Okay, Let's Talk About Energy: Biofuels

By Sheril Kirshenbaum | October 13, 2009 11:13 am

CM kicked off the day with a post on solar energy. I covered the prospect over a year ago at Seed’s Next Generation Energy:

Storage and back-up systems are going to be very important given the sun doesn’t deliver that much energy to any one place at a time. The solution would be photovoltaic panels and solar heating troughs over huge tracts of land along with a direct-current transmission backbone to send that energy efficiently across the nation..Imagine a future where solar panels pave the desert between Phoenix and Los Angeles and consider whether that be worth the ecological footprint?

We know lot that can be done with the existing solar technology today that would reduce our dependency on fossil fuels. Solar thermal plants are assuredly one part of the solution, but there is the water conflict which cannot be overlooked. In short, this alternative has the potential to create a great deal of electricity–now–and I hope the policy catches up and we integrate it into landscapes in a way that doesn’t add pressure on other limited resources.

switchgrassAlso remember that our energy needs exceed what solar power generates. So while I think we should be powering our cars and appliances on electricity, we must depend on many sources for a more sustainable future. We will still need combustible liquid fuels for shipping and air transportation.

Personally, I continue to be interested in plant based biofuels. There is no better solar panel than the leaf of a plant. Alone it will not be the only answer, but may eventually contribute to a significant percent of our energy budget.


Comments (27)

  1. Lindsay

    Yeah, you guys definitely need to read “Sustainable Energy – Without the Hot Air.” The author gives exactly one paragraph of the entire book to biofuels.

    The way I understand this problem is that we have to figure out 1) a plant that takes very little energy to grow and harvest without competing with food crops for land or resources, 2) a way to harvest and process this plant into ethanol that uses *less* energy than you put into it, and 3) a system involving 1 and 2 that could be massively scaled up. I haven’t looked at this in awhile, but last time I checked, they were still struggling with 1. Corn was a miserable idea because it failed 1 and 2, algae probably fails 2 and 3, and switchgrass fails 3. I mean, maybe it is worth failing 2 if you really want it in a liquid form, but really, it’s a hard problem to solve.

  2. Erasmussimo

    My own assessment of biofuels is pretty pessimistic — at the moment. Right now they really don’t work as well as most other forms of energy. However, once we start doing some serious genetic modification, I think we can do very well this way and in the long run I believe that biofuels will be the most efficient form of solar energy — but only in the long run. I think we have a lot more work to do here. We need to engineer plants that do not handle all their needs themselves, plants that depend upon us for some of the basics that we can easily supply and concentrate their metabolism solely on churning out the carbohydrates.

  3. JEM

    I would take issue with the idea that there is no better solar panel than a leaf. I used to think this was the case, but have come to believe the actual picture is more nuanced. Certainly a leaf is an incredible thing, but also an incredibly complex thing, and a plant must do more than make fule for us. On the plus side, plants are self replicating and have a built in carbon capture mechanism (granted this is big). On the minus side the efficiency of photosynthesis is very limited – good enough for the plant but very low overall. Perhaps genetic engineering will improve this, but that has its own perils. Also, the energy-water problem is particularly apparent for bio-fuels. Tough to imagine biofuels being produced where the solar thermal plants will be situated for this reason. I do believe bio-based fuels must play a role, but they can not fill the bill entirely.

    I think maybe there is no more beautiful or inspiring solar panel than a leaf.

  4. @3 JEM:

    the energy-water problem is particularly apparent for bio-fuels.

    I’d like to see more research directed toward producing drought tolerant biofuel crops that can grow on marginal lands without supplementary water required.

  5. Jon

    If you compare solar-generated electricity to say, corn ethanol, corn ethanol is incredibly inefficient. Lots of trouble for not much energy. But then again, ethanol does not have the limitations in terms of storage and transport that electricity has. The best thing would be to use biofuels whenever necessary (and improve them: e.g., burnable algae and plankton could probably do much better than corn, I’ve heard), but you should rely, whenever possible, on electricity for your energy infrastructure, which means direct solar would be far more efficient (unless you’re talking about waste-based biomass) because it’s straight from the source.

  6. Sorbet

    There is also a proposal to grow plants with silicon-based leaves that would be much more efficient than current carbon-based leaves at capturing sunlight.

  7. Colin

    Ethanol has a energy content of 23.5 MJ/L. It takes 3.25 m^2 of corn to make a liter of ethanol. If you assume 1000 W/m^2 solar radiance then you hit 23.5 MJ on that 3.25 m^2 in 2 hours. In other words you see the equivalent energy from the sun as a liter of ethanol in two hours of normal sunlight. Yet it takes a whole season to grow that corn.

    Even if you get that 3.25 m^2 down to 1 m^2 you are wasting a massive amount of solar energy just making corn. I’d consider 3.25 to 1 m^2 as major step for efficiency’s sake but still nowhere near enough.

    Even if you make harvesting of corn perfect (i.e., no energy required to harvest) you are wasting a massive amount of solar energy just making corn.

