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effective manner, wood glucose can, to a large extent, replace
cereals as a feed source for both ruminants and monogastric
animals. Other fibrous plant sources such as straw, leaves and
nutshells are also available in large quantities. Finding ways
to feed the world’s livestock is therefore a primary challenge
(Keyzer
et al
., 2005).
Other sources for feed that are not fully exploited include sea-
weed, algae and other under-utilized marine organisms such as
krill. However, their potential is uncertain, since technological
challenges still remain. In addition, the impact of their harvest-
ing on the ecosystem is of concern. The use of waste provides a
much greater potential for alternative sources of animal feed.
availability of cereal for human consumption. For other feed
sources to become a sustainable alternative to the current use
of cereals, their exploitation must not be resource-demanding.
This poses a big challenge, since most of the easily available
feed sources have already been fully exploited, although some
alternatives still exist.
Cellulose is the most abundant biological material in the
world, but the energy it contains is not readily available for ani-
mal production. Due to the interest in using this material for
bioethanol production, there are currently large research pro-
grams underway to chemically and enzymatically degrade this
cellulose into glucose. If this becomes possible and in a cost-
By 2050, 1,573 million tonnes of cereals will be used annually for
non-food (FAO, 2006a), of which at least 1.45 million tonnes
can be estimated to be used as animal feed. Each tonne of ce-
real can be modestly estimated to contain 3 million kcal. This
means that the yearly use of cereals for non-food use repre-
sents 4,350 billion kcal. If we assume that the daily calorie need
is 3,000 kcal, this will translate into about 1 million kcal/year
needed per person.
From a calorie perspective, the non-food use of cereals is thus
enough to cover the calorie need for about 4.35 billion people.
It would be more correct to adjust for the energy value of the
animal products. If we assume that all non-food use is for food-
producing animals, and we assume that 3 kg of cereals are used
per kilogram animal product (FAO, 2006b) and each kilogram
of animal product contains half the calories as in one kg cereals
(roughly 1,500 kcal per kg meat), this means that each kilogram
of cereals used for feed will give 500 kcal for human consump-
tion. One tonne cereals used for feed will give 0.5 million kcal,
and the total calorie production from feed grains will thus be
787 billion kcal. Subtracting this from the 4,350 billion calorie
value of feed cereals gives 3,563 billion calories.
Thus, taking the energy value of the meat produced into con-
sideration, the loss of calories by feeding the cereals to animals
instead of using the cereals directly as human food represents
the annual calorie need for more than 3.5 billion people.
How many people can be fed with the cereals
allocated to animal feed?