Why My Chemistry Students Are Ethanol Skeptics

The chemistry behind ethanol and gasoline tells a slightly different story than the one most commonly told by proponents on both sides of the ethanol debate. Should ethanol investors be worried about how these numbers are interpreted?

May 4, 2014 at 1:10PM

Ethanol has more than its share of critics, most often due to issues with using food crops for fuel or negative effects on the performance of small engines. At the center of the argument for or against the use of ethanol as a fuel is the environment, with recent reports of more harm than help being done for the environment when considering the use of conservation land for corn planting and total carbon dioxide emissions throughout the entire process from planting to production of ethanol.

Even more core to the issue of ethanol as a fuel is the chemistry that explains and quantifies how much energy is generated by the fuel. I ask my students to evaluate ethanol based solely on its merits as a combustible fuel and the amount of carbon dioxide (CO2) generated from its combustion, leaving arguments over process efficiencies to Archer Daniels Midland (NYSE:ADM) and the arguments over engine performance to Briggs & Stratton and the American Petroleum Institute, which lobbies heavily on behalf of ExxonMobil (NYSE:XOM), Chevron (NYSE:CVX), and other American oil companies. Instead of listening to proponents and critics citing contrasting studies, let the chemistry of gasoline and ethanol tell the story.

Simplifying things
To compare the amounts of energy generated by gasoline and ethanol using just the knowledge gained in a General Chemistry course, a few significant assumptions need to be made. For ease in the calculations, gasoline is assumed to be 100% octane (C8H18), thus not taking into consideration longer, shorter, and unsaturated hydrocarbons or the 10% ethanol that would typically be found in a gallon of non-premium unleaded gasoline.

The two components used to evaluate the two fuels are energy generation per gallon, measured in kilojoules (kJ), and the environmental impact as determined by the amount of CO2 produced, in pounds, per gallon of fuel.

Energy per gallon
The reaction enthalpy (amount of heat produced by the reaction) for the combustion of octane is calculated by applying Hess' Law to well-established enthalpies of formation for the reaction products (CO2 and water) and reactants (the fuel and oxygen). The initial calculation gives a value in units of kilojoules per mole, which is then converted using molar masses, densities, and standard measurement conversions to units of kilojoules per gallon. When all of the conversions are complete, octane is shown to generate approximately 118,000 kJ per gallon, and ethanol is shown to generate approximately 80,000 kJ per gallon.

These chemistry calculations provide the fundamental reason why the fuel efficiency of a flex-fuel vehicle drops considerably with the use of E85 (a fuel blend of 85% ethanol and 15% gasoline) versus premium gasoline fuel. Across the board independent of the specific vehicle or manufacturer, EPA estimates for flex-fuel vehicles show a 25%-35% decline in realized miles per gallon when E85 is used in place of premium gasoline, which matches very closely with the 32% decline in energy generated between the two fuels in the chemistry calculations above.

As a consumer, the often bigger consideration is the cost of filling up one's vehicle. Given an expected 30% decline in fuel efficiency when using E85 over gasoline, the cost of E85 would need to be over 30% lower than the cost of regular gasoline to be the better financial choice. In other words, with the average price of premium fuel at $4.01 per gallon, the price of E85 would need to be under $2.80 per gallon to provide a financial justification for its use (the current national average is $3.21 per gallon).

Carbon dioxide per gallon
Consumers using E85 in favor of gasoline often cite environmental reasons for their choice, having been sold on the idea that ethanol is a cleaner fuel that produces less greenhouse gases than gasoline. A look at the reaction stoichiometry (remember balancing reactions in chemistry class?) can quantify just how much CO2 is produced. Per gallon, the combustion of ethanol produces about 12.6 pounds of carbon dioxide. The combustion of one gallon of octane produces about 18.1 pounds of carbon dioxide.

When comparing gallons to gallons, ethanol comes out on top as the clear victor in the carbon dioxide emissions test, which is just one component in the overall greenhouse gas emissions consideration. The grander view of the situation, however, should take into account how the amount of CO2 produced relates with the amount of energy produced because emitting less carbon dioxide per gallon does little help for the environment if more gallons need to be used to travel the same distance. When all of the calculations are combined, the amount of carbon dioxide generated by ethanol per kilojoule of energy generated is within 5% of that for gasoline.

The takeaway
The more important consideration than the chemistry behind the fuels is how the general population chooses to interpret the chemistry. A portion would undoubtedly cite the chemistry as a reason why gasoline remains superior to ethanol while a different portion would argue that the chemistry shows ethanol is a reasonable substitute for gasoline that supports the goal of American energy independence. In either case, the nation's largest ethanol producers have little to worry about in terms of a mass revolt against their fuel.

