Environmental Engineering Reference
In-Depth Information
The biorefinery chain starts at the top with carbon fixation from the atmosphere via
photosynthesis, or, as it occurs in this case study, biomass C taken as biomass waste from the
forest sector. At the end of the biorefinery chain a certain amount of useful energy and products
are supplied. Along the whole process chain, all the energy and material inputs and emissions
occurring for planting and harvesting the crop (or collect the raw materials), processing the
feedstock into fuels and products, transporting and storing of the feedstock, distributing and final
use of the products must be accounted for in a life cycle perspective (Schlamadinger et al., 1997).
Particular importance should be given to the numerous co-products which a biorefinery may
produce, because they can have relevant implications in the assessment of the overall system.
The fossil reference system is dealt with in a similar way, considering all the material and
energy inputs and emissions associated with its life cycle stages: production of the raw fossil fuel,
refining, storage, distribution and combustion. If compared in this manner, the differences between
the two systems producing the same product/service can be presented.
Table 3 reports the bioproducts produced by the investigated biorefinery and the fossil
conventional counterparts that they replace. In the right part of the table the environmental
impacts, in terms of GHG emissions and total energy demand, of the fossil derived products
are listed: these are the GHG emissions and energy consumption saved by the biofuels and
biochemicals of the biorefinery. These values, reported in the right part of the table, have
been calculated by means of the LCA software tool Gemis (Gemis, 2008).
Table 3. Table reporting the conventional alternatives of the different products
of the biorefinery and their specific factors for GHG emissions and fossil
energy consumptions.
Biorefinery
Fossil reference system
MJ
tot./unit
a
Bioproducts
Conventional alternative
Unit
g CO
2
-eq./unit
Bioethanol
Gasoline
km
189
2.36
Electricity from natural gas
b
Electricity
MJ
120
1.96
Heat from oil
c
Heat
MJ
106
1.32
Conventional methane
d
Biomethane
MJ
76
1.31
MTHF
Gasoline
km
189
2.36
H
2
H
2
from natural gas
MJ
72
1.24
Furan resins
Epoxy resins
g
6.07
0.13
Fumaric acid
Conventional fumaric acid
g
1.29
0.05
O
2
Conventional O
2
(from air)
g
0.07
0.001
Fertilizer
No benefits
a
Mainly fossil energy (> 98%)
b
Large scale gas-fired combined-cycle (CC) power plant with efficiency of 57% and low NO
x
burner; it
is assumed that 1/3 of the electric capacity comes from the steam turbine.
c
Heavy oil boiler for industrial process heat, efficiency
8
5%.
d
Including emissions from combustion in natural gas boiler (66.15 g CO
2
-eq./MJ), efficiency 85%.
