Page 8 - Academic Press Encyclopedia of Physical Science and Technology 3rd BioTechnology

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Encyclopedia of Physical Science and Technology EN002C-60 May 17, 2001 20:23

164 Biomass Utilization, Limits of

price for ethanol does not compare favorably with that for Furthermore, some of the economic and energy con-
the production of gasoline fuels which presently is about tributions of the by-products are negated by the environ-
25c / per liter. mental pollution costs associated with ethanol production.
Based on current ethanol production technology and re- These are estimated to be about 6c / per liter (Table IV). In
cent oil prices, ethanol still costs substantially more to pro- United States corn production, soil erodes about 12 times
duce in dollars than it is worth on the market. Clearly, with- faster than it can be reformed. In irrigated corn acreage,
out the approximately $1 billion subsidy, United States ground water is being mined 25% faster than its natural
ethanol production would be reduced or cease, confirming recharge rate. This suggests that the environmental system
the fact that basically ethanol production is uneconomical. in which corn is being produced is being rapidly degraded.
Federal subsidies average 16c / per liter and state subsidies Further, it substantiates the finding that the United States
average 5c / per liter. Because of the relatively low energy corn production system is not sustainable for the future,
content of ethanol, 1.5 l of ethanol is the energy equivalent unless major changes are made in the cultivation of this
of1lofgasoline. This means that the cost of subsidized major food/feed crop. Corn should not be considered a
ethanol is 68c / per liter. The current cost of producing renewable resource for ethanol energy production.
gasoline is about 25c / per liter. When considering the advisability of producing ethanol
At present, federal and state subsidies for ethanol pro- for automobiles, the amount of cropland required to grow
duction total about $1 billion per year and are mainly paid corn to fuel each automobile should be understood. To
to large corporations (calculated from the above data). The clarify this, the amount of cropland needed to fuel one au-
costs to the consumer are greater than the $1 billion per tomobile with ethanol was calculated. An average United
year used to subsidize ethanol production because of in- States automobile travels about 16,000 km/yr and uses
creased corn prices. The resulting higher corn prices trans- about 1900 l/yr of gasoline. Although 8000 kg/ha of corn
late into higher meat, milk, and egg prices because cur- will yield about 3100 l of ethanol, it has an energy equiv-
rently about 70% of the corn grain is fed to United States alent of only 1952 l because ethanol has a much lower
livestock. Doubling ethanol production can be expected to kilocalories content than gasoline.
inflate corn prices perhaps as much as 1%. Therefore, in However, even assuming zero or no energy charge for
addition to paying tax dollars for ethanol subsidies, con- the fermentation and distillation process and charging only
sumers would be paying significantly higher food prices for the energy required to produce corn (Table III), the net
in the market place. It should be noted that the USDA is fuel energy yield from 1 ha of corn is 433 l. Thus, to pro-
proposing to increase the subsidies to the large corpora- vide 1900 l per car, about 4.4 ha of corn must be grown to
tions by about $400 million per year. fuel one car with ethanol for one year. In comparison, only
Currently about 3.8 billion liters of ethanol are being 0.6 ha of cropland is currently used to feed each American.
produced in the United States each year. This amount of Therefore, more than seven times more cropland would be
ethanol provides only about 1% of the fuel utilized by required to fuel one automobile than is required to feed
United States automobiles. To produce the 3.8 billion liters one American.
of ethanol we must use about 1.3 million hectares of land. Assuming a net production of 433 l of fuel per corn
If we produced 10% of United States fuel the land re- hectare and if all automobiles in the United States were
quirement would be 13 million hectares. Moreover not all fueled with ethanol, then a total of approximately 900
the 3.8 billion liters would be available to use, because a million hectares of cropland land would be required to
lot would be needed to sow, fertilize, and harvest 13 mil- provide the corn feedstock for production. This amount
lion hectares. Clearly, corn is not a renewable resource for of cropland would equal nearly the total land area of the
ethanol energy production. United States.
The energy and dollar costs of producing ethanol can Brazil had been a large producer of ethanol, but has
be offset in part by the by-products produced, especially abandoned subsidizing it. Without the subsidy, economic
the dry distillers grains (DDG) made from dry-milling that ethanol production is impossible.
can be fed primarily to cattle. Wet-milling ethanol plants
producesuchby-productsascornglutenmeal,glutenfeed,
and oil. Sales of the by-products help offset the energy III. BIOGAS
and economic costs of ethanol production. For example,
use of by-products can offset the ethanol production costs Biomass material that contains large quantities of water
by 8–24% (Table IV). The resulting energy output/input can be effectively converted into usable energy using nat-
comparison, however, remains negative (Table IV). The urally occurring microbes in an anaerobic digestion sys-
sales of the by-products that range from13 to 16c / per liter tem. These systems use feedstocks, like dung and certain
do not make ethanol competitive with gasoline. plants such as water hyacinth, although production and