« A Veteran's Day Walk Around | Main | Lichens »

Sugar Cane & Ethanol

Ethanol has lots of advantages, according to what I heard during a program on biofuels at the Brazil Institute at the Wilson Center. One of the biggest advantages is that it is dispersed, both nationally and internationally. Within a country, ethanol production tends to be in rural areas. It is difficult to over centralize, since moving the feed stocks is much more expensive than moving the ethanol.  (This is a very old advantage, BTW.  In our own history, the whiskey rebellion was fueled by exactly the same consideration. It was much more effective to move whiskey made from grains than move the bulky raw materials.)  It is also dispersed internationally, unlike petroleum, which is heavily concentrated in the Middle East. Feed stocks for ethanol can be grown almost anywhere in the world, which is why people can make booze all over the world. Of course, not all feed stocks are equally good, but sugar cane, one of the best feed stocks, can be grown all over the tropics.

Sugar cane is especially well suited to Brazil. The climate is nearly perfect in many regions. Sugar cane requires lots of water during some seasons and not much later on. The sugar doesn’t form well unless the plant is stressed by drought.  This is why sugar cane does not grow well in the Amazon, where it rains throughout the year, but other areas of Brazil have very distinct wet and dry seasons. 

The sugar cane wet/dry rotation also works well in Brazil’s energy equation in another way.  Brazil is heavily dependent on hydro-power and hydro is heavily influenced by rain.  During the wet seasons, there is a lot of river flow, but not so much in the dry season.  Dry season shortfalls are filled with thermal plants, usually burning fossil fuels.  This is where sugar cane comes in again.  Besides the ethanol produced by the cane, there is also the biomass (i.e. canes).  Refiners have long used the biomass as an energy source, but this co-generation potentially produces much more energy than is needed in the refineries. Sugar cane is harvested in the dry season, which means that the fuel is available exactly when it is most needed.

Sugar cane is a six year crop, i.e. it must be replanted every six years.  They use a kind of six field rotation in Brazil.  A grower divides his land into seven sections for each of the growing seasons for the cane, plus a non-cane rotation.  So each year, one section gets the final harvest. This one is then planted with a alternate crop, usually a legume such as beans or soy.  These crops fix nitrogen and restore the soil fertility.  The non-cane rotation also serves to allow diseases of cane to die out on those fields.  After the year, cane is again planted, but a different variety in order to avoid blight.  There are more than 400 varieties of sugar cane.  

The Brazilian biofuels endeavor has meant an increase in land devoted to cane, but not really very much.  Less than 1% of Brazilian land is devoted to cane for ethanol or crops for biodiesel.   Better plant varieties and methods of growing have allowed more production.  Of course, there has been expansion onto other land.  Most of this land was degraded pasture land.  Brazil is a high intensity cane producer, but beef production has been extensive, i.e. requiring a lot of land per unit of production.  Brazil has only 1.1 head of cattle per hectare of pasture.  This could be greatly improved and since Brazil has a lot of pasture land (more than 20% of Brazil is pasture) there is significant scope for cane production w/o contributing to deforestation.

Sugar cane production in Brazil is almost entirely rain fed and Brazil has a lot of water in general.  Brazil accounts for 19% of the world’s total river discharge.  Of this, 13% of the rain actually lands on Brazil itself.  The rest comes from water flowing into the country from neighboring countries.

Sugar cane culture is being mechanized. All new plantations must be harvested mechanically and by 2014 it will no longer be legal to burn stalks, which means that all plantations will need to be harvested mechanically. Why?  It is actually very practical Sugar cane has sharp leaves, so sharp and still that they cut people working among the plants. For centuries, growers have used surface fires to singe the leaves off, which allow workers to go into the cane and harvest it. W/o fire, it is practically impossible to harvest cane by hand. Mechanical harvesting eliminates the need for surface fire. Even with the singeing fires, work in the cane fields is dirty & brutally hard. While it is always difficult to throw lots of this kind of semi-skilled labor out of work, these are not the kinds of jobs you want to preserve going into the next century.


Hosting by Yahoo!

Post a comment

(If you haven't left a comment here before, you may need to be approved by the site owner before your comment will appear. Until then, it won't appear on the entry. Thanks for waiting.)