Chemistry Reference
In-Depth Information
Scheme 14.19
level of the chemical industry with these, as yet,
unfamiliar materials. New, non-biological methodol-
ogy for the use of renewables will grow in parallel.
work [77] projects that world oil production could
peak and then begin to decline in the next 5-10
years. It is unlikely that demand will decrease in line
with production. In the USA, energy consumption
has increased by more than 28% (about 21 EJ)
during the last 25 years, but more than half of this
energy growth (about 11 EJ) has occurred during the
last 6 years, indicating that other feedstock sources
will be needed [78]. Of course, a wider use of renew-
ables always begs the question: is there enough to
fulfil the traditional biomass needs in food, feed and
fibre and still use the material for the production of
chemicals? Several analyses indicate that there
should be little problem [79].
Yet our chemical feedstock supply is overwhelm-
ingly dominated by non-renewable carbon. Only
about 2% comes from renewable sources [80], thus
relatively few examples exist of large-scale industrial
processes based on renewables. Two notable exam-
ples are the pulp and paper and the corn wet milling
industries. Both convert huge amounts of renewable
feedstocks into market products. The corn industry
alone produces 8-10 (¥ 10
9
) bushels of corn per year.
Each bushel contains 33 lb of renewable carbon as
glucose, and a corn harvest of 10 ¥ 10
9
bushels is
equivalent to 500 ¥ 10
6
barrels of crude oil [81]. Over
1 ¥ 10
9
bushels of this supply is converted to ethanol
and high-fructose corn syrup. The pulp and paper
industry consumes over 100 ¥ 10
6
t year
-1
of wood
[82]. Some of this production is used for the manu-
facture of chemicals. Speciality dissolving-grade
celluloses are used for the production of over 1.4 ¥
10
6
t year
-1
5.1 The case for renewables
Well into the twentieth century, renewable feed-
stocks supplied a significant portion of the nation's
chemical needs. It is only in the period of time
between 1920 and 1950 that we have witnessed
the transition to a non-renewables-based economy
[73].
A vast amount of renewable carbon is produced in
the biosphere; about 71 ¥ 10
9
t is fixed annually, an
amount that could supply almost all domestic
organic chemical needs, which is currently about
7-8% of our total non-renewables consumption
[74]. (In 1995, the USA consumed 5.6 EJ (10
18
joules) of energy for the production of synthetic
organic chemicals. This corresponds to about 7% of
the fossil fuel feedstocks used in the USA.) When
measured in energy terms, the amount of carbon
synthesised is equivalent to about ten times the
world consumption [75]. Cellulose, the most abun-
dant organic chemical on earth, has an annual pro-
duction of about 90 ¥ 10
9
t [76]. These values
correspond to the production of 171 ¥ 10
9
total
tonnes of biomass and assumes that biomass is 45%
carbon.
The yearly availability of renewables is most
important, because it makes this resource almost
unlimited if used in a sustainable manner
.
This con-
trasts with world supplies of petrochemicals. Recent
of cellulose esters, ethers and related
