The Silver Bullet: Plug-in Biofuel Hybrids

The trash bin of car history is filled with failed attempts to produce an emissions-free petroleum-liberated automobile. Hydrogen, ethanol, compressed natural gas, battery-electric, and ultra-lightweight cars have all been trotted out as silver bullet solutions, only to fail the tests of practicality and/or market acceptance. Environmentalists and policy wonks fed up with the next technology-du-jour have swapped silver bullets for silver buckshot, often described as a “portfolio” approach to reducing tailpipe emissions and oil dependence.

Unfortunately, by giving up on an ultimate answer, we have become too timid to choose any winners and losers. That’s a shame, because it looks as if the silver bullet is right before us: the plug-in biofuel hybrid. Let’s parse these words and technologies.

Why Plug In?

We should definitely be plugging in our cars—for one main reason: electric ‘fuel’ is cheap. At $2 a gallon, it costs about 13 cents per mile to gas up a conventional vehicle with a city EPA rating of 15 mpg. The same vehicle cost 26 cents per mile with $4 gas—which hopefully we won’t see again (but don’t count on it). Of course, Europeans are still paying more than $6 a gallon, most of it tax.

How much does it cost to run a 4,000-pound car on grid electricity? If you charge it overnight, about 2 cents per mile, and during a relatively expensive recharge during the day, about 6 cents per mile even with relatively expensive public re-charging.

There are obvious environmental benefits for running as many miles as possible from electrons, but the limited range of full battery-electric cars, and the cost of those batteries—considering limited battery durability—means that lifetime costs are prohibitively high. For example, if a battery lasts 50,000 miles—say 2,000 recharge cycles times 25 miles per day—and costs $5,000 to replace, it adds 10 cents per mile to the overall cost-per-mile of the vehicle. Until battery durability improves and costs fall much further, it will be difficult for most economically rational American car buyers to justify purchasing a battery-only vehicle. But that doesn’t mean throwing away the batteries. Time to hybridize.

Why Hybrids?

It’s a matter of physics. As a car speeds up, it requires more energy to cover each mile, and the main reason is air resistance. At city speeds, air resistance is almost irrelevant, so small battery-only cars and delivery vans will be able to provide acceptable range with small and relatively inexpensive batteries when running at city speeds. However, take a battery-only vehicle on a free-flowing freeway—if you can find one—and a tall, blunt, electric van or SUV might need twice as heavy and expensive a battery to cover the same distance.

The answer is to extend the range of an electric vehicle by adding a small engine running liquid fuel. That was the idea behind the original hybrid concept—from more than 100 years ago. Get the batteries to carry you for the first few miles of each trip, but once the batteries have been drained, fire up the engine to drive the wheels.

Dramatic reductions in battery cost, size and weight will be needed before an all-electric vehicle will become as economically viable as a plug-in hybrid with the same functionality. Don’t hold your breath.

Why Biofuel?


Electricity can take us most of the way toward reduced oil consumption. Biofuels, like cellulosic ethanol from switchgrass, can get us the rest of the way.

The general enthusiasm for electric drives—especially from renewable grid energy—doesn’t mean throwing away liquid fuels entirely. As batteries get cheaper and more robust, the proportion of annual mileage powered by a hybrid’s engine should shrink, but it is unlikely that ‘engine-less’ cars will gain more than a small percentage of light-duty vehicle sales for the coming decade. The latest forecast from the Boston Consulting Group suggests it will take until at least 2020 before all forms of plug-ins take more than 5 percent of the US market.

Here’s the good news. If sleek, energy-efficient, plug-in hybrids gain a foothold in the market, we could be much closer to energy independence for transportation. The rest of the distance can be made up with domestically produced advanced biofuels and our remaining petroleum resources.

The US has sufficient land already set aside from food production to be able to grow enough environmentally benign crops—such as indigenous switchgrass and miscanthus—to meet most of the remaining demand for liquid fuels in a national fleet of plug-in hybrids.

