Yes, the tasty, tuberous root is superior to corn and almost as good as sugar cane for producing ethanol for fuel, according to a new USDA study.
Scientists with the agency’s Agricultural Research Service (ARS) compared sweet potato and cassava grown in Maryland and Alabama to corn grown in those states. They found that sweet potatoes yield two to three times as many carbohydrates for fuel ethanol production, per acre, as corn does. That puts sweet potatoes at the low end of yields for sugar cane — the top ethanol crop. Cassava performed similarly in Alabama.
“Sweet potato looks really good and could serve as one potential source of bioethanol for the future,” said Lew Ziska, an ARS plant physiologist at the Crop Systems and Global Change Laboratory in Beltsville, Md.
Here are the numbers from the study: For the sweet potatoes, carbohydrate production was 4.2 tons an acre in Alabama and 5.7 tons an acre in Maryland. For corn, carb production was 1.5 tons an acre in Alabama and 2.5 tons an acre in Maryland.
Planting more sweet potatoes for fuel production would allow farmers to move corn crops out of the ethanol market and back into production for food or animal feed. This could help lower food prices related to corn worldwide (tortillas, high fructose corn syrup).
Ziska said his team were looking for crops that could be grown on marginal land with few synthetic inputs, such as fertilizers and pesticides, and could compete with corn in ethanol production.
Sweet potato and cassava fit the bill.
Right now we get most of our ethanol from the starch, or carbohydrates, in corn kernels. It’s a two-step process: First the starch gets converted into sugar, then the sugar into ethanol.
“There are a couple of advantages with sweet potato over corn,” Ziska said in an interview. “The first one is that you have a lot more carbohydrates overall. Corn typically has about 60 to 65 percent starch in the kernels; and that’s the principal source for ethanol. Sweet potato has about 80 to 90 percent total carbohydrates in the tuber. The other advantage is that, of those carbohydrates, in sweet potato, about 20 to 30 percent of them are sucrose, are sugar, and can be more easily converted into ethanol than starch can.”
Sweet potato has another advantage: It does not require as much fertilizer or pesticide as corn does. Corn uses large amounts of nitrogen fertilizer to grow and Ziska estimates that at least half of the nitrogen in use in the United States is converted from natural gas — a fossil fuel for which prices have shot up recently.
Ziska said sweet potatoes can be grown along the Eastern seaboard from New Jersey to Florida, and possibly in the Northwest as well.
We’re not talking small potatoes, either.
“These are not the sweet potatoes you would buy at Thanksgiving. These things are 20-, 30-pound tubers. So they’re huge,” said Ziska. These roots are bred to be very large and are normally chopped up and used as animal feed, he explained.
(I spoke today to John Kimber of the North Carolina Sweet Potato Commission Foundation, who said that not many sweet potatoes are grown for animal feed in the U.S., but in China — the world’s largest producer of sweet potatoes — about 80 percent of them are grown for animal feed. And those potatoes are higher in dry matter or carbs.)
Sweet potatoes sound like a sweet solution to the biofuel vs. food problem, but there are some hurdles to overcome. Start-up costs for sweet potato are high, due to the labor needed. “A lot of the sweet potato acreage is not entirely mechanized either for planting or for harvesting,” said Ziska. Sweet potato harvester machines are coming on line now and could make it more practical for more farmers to grow the crop commercially.
Ziska has submitted the paper describing the study to the journal Biomass and Bioenergy. The ARS published a press release August 20.
I think this is a great development. Now we have a crop that can efficiently produce ethanol — and we don’t have to saturate the environment with chemicals to do it. Remember, all that fertilizer leads to dead zones in the oceans.
We should ramp up sweet potato production for ethanol, so that we can put more corn back into the food supply. Balance is good, diversifying ethanol sources is good. What do you think? Post your comments below!
This is still food for fuel. Exchanging one plant for another doesn’t make a difference – proponents of corn ethanol also argued that the corn used would not be used for human consumption, anyway. And still, we saw a huge spike in food prices. True, corn is a much more intensive crop to grow than potatoes. But that doesn’t make the big difference. No matter what, if you are devoting arable to growing fuel rather than food, you are negatively impacting people who need to eat. And you still have a major fossil-fuel input to grow the crop.
