November 12, 2012 § Leave a comment

There are some that say ethanol is for drinking not driving.  Other than the clever phrasing, the origins of this aphorism are in the low calorific content of ethanol as compared to gasoline, about a third less.  There is a reason that gasoline has endured for over a century as the transport fuel of choice: the energy density is high.

The country as a whole is seeking gasoline substitutes for environmental and balance of trade reasons.  The North Carolina legislature laid down a target for 10% of all transport fuel to be produced in state by 2017.  Biofuel was seen as the avenue and the Biofuels Center of North Carolina in Oxford took a lead in pointing the way.  Here we make a case for alcohol, both ethanol and methanol, to be considered as the dominant means of achieving that objective.

Both alcohols blend with gasoline effectively.  E85, a blend with 85% ethanol, is already available in many states.  The methanol analog, M85, was piloted in California some years ago.  Enabling either requires that cars are Flex Fuel cars, as many are today.  The conversion cost is in the neighborhood of $125 when done at the original factory.  Bills in Congress today on the Open Fuels Standard would require that most new vehicles by 2017 have flex fuel capabilities.

But North Carolina may not need the adoption of the high alcohol blends to meet the targets.  Both ethanol and methanol at the 10% level act importantly as oxygenates.  This is a property that allows a more complete burn of the fuel, which is good both for fuel economy and the environment.  But even if every drop of gasoline contained state grown alcohols, the legislative target would not be met because the state uses about a third as much diesel as gasoline.

There are two potential solutions to this numbers game.  One would be to simply increase the normal blend to 13% alcohol.  This would account for the diesel use without even counting the increasing use of biodiesel.  There are moves afoot in other states to permit an increase to 15% ethanol in gasoline.

The other measure to help with the problem would be to progressively require all diesel used in the state to contain 20 to 25% di-methyl-ether (DME).  This is completely feasible without engine modifications.  Furthermore, DME produces zero particulates and has a higher cetane rating, so it is an improvement over diesel in that regard.  From the standpoint of production, DME is easily manufactured in a methanol plant by using a simple additional process step.  So, a policy standardizing on alcohol as a gasoline substitute enables the production of a diesel substitute.

All biomass suffers from having low energy density.  One solution is to process the material to be denser prior to transport.  High pressure baling of cellulosic fiber and Torrefaction to produce high density pellets are two such measures.  Another approach is to bring the processing facility to the source.  This is particularly feasible for crops, because co-location can be planned.  The recently announced Chemtex plant to produce cellulosic ethanol additionally plans to take advantage of the low cost nitrogen fertilizer available in parts of North Carolina.  The source for the nutrient is hog waste stored in “lagoons”.  The liquid is sprayed onto fields and provides the fertilizing action at a fraction of the cost of ammonia fertilizer, which trades for over $600 a metric ton.  This underlines an interesting advantage for the state, provided all of this can be accomplished with acceptable air emissions, volatile organic compounds (VOC’s) to be specific.

Woody biomass is by far the most available biofuel raw material in NC.  The lignin component is notoriously difficult to break down for ethanol production.  But thermal processing to synthesis gas (syngas) is straightforward.  From syngas a variety of fuels can be synthesized.  Methanol is the simplest, closely followed by DME.  Both of these figure prominently in our proposed course of action described above.

An alternative starting point for syngas can also be natural gas.  In fact at prices today, it will be more cost effective than woody biomass.  The natural gas could be produced in state or imported from a neighboring producing state.  Regardless of where the raw material was sourced, the value added product would be produced in state and the jobs would be created here.

Some combination of ethanol, methanol and DME, augmented by existing biodiesel initiatives, is a viable means to achieve the legislative goal of 10% of transport fuel being produced in state by 2017.  For the state that pioneered prohibition there is a mild irony in alcohol playing a legitimate role in shoring up the economy.

Vikram Rao


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