26 Introduction to Renewable Biomaterials
behind such processes. It provides another example of how basic science is translated
into industry.
1.3.10 Expectancy of Resources
As it is the case with fossil feedstock, bio-based raw materials are also not available
without any limitation. However, the kind of limitation is different. In contrast to fossil
materials, biomass is renewable and regrows continuously. The only limiting factor is
the annual growth rate of the biomass source. In principle, vegetable as well as animal
biomass is renewable but only plants build biomass through photosynthesis and trans-
form atmospheric CO 2 into carbohydrates according the following chemical equation:
6CO 2 +12H 2 O→C 6 H 12 O 6 +6O 2 +6H 2 O
Only vegetable biomass is therefore directly involved in the photosynthetic carbon
cycle and should be considered as a major industrial feedstock.
Nature is estimated to produce annually 210 billion tons of vegetable biomass. Most
of it is lignocellulose (40–55% cellulose, 10–35% hemicellulose, and 18–41% lignin) with
an estimated carbon content of about 50%. Therefore, it can be reasonably assumed that
photosynthesis fixes globally about 105 billion tons of carbon.
However, because of economical, ecological, and societal reasons not all biomass
is available for human purposes. Sustainably available is biomass from agriculture,
forestry, and marine sources. The use of agricultural biomass for industrial purposes has
already been established. Today, global agriculture produces 14 billion tons of biomass
(containing about 7 billion tons of carbon) annually for providing food, feed, fiber, and a
little heat, fuel, and chemistry. A significant share is considered waste and utilized not at
all, of only little value or under valued: (i) agricultural side streams like straw, rice husks,
corn cobs; (ii) silvicultural materials like branches and saw-cut, and (iii) processing
residues like milling or food-processing residues (Table 1.31). These resources are going
to be realized for industrial purposes by second- and third-generation processing.
In addition to plant breeding, soil management, fertilization, and plant protection,
more efficient harvesting and storage methods will still be improved. Plant breeding
alone sets since decades the still unbroken trend of annual crop yield improvement
of about 2%. On the contrary, a growing world population (9 billion by 2050) will
ask for more food, feed, and fiber. Considering currently neglected resources, yield
improvement, and food demand a range of 0.5–1.4 billion tons of biomass has been
estimated to be sustainably available for industrial purposes by 2030 (Kircher, 2012;
Bang, Follér, and Buttazzoni, 2009).
1.3.11 Green House Gas Emission
In the photosynthetic carbon cycle, CO 2 is fixed in biomass and released into the
atmosphere again when biomass degrades (or is burned). Theoretically producing and
using vegetable biomass should not emit any CO 2. However, plants not only consist
of photosynthetic leaves but have roots interacting with the microbial soil flora. Soil
management (e.g., tilling) aerates soil thus activating microbial metabolism and the
related CO 2 emission further. It is estimated that a CO 2 amount equivalent to about 4%
of the harvested biomass is emitted by the microbial soil flora from agricultural areas.
Therefore, non-tilling land-management methods have been developed in order to at
