Driving on sunshine

Can the fossil fuels we use in internal combustion engines be practicably replaced by fuels derived from plant materials – biofuels? This question has, in these times of high oil prices and climate change worries, risen quickly up the agenda. Plants use the sun’s energy to convert carbon dioxide into chemically stored energy in the form of sugar, starch, vegetable oil or cellulose, so if one can economically convert these molecules into convenient fuels like ethanol, one has a route for the sustainable production of fuels for transportation. The sense of excitement and timeliness has even reached academia; my friends in Cambridge University and Imperial College are, as I write, frantically finalising their rival pitches to the oil giant BP, which is planning to spend $500 million on biofuels research over the next 10 years. Today’s issue of Nature has some helpful features (here, this claims to be free access but it doesn’t work for me without a subscription) overviewing the pros and cons.

The advantages of biofuels are obvious. They exploit the energy of the sun, the only renewable and carbon-neutral energy source available, in principle, in sufficient quantities to power our energy-intensive way of life on a worldwide basis. Unlike alternative methods of harnessing the sun’s energy, such as using photovoltaics to generate electricity or to make hydrogen, biofuels are completely compatible with our current transportation infrastructure. Cars and trucks will run on them with little modification, and existing networks of tankers, storage facilities and petrol stations can be used unaltered. It’s easy to see their attractions to those oil companies which, like BP and Shell, have seen that they are going to have to change their ways if they are going to stay in business.

Up to now, I’ve been somewhat sceptical. Plants are, by the standards of photovoltaic cells, very inefficient at converting sunlight into energy; they require inputs of water and fertilizer, and need to be converted into usable biofuels by energy intensive processes. The world has plenty of land, but the fraction of it available for agriculture is not large, and while this is probably sufficient to provide enough food for the world’s population the margin is not very comfortable, and is likely to get less so as climate change intensifies. One of the highest profile examples of large scale biofuel production is provided by the US program to make ethanol from corn, which is only kept afloat by huge subsidies and high protective tariff barriers. In energetic terms, it isn’t even completely clear that the corn-alcohol process produces more energy than it consumes (even advocates of the program claim only that it produces a two-fold return on energy input).

The Nature article does make clear, though, that there is a much more positive example of a biofuel program, in ethanol produced from Brazilian sugar-cane. Estimates are that it produces an eightfold return on the energy input, and it’s clear that this product, at around 27 cents a litre, is economic at current oil prices. The environmental costs of farming the stuff seem, if not negligible, less extreme than, for example, the destruction of rain-forest for palm oil plantations to produce biodiesel. The problem, as always, is scaling-up, finding enough suitable land to make a dent on the world’s huge thirst for transport fuels. Brazil is a big country, but even optimists only predict a doubling of output in the near future, which would still leave it accounting for less than one percent of the world’s demand for petrol.

Can there be a technical fix for these problems? This, of course, is the hope behind BP’s investment in research. One key advance would be to find more economical ways of breaking down the tough molecules that make up the woody matter of many plants, cellulose and lignin, into their component sugars, and then into alcohol. This brings the prospect of being able to use, not only agricultural waste like corn husks and wheat straw, but new crops like switch-grass and willow. There seems to be a choice of two methods here – using the same technology that Germany developed in the 1930’s and 40’s to convert coal into oil, using high temperature and special catalysts, or developing new enzymes based on the ones that fungi that live on tree stumps use. The former is expensive and as yet unproven on large scales.

What has all this got to do with nanotechnology? It is very easy to get excited by the prospect of a nano-enabled hydrogen economy powered by cheap, large area unconventional photovotaics. But we mustn’t forget that our techno-systems have a huge amount of inertia built into them. According to Vaclav Smil, there are more internal combustion engines than people in the USA, so potential solutions to our energy problems which promise less disruption to existing ways of doing things will be more attractive to many people than more technologically sophisticated but disruptive rival approaches.

