One of the big advantages of Brazil’s sugar cane ethanol program is that it can generate its own energy by burning the left-overs of the cane crushing process. Most of Brazil’s ethanol mills make enough energy from burning the leftover roughage, known as bagasse, that they can power their own operations while still having enough electricity to sell power to the grid. This contrasts with US corn ethanol, which has to use copious amounts of natural gas to power its boilers (which makes one wonder how “alternative” a fuel corn ethanol really is).
Now, state oil company Petrobras wants to make ethanol not only out of the sugar cane, but also out of the bagasse itself. I have to admit, I don’t get it.
The campaign is part of the effort to develop “second-generation” or “cellulosic” ethanol that does not use food crops but rather leftover waste. Responding to criticism sparked by the food-vs-fuels debate, the biofuels industry has always promised that ethanol of the future will be made out of things like corn cobs, plant stalks or waste wood. These efforts aren’t going very well (I’ll get to that later), but the logic of them is clear – take something that’s not food, and not being used for something else, and turn it into fuel.
But this logic just doesn’t extend to sugar cane bagasse, because it already is being used for something else – it’s being used to make energy. Brazil over the next decade is going to need a lot more electricity and a lot more liquid fuel, so there’s no chance that biomass electricity generation from cane bagasse is going to create a glut of power. And it seems to me the most direct way of getting energy from bagasse is to turn it directly into electricity by burning it – I honestly don’t see how this could ever be less efficient than turning bagasse into liquid fuel and then burning that.
I haven’t heard many clear responses to this question. One Petrobras executive just flat out said he didn’t know. One researcher has said sugar cane roughage has large amounts of a chemical called lignin, which can be used to create biofuels. I found this a bit confusing as well, because lignin is a chemical that stiffens the cell walls of plants and makes it harder to access the types of biomass that can be most easily turned into biofuel. In fact, this researcher is trying to figure out how to modify lignin in plants to make it easier to access the cellulose that can be used for biofuels. And if lignin does have energy potential, couldn’t that potential be tapped simply by burning the bagasse for electricity?
I do not have a technical background and may be missing the plot on this one, and would welcome somebody coming along to set me straight. But it seems to me that the logical solution to this problem would simply be to grow more sugar, make more ethanol, and burn more of the bagasse to generate more electricity.
But Brazil, much like anyone involved in the biofuels world, is pretty insistent on pushing ahead with cellulosic biofuels even though it’s not going very well. In 2008, Brazil launched an ambitious program to diversify the crops it uses for making biofuels, following withering criticism that its sugar-cane ethanol and soy-based biodiesel were pushing up world food prices. It recruited small farmers in the arid northeast to plant alternative crops including castor beans and jatropha to make biodiesel out of non-food plants. It didn’t go well. One of Brazil’s top biodiesel producers had to close down a factory built to make castor-based biodiesel because the economies didn’t work out. “It was a disaster,” one poor farmer from the state of Mato Grosso once told me, shaking his head. “They had us planting jatropha to make biodiesel. You can’t grow that stuff here. It gets eaten up by bugs. A complete waste of time and money.” As of last year, nobody had ever managed to make biodiesel out of castor beans because it is always more profitable to sell them off to the chemical industry for production of castor oil.
The United States, the world’s top producer of ethanol, last year began requiring gasoline blenders to use a minimum amount of ethanol made from things like corn cobs or agricultural waste and mandating target volumes of 100 million gallons in 2010 and 200 million gallons in 2011 – but the total certified production of this type of biofuel is still 0. As the energy blogger extraordinaire Robert Rapier points out, gasoline blenders are being fined for not buying cellulosic ethanol that isn’t being produced.
The idea of turning trash into fuel is a very appealing one, I admit. It’s not that it can’t be done – there are plenty of examples showing that it can. What has not been demonstrated is that anyone can do it at an industrial scale and at a cost that competes with dominant fossil fuel energy.
I would not be surprised if there’s enough energy held in waste wood, sawdust and corn cobs to displace a significant amount of the world’s oil consumption. But then again, the amount of food wasted every day in America would be more than enough to feed all the Somalis facing drought-induced famine. This doesn’t mean we could realistically expect to collect all the restaurant table scraps and left over bagels rotting in trash cans around America, fly them to Somalia and use them to feed the hungry. Cellulosic biofuels, in the environment of a dominant oil industry that is protected by consumers and politicians alike, often strikes me as that sort of pipe dream.
I wouldn’t give up on them per se – but the appeal of turning waste into liquid fuel needs to be weighed with the reality of whether or not it makes sense to do so. It’s not clear to me that Petrobras has struck an adequate balance here.