Chemistry Reference
In-Depth Information
Table 14.3
Costs of some selected
renewable feedstocks
Material
US$ kg
-
1
US$ lb
-
1
Type of cost
Source
Polymers
Cellulose
0.44-1.10
0.20-0.50
Production
a
Lignin
0.07-0.13
0.03-0.06
Production
Fuel value
Carbohydrates
Glucose
0.60-1.10
0.27-0.50
Sales
b
0.13-0.26
0.06-0.12
Production
a
Xylose/arabinose
0.07-0.13
0.03-0.06
Production
a
Sucrose
0.40
0.1
8
Sales
c
Lactose
0.65
0.30
Sales
c
0.50-1.50
0.23-0.6
8
Sales
b
c
Maltose
2.69
1.23
Sales
b
Fructose
0.90
0.41
Sales
b
Sorbitol
1.60
0.73
Sales
Other
Levulinic acid
a
0.1
8
-0.26
0.0
8
-0.12
Production
a
Range of estimates from discussions with various industrial sources.
b
Bols, M.
Carbohydrate Building Blocks
. Wiley-Interscience, New York, 1996.
c
Cichtenthaler, F. & Mondel, S.
Pure Appl. Chem.
, 1997,
69
, 1
8
53.
materials. Lignin production by the pulp and paper
industry is 30-50 (¥ 10
6
) t year
-1
[83]. The experience
of these industries would seem to indicate that
renewables hold considerable promise as a feedstock
complementary to those used by the chemical indus-
try. However, the scope of renewables-based chemi-
cals production is narrow.
The necessary economic comparison reveals that
a number of polymeric (cellulose, lignin) and
monomeric (carbohydrates such as glucose, xylose;
other materials such as levulinic acid) materials
compete favourably with non-renewables [84]. Table
14.3 summarises some sales or production costs of a
few typical renewable building blocks. Other evalu-
ations show that two of the most basic renewable
feedstocks—corn and cellulose—are competitive
with several fossil feedstocks on both a mass and
energy basis (Table 14.4) [85]. This evaluation also
determined that the break-even price for oil when
compared with cellulosic biomass at $40 t
-1
is $12.7
per barrel on an energy basis and $6 per barrel on a
mass basis, a projection that takes on more signifi-
cance because oil prices are currently above $30 per
barrel at this writing (late 2000).
Although the economic issues are small, one finds
that the technological barriers to a renewables-based
green chemical industry are significant. A stark con-
trast exists between renewables and non-renewables
in terms of the range of methodology available for
their conversion into products (e.g. the 'recalcitrance
of cellulose' referred to by Lynd) [85]. A green chem-
ical industry based on renewables currently suffers
from a much narrower range of discrete building
blocks, fewer methods to convert those building
blocks to other materials, a lack of fundamental
understanding of how to convert starting raw
materials (lignin, carbohydrates, oil crops, protein,
biomass polymers, etc.) into single products in high
yield and a lack of information about the properties
and performance available from the final products.
We are faced with the puzzle of possessing an almost
limitless source of raw material, while being unable
effectively to convert it to a wide range of useful
products. This technology gap is not the result of an
inherently greater level of difficulty in the process-
ing of biomass. Instead, it is the result of technology
to date being focused almost exclusively on highly
reduced oil-based hydrocarbons, rather than on
highly oxygenated carbohydrate-based materials.
Increased use of renewables as chemical feedstocks
will grow in parallel with molecular-level under-
standing of their reactivity. The past and continuing
success in catalyst design and product control in the
petrochemical industry indicates that defining phe-
nomena at a molecular level leads to control of reac-
tions and practical applications. Process control and