13 thoughts on “Driving on sunshine”

  1. The only bio fuels approach that seems to have any promise to me is biodiesel from algea . The yields per acre are reported to be orders of magnitude higher than plants, the only real problems seem to be engineering ones rather than anything fundemental. Definitely seems to be a better bet than oil shale anyway.

  2. Yes, I think the algae route needs more research. Scaling up cane sugar enough for it to make a difference would probably result in the destruction of just about every last wild ecosystem in the areas that can grow cane sugar, which would not be very helpful, to say the least.

  3. A combination of things need to be developed.

    Far lighter vehicles. Using carbon fiber and/or nanograined metals (aluminum is 10 times stronger with nanograin). Lower the overall demand for fuel for transportation with greater efficiency.

    Develop and deploy plug in hybrids. Needs better batteries for longer range on electricity. 2008-9 plug in hybrids will start to be deployed by Honda and Toyota. 100+mpg. With far lighter vehicles could expand the battery powered range. Get the battery range significantly past regular commute distance and fuel use drops to almost nothing.

    Expand clean electrical power sources. In the near-mid term, that is mainly nuclear power.

    Use genetic engineering to get higher efficiency from crop to biofuel.

    Have government policies geared to accelerate the early retirement of inefficient vehicles and provide support for mass transit. Also, support all electric folding bikes and mopeds which would have less of a technological hurdle for clean transportation.

    Recent study says hydrogen is more inefficient than electricity as power storage.

  4. Much potential for the reduction of fuel use comes down to politics, of course, which neither of our countries seem to have much stomach for implementing at the moment (though of course the UK has very high gas taxes bu US standards). I’m not convinced about pushing fast forward with electric vehicles until the fraction of clean energy on the grid is much higher. Otto engines are actually pretty efficient, and I’m not at all convinced that you do better by getting electricity from fossil fuels and charging up batteries, when all transmission losses are taken into account. But incremental improvements in efficiency via cutting down vehicle weight is of course well worth doing.

  5. “Recent study says hydrogen is more inefficient than electricity as power storage. ”

    I don’t see anything in that physorg recent study (not the link in the previous post, a different one on the physorg site yesterday I’m not gonna bother linking here) that I didn’t already know. It says to convert (presumably wind/solar) power sources for transportation needs via hydrogen, you only are left with 16% of your starting power.

    Hydrogen’s strength was never its efficiency or its power density, its strength is that it is emissions free and only requires fresh water and room temper-ish ambient temps to form a system of almost full closure.

    That study in question suggests we should build power plants exactly where we need the power. The study doesn’t consider other potential batteries such as Li-ion, flywheels, gravity-water systems, or air compression, as gasoline alternatives (hydrogen looks good by comparison). The study doesn’t mention transportation is only 15-20% of our energy needs. The study doesn’t consider that 21st Century renewable energy sources (wind/solar) won’t work at night or during the 2/3rds of the time windspeed isn’t optimal.
    The study is basically saying we should just keep using oil indefinitely.

  6. Lets see,
    Gas Powered car will go 0.3 to 0.7 km/ MJ but the Tesla Roadster will go ~2.2 km /MJ. The electric car will use 3 to 7 time less energy!!!

    Li ion batteries are ~85% efficient and transmission over the grid is ~92% efficient . And nano-tech can improve both batteries and transmission over the grid.

    And there is still plenty of electricity this is currently used inefficiently, and it is typically much cheeper to create more energy by improving efficiency than by generating more power.

  7. Discarded Lithium Ion batteries are toxic waste. They are fine for transportation uses, I guess. But industrial productivity levels will eventually be hampered unless better battery recycling technologies become available (maybe), bettor waste disposal methods occur (lift it to one of the Gas Giants or the Sun?!), or a clean battery is developed (PEMs for example). Efficiency is only one metric, otherwise we’d use nuclear bombs for everything.

