I recently visited Brazil, which has a world leading bio-fuel industry. Ethanol from sugar cane, is readily available at petrol-stations throughout Brazil. In fact its often quite a bit cheaper than gasoline. Despite the relatively low efficiency of the “sunlight to wheels”, power-delivery, there are certain situations where some form of fuel and combustion are for the time being unavoidable, as such, bio-fuels provide a very sensible solution, and can do so at a similar costs to fossil fuels.
Brazil is a pioneer in ethanol, starting in the early 1900’s when automobiles came available. The second world war, and the supply constraints that came with it, led to a boom in ethanol production, and throughout the years, ethanol production went up and down, depending on what the oil markets were up to. Even today, retail gasoline must contain at least 22% ethanol, further I found 100% ethanol to be widely available at gas stations, usually for 15-20% less than gasoline. All-told, ethanol has about 50% market share compared to gasoline (source).
Economically, ethanol makes a lot of sense, as Brazilian producers are able to make ethanol for as little as $0.22 USD/l. Compared to gas, that’s a steal. We do need to do a little math to understand why, signs are up in my neighbourhood for $1.5 CAD/l as I write this in March 2025. And apparently, 63% of that goes to procure gasoline from the refiner (some of that is spent on crude-oil), the rest on other things, such as taxes and distribution. That’s $0.66 USD/l for gasoline, 3 times more expensive than ethanol! Factoring in the 67% energy content of ethanol, still leaves you with a healthy cost advantage of ethanol (source).
Efficiency wise, ethanol makes far less sense. Only about 2% of the solar energy that hits sugar-cane, winds up producing useful feed-stock for ethanol production (source). Presumably the distilling reduces this a bit, but you would still be left with the 80% loss of energy when fuel is burned to move a car (source). All-told, that’s only 0.04% conversion efficiency from sunlight to wheels! Compare this to 20% efficiency of a solar system (source), and 88% battery to wheels efficiency (source). The solar-panel, electric vehicle (EV), combo, is 17 % sun to wheels efficient. A whopping 440x improvement in efficiency. Hence where a field of crops is required for ethanol, a rooftop might do for the EV.
Nevertheless, there are situations where the weight penalty of batteries is simply to high. Take aviation for example, the Airbus 320, a narrow body aircraft widely used to fly people around the world (source), it would be very difficult to electrify it, or come up with something similar (source). Batteries are simply too heavy.
Perhaps ethanol is a sensible idea? Well the Brazilians have been flying on ethanol for decades (source).
Electric car adventures 