Environmental Engineering Reference
In-Depth Information
Figure 14. Chemical structures of the bioproducts from the biorefinery: bioethanol, biomethane, MTHF,
furfural and fumaric acid
4.2.3. Biorefinery energy products
The energy products of the biorefinery are bioethanol, MTHF, biomethane, hydrogen,
electricity and heat. The production of large quantities of biofuels or fuel additives via
renewable feedstocks offers perhaps the greatest potential for mass-market penetration of
biorefineries.
Bioethanol is one of the most common transportation biofuels currently produced in the
world and can replace gasoline in vehicles. Biomethane is obtained from upgrading of biogas
by removing CO
2
and other undesired elements, like H
2
S. Biomethane can be used as a
transportation biofuel or can be transported through the existing gas infrastructure and
substituting natural gas in all its existing applications.
Methyltetrahydrofuran (MTHF) is produced from furfural by reduction to methyl furan,
which is then reduced to MTHF (both reductions occur with H
2
). MTHF is a very important
compound because it can be added to gasoline (to be blended at the refinery rather than later
in the distribution process) or bioethanol up to 30% by volume without effects on
performances and engine modification. Using MTHF as a fuel additive increases the
oxygenate level in gasoline without adversely affecting engine performance. MTHF also
boasts a high octane rating (87) and a low vapour pressure, thereby reducing fuel evaporation
and improving air quality. Although it has a lower LHV than gasoline, it has a higher specific
gravity and hence mileage is competitive. Properties of MTHF as fuel are reported in Table 2.
Hydrogen is produced via alkaline water electrolysis and is used as a reducing agent for
conversion of furfural to MTHF at the biorefinery plant site. This can be seen as an
innovative way to safely store H
2
in a transportation biofuel. The remaining H
2
fraction is
delivered to the market.