Regardless of the energetics, America has accepted ethanol as a viable blending component for gasoline. Even the American Petroleum Institute has accepted ethanol as a part of America's energy future, and they have gone so far as to conduct initial research suggesting the safety and effectiveness of increasing the ethanol blend limit from 10% to 12%. As for my students and the rest of the American public, very few will actively seek out higher ethanol blends while the vast majority remains content filling their gas tanks with whatever is cheapest and most readily available at the pump.

3 stock picks to ride America's energy bonanza
Record oil and natural gas production is revolutionizing the United States' energy position. Finding the right plays while historic amounts of capital expenditures are flooding the industry will pad your investment nest egg. For this reason, the Motley Fool is offering a look at three energy companies using a small IRS "loophole" to help line investor pockets. Learn this strategy, and the energy companies taking advantage, in our special report "The IRS Is Daring You To Make This Energy Investment." Don't miss out on this timely opportunity; click here to access your report -- it's absolutely free. 

 

Shamus Funk has no position in any stocks mentioned. The Motley Fool recommends Chevron. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.

1 Key Step to Get Rich

Our mission at The Motley Fool is to help the world invest better. Whether that’s helping people overcome their fear of stocks all the way to offering clear and successful guidance on complicated-sounding options trades, we can help.

Feb 1, 2016 at 4:54PM

To be perfectly clear, this is not a get-rich action that my Foolish colleagues and I came up with. But we wouldn't argue with the approach.

A 2015 Business Insider article titled, "11 websites to bookmark if you want to get rich" rated The Motley Fool as the #1 place online to get smarter about investing.

"The Motley Fool aims to build a strong investment community, which it does by providing a variety of resources: the website, books, a newspaper column, a radio [show], and [newsletters]," wrote (the clearly insightful and talented) money reporter Kathleen Elkins. "This site has something for every type of investor, from basic lessons for beginners to investing commentary on mutual funds, stock sectors, and value for the more advanced."

Our mission at The Motley Fool is to help the world invest better, so it's nice to receive that kind of recognition. It lets us know we're doing our job.

Whether that's helping the entirely uninitiated overcome their fear of stocks all the way to offering clear and successful guidance on complicated-sounding options trades, we want to provide our readers with a boost to the next step on their journey to financial independence.

Articles and beyond

As Business Insider wrote, there are a number of resources available from the Fool for investors of all levels and styles.

In addition to the dozens of free articles we publish every day on our website, I want to highlight two must-see spots in your tour of fool.com.

For the beginning investor

Investing can seem like a Big Deal to those who have yet to buy their first stock. Many investment professionals try to infuse the conversation with jargon in order to deter individual investors from tackling it on their own (and to justify their often sky-high fees).

But the individual investor can beat the market. The real secret to investing is that it doesn't take tons of money, endless hours, or super-secret formulas that only experts possess.

That's why we created a best-selling guide that walks investors-to-be through everything they need to know to get started. And because we're so dedicated to our mission, we've made that available for free.

If you're just starting out (or want to help out someone who is), go to www.fool.com/beginners, drop in your email address, and you'll be able to instantly access the quick-read guide ... for free.

For the listener

Whether it's on the stationary exercise bike or during my daily commute, I spend a lot of time going nowhere. But I've found a way to make that time benefit me.

The Motley Fool offers five podcasts that I refer to as "binge-worthy financial information."

Motley Fool Money features a team of our analysts discussing the week's top business and investing stories, interviews, and an inside look at the stocks on our radar. It's also featured on several dozen radio stations across the country.

The hosts of Motley Fool Answers challenge the conventional wisdom on life's biggest financial issues to reveal what you really need to know to make smart money moves.

David Gardner, co-founder of The Motley Fool, is among the most respected and trusted sources on investing. And he's the host of Rule Breaker Investing, in which he shares his insights into today's most innovative and disruptive companies ... and how to profit from them.

Market Foolery is our daily look at stocks in the news, as well as the top business and investing stories.

And Industry Focus offers a deeper dive into a specific industry and the stories making headlines. Healthcare, technology, energy, consumer goods, and other industries take turns in the spotlight.

They're all informative, entertaining, and eminently listenable ... and I don't say that simply because the hosts all sit within a Nerf-gun shot of my desk. Rule Breaker Investing and Answers contain timeless advice, so you might want to go back to the beginning with those. The other three take their cues from the market, so you'll want to listen to the most recent first. All are available at www.fool.com/podcasts.

But wait, there's more

The book and the podcasts – both free ... both awesome – also come with an ongoing benefit. If you download the book, or if you enter your email address in the magical box at the podcasts page, you'll get ongoing market coverage sent straight to your inbox.

Investor Insights is valuable and enjoyable coverage of everything from macroeconomic events to investing strategies to our analyst's travels around the world to find the next big thing. Also free.

Get the book. Listen to a podcast. Sign up for Investor Insights. I'm not saying that any of those things will make you rich ... but Business Insider seems to think so.


Compare Brokers