Biofuels Digest estimated that US venture capitalists invested $437 million in cellulosic ethanol firms during 2008. Verenium Corporation just announced it will start building its first commercial cellulosic ethanol plant in Florida later this year. The plant will be able to produce up to 36 million gallons a year, starting in 2011. So ‘cellulosic’ is no longer just a clever lab experiment but is set to take over from corn ethanol, releasing more corn for animal feed, etc. The large-scale production of biofuels does not necessarily reduce US food production. (Also, see “The World’s Energy Problem and What We Can Do About It,” a lecture by Steven Chu, US Secretary of Energy. Dr. Chu’s lecture begins at the 9:00 mark in the video.)

In addition, the next generation of hybrid drives will be much more efficient allowing the use of smaller engines—that can take full advantage of the superior combustion efficiency of biofuels. As a result, biofuel will cost less per mile than gasoline. And smaller engines will be less expensive, partially offsetting the cost of adding hybrid functions.

Boldly Look Ahead

The combination of electric fuel and biofuel is a winner. So forget mpg. That’s so ‘last millennium!” From now on, it’s going to be about total cost of ownership and cents per mile, and for most governments and all manufacturers, it will be net CO2 per mile. The plug-in biofuel hybrid is the silver bullet we shouldn’t be afraid to use.

This article was contributed by Chris Ellis, CEO, HyKinesys.

  • James Kempf

    I had my Prius converted to a pluggable hybrid so now I’m looking into getting it converted to E85. Unfortunately, the EPA and CARB forbid E85 conversions unless the conversion kit manufacturer tests the particular make, model, and year of the car with the conversion. So, for example, to license a kit for a Corolla, you would need to test specifically a 2004 Corolla and only market the kit for that year, even though the actual drivetrain might not have changed from 2003 through 2008. Each test costs upwards of $25K, a daunting amount of money if you are a small startup.

    The rules were changed in the early 1990′s, and, one suspects there must have been some oil company involvement in the rulemaking. This kind of thing happens frequently when the FCC makes rules so it would not suprise me if the same thing happened with the EPA as well. Since there are already millions of cars on the road, it seems like targeting a $500 E85 conversion kit together with a mandate or subsidies to get E85 widely available is more likely to make a dent considerably sooner in GHG emissions and foreign oil importation. Plug-in conversions are really, really expensive, and new plug-ins even more so.

  • Samie

    One sided story “cellulosic ethanol from switchgrass, can get us the rest of the way”. What? Lets see, cellulose ethanol means land set aside for wildlife or marginal crop land would be used for production. That means in some areas tree stands, watershed areas, or native prairie land will be turned over or burned releasing CO2 into the atmo. This policy DOES not just mean the U.S. b/c market conditions let lower/cheaper supplies into the market from other countries so you end up with the possibility of huge envr. problems that we do not control or humanitarian problems with crops grown for fuel. Also farmers may switch to biofuels if P is high increasing demand for other products grown elsewhere eg corn ethanol soybeans replaced by corn so Brazil replaces rainforests with new demand for soybeans. What about the energy/cost it takes to develop new strains of switchgrass, with fertilizers, chems and energy in harvesting????

    Annoying story and I’m sure supported by some farmers association no one should ever try to find a silver bullet with fuels bc its not there. B/c biofuels sometimes produce less mpgs, cost more, keep us dependent on a fuel source, and take up land resources. We are progressing towards EV’s slowly yes but it will happen so lets not screw this up or get so bent over about petroleum if we just focus on efficiencies that already are underway instead of getting sidetracked by short term green schemes!

  • Anonymous

    But wait, there is more. :)

    The Volt with its ICE running on E-85 for 1/3 of its annual mileage, the rest powered by the plug, will provide energy independence from foreign oil. As demand drops the price of fossil fuel will drop and so everyone wins. Therefore $10,000 incentives from taxes should be used to get the ball rolling with the first 150,000 volts. And if Toyiota brings out a PHEV Prius with at least a 25 mile AER, they should get the incentive from government funds too.

    The Question is, why does my local filling station not have a E-85 pump?

  • hamilton

    Samie, for a present-day environmental and CO2 nightmare, google ‘tar sands’.

    When oil prices spike up to $100/barrel – as they surely will again – oil supply from this lovely source goes into high gear TODAY. Not hypothetically, in a future scenario that assumes no policy, but right now. This technique is right up there with harvesting mountain tops for coal.

    By comparison, pushing battery technology as far and as fast as it will reliably and safely go, while switching to cellulosic ethanol over gasoline as a liquid fuel supplement, makes far more sense. Environmentally as well as security-wise.

