Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
wood would be at disposal after a period of reforestation. Finally, whole-tree utilization
combined with a reorganization of the paper cycle would supply abundant
ethanol from grasslands, restricting, however, their use as pastures for grazing
animals. Entirely new horizons will be opened for lignin, 21 for example, for selfcrimping
fiber 22 or as an extender for biodegradable polylactides. 14
21.11 CONCLUDING REMARKS
The grass-covered global surface with about 23 × 10 8 ha photosynthesizes a gargantuan
amount of polysaccharides (PS), proteins, and lignins. If extensively cultivated,
probably half of this area would be sufficient to produce enough ethanol to serve as
the world’s fuel source, exceeding the efficiency of oil by ca. 85% (electric plus
thermal) when feeding fuel cells, almost doubling the output of a Carnot cycle. It
is also astonishing that temperate regions yield much higher PS harvests than the
tropics do. For example, sugar harvest in more south located Cuba yields ca. 2 t/ha
whereas that in more north located Bavaria ca. 12 t/ha despite more intense sunshine
in the South. However, maximal rainfall in the North concentrates closer to the
harvest (20 to 30 in. for agriculture and beyond 30 in. for forests) of grasses and
energy crops such as Sudan grass.
Another surprising feature is the amount of DM in crops of forests (3 t/ha ·
annum) and grasslands (7 to 20 t/ha · annum) caused by interaction of sunlight and
chlorophyll but governed by water supply at the right time. Hence, green biorefineries
can replace the present oil flow of nearly 3.5 bt/annum by ethanol if the explosive
growth of population can be controlled.
A beneficial side effect is the supply of proteins up to 15% of DM. This
indispensable food component is lost if fermentation produces biogas instead of
ethanol. At any rate, lignin plus ash return to the soil as a humus preserver, increasing
nitrogen assimilation fourfold. The practice to burn lignin appears in hindsight an
offence against nature.
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