It beguiles me why certain scientists, farmers, powerful agribusiness lobbying groups, continue to research and push food sources for alternative fuel. It’s not efficient. What is efficient is developing ways to harness the solar and wind power that is bestowed upon Earth in massive quantities every single day.
That’s what I think.
I think it does make a difference. We need look at all fuel sources and figure out which ones work best. If a crop is better than corn for making ethanol, we need to know that, especially if it can be grown on marginal farmland with less fertilizer and pesticide. Ethanol burns cleaner than gasoline, and although there’s no way we can grow enough plants for ethanol to replace all of our gasoline (we don’t have enough land), maybe we can continue to use ethanol blends for some part of our fleet — taxis, buses. If our cars end up being mostly hybrid plug-ins, maybe there’s a role for ethanol outside of it. I think we need to at least do the research to know what the best ethanol crops are.
In terms of solar and wind power, I agree, we should improve those and max those out because those are free sources of energy. But they are not fuels for vehicles, and even if we do have lots of plug-in hybrids one day, some vehicles are likely going to need fuels (trucks, tractors, etc).
Along those lines there’s an interesting story today about how some farmers in New York state are planting stinkweed for use as an alternative to soybeans for biodiesel fuel.
Stinkweed in your fuel tank? Maybe some day
http://www.msnbc.msn.com/id/26547441/
The advantage with stinkweed is that it is not a food crop, so it could be grown purely for fuel.
I think this has great potential for reducing fuel and food prices. Sweet potatoes produce more ethanol per acre than corn. With a greater yield, the balance between ethanol-producing land and food-producing land could be tipped in favor of food production.
As long as the tubers don’t prove to impact the price of animal feed too much we should see a reduction in food prices. With any luck, the price of ethanol will drop considerably as well. Imagine the oil companies trying to keep up with ethanol that’s a dollar less per gallon than gasoline. I hope they enjoyed their 40 billion dollar profits.
I don’t see this helping to reduce the amount of fertilizers and pesticides that we use. If we plant more crops for food, we’re going to need to use chemicals to protect them. We just wouldn’t need to use as many chemicals on crops meant for fuel.
That’s fantastic news. I’ve always known sweet potatoes were super. I use them as part of the foods I promote for preventing/getting rid of malnourishment. It’s a wonder root for sure. :) Thanks for sharing. This is great news.
Please publish cost data for Ethanol process from different sources such as Corn,Cane,Sweet Potatoes,Cloth/paper waste,wood/tire waste & CO2 capture system of coal/gas power plant stacks.This can be updated every year with change in price of
resources.
hey we can do it sweet potato is the best way to go lot”s of land in yuma AZ
west of pittsburgh and south of miami look and let’s get some GRANTS going
no time be wasting we are the USA we do big thing stop crying penut’s to let’s do it all lot’s of job’s and new job two SBA money needed we need GOV
to give lot’s of funding to get moveing no inport’s must be stop on or As long as the tubers don’t prove to impact the price of animal feed too much we should see a reduction in food prices true
Here is a study done in 1990 showing Jewel sweet potato to be the most productive ethanol producer.
http://www.hort.purdue.edu/newcrop/proceedings1990/v1-260.html
Think of this. What if you produced the 30/40 lb. tubers in a hydroponic greenhouse, sent them to cutting and mixing bowls, distill and produce ethanol right on the premises. No insecticides, no field preparation and harvesting, 1/10 the amount of water, 1/2 the amount of fertilizer/nutrient, and 1/10 the amount of labor.
Add solar panels for power for running the greenhouse and the distillery.
How cheap could alcohol be made?
DaEl
Dan, what is the name of the type of sweet potato that averages 20/30 lb. tubors?
DaEl
Do you have Lew Ziska’s email address?
Ethanol can be mass-produced by fermentation of sugar
The numbers look good and are very convincing when compared to other feedstock. Besides, sweet potatoes require very little from nature to grow and produce.