  • crookmatt


    You are not in-correct in your assumption that some land would be needed to grow switch grass. However switch grass is not like corn. It grows naturally in enormous amounts in the prairies of the Midwest United States, currently it is not put to any use (that I know of). Additionally there are very few trees or growing in this region due to limited water. (

    The one point the article did not make is that ethanol from corn only yields about 30% more energy than it takes to produce it in the first place, much of which comes from fossil fuels (and this number is debated). So the ratio is 1.3 to 1. Ethanol derived from switch grass on the other hand produces a 10 to 1 ration of energy for every unit of fossil fuel energy it takes to produce it.

    The bottom line is that the environmental effect of ethanol is HEAVILY dependent on what exactly it is derived from, and ethanol derived from corn vice switch grass are two very different things.

  • massey

    Don’t discount corn ethanol. Changes in yield still have the potential to double per acre at the expense of cellulose. I would rather allocate the solar energy in seed than into the stalk. The seed portion is storable and can always be used as food versus grass and its susceptibility to mold and fire.

    Double yields in the U.S. of corn and quatruple the current yields of corn in China, Brazil and other corn growing areas in the world and ethanol from corn will certainly be the most viable solution to dependence on fossil fuel. Fuel cells can triple the efficiency of energy gleaned from a gallon of liquid fuel. Ethanol mixed with water is rich in hydrogen and the right combination may optimize fuel cell potential energy. The hybrid is the right choice because the road map leads to the use of electricity and bio-liquid fuel.

  • Gary Hubbard

    Perhaps the answer should be silver bullets, plural, to include bio-diesel as well. I really like the idea of PHEV’s using some bio-derived liquid fuel, initially as a percentage of petroleum-based fuel. But the sources of the liquid fuel need to go beyond ethanol, and include bio-diesels created from algae and other sources in the mix. First, gas and diesel have co-existed for decades as successfully competing liquid fuels. Second, algae farms aren’t food stocks, and take up much less space to produce the end fuel product — and absorb some of our waste in doing so. Other, now-wasted, organic materials can create a smaller, but significantly useful sources of bio diesel to be part of the mix. None of this is to say that there won’t be continued niche use for purely electric vehicles in both short haul commercial and consumer applications. I’m convinced that better, cheaper batteries will be developed to replace those that wear out in the current vehicles. The key is to use a variety of viable solutions appropriate to both the applications and the fuel available — to avoid dependency on too few sources, with the inevitable negative economic and environmental consequences. And, just because one technology leap frogs ahead of all other for now, shouldn’t mean that we don’t continue to develop all promising alternatives — with the educated suspicion that one or more of those will in turn, leap frog the current champion for the dominant vehicle propulsion source.

  • The vgtech

    The author uses an example where the life of a battery pack is stated as 50,000 miles. Prius taxis in Vancouver, BC are already passing 400,000 km’s (250,000 miles) with absolutely no battery failures. See the article below:

  • AlP

    Has anybody noticed that most of the food crops consist of 2 parts, one part (seeds, fruits, etc) is suitable for humans and for ethanol, and the second part (stalk) is mostly cellulose could be usable for cellulose ethanol.
    Following the above: Corn ethanol is produced from corn seeds, when the cellulose ethanol technology is ready, then corn stalk can be used as well. I think both technologies are very attractive and when both combined, there is no need for additional land.

  • Boom Boom

    Corn ethanol is a waste of energy, water and resources. Many independent studies to look at the energy balance of corn to ethanol have concluded this. When E85 is produced without using Corn, I say distribute it far and wide. Until then, stop the government subsidies of corn ethanol and shut them down. Tell them that if you don’t produce cellulosic ethanol, you don’t get any assistance. (And if cellulosic ethanol is as close as the writer says, that shouldn’t be a problem.) Simple.

  • LaMoine

    Please get your facts straight. When you say MANY independent studies have shown a negative balance you are partly right. Dr. Pemental is the only person to find a negative number, but he has published many studies since the early ’70. Although, he has never turned any of them over for peer review before he publishes them, I wonder why? He has used a different grad student for each study, gives them the parameters to work with, and guess what, they come up with the same results. Talk about flawed science.

