Polyhydroxyalkanoate-based Multiphase Materials - Polyhydroxyalkanoate (PHA) Based Blends, Composites and Nanocomposites - page 120

for energy production yields toxic emissions (e.g., dioxin) while material
valorisation is limited due to the diculties in validating an economically
relevant method. In addition, plastic recycling shows a negative eco-balance
due to the necessity of large volumes of water and energy consumption
(waste grinding and plastic processing) during all the different phases of
recycling. As plastics represent a large part of the waste collection at local,
regional, and national levels, institutions are now aware of the significant
savings that compostable or biodegradable materials would generate. Thus,
for these different reasons, it has become important to replace conventional
plastics with biodegradable polymers, particularly for packaging appli-
cations that are of major interest to society (industry to citizens to nature).
The potential of biodegradable and bio-based polymers is being recog-
nized as seen in growing research areas involved in helping us to overcome
the limitations of petrochemical resources at present and in the future.
Fossil fuels and natural gas can be partially replaced by greener agricultural
sources, which would also participate in the reduction of CO 2 emissions. The
major drawback in preventing their large scale exploitation is the high
production cost of bacterial fermentation-based polymers, the poor mech-
anical properties of the agricultural-based polymers, and industrially dif-
ficult methods of homogeneous modifications. However, biodegradable and
bio-based polymers often present macromolecular architectures and so new
properties that cannot be found with conventional polymers.

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6.1.1 Renewability and Sustainable Development
The concept of renewability and sustainable development is often described
and understood in terms of ''carbon economy''. The UN World Commission
on ''Environment and Development in our Future'' defines sustainability as
the development that meets the needs of the present time without com-
promising on the ability of future generations to meet their own needs. One
approach that meets this requirement is the ''concept of reincarnation'' or
the ''cradle to grave'' approach, which pertains to short term applications of
polymers such as packaging. 1 The use of annually renewable biomass must
be understood in terms of carbon economy or carbon cycle. A low carbon
economy (LCE) refers to the minimum greenhouse gas emissions in the
atmosphere, specifically CO 2 and methane. The common approaches to
achieving LCE are using renewable sources and technology that is energy
ecient. The carbon cycle, on the other hand, refers to the source of carbon
and the final destination of the converted carbon. The four main carbon
sources on the planet are: the lithosphere (e.g. limestone), the biosphere
(vegetal and animal), the hydrosphere (e.g. bicarbonate dissolved in the
oceans) and the atmosphere (CO 2 ,CH 4 ); the carbon cycle is thus the complex
process in which carbon can get exchanged between the four main reservoirs
of carbon. The exchange of carbon among these four reservoirs remains
balanced by natural processes but recent human activities (burning fossil
fuel and massive deforestation) have led to an important imbalance in the

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