    I wholly disagree that the current plants are the answer or that plants are perfect sources of energy conversion. Never mind that the green frequencies have less solar energy than yellow and oranges.

    Chlorophyll photosynthesis isn’t even a contender when you poke at the basic math. It’s a joke.

  8. Anthony McCarthy

    I’m impressed with the ARTI work on biogas digesters using food waste and plant products. They’re so simple and easy to use that I’m in the early stages of experimenting with using invasive plants that plague my garden.


    Though I suspect that’s not exactly what you meant.

  9. my personal favorite choice, though not applicable in most circumstances, remains the bicycle!

  10. Jon

    What Colin said.

  11. Kristine

    I work for a research funding agency that is looking specifically at this issue, and I would agree that there are still no definitive answers. Bioethanol can be made in a variety of ways, but its inefficient and expensive. There are other interesting projects on developing butanol as a fuel, using agricultural waste products for fuel, and several attempts at making algae viable (see major investment from the Carbon Trust: http://www.carbontrust.co.uk/technology/directedresearch/algae.htm). But there still remain some basic issues with plant-based biofuels, not the least of which is a very inefficient breakdown process caused by the complex lignocellulosic structure of most plant materials. In addition, if we did figure out an efficient way to breakdown plant materials to easily make high-energy density biofuels, there are logistical issues around transporting low-density plant material. Is it possible to have on-farm fermenters? Farmer co-ops for biofuel production? It is unlikely that we will be able to adapt renewable fuels to the same systems currently used for petrol-based fuels and the development of these solutions need to go hand-in-hand with the science for developing fuels from renewable materials.

  12. As I’ve written before, corn ethanol isn’t the solution. Instead, it’s paving the way for alternatives by getting the infrastructure in place for second generation cellulosic biofuels made from the leaves, stems, and stalks of other plants.

  13. JEM


    Drought tolerant is a step in the right direction. Not an expert but I think we may be closer in salt adapting plants (food crops anyway) for salt tolerance. The question I have is whether one can get low water usage (low transpiration) and still have high growth rates (high solar efficiency). Desert plants tend to be slow growing, but they can explode with life during damp periods. I’d be interested in any insights folks might have.


    It is clear that we must use the whole plant. Whether we use biological approaches (hydrolysis, fermentation, etc.) or chemical approaches (pyrolysis, gasification, reforming to syngas, etc.) is less clear. I’ve been more of a believer in the chemical approach, but a recent chat with a scientist/engineer egaged in trying to commercialize this has given me cause to rethink. Of course some of the problems are related to the incentivization (is that a word) of ethanol in particular over other potential biofuels. In either case, the overall efficiency is still given an upper limit by photosynthesis and currently that limit is pretty low. Unfortunately neither approach solves a lot of the other problems commonly cited problems either, water content of biomass, diffuse resource, capital cost for a intermittent resource etc.

  14. Colin

    Sheril, I still contend that “There is no better solar panel than the leaf of a plant.” is wrong because chlorophyll-based photosynthesis does not use the entire spectrum of light (if it did the leaves would be black).

    If you define efficiency as the fuel energy (as ethanol or whatever) to solar insolation taken to make that fuel then biomass as we know it is not it and, really, everything comes from solar energy so that should be the benchmark.

    Corn ethanol is pathetic and even if you increased your yield from corn by a factor of 10 or 20 by fermenting the cellulose you’re still at an abysmal efficiency (compared to the solar insolation).

  15. @13 JEM:

    Not an expert but I think we may be closer in salt adapting plants (food crops anyway) for salt tolerance.

    Both salt and drought tolerance. And yes, we are close.

  16. Tuatara

    Corn ethanol is a government handout. No one sensible thinks it is a good idea. However, it is important not to throw the baby out with the bath water.

  17. I think it is important keep a conceptual ideal or image in mind when discussing alternative fuels. It is very easy to narrow your focus to one or two sources, when solutions will inevitably come from many.

    More importantly, this is (primarily) an issue of consumption and personal behavior choices. Each bio fuel suggestion renders great impact on natural communities and resources, potentially altering or changing the structure of carbon sinks, naturally functioning ecosystems etc… We need to talk about how the restructuring of communities (the ways we live, eat, transport and work) can drastically limit the amount emissions, and how we can create a system that values open and protected areas that can enhance biodiversity and mitigate some emissions… Biofuel / alternative energy research will take much time.. Wouldn’t this be a prudent focus in the interim? Why isn’t it?

    Sorry for the digression..

  18. From what I understand, bio-fuels are and will remain a set of solutions to niche markets rather than the overall solution to everything. Even the best is not ready to scale up to what we need to do that. According to the Biofuels Digest, even Sec. Chu would seem to agree.

  19. lets talk about wind, thats what i am getting into

  20. JEM


    Well said Michael. Society seems to think we will create a technological silver bullet that will support our current life style with no pain or cost. Life is never that simple. In many cases we have technological solutions (imperfect as they may be), but lack the political will to implement them; instead we choose to externalize the cost. Technology will advance, we will get better, but ultimately, we have to look at our value system and make adjustments.