  • Boom Boom

    Facts? And where are your references, LaMoine? (This is a news story that references the articles.)

    These studies (and many others) have found that you get only 20-40% more energy out of ethanol than you put into it. This doesn’t even factor in the wasted water. When you add in the 20-30% reduction in MPG from an ethanol vehicle, you basically burn just as much petroleum to get a tank of corn-based E85 to market as you do just burning regular gas.

    Making ethanol from corn is wasteful and only is profitable because of the massive subsidies (much bigger than any other subsidy for renewable energy from the US: Wind, Solar, etc.).

  • Samie

    Surprised to see so many over look my concerns w/ biofuels but there is nothing you can do to get people to look at long term problems but I think that’s a problem with some in the green movement… Another problem that many don’t think about is that you just don’t stop a alt. fuel that is suppose to be used in a short term period. Example could be if we are at the point of say moving to EV’s with government subsidizing this heavily in promoting moving away from fuels we could at the sametime subsidize farmers to promote “growing fuels” think of this as the classic tobacco example. I urge people to look also at how this could change markets, w/c again people don’t! Eg. CNG lovers fail to look at how cheaper CNG enters the market (this leaves the question of U.S. supply out) Russia has huge plans for its CNG production also some Middle East countries do too…

    With biofuels land is a serous issue w/c puts strains on wildlife programs, watersheds and filtering of ground water and if the price is right the possibility that land besides marginal areas will go into production for switchgrass. Also this goes well beyond the boarders of the U.S. and again land is a issue and at no point would biofuels account for 100% of fuel production b/c the land is not there or the real possibility that production of biofuels would not meet a point of 30-40% production needed to be viable as a real market competitor with petroleum. The only argument one could have is using algae (that takes some land issues out of the equation) like a comment above but this has been around for what seems forever w/ little or no results.

    I’m glad someone brought up the issue with coal, w/c is true like anything eg solar panels or batteries using metals that are mined.
    EV’s at some point will offer us multiple ways we can “fuel” are cars as opposed to any fuel/biofuels that are dependent on external sources. Also lets not get carried away w/ hybrids w/c account for 2-3% of all vehicle sales plugins almost 0% and the same for EV’s, world wide numbers are less… So taking resources out of moving hybrids to plugs to EV’s is a waste of time and money. I would support biofuels if say hybrids accounted for 30-40% of the market and plugins along with EV technology were delayed by no new advancements in the world for 20-30 years but that will not be the case! So while hybrids develop more on the market allowing automakers to make getter advancements in batteries and other tech needed for EV’s we can develop solutions to our problems with the energy grid and using money plugged into gov. biofuel schemes to promote more alt energies eg wavetitle, solar ect.. and using energy that is independent of a energy grid.

  • harrison

    Again, we see the perfect being the enemy of the good. Since we now know that biofuels have some warts we are willing to live with petroleum for as long as it takes to get to the nirvana of EV. Dream on! EV’s will not be perfect either, especially if the E is produced by coal. Inaction is the worst ill and putting up with imported oil for fear that biofuels might actually be successful is terrible public policy not to mention typical “green enclave” attitudes. Steady investment in technologies that build momentum toward enduring change away from oil is the only way to get to that place we all want.

  • AP

    From the “broken record” department (sorry):

    Phasing in a revenue-neutral gas tax encourages all of the alternatives, perfect or imperfect, by making petroleum fuels less competitive over time. Returning the money at income tax time as a “Strategic Fuel Tax Rebate” would also keep it from harming the economy.

    There would be little need for favoring one bio-fuel over another with government subsidies (less government, lower taxes), because they would all have a better business plan and be able to attract private investment – if they are really viable. The private sector is much more able to evaluate that than the government. The government should only set the stage, not pick the winners.

  • Samie

    Some Warts… that maybe a understatement.
    If it turned out to be the case that biofuels cellulose or any other does not contain the same combustion rates as petroleum and if you add ALL the processes of energy needed to grow harvest and turn biofuels into energy together and it equaled or produced more greenhouse gasses than petroleum would you support it?????

