Environmental Engineering Reference
Because of a lack in available data, the GHG emissions from MTHF combustion and its
specific consumption in cars are assumed to be equal to bioethanol. Since the combustion of
these biofuels (e.g. lignin and biomass residues, bioethanol, biomethane and MTHF) releases
CO 2 which has a biological origin, it is not accounted for as a GHG and the above emission
factors are mainly due to N 2 O and CH 4 .
This biorefinery plant requires 0.16 MWh of electricity and 0.60 MWh of heat per ton of
feedstock for producing bioethanol and furfural (Kaylen et al., 2000), while 7.5 kJ of heat per
g water are needed to distil the water required by the electrolysis process (Gemis, 2008). The
anaerobic digestion step and following biogas upgrading requires 0.65 GJ of electricity and
0.1 GJ of heat per tonne of dry matter in wastewaters (Berglund and Börjesson, 2006).
4.2.2. Biorefinery material products
All the products produced by biorefinery systems can be grouped in two broad
categories: material products and energy products. Energy products are those products which
are used for their energy content, providing electricity, heat or transportation service. On the
other hand, material products are not used for an energy generation purpose but for their
chemical or physical properties. The chemical structure of energy and material products of the
investigated biorefinery system are reported in Figure 14.
The market share of products produced from biomass is expected to rise from the current
level of 5% to 20% in the short run (Sauer et al., 2007). In fact, these products are favourable
from a chemical point of view. Functional groups that must be introduced by costly oxidative
process steps into oil are already available in plant materials. It is noteworthy that for many
biomass derived chemicals the actual market is small, but an economical production process
will create new markets by providing new opportunities for the chemical industry. For
example, succinic acid and formic acid could replace the petroleum-derived commodity
chemical maleic anhydride. The market for maleic anhydride is huge, whereas the current
market for the organic acids mentioned is small.
The material products of the analyzed biorefinery system are fumaric acid, furan resins, O 2
and fertilizers. Fumaric acid (HO 2 CCH=CHCO 2 H) is a carboxylic acid currently produced from
the oxygenation of the fossil derived product benzene. It is mainly used in medicine, in food
industry as a food acidulent, in chemical industry and in the manufacture of polyester resins and
polyhydric alcohols. Fumaric acid has an annual production of 12 ktonnes but a projected
market volume of more than 200 ktonnes (Sauer et al., 2007). The uses are the following: 35%
as paper size resins, 22% as food acidulant, 15% in unsaturated polyester resins, 6% in alkyd
resins, 5% as plasticizers and 17% miscellaneous (including lubricating oils and oil field fluids,
esters, inks, lacquers, carboxylating agent for styrenebutadiene rubber) (CMR, 2008).
Furan resins are made by polymerization or polycondensation of furfural, furfuryl alcohol
or other compounds containing a furan ring, or by reaction of these furan compounds with
other molecules (not over 50%). The major uses of furan resins are as foundry binders and
their production in biorefinery is assumed to play a major role in chemical conversions of
furfural. Another chemical product is oxygen in its diatomic form (O 2 ), which can be used in
a lot of chemical applications like oxidizing agent. Fertilizers are the residues of the anaerobic
digestion step which can partly replace the use of synthetic fertilizers. However, due to a lack
of data on its use and fossil fertilizers replacement rate, no benefits from this material output
are considered in LCA calculation.