  21. MadScientist

    Liquid hydrocarbons will remain essential for air transport but not necessarily for shipping. Nuclear reactors are a viable power source for large ships.

    Solar PV + DC distribution is not so good; maybe some other solar technology with chemical energy storage would do even if it ends up less efficient overall than solar PV – if only because the availability through no-sun periods will be better. On the other hand you need so many PV panels to match a wind turbine (and so many wind turbines to match a single steam or hydro turbine). If you’re going to throw in DC distribution (more efficient than AC for very long runs) you may as well go wind + DC. Personally I think those wind turbines are rather pretty; I don’t know why people whine about them. There are numerous proposals around the world for wave energy systems as well; although small scale demonstrations have been around for a while, I’m waiting to see if wave generation can be turned into something really big.

  22. Harry Abernathy

    Two points: 1. Biofuels should also be considered in their role as a renewable form of energy storage. Yes, energy is needed to convert the plant into a liquid fuel, but that liquid fuel can be used at night (when solar isn’t working) or can be used as fuel in areas that don’t have ideal solar or wind resources.

    2. Also don’t discount that plants are also temporary CO2 sinks, even if most of CO2 will be returned to the atmosphere when the liquid fuel is burned.

  23. Sean McCorkle

    Personally, I would like to see us take carbon out of the picture entirely and develop a hydrogen economy. It could be used as a storage mechanism for any sort of electricity generation, not just PV; all you need to do is electrolyze water, and it could be used as a fuel as well.

    We’ll probably end up with biofuels, however. Home and industrial power can come from many types of sources and storage mechanisms, but the BIG constraint is that we Americans must have our cars. People have been talking about improving the range of electric cars, they seem to be maxing out at 100 miles per charge, so the range falls short of hydrocarbon engines.

    There will almost certainly be repercussions to biofuels: If grown on farmland, how much food crop will be displaced and what will happen to prices? Will industrially produced fertilizer be used, and if so how much? If trees or switchgrass are eventually used, where will they be grown? national forests? national grasslands? If algaes are used, where will the water come from? Will it be grown in the ocean? There’s a real minefield of potential ecological disasters to be navigated no matter what route is chosen. When its the environment vs the publics addition to automobiles, I fear for the environment.

  24. Sheril said: I’d like to see more research directed toward producing drought tolerant biofuel crops that can grow on marginal lands without supplementary water required.

    Then someone needs to talk to their Senators and have them direct money to the USDA (you know, the Department of AGRICULTURE), rather than the DOE!

  25. Exciting post. I have been searching for some excellent resources for solar panels and found your blog. Going to bookmark this one!


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About Sheril Kirshenbaum

Sheril Kirshenbaum is a research scientist with the Webber Energy Group at the University of Texas at Austin's Center for International Energy and Environmental Policy where she works on projects to enhance public understanding of energy issues as they relate to food, oceans, and culture. She is involved in conservation initiatives across levels of government, working to improve communication between scientists, policymakers, and the public. Sheril is the author of The Science of Kissing, which explores one of humanity's fondest pastimes. She also co-authored Unscientific America: How Scientific Illiteracy Threatens Our Future with Chris Mooney, chosen by Library Journal as one of the Best Sci-Tech Books of 2009 and named by President Obama's science advisor John Holdren as his top recommended read. Sheril contributes to popular publications including Newsweek, The Washington Post, Discover Magazine, and The Nation, frequently covering topics that bridge science and society from climate change to genetically modified foods. Her writing is featured in the anthology The Best American Science Writing 2010. In 2006 Sheril served as a legislative Knauss science fellow on Capitol Hill with Senator Bill Nelson (D-FL) where she was involved in energy, climate, and ocean policy. She also has experience working on pop radio and her work has been published in Science, Fisheries Bulletin, Oecologia, and Issues in Science and Technology. In 2007, she helped to found Science Debate; an initiative encouraging candidates to debate science research and innovation issues on the campaign trail. Previously, Sheril was a research associate at Duke University's Nicholas School of the Environment and has served as a Fellow with the Center for Biodiversity and Conservation at the American Museum of Natural History and as a Howard Hughes Research Fellow. She has contributed reports to The Nature Conservancy and provided assistance on international protected area projects. Sheril serves as a science advisor to NPR's Science Friday and its nonprofit partner, Science Friday Initiative. She also serves on the program committee for the annual meeting of the American Association for the Advancement of Science (AAAS). She speaks regularly around the country to audiences at universities, federal agencies, and museums and has been a guest on such programs as The Today Show and The Daily Rundown on MSNBC. Sheril is a graduate of Tufts University and holds two masters of science degrees in marine biology and marine policy from the University of Maine. She co-hosts The Intersection on Discover blogs with Chris Mooney and has contributed to DeSmogBlog, Talking Science, Wired Science and Seed. She was born in Suffern, New York and is also a musician. Sheril lives in Austin, Texas with her husband David Lowry. Interested in booking Sheril Kirshenbaum to speak at your next event? Contact Hachette Speakers Bureau 866.376.6591 info@hachettespeakersbureau.com For more information, visit her website or email Sheril at srkirshenbaum@yahoo.com.


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