Renewable Energy in Industrial Applications – an ... - Unido

BIOMASS
product if second generation ethanol production
takes off. This would offer new opportunities for
the development of biorefineries.
The most promising petrochemical biofeedstocks
other than bio-ethylene, are polylactic
acid (PLA) as a substitute for polyethylene
terephthalate (PET) and polystyrene (PS), poly
hydroxy alkaonates (PHA) as a substitute for
high density polyethylene (HDPE), and bio poly
trimethylene terephtalate (PTT), as a substitute
for fossil-based PTT or nylon 6 (Dornburg et al,
2008).
Traditional fossil feedstocks can be substituted
with bio-derived ones at a number of points in
the petrochemical products production chain:
• fossil feedstock can be substituted with a biobased
one (e.g. natural gas can be
substituted with synthetic natural gas from
biomass gasification and subsequent
methanisation);
• petrochemical building blocks can be
substituted (e.g. ethylene can be substituted
with bio-ethylene);
• traditional plastics can be substituted with a
bio-based substitute (e.g. PET can be
substituted with PLA); or
• a petrochemically produced material can be
substituted with a bio-based material with
similar functional characteristics (e.g. plastic
can be substituted with wood or nylon with
silk).
Several substitution processes are discussed in
more detail in Annex 3.
Worldwide plastics consumption amounts to
approximately 245 Mt/yr. Olefins (ethylene and
propylene) are the most important feedstock.
The steam cracking of naphtha, ethane and gas
oil is the dominant production technology. Large
amounts of aromatics are also produced from
refinery streams. World-wide, steam cracking
accounts for approximately 3 EJ of final energy
use and approximately 200 million tonnes of
CO2 emissions. This represents around 20% of
the total final energy use and about 17% of the
total CO2 emissions from the chemical and
petrochemical sector. A number of new
technologies are being developed to
manufacture olefins from natural gas, coal and
biomass. Only those based on biomass offer the
potential to eliminate fossil fuel use and GHG
emissions.
The first chemicals and man-made plastics,
commercialised in the 19th century, were made of
bio-based polymers. Most of these materials
were gradually displaced by synthetic polymers
as the petrochemical industry grew after the
1930s, although some, such as man-made
cellulose fibers, maintained a market niche. In
the last twenty years, bio-based chemicals and
plastics have been receiving increased attention
as a means of responding to problems with
waste management (limited capacities and
littering), high prices for fossil fuels and
feedstocks, questions about the medium- to
long-term supply security of these feedstocks,
technological progress, and policy goals including
climate policy.
Bio-based polymers are produced in three main
ways:
• by using natural polymers such as starch and
cellulose which can be modified;
• producing bio-based monomers by
fermentation or conventional chemistry and
polymerising them, for example to produce
PLA; or
• producing bio-based polymers directly in
microorganisms or in genetically modified
crops.
The first of these three production methods is
currently by far the most important, being
involved for example in the use of starch in
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