72 Introduction to Renewable Biomaterials
we use on everyday basis such as plastics, synthetic rubber and textiles, cosmetics,
fragrances, adhesives, dyes, cleaning agents and so on. With the depletion of fossil
resources and inevitable transition to low-carbon economy, most of these products will
need to be replaced with renewable alternatives to maintain the standards of living.
Because of its chemical composition and ability of various microorganisms to ferment
carbohydrates into array of different products, utilisation of biomass is the most
suitable way for the replacement of fossil-derived chemicals. The renewable chemicals
and renewable materials are equally important for the development of carbon free
economy as are renewable energy and renewable fuels.
Plant biomass is composed of many different chemical compounds synthesised at var-
ious stages of plant growth and development. Both presence and relative abundance of
these compounds vary significantly between different plant structures like seeds, fruits,
stems or leaves. From the chemical point of view, the structures synthesised in plant cells
can be divided into carbohydrates, lipids and phenolics, whereas taking into considera-
tion their function for the plant they could be divided into two groups: structural and
storage compounds (Figure 3.4). Biomass fraction composed of carbohydrates include
cellulose, starch, sucrose and heteropolysaccharides (hemicelluloses and pectins); the
phenolic fraction of biomass consists of lignin, whereas the lipid fraction comprises
triglycerides. The knowledge of basic chemistry of each of these groups will help to
understand the implications that the chemistry of these compounds has for potential
routes of conversion; therefore we strongly advise readers to familiarise with the
Function: Chemical structure:
Plane structure:
O 2
H 2 O CO 2
NADP+
ADP
AT P
NADPH
Pi
CH 2 O
Carbohydrates:
Sucrose
Starch
Cellulose
Lignin
Phenolics:
Lipids:
Triglycerides
Cellulose
Heteropolysaccharides
Heteropolysaccharides
Lignin
Plant storage:
Sucrose
Starch
Triglycerides
Figure 3.4Ultimate biological compounds produced via CO 2 fixation in chloroplasts during the
process of photosynthesis divided according to their function and chemical structures.
