and the radioactive materials trapped in the shale along with the methane, which could, once released, seep into groundwater.
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Synth-fuels: A rose by any other name?

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Another option is to create synthetic fuels, which are liquid fuels created from other fuel sources such as coal liquefaction or gas liquefaction – both of which are conversion from one fossil fuel to another (thus not solving the greenhouse gas issue) and they require extra energy to create, or create fuels completely from basic components using a variety of chemical and biological processes. Using coal (which is abundant in the US) we can expand our reserves of gasoline, but at a larger energy cost with potentially even more environmental impact, as coal contains more impurities than crude that have to be disposed of in refining. Synthetic fuels processes have existed since the 1920s, but have not been developed into a major fuel resource due to their energy cost and lack of concern for the unavailability of other specific fossil fuels. Canadian Oil sands (tar sands, oil shale, officially known as bituminous sands) are today converted into crude oil with processes developed through fuel synthesis. Canada is the largest single supplier of crude to the US (20%), and almost half of that oil comes from tar sands. Thus tar sands represent about  6% of the total US consumption of crude, from a partially synthesized product. But while it is an addition to fuel sources for gasoline, it is not necessarily an alternative, and suffers from the same issues of pollution, climate change and eventual resource depletion, and potentially worse environmental degradation than coal mining. To avoid using more fossil fuels, we have to use less energy in cars or use a different energy source – such as ethanol, fuel cells or batteries.
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Delicious sugary ethanol

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Despite the US focus on corn, the second largest producer of ethanol in the world is Brazil, which sources it strictly out of sugarcane. Sugarcane ethanol has about twice the yield of ethanol from feedstock per hectare when compared to corn. Comparing the US & Brazil, input energy productivity (ratio of energy gained from energy used) for sugarcane is about 8 to 10 (this holds true only for Brazil, which has amazing conditions for sugarcane), whereas for corn ethanol it is about 1.3 – 1.6. Due to both of these factors, the greenhouse gas emissions reductions are roughly 86-90% of gasoline for sugarcane ethanol vs. 10 – 30% for corn ethanol. Other sources used for sugar ethanol are beets and molasses. While developing in the US, especially in the traditional sugarcane regions such as Louisiana, one of the reasons of the dominance for corn in the US are ethanol subsidies (currently at $.45 per gallon of ethanol produced from corn), and various other subsidies for corn production in general. Another reason is that the price of sugar that can be produced from the same sugarcane as ethanol is higher than the price of the ethanol. While growing, sugar-based ethanol is imported from Brazil and the Caribbean (despite the tariff on imported sugarcane ethanol from Brazil) to the tune of only 2% of total demand. The production of sugar-based ethanol is less than 2% of the total production of ethanol in the US. However, given the potential for growth in the Caribbean, sugarcane products might see a resurgence in the region as ethanol.
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The Giving (Ethanol) Tree

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Cellulosic ethanol refers to any ethanol that is produce from the cellulose membrane of the plant. There is a chemical (enzymatic) and biological (bacterial) ways of decomposing the cellulose and creating ethanol from it. This differs substantially from corn or sugar ethanol as the process can be used on new whole plants (corn, soy, wheat silage), non-edible parts of plants (corn and sugarcane bagasse), plant waste (wood-chips, lawn and tree clippings) and even trees (poplar trees) or algae. Other than starch/sugar content of plants, it covers most other ways to convert biomass into ethanol. These processes are less commercially available currently, and some of them have not been piloted yet, but there is a lot of academic work in the field. Several projects at Argonne National Labs are engaged in using switchgrass and poplar trees for the dual purpose of phytoremediation (removing toxins and metals from the soil using plants) and biomass growth for biofuels. Other projects at Argonne, such as the Institute for Atom-Efficient Chemical Transformations (IACT) are working on better and more efficient methods at producing ethanol from various feedstocks using enzymes and catalytics. These are some of many initiatives around the world furthering the knowledge and expertise necessary to build better fuels. While all of that is promising, in the world of ethanol, even if we use perfect other processes and use better feedstocks, the short-term future indicates that Corn is King. But even then, ethanol is far from an ideal replacement for gasoline.

