Environmental Engineering Reference
In-Depth Information
Wood industrial residues are used as raw materials and are delivered to the plant in the
form of pellets (chemical and elemental composition in Table 1). The results of the
biorefinery systems are shown in comparison with a fossil reference system providing the
same amount of energy and chemical products from fossil sources. The software tool Gemis
is used to model LCA calculations and as database source (Gemis, 2008).
Environmental concerns are focused on energy and greenhouse gas (GHG) balances of
biorefinery and fossil reference systems, because reduction of GHG emissions and decrease
of fossil fuel consumption are two driving forces of biomass utilization strategies. As a direct
consequence of the definition, a biorefinery is characterized by multiple useful outputs (both
energy and material products). This fact gives rise to an allocation issue, which was addressed
using different allocation methods.
Finally, biorefinery system performances are investigated by means of several indices
and indicators such as conversion yields and mass, energy, exergy and C efficiencies.
4.2.1. Biorefinery: scope and system boundaries
Wood industrial residues are the raw materials for this biorefinery system. The feedstock
is assumed to be collected from industries, transported to a pellet facility (20 km), where it is
dried and pelletized, and transported to the biorefinery plant (100 km). The GHG emissions
estimated for collecting, processing and delivery of raw materials to biorefinery gates are
equal to 1.94 g CO
2
-eq./MJ
pellets
, while the primary fossil energy consumption is 8.47
kJ/MJ
pellets
(Gemis, 2008).
MTHF
H
2
Acid
treatment
Chemical
reactions
Furfural
Furan resins
C5
sugars
O
2
FUMA
CO
2
Pre-
treatment
Feedstock
Hydrolysis
Fermentation
Distillation
C6
sugars
Bioethanol
Fertilizer
Legend
Waste-
water
Anaerobic
digestion
Biogas
Upgrading
Biomethane
Feedstock
Process
Lignin &
residues
Alkaline water
electrolysis
Combustion
Electricity
Hydrogen
Output not
exploited
Intermediate
Heat
Energy
Product
Material
Product
Oxygen
Figure 11. Process scheme of the investigated biorefinery.
This biorefinery produces bioethanol from fermentation of C6 sugars, furfural from
hydrolysis of C5 sugars (which is then chemically converted to fuel additive and other
chemicals), electricity and heat from combustion of lignin and residues, hydrogen and oxygen
through alkaline water electrolysis and biomethane and fertilizer via anaerobic digestion of
wastewaters (Figure 11).