    To throw darts blindfolded seems silly w/c is what some like to do when they call themselves green. If AP is right you have private investment with no policy or subsidizing by the gov. that would be one thing but we know that will never be the case w/ biofuels. Short term ideas get us nowhere and there is a lot of public tax dollars thrown in to the wind w/c avg Joe in America starts to believe in stereotypes of those who want to reduce greenhouse gases as wasting his money.

    Again hybrids are a tiny part of the market so why not devote the time and resources into developing this into a major sector of the car buying market? As for coal again why not start developing more alt energies or independent grid options for consumers? This takes time & lots of resources & does not happen overnight! To say that EV’s are the final answer is silly w/c in my view its just a middle step to water vapor or hydrogen vehicles but the key is that this would improve on the energy system that helps power our homes and businesses, spurring more innovation in the energy sector and reduce greenhouse gasses.

  • LaMoine

    Boom Boom, if you want some references try looking up Dr. Pemental at Cornell University, or read some books, for example. “The end of oil” by Paul Roberts, “Energy Victory” by Robert Zubrin, or “A thousand Barrels A Second” by Peter Tertzakian, These are independant writers who have no interest in biofuels. They simply address our energy problem we have in the USA and they do give some background and some solutions to our problem other than going to war over oil.

  • Lina

    Can you guys help me? I can see by your posts that you are much more sophisticated in green car info. than I am, but I have a dilemma and I can’t seem to figure it out through the
    research I’ve done online so far. Here’s the deal:

    - I have to buy a car in the next month (before March).
    - I want it to be green, fuel efficient, and inexpensive to run.
    - I know many new vehicles are coming out in 2010-11-12,
    that are plug-ins but I can’t wait.
    - I’m looking at the 2009 Prius, Camry Hybrid, Civic Hybrid,
    Altima Hybrid and the Jetta Diesel.
    - I’m thinking it might be good to get something that can
    later be converted to a plug-in?
    - Do you think that Obama’s plan will allow tax credits on
    all of the above vehicles? As far as I know, only the Altima
    currently has a credit.
    - The above cars are all more or less in my price range; I
    know the Camry is more, but I know of a good deal on a
    2007 loaded hybrid with 16,500 miles – for $23,500 and
    I like it because driver seat adjustment/comfort is a factor
    that is important.
    - Finally, given the economy, it is a good time to get a good
    deal on a car and I just sold my house, so I want to buy a
    car before I look for a new, smaller place.

    Thanks so much for any advice you may have!

  • Achilles


    Thank you for reading my article.

    I’m going to advise you to consider an alternative to the obviously ‘correct’, ‘safe’, answer you’ve already identified.

    The last paragraph of my article suggests we should all focus on ‘total cost of ownership’, rather than fixate on mpg. For the next few years gasoline is going to be cheap, so fuel is probably going to be the least of of your significant costs, certainly relative to depreciation on a new car. So I suggest you look again at what is on offer pre-used, as you already have with the Camry deal. But now look further up-market, at the cars redundant bankers are dumping. For example, if you can live with the image, check what you would have to pay for a BMW 328i. A quick look on shows asking prices just below (and above, naturally!) your Camry, for 2007 cars with less than 30,000 miles. Bear in mind that a 328i is designed to last longer and ‘take more stick’ than a Camry and should lose significantly less money when you come to trade it in for your new plug-in version of the Honda Insight(?), in 2011(?). Note the EPA highway estimate for a 2007 328i is 28 mpg, manual or automatic, which is not bad for a much better car.

    I think that would be the smart play, substituting with something more to your taste if you don’t like a BMW, and buying time and saving value until your ideal car arrives. But there’s nothing much wrong with the Camry choice, either. Apart from the image thing…

    Have fun choosing,


  • John Saxon

    It seems to me that a huge part of the inefficiency of our current fleet of cars is the excessive size and weight of the cars, considering the light tasks they are used for most of the time. What about an inexpensive, easy to store trailer that could be attached on those rare occasions when you need lots of storage. Then we could all think about driving Honda Insights, etc. This giant SUV thing is totally out of hand.

  • michael a.

    There is a lot of research going into biofuels from algae. If algae biofuels could be commercialied, the bio-fuel impacts on land, food, and wildife would be greatly reduced.

    My guess that an algae bio-fuel would consume water, but if the factoy was near an ocean desalinization could remedy this problem. And, desal costs are falling.

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