There are still several issues with ethanol replacing gasoline; it is only 70% as energy dense, it requires retrofitting vehicles to use more than 30% of it in blended fuel (costing on average less than $500 per vehicle), and the current pipeline infrastructure needs to be adjusted to carry it. The biomass itself is expensive to transport (due to the weight of water in it), and unlike crude, it doesn’t have the same value-adding byproducts that make refining crude such a lucrative proposition. We also don’t know enough about long-term effects on using ethanol in regular engines, and what additional costs or benefits it might carry due to the difference in chemical composition. Finally, in the short term period of transition, each gas station would need to add another tank an pump that would carry the ethanol fuel, to a cost of about $200,000 per gas station. Retrofitting half of the cars in the US and half of the gas stations would cost $90 billion (125M cars, 100k gas stations), or roughly half of what we currently spend on oil imports. Which forces us to look at further alternatives to gasoline, currently: fuel cells and electric cars.
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Lighter than air, further away than fusion?

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While there are varied potential fuel cell technologies employing a wide variety of fuel including methanol and ethanol, alkaline solutions and polymer membranes, hydrogen has been touted as the most efficient and cheapest method to use. Hydrogen in a wonderfully energy dense fuel, and using it in fuel cells to create electricity for cars bypasses Carnot limits (which limit the regular Otto engine to maximum of 50% efficiency). Electricity gained there can be used to power very efficient, quiet and sustainable vehicles, with the only emission a steady drip of water. Because of no moving parts or combustion, fuel cells can ideally be extremely reliable. However, hydrogen is very expensive to store, and makes every container brittle over time. As it boils at -280 degrees centigrade, requires energy to be reduced to and kept at that extremely low temperature or under very high pressure to achieve the liquid form. It is also not readily available in nature, and requires either electricity and water, or fossil fuels to generate, and thus is energy costly to produce, and thus doesn’t resolve some of the issues that exist with regular gasoline in the first place, as we must use energy derived from fossil fuels to produce it. If there could be an economical way to produce, store and transport hydrogen, it would take off as the main fuel of the US economy, but as off yet, that hasn’t occurred despite efforts in California, S. Carolina and internationally, most notably Japan. In 2009 President Obama cut off hydrogen fuel cell funding from the federal budget, as other projects were deemed likely to have a faster impact on the market, and hydrogen to be “10 to 20 years out”.
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Cars with a buzz

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Electric cars actually predate the gasoline cars, but due to availability of gasoline as cheap fuel haven’t been developed in the same way over the last 150 years. Lately, however, needs for greater efficiencies and desire to overcome Carnot limits have resulted in a renewed pursuit of electric technologies in cars. The first generation of hybrid cars, using breaking and cruising speed to recharge batteries used in low speed acceleration, are a welcome addition to the market for those that wanted greater efficiency without sacrificing features or design, and will likely be implemented in all cars by over the next decade. However, pure electric vehicles (without a gasoline engine) have 2 major drawbacks. Firstly, energy storage in either fuel cells or batteries is currently neither economical nor practical (either expensive or weights too much), but it is none-the-less being developed by several major (Chrysler, Ford, GM, Daimler AG, Peugot-Citroen, VW, Toyota, Mitsubishi, etc.) and minor companies (domestic examples are Tesla and Zap). Secondly, unless using own generation means, consumers would use electricity from the grid, and add on to the base-load electricity demand, which is currently produced by coal, nuclear and natural gas. An electric car today is just a vehicle with an external fossil fuel combustion engine.
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So, what is the future?

Ethanol is not without its own economic, agricultural and environmental impacts, and in the long run we shall hopefully see other types of fuel developed as well, or use less impactful feedstocks, creating greater efficiency than currently available with corn. Greater knowledge of catalytics could improve processes and broaden the range of feed-stocks by which we obtain ethanol, as well as creating beneficial byproducts. Better battery technology would mean more efficient hybrids and less gasoline demand. Laterally disruptive technologies – such as more efficient and wide spread network of trains and rail, better commuter public transportation could reduce demand for fuel if they are economically attractive to the consumers. In the very long term, we might even want to re-examine the way cities are designed, how we travel, why we travel and how we transport goods and services in this country. But in the short term, we still need liquid fuels, and ethanol is currently the only marketable substitute, but that doesn’t mean that we are short on possible alternatives. The future, as always, looks very interesting, indeed.