Suppose I planted 1/4 acre of my backyard or lawn with switchgrass. If I harvest the growing biomass over a year and assuming I was able to efficiently convert it to ethanol in my garage, how many gallons of useful automotive fuel could I produce?
I’ve read that the main hurdle with biofuels is producing enough and getting it to the consumer. If I could buy an aquarium-sized kit to create my own fuel, that would potentially solve both those issues. Furthermore, I would be carbon-neutral as far as my automotive needs go (even more so if I power my home with a generator run on biofuel). Is this idea as economical and ecological as it appears?
The resulting ethanol is the same stuff as in alcoholic beverages, so would I need some sort of license or permit? Is it easy to denature the stuff so neighborhood kids won’t try to break in and steal it? Would people buy the kits to make home-brewed Everclear-like moonshine?
Hmmm. Not as far-fetched an idea as it might appear on the surface. According to this, an acre can produce up to 1150 gallons of ethanol. So your 1/4 acre would produce a little under 300 gallons. Depending on how often you fill your tank and what you drive, that’s probably 1/2 to almost a full year of driving (although ethanol doesn’t pack as much energy as gasoline).
Obviously, there are practical difficulties. Switchgrass is apparently tough stuff and you’re talking 3-4 tons of grass (after drying). So harvesting by hand would be a chore. Renting a machine to harvest the crop would cut a big swathe in the $1000.00 or so of fuel savings you’re trying to generate. I’m thinking like most agricuture, switchgrass to ethanol is a process that benefits greatly from economies of scale.
Again, 4 tons of grass isn’t going to fit very snugly into an “aquarium-sized kit” unless you processed it in batches.
Oops, forgot to mention that switchgrass isn’t your friendly croquet and frisbee style grass. Hope the neighbors don’t mind a quarter acre of 8 foot high grasses growing next door and blowing their seeds everywhere.
In the last 7 years, I’ve consistently used only 100 gallons of gasoline each year. I figure I’d need 150 gallons of ethanol to do the equivalent amount of driving. So, if I only use half the amount, I just sell the other half to a neighbor or power a home generator. If gas prices keep going up, perhaps the neighbors will have switchgrass in their yard, too. In that case, I doubt they’d mind my swath.
As far as harvesting, I figure going at it with a machete is good exercise. I’m solving global warming and obesity at the same time!
As far as the kit, I think it will eventually be possible to have something the size of a 55 gallon aquarium (with stand) that fits in everyone’s garage. It could use bio-engineered bacterium to do the conversion, which works fine for smaller quantities but actually doesn’t scale UP very well. I think people would be willing to spend up to $1000 on a working kit, especially if it produces drinkable home-brewed alcohol too.
I didn’t realize they differentiated between the types of stills. I couldn’t find licensing info for Texas (the OPs location) with a quickie search. For a distilled liquor, you have to get a federal BATF license as well as a state license.
Way back when (early '80s), I met someone who was operating a farm still on an experimental basis. They had a necessary permits and it was a low-budget operation, so I’m sure they didn’t spend a lot.
Don’t get too excited there. While you can ferment and distill starches easily, cellulose (essentially where all of the energy is in switchgrass) requires a lot more processing. It needs to be broken down into sugars by various processes, none of which have yet become commercially viable. Personally, I’m optimistic, but at this point it’s not something you can do in your garage. The most promising approach uses enzymes to break down the cellulose, but unless you have a biotech firm hidden in your basement, you won’t be able to do that yourself. I’m not familiar with the chemical alternatives, but I’m under the impression that they are all pretty unwieldy.
Wouldn’t it be more effective to just produce ethanol from sugar and yeast A mix of sugar, water and yeast usually gets the alcohol content up 10-13%, so from 200 liters of still you get about 20 liters of 80-96% ethanol.
Traditionally you need approximately 220 g sugar per liter of still using normal baking yeast that will ferment up 13%, implying you need approximately 44 kg of sugar for 200 liters of still.
Which is more cost effective? Sugar or switchgras?
Here’s a quick calculation: I can buy a 10 pound bag of sugar at the supermarket for $4. I’m going to need 10 of those bags (i.e. 100 pounds or 45 kg) to make 200 liters of still to make 20 liters of ethanol. So, for $40 worth of sugar, I can produce about $10-$15 dollars worth of ethanol. So it’s a losing proposition for automotive fuel at today’s prices, but possibly worthwhile if I plan to drink the result or trade it with local friends. Now, if gas prices rise sharply in the future, it could become profitable to do this.
Might be too dry out west near austin but over here in the Orange- Beaumont area, growing your own ribbon cane is fairly easy. Whats more is you don’t even have to refine it down to sugar, just squeeze out the juice and add yeast. As far as energy content for every square meter of cane exposed to sunlight you can produce up to 20 Kg of sugar.
The short story: Corn ethanol gives you maybe 40% more energy than you put in, but switchgrass yields over 500% more energy. Still, you can ferment and distill any sort of starch you grow at home, but cellulose requires a lot more effort to extract usable energy.
You can use it yourself, but if you sell it as fuel, then technically, you’re breaking the law (unless you jump through a lot of hoops to get the fuel certified). I highly doubt the EPA is going to be concerned about anyone selling a few gallons to their neighbor (particularly since it’s renewable), but since we’re at the level of detail of still fees, wanted to point this out for completeness.
A mix of sugar, water and yeast usually gets the alcohol content up 10-13%, so from 200 liters of still you get about 20 liters of 80-96% ethanol.