Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
orographic (mountains cause windward rains), or cyclonic rains. The last type
prevails in temperate latitudes, yielding water steadily pouring out of dull, overcast
skies, and in winter as snow, sleet, or hail. Cyclonics reach their main precipitation
between latitudes of 45 and 55°North, primarily in the Northern Hemisphere, with
a preponderance of summer rainfall. 7
Forests and grasslands represent the two major vegetations. The former stabilize
the climate, including moisture or dust content of air and the water table. The role
of grasslands is less appreciated. For example, most authors credit 90% of the
planetary biomass to forests — allegedly 50 × 10 9 t 1 — of which only 2.3 × 10 6 t
(4.5%) is consumed by humans 2 , primarily as fuel in the Third World besides timber
and pulp for paper in the First World.
Regarding wood as a possible energy source, one has to consider that only 14
to 18% of forests are accessible. About 1 to 2 × 10 5 km 2 of tropical forests are
eradicated yearly. The annual yield per hectare declines from the tropical 20 t
wood/ha to merely 3 t/ha in Central Europe (timber quality) and still less in Northern
Europe (1 to 2 t/ha). However, improved forest management and reforestation could
possibly double the timber harvest. Complementing such endeavors could be the
perfection of the burgeoning technique to utilize whole trees, rendering their lignin
and carbohydrates into saleable products to boost the revenues per hectare to be
reinvested in forestry.
As regards grasslands, one has to discern drier (steppe) and moister (prairies)
areas allowing trees to grow turning to a savannah, whereas vanishing precipitation
diverts the steppe to desert. The total grass-bearing surface is estimated to cover a
fifth of all continents close to 30 × 10 6 km 2 , including the mentioned 23 × 10 6 km 2
attended by farmers or stock-breeders for animals, etc. For extensively cultivated
grasslands, a biomass of 4 t/ha of dry matter (DM) can be interpreted as modest.
Nevertheless, even by such an assumption, nearly 12 × 10 9 t of DM/ha would contain
at least 50% of cellulosics capable of yeilding 3 × 10 9 t of ethanol, energetically
virtually equivalent to oil if upgraded by burning in fuel cells, furnishing electric
and thermal power approaching almost the 7.3 billion OE spent in 2001. 2 The
supervised, and, if intensively cultivated, grasslands in temperate zones would be
capable of producing between 7 and 12 t of DM/ha, possibly amounting to a global
23 × 10 6 km 2 , bearing ca. 23 × 10 6 km 2 × 10 2 ha × 10 t/ha = 20–23 × 10 9 t of
DM/ha made up of approximately 60% polysaccharides, 15% lignin, 10–15% ashes,
and 10% protein. Such polysaccharides include a soluble fraction and solid fibers,
both convertible to ethanol, whereas proteins are suitable for forage and human food
(especially the rubisco-fraction rich in magnesium). Lignin and ash are returned to
the soil, furthering humus of enhanced nitrogen assimilation.
The actual share of grass-bearing lands is closer to 25% (37 × 10 6 km 2 ) of the
terrestrial surface because large sections of arable land bear grasses such as cereals,
corn, sugarcane, or bamboo. Cereals in temperate zones yield 3 to 4 t/ha of starch
crops compared to sugar from cane of 1 to almost 9 t/ha (in Hawaii), depending on
soil, age of crop, sunshine, and rain. Carbohydrates stored below the surface of soil
furnish even more starch, for example, potatoes about 6 to 7 t/ha starch or sugar
beets up to 12 t/ha pure sugar. Obviously, intensive agriculture yields impressively
more carbohydrates than extensive forest management in northern latitudes. Wood