A small group of Mexicans from the academic and private sectors has been trying to get an Agave-to-ethanol project up and running. High in sugar content, the project team estimates that varieties of Agave tequilana weber can yield up to 2,000 gallons of distilled ethanol per acre per year and from 12,000-18,000 gallons per acre per year if their cellulose is included, some 14 dry tons of feedstock per acre every year.The numbers seem really optimistic to me. If Agave could produce so much more sugar per acre than sugar cane, without any need for nitrogen fertilizers and with low water requirements, why aren't we producing sugar from it right now? I am skeptical that they can really get 2,000 gallons per acre per year or 2.5 times as much as sugar cane. But, even if they were just competitive with sugar cane, it seems like it would make sense given its ability to grown on semi-arid wastelands. It would also be much better than using corn, if their numbers are anywhere near accurate.
Corn ethanol, for example, has an energy balance ratio of 1.3 and produces approximately 300-400 gallons of ethanol per acre. Soybean biodiesel, with an energy balance of 2.5, typically can yield 60 gallons of biodiesel per acre while an acre of sugar cane can produce 600-800 gallons of ethanol with an energy balance of 8.0. An acre of poplar trees can yield more than 1,500 gallons of cellulosic ethanol with an energy balance of 12.0, according to a National Geographic study published in October 2007.
"High quality agaves are very good feedstock material for biofuel...for the following characteristics: high total sugar density and content; high weight of the fruit and stems; cultivation and harvest cycles of six years; high density of plants per hectare; genetic diversity and high adaptability, low water requirements; CO2 and capture; methane metabolism; soil retention; plant nutrition; products from inulin; and low maintenance during cultivation," Madrigal said.
"Our enhanced Agave tequilana weber variety plants have a sugar content of 27º to 38º Brix, [which is] 3-times sugarcane's and weigh around 300 kilos (660 pounds) each individual. But we've got plants from another agave species that weigh 1.2 metric tons each with sugar content around 25º Brix, double that of sugar cane. This means that annually per acre, we could easily get 5,000 gallons of distilled ethanol and fifty metric tons of dry biomass, with 33 metric tons of cellulose content."
According to Velez's calculations, 7 million hectares of the Agave-to-ethanol team's enhanced Agave tequilana weber variety could provide the entire 36 billion gallons of ethanol the U.S. government needs by 2022 to comply with the renewable fuel standard set forth in December of last year, as well as 250 million metric tons of the dry biomass it is aiming to obtain by 2017.
"Agave thrives in semi-arid wastelands — 50% of Mexico — needs no watering or agrochemicals, requires very scarce field labor and grows well in any type of soil, even highly degraded and steep terrains, because it takes nitrogen from the air. One-third of the world's habitable land is arid and semi-arid where agave can be cultivated. Some agave species accept temperature ranges from -14ºC to 50ºC," he said.
And as one who has suffered a bad tequila experience, I would much rather use it to fuel my car than to drink it.
via Renewable Energy World