Renewable Motor Fuels (Past, Present and Uncertain Future)

By Arthur M. Brownstein, formerly Manager, New Ventures Technology Division, ExxonMobil

Growing concerns over global warming have led to Congressional enactment of renewable fuels legislation for motor vehicles.  This has led to considerable international activity in the development and commercialization of such fuels.

This activity is concisely captured in a new book published by Elsevier Inc. in November 2014 — you can find out more here. The author, Arthur M. Brownstein, is retired from ExxonMobil where he was the Manager of the New Ventures Technology Division.. The following is an abstract of the book.

The 2005 biofuels legislation had the Renewable Fuels Standard (RFS) as a centerpiece.  This stipulated that a minimum volume of biofuels by type, such as ethanol, must be used annually in U.S. motor fuels.  The basis for the RFS was the Energy Policy Act of 2005 that provided tax incentives and loan guarantees for innovative energy development of various types. This was quickly followed by the Energy Independence and Security Act of 2007 (EISA).  The second Act extended the domestic biofuels target to 36 billion gallons by 2022, established new categories of renewable fuels, and set minimum targets for each.

The legislative rush to renewable fuels to solve a perceived energy shortage and to minimize global warming, resulted in a boom in the fermentation of cornstarch for production of ethanol. The quick decision to focus on cornstarch to produce ethanol was not surprising since its technology was well established and corn supplies were abundant.  Congress was also aware of the success of Brazil who had developed energy independence based on the successful fermentation of their sugar cane to fuel ethanol.

In the years following 2002, U.S. production of fuel grade ethanol soared from 2 to 14 billion gallons.  Motor fuel quickly commanded 40% of U.S. corn consumption and food prices rose dramatically. This was the unintended consequence of the 2005-07 legislation.  To resolve an untenable situation, EPA pressed fuel ethanol producers to use cellulosic waste materials in place of cornstarch. The producers were fined in 2012 for non-compliance for the use of cellulose technology that was clearly only in the early stages of its development and unavailable commercially. This was rescinded after a court action.  Efforts to develop the technology are continuing with some recent commercialization of new plants.   Since then, ethanol production by cornstarch fermentation has fallen out of favor and its growth has declined dramatically.

There are two general avenues of approach in the production of ethanol from waste cellulose.  One is to ferment the cellulose directly, and the other is to first convert it to synthesis gas and then ferment the resulting syn gas to isobutanol and/or ethanol. Interest in isobutanol as a fuel has increased dramatically, and there are efforts to convert existing cornstarch and cellulose fermentation plants to isobutanol in place of ethanol.  As a motor fuel, isobutanol has a number of advantages over ethanol and could conceivably replace it entirely. The synthesis gas based processes that produce isobutanol can also produce diesel fuel.  Both isobutanol and diesel , when based on biomass, qualify under the EISA legislation as a renewable fuel.  Some major oil companies expect biodiesel to surpass gasoline as the primary motor fuel by 2020. In the view of the U.S. Energy Information Agency, diesel and isobutanol may account for the majority of all renewable fuels by 2022.

Natural gas has hovered in the background over renewable fuels development since 2005.  It plays a competitive as well as a complementary role. It must be borne in mind that combating global warming was as much a factor in Congressional renewable fuels legislation as the alleviation of a perceived energy shortage. The advent of fracking was simultaneous with the introduction of the Renewable Fuels Standard. Global warming notwithstanding, although the subsequent enormous growth in U.S. natural gas and oil reserves might slow the growth of renewable fuel, many developers have looked to natural gas for the production of the synthesis gas to be used for renewable fuels.

Insofar as natural gas is concerned, there is an expectation that heavy duty vehicles and passenger cars may be powered by natural gas itself.  Finally, there is the electric automobile as a hybrid or as a fully battery or fuel cell powered vehicle.  The fuels use to power such cars, can also be could be used to generate the electricity from the power plant itself.

Billions of dollars have been expended in federal, state and private funding to develop a large number of renewable fuels technologies.  Many of these expenditures have gone for naught.  There will be a few winners until history repeats itself and introduces issues not yet contemplated.  The history of  motor fuels is littered with the bodies of past innovations.  Diesel was introduced in the 19th century, then abandoned and later rediscovered.  The electric automobile was the primary means of powering a vehicle in the early 20th century until petroleum derived gasoline became more economical.