Chemical Engineering May 2022 - 12

Newsfront
SAF Production Expands for
a Low-Carbon Future
To lower their climate impact, petroleum refiners are increasingly assessing greenhousegas-emission
intensities as they consider processing lower-carbon feedstocks. One area of
particular activity is sustainable aviation fuels (SAF), where demand growth is accelerating
W
hile the oil-and-gas industry
has been on a
profitable run since the
economic recovery from
the pandemic, 2022 has brought a
host of complications for the industry,
including
the
ongoing effects
of the Russian invasion of Ukraine
on fuel markets, and exacerbated
supply-chain and labor-force disruptions.
These issues are overlaid onto
a landscape in which the pressure to
transition to climate-sustainable energy
and to achieve global net-zero
carbon emissions by 2050 continues
to grow.
The recently released 6th assessment
report from the U.N. Intergovernmental
Panel on Climate Change
(IPCC; Geneva, Switzerland; www.
ipcc.ch) emphasizes the need for aggressive
and comprehensive actions
to achieve net-zero emissions by midcentury.
Stéphane de la Rue du Can,
a researcher from Lawrence Berkeley
National Laboratory and lead author
of the industry chapter, noted " Significant
cuts in global greenhouse
gas emissions ... can be achieved
by 2050, but it will require ... transformational
changes in energy and
feedstock sourcing. "
The current environmental and
geopolitical situation is prompting
petroleum refiners across the
globe to evaluate their assets and
explore how to adapt to a carbonconstrained
future, and one in which
the negative climate effects of greenhouse-gas
(GHG) emissions from
fossil fuels will increasingly be priced
into refinery products (see sidebox
on carbon accounting, p. 16).
One area that has seen a marked
uptick in activity and an acceleration
12
in production is sustainable
aviation fuels (SAF).
SAF pathways
The International Civil Aviation
Organization (ICAO) defines
SAF as alternative aviation
fuels that achieve net GHG
emissions reduction on a lifecycle
basis, while respecting
conservation of ecosystems and
biodiversity, and that contribute to
local social and economic development
without competing with food
and water.
FIGURE 1. Demand for sustainable aviation fuel (SAF) is
growing, driven by the commercial aviation industry
Because commercial aircraft are
likely to continue to require high-energy-density
liquid fuels for propulsion,
reducing the GHG emissions
associated with commercial air travel
and air shipping thus depends heavily
on SAF. The aviation industry is
expressing its desire for low-carbon
SAF through purchasing agreements
and collaborations.
In order for the aviation industry
as a whole to achieve net-zero carbon
emissions by 2050, a massive
increase in production of SAF will be
required (Figure 1). The International
Air Transport Association (IATA) estimates
that SAF production would
need to reach 449 billion L/yr by
2050 in order to mitigate the majority
of global emissions by the aviation
industry. Several SAF pathways
are currently under development and
scaleup, but all face questions of
high feedstock and production costs,
which are currently substantially
higher than conventional jet fuel.
From a processing perspective,
SAF production pathways can be
grouped into at least four categories,
each of which have multiple variations:
alcohol-to-jet (ATJ) processes;
hydroprocessing of waste fats and
oils, and plant-based oils to jet fuel
(similar to the hydroprocessed esters
and fatty acids (HEFA) process for
renewable diesel); gas fermentation
with Fischer-Tropsch (F-T) synthesis;
and converting sugars to jet fuel.
Perhaps the most straightforward
pathway for producing SAF is
by hydrotreating triglycerides, such
as plant oils, used cooking oils and
waste animal tallow (HEFA route). The
most technologically mature technologies
for achieving this are Topsoe
A/S' (Lyngby, Denmark; www.topsoe.com)
HydroFlex technology and
Honeywell UOP's (Des Plaines, Ill.;
uop.honeywell.com) Ecofining technology,
co-developed by Eni S.p.A.
Others are Axens' (Reuil-Malmaison,
France; www.axens.com) Vegan and
Sulzer ChemTech's (Winterthur, Switzerland;
www.sulzer.com) BioFlux
technologies.
Advantages of the HEFA route to
SAF include a nominally better liquid
yield than ATJ (80 vol.% versus 60
vol.%) and a higher level of technical
maturity, explains Dave Collings,
senior technical advisory consultant
at 1898 & Co. (Kansas City, Mo.;
1898andco.burnsmcd.com). Also,
HEFA lends itself better to petroleum
refinery conversions, and has lower
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Chemical Engineering May 2022

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