RENEWABLE METHANOL 25
1.2. Methanol as a fuel
The use of methanol as a fuel, either by itself, in a blend with
gasoline, for the production of biodiesel, or in the form of
methyl tert-butyl ether (MTBE) and dimethyl ether (DME),
has also grown rapidly since the mid-2000s. Together
these fuel uses now represent about 31% of methanol
consumption. MTBE has been used as an oxygenated
anti-knock fuel additive in gasoline since the 1980s. While
MTBE has been banned in some countries such as the
UnitedStates because of groundwater contamination
issues, its use has been increasing in other regions
including Asia and Mexico. Biodiesel can be obtained by
reacting methanol with fats and oils. However, direct use
of methanol as a fuel has seen the largest growth; from
less than 1% in 2000, the share of methanol consumption
for that purpose has now increased to more than 14%.
Due to its high octane rating, methanol can be used as an
additive or substitute for gasoline in internal combustion
engines (ICEs). Methanol can also be used in modified
diesel engines (Bromberg and Cohn, 2009; Bromberg and
Cohn, 2010), and advanced hybrid and fuel cell vehicles.
Notably, methanol has only about half the volumetric
energy density of gasoline and diesel. If pure methanol
is used as a fuel, adjustments to the tank size have to be
made if a similar range is to be achieved. Direct methanol
fuel cells (DMFCs) can also convert the chemical energy
in methanol directly into electrical power at ambient
temperature (McGrath et al., 2004).
Because methanol does not produce soot, fumes or
odour, it is also widely used in cook stoves (over 5 Mt
in 2018 in China alone) (Dolan, 2020). DME, produced
from methanol by simple dehydration, is a gas that can
be liquefied at moderate pressure, much like liquefied
petroleum gas (LPG). DME as a diesel fuel substitute with
a high cetane rating and producing no soot emissions
(particulate matter [PM]) has also attracted much interest
(Semelsberger et al., 2006; Arcoumanis et al., 2008).
DME can also replace LPG in applications such as
heating and cooking. Up to 20% DME can be blended
with LPG with no or very limited modifications to
existing equipment. Methanol can also be used as a
fuel to produce heat and steam in industrial boilers,
and for electric power generation in gas turbines
(Temchin, 2003; Basu and Wainwright, 2001). More than
1000boiler units in China consumed 2 Mt of methanol
in 2018 (Dolan, 2020).
Methanol has historically been a candidate as an
alternative to conventional crude oil-based fuels. This
was initially the case at the time of crude oil supply
constraints in the 1970s and 1980s. Methanol (fossil) has
a high octane rating, and during the 1980s and 1990s was
widely tested both as a low blend component and as a
pure fuel in large test fleets in many countries, mainly
with the goal of reducing air pollution. This interest was
driven by the knowledge that methanol is relatively
cheap to produce from coal and natural gas, and that it
can be used with only minor modification to the existing
vehicle fleets and distribution infrastructure.
By the late 1990s, various technological advances were
achieving wide acceptance in the automobile industry:
direct fuel injection, three-way catalytic converters,
reformulated gasoline, etc. These reduced dramatically
the emission problems associated with gasoline-powered
vehicles, but decreased at the same time the benefits of
methanol-based fuels. Simultaneously oil prices remained
low meaning that despite being a technical success,
methanol was not a commercial success (Olah et al., 2018).
While the interest in methanol-powered vehicles diminished
in developed countries, China has recently been active in
promoting methanol as a transport fuel, largely to decrease
its dependence on imported fuel. Numerous Chinese
automotive manufacturers are oering methanol-powered
vehicles, including cars, vans, trucks and buses able to run
on M85 (85% methanol, 15% gasoline) and M100 (pure
methanol), as well as methanol/gasoline blends with lower
methanol content (SGS, 2020). Flexible-fuel vehicles able
to run on various mixtures of methanol and gasoline, or
so called GEM fuels (gasoline/ethanol/methanol), are also
available (IRENA, 2019a; Olah et al., 2018; Schröder et al.,
2020). These vehicles cost a similar amount to regular cars.
Methanol can also be used in diesel engines, either by
co-feeding with a small amount of diesel pilot fuel, the
addition of ignition improver (MD95), or the installation
of glow plugs. Use of engines specifically optimised for
methanol that allow for higher compression ratios are
also possible (Schröder et al., 2020). Examples of a fleet
of methanol-fuelled taxis and heavy-duty trucks can be
seen in Figure 9 and Figure 10. China currently consumes
4.8 Mt of methanol per year for road transport (Dolan,
2020). Methanol as a road fuel is also attracting growing
interest in other parts of the world, including Israel, India
and Europe, as well as for other applications such as
trains and heavy machinery (Landälv, 2017).