16 Introduction to Renewable Biomaterials
biomass consists primarily of lignocellulose. Miscanthus is grown in Canada yielding
up to 44 tons dry mass per hectare. Today, it is utilized thermally but the future poten-
tial is seen in second-generation energy carriers and chemicals. It can be cultivated on
grassland (globally 3.55 billion hectare (Raschka and Carus, 2012))
Woody biomass from short-rotation trees like poplar yields 10–15 tons per hectare
annually within 4–6 years. The trees sprout after harvest again over a period of at
least 20–30 years and are harvested every 2 years. Lignocellulosic biomass consists of
42–49% cellulose, 24–30% hemicellulose, and 25–30% lignin. It is today used for gen-
erating heat by burning. The material is quite identical with forestry waste (hardwood
contains 42–51% cellulose, 27–40% hemicellulose, 24–28% lignin) or oil palm residues
which is also basically lignocellulose. Its future potential is in second-generation energy
carriers and chemicals. Under European conditions, forests add 12.1 m^3 wood per
hectare per year with an average density of 470 (pine) to 690 kg m−^3 (oak). Global forest
area is about 4 billion hectare with 264 million hectare planted (Adams, 2012).
1.3.5 Lignocellulosic Biomass
Straw from cereals represent another lignocellulosic biomass. Today, it is used for
livestock bedding and more low-value applications. As it is a by-product of cereal
agriculture, thus part of an existing harvesting process, it draws special attention as a
future second-generation carbon source. With an average cereal/corn relation of 1 to 1
100 million tons of cereal comes with about 100 million tons of straw. As 20–30% of the
straw should be left on the ground for rotting and keeping the soil fertile about 70–80
million tons could be available from 100 million tons of cereal biomass for industrial use.
1.3.6 Algae
Microalgae consist of a single or only a few cells and produce fatty acids, carbohydrates,
and some special ingredients by photosynthesis. Algae are cultivated commercially only
for special compounds like astaxanthin, which is added to fish and poultry feed giving
salmon and egg yolk its typical color. As biodiesel gets growing commercial attention,
algae are evaluated as a source of lipids (up to 70% lipids of fresh algae biomass).
Microalgae are seen superior to land plants due to high rate of growth, high yield per
hectare, high energy content (Table 1.19), lack of lignin, and low cellulose content.
They are cultivated in open ponds or specific photoreactors. In both the methods,
algae are grown under light and supplied with atmospheric CO 2 or CO 2 emitted by
an industrial plant. Therefore, such production systems neither occupy fertile land nor
Table 1.19Performance of microalgae, corn, and short-rotation trees (Fachagentur
nachwachsende Rohstoffe, 2012).
Biomass
Yield(tondry
mass ha−^1 year−^1 )
Fixed CO 2
(ton ha−^1 year−^1 )
Energy
(MWh ha−^1 )
Energy
(MJ kg−^1 )
Microalgae (open pond) 40–60 66–100 166–250 9.0
Microalgae (reactor) 80–120 130–200 333–500 9.2
Corn (whole biomass) 15–20 25–35 75–100 10.8
Short-rotation trees 6–20 10–35 30–100 10.8
