Starch comes mainly from wheat, and corn,rice, tapioca etc.
At present 28% (not 40% as is often quoted) of the corn grown in the USA is converted to ethanol for cars.
Calculations in the US show that if all the corn crop was used to produce ethanol, it would replace only 18% of the fuel. To replace all the liquid fuel, the farmed area would need to be 3 times the size of USA.
The US government subsidies are being removed from ethanol-from-corn.
However subsidies are being kept for cellulosic ethanol made from lingo-cellulose, or wood. (see energy balance below)
Energy profit of ethanol production
The greatest problem with ethanol is that it takes energy to make it. The question is how much energy profit is there from each method, and is it worth it?
It is very difficult to get a consistent view on this. The results are often driven by commercial or political agenda.
Do you include the goods the workers consume? Do you give the bye-products any share of the energy cost?
For example, counting the energy in the byproducts changes an energy yield of 1.06 to 1.67.
As an example of varying numbers, a search of the USDOE website and Wikipedia gives the following results:
The report below concludes that for every unit of energy invested in producing ethanol from corn, 2.3 units are produced in the ethanol.
The conclusion of the study summarised in the table on the right is a profit of 40% or 1.4
Different crops and different climates are very different so the numbers will vary accordingly.
There is a lot of political and commercial pressure to show that ethanol has more energy than is required to produce it. And there are reports proving it.
However some say if you include everything such as food for the workers, and packaging etc for their goods, and so on, that more energy is used than the ethanol can release.
Cornell ecologist's study finds that producing ethanol and biodiesel from corn and other crops is not worth the energy. However this study has been criticised widely for assuming all crops are irrigated, and allocating none of the energy costs to the bye-products. There are claims the author has an agenda.
Energy balance for ethanol production
Source US Dept of Energy
Corn stover is the leftover leaves, stalks, husk, and cob. If this is burnt and used to distil the ethanol out of the water, then this is a huge energy saving. The problem with ethanol is, it takes about half the energy it contains to separate it from the ferment by distillation.
The credit for the bye-products probably assumes they are produced with non biofuel.
Political "donations" (bribes?)
Manildra, Australia's main ethanol producer, is one of the largest political donors in Australia. There are records in Hansard of criticisms of the financial support Manildra has received in return. Surely this is a bribe?
It is quite likely that there is now a large lobby group of voters who rely on subsidies. Like the arms industry, they may be hard to stop.
Logically, politically, economically, and sustainably, this issue is a mess.
My feeling is that ethanol from corn/wheat/starch is not worth pursuing. Even if there was a 40-140% energy profit, it is not nearly enough.- John Davis
Hansard 22382 Bob Brown, Greens senator
Other mentions of Manildra in Hansard
Research at USDA and UC–Berkeley involves patching a gene from corn called corngrass into switchgrass, to create a grass that is incapable of aging.
The new switchgrass stays in an early stage of life in which it never goes dormant, and it never produces seeds or flowers.
Without the need to expend energy on flowers and seeds, the grass keeps up to 250 percent more starch in its stem than other varieties, yielding more sugar for fermentation into biofuels.
The leaves are much softer than those in unmodified switchgrass, and they contain a different kind of lignin.
Ref: Clean Technica