  8. It’s about time someone said it, I say let’s use the ‘natural’ resource we’ve been waiting for! (Nuclear bomb combustion!) 🙂

  9. Jim, Brian, the point I would make is that while electricity is made predominantly from fossil fuel sources, as it is just about everywhere apart from France, then electric cars don’t really make a big impact on the problem. Even if the electricity is generated off-peak, it still involves the burning of fossil fuels and the release of CO2. Jim left out the most important source of inefficiency in the energy cycle of an electric car powered this way – the efficiency of conversion of fossil fuels to electricity in the first place. I don’t have an up-to-date figure for this to hand, but my trusty Physicists’ Desk Reference quotes the average figure for the USA in 1987 to be 33%. It’s probably gone up since then, but not by a lot.

    I agree entirely with Jim that it is easy to “create” electricity by increasing efficiency, though. White LEDs for lighting are one significant example.

    Of course the market is a powerful method for driving change here, but as endlessly discussed one has to properly cost the externalities.

  10. I agree that we need to simultaneously get off of fossil fuels. First coal then oil. The way to do that is primarily (as I said in the 4th paragraph in my first post) massive nuclear power expansion.

    I have a series of articles on my website where I indicate the 10-20 year for Thorium power development and other systems that can use the 10,000 year waste we currently have as part of fuel. The quickest start is to up power current nuclear plants by 50%. 443 plants worldwide, generating 369GW.


    Recent work at MIT indicates that if we change the fuel from rods to cylinders that have more surface area and use some nanoparticles in the coolant water (allows the plants to safely run hotter) we can up power the standard boiler reactors by 50%. Do that and we get 150GW more. Then India and China are already building nuclear plants at a pretty good clip. The US and other countries can start doing that as well. Probably easiest to try to squeeze them onto existing locations. We also try to add wind and solar. But those only added 12GW for wind in 2005 and 1.7GW for solar in 2005. Efficiency is important too as I indicated in prior post. Tripling the up-powered plants we go from 500GW to 1.5TW. Assessing some of the carbon costs to coal makes nuclear cheaper in almost all scenarios. It is cheaper now in some situations.

    It will take all of it to make up the 200GW or so per year of global power that is added which does not include transportation power. 4TW of electricity and 13TW of total power usage globally and looking to double by 2030. Most of the new power will be coal without strong action. Even though coal is 80% cleaner in most places than it was in 1952. There was the London fog
    where thousands died from coal pollution over a few weeks.

    Although most who die now are not as dramatic as keeling over in the streets usually it is asthma, lung problems and cancers where people die in hospitals. But the premature deaths are still real. China has about 400,000 per year dead from coal. 10,000 in mining accidents.

    So hybrid cars are just one piece of the bigger solution because the problem is huge. Spewing billions of tons of carbon, plus 20,000 tons of thorium and uranium, plus thousands of tons of mercury and arsenic into the air and our lungs is just stupid. It is especially wrong for people to fear nuclear power whose worst accident was Chernobyl with 50 dead and 4000 made very ill when coal kills more than that in about an hour. (Thorium handles non-proliferation. It has to do with the fuel cycle.) I also think anyone who is looking at approving nanoparticles and other new technology needs to consider what the benefit of a new technology is and if it is displacing something that is already superdeadly we can still proceed with some caution but if the overall picture makes sense we should still proceed.

    Volume production of nuclear reactors is key to the near mid term solutions. When nanotech can volume produce the solar power cheaply we can shift to that. But we probably need all of it until coal and then oil are eliminated.

  11. I don’t mind nuclear reactors (waste and proliferation are easier issues to deal with than cancer/asthma and Global Warming), but a “moderate term” 10-20 year investment in thorium is really seems like a long-term embedded capital investment when viewing alternative enrgy research time-scales.

    I think Nanosolar already has developed the technology to scale up solar power cheaply. Wind may still be a decade away… Now the issue is energy storage technologies and I think the 10-20 years to bolster nuclear power R + D could be better spent looking at better nanotech-ed storage techniques: better Li-ion batteries, better PEMs, researching storage capabilities of novel clays and other nanomaterials, etc.

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