Automotive Engineering - May 2023 - 31

'GREEN' FUELS FEATURE
maintain. Using the attributes of both technologies,
including low-carbon fuels, will enable the industry to
achieve net-zero goals as quickly as possible.
David Foster, professor emeritus at the University
of Wisconsin-Madison's Engine Research Center, is
one of many engineers who see logic in a muti-mode
approach to CO2 reduction. " As much as EVs as the
ultimate solution are wonderful, the constraints surrounding
their mass adoption - mineral resources,
mining activities, charging infrastructure, battery cost
- are delaying them, " he said. " And that means legacy
vehicles will be around even longer, exacerbating
CO2 emissions.
" EVs can be great - but they won't be great for everything
and everyone, " Foster observed. He and others
support development and deployment of " green fuels "
to help reduce the global legacy fleet's emissions footprint
during the long shift to EVs. Green fuels encompass
synthetic and electrofuels (e-fuels) - liquid or
gaseous fuels produced with electricity from renewables
and/or biomass. Examples include synthetic natural
gas (SNG), green methanol and green hydrogen.
Green fuels are carbon-neutral when burned, emitting
only the amount of CO2 absorbed during their production.
So-called 'drop-in gasoline' contains constituents
produced from biomass sources through a variety of
biological, thermal, and chemical processes.
" If we look at making synthetic fuels, using the term
in a broad sense, there is a very strong argument for
engaging with the energy industry in doing this, "
Foster noted, " because the more we can make the
synthetic fuels compatible with today's engines, the
faster we can start bringing down the total CO2 emission.
The legacy fleet worldwide is huge, " he said, and
is vital for millions of vehicle users.
Foster explained that a drop-in fuel solution would
be where the fuel feedstock is introduced at the refinery
or is sufficiently compatible where it is added
as a mixing agent after the refinery. " You'd bring
down the carbon intensity of the fuel, and that fuel
would be backward-compatible with legacy fleets.
Those fleets are going to be around for a long, long
time, " he said. eFuels can be used in existing infrastructure,
he added.
There is much activity in 'green' fuels in Europe
and the first production plant was launched by
Porsche, Siemens Energy and partners in December
2022 in Chile (see page 28). Interest is growing in
North America, particularly in the commercial vehicle,
power generation and marine sectors, and from those
seeking a way to progressively mitigate the legacy
fleet's fuel and emission needs. The technology's potential,
Foster said, is " to progressively lower the carbon
intensity of fuel. " The goal would be to make a
net-zero carbon fuel, one which is a hydrocarbon -
AUTOMOTIVE ENGINEERING
Engine research
veteran Dr. David Foster:
Bringing down the
carbon intensity of the
fuel to make it backwardcompatible
with legacy
vehicle fleets.
" Legacy vehicles will be
around for a long time,
exacerbating CO2 emissions. "
like methanol for example, but where you're getting the carbon out
of the atmosphere [the Porsche e-fuel process does this]. If you were
to capture that carbon and turn it around and put it into a fuel, there
would be no net increase in carbon because of that fuel. "
A hot topic
" E-fuels are a hot topic, offering a way for an industry undergoing
enormous change to get some politically useful concessions from
regulators, " Al Bedwell, director of global powertrain forecasting at
LMC Automotive, commented in a recent blog post. " But the evidence
today points to e-fuels in Europe's light-vehicle sector being
backed into a very small corner, or not getting off the ground at all. "
Cost is a major hurdle. Making e-fuels requires renewable electricity
to split hydrogen molecules from H2O and combine it with carbon.
The process at present scale is expensive and relatively inefficient;
according to BloombergNEF, the current wholesale price of synthetic
diesel in Europe is up to seven times that of conventional diesel
fuel. Analyst Bedwell estimates retail e-fuel for light-vehicle use will
remain roughly four times more expensive than traditional gasoline
even as production scale increases. Meanwhile, battery technologies
continue to improve, bringing down EV cost.
Multi-solutions advocate Foster remains pragmatic as he views the
transition to BEVs. As the challenges of global electrification, economics,
human behavior and geopolitical realities become apparent,
hundreds of millions of legacy vehicles should be part of the decarbonization
discussion and its quest for equitable solutions.
May 2023 31
DAVID FOSTER
Automotive Engineering - May 2023

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