Fueling Change: Decarbonizing Heavy Transport With Sustainable Fossil Fuel Alternatives
A range of inputs can generate lower-carbon fuels for airplanes and heavy industry. To more cheaply and efficiently convert waste from municipalities, agriculture, and cooking into hydrocarbons for fuel, innovations are needed. Natural feedstocks, notably sugars and algae, can also contribute to low-emissions fuels, though we’ve yet to see sustainable production at scale.
Planes, ships, and long-haul trucks keep the global economy moving — but they burn fossil fuels to do it. Heavy transport generates more than half of all transportation emissions, and electrification of the largest vehicles will require batteries with a energy density that doesn’t exist — yet. Sustainable fuels offer an alternative route: substitutes made from low-carbon resources or with clean electricity can power existing engines while slashing lifecycle emissions. From biofuels produced from algae to e-fuels synthesized using green hydrogen, these technologies have the potential to decarbonize the hardest-to-electrify sectors without requiring a total overhaul of vehicles or infrastructure. If scaled quickly and if costs come down, sustainable fuels could replace a significant share of petroleum use, cut billions of tons of CO₂ each year — and keep the world moving toward a more climate-friendly future.
Using IPCC and GCAM data, Energy Innovation projected future “greenhouse gas emissions at stake” in 2050, assuming current policies remain in place. The resulting estimates overlap because different technologies may reduce the same emissions pool.
The Path We're On
For the long haul: heavy transport’s big emissions problem
We’re a world in constant motion — and it comes with a heavy climate cost. That’s because modern transportation still runs overwhelmingly on liquid fossil fuels. From jet fuel and diesel to bunker fuel and gasoline, hydrocarbons power nearly every plane, ship, and long-haul truck on the planet. That dependence carries a heavy climate cost: in 2025, transportation accounts for roughly 14% of global greenhouse gas emissions. Without major changes, those emissions are projected to reach 9.4 gigatons by 2050.
Decarbonizing transport has a clear right of way. First, we reduce the need to travel wherever possible. Next, we shift necessary trips to lower-energy modes like rail, mass transit, walking, and cycling. Where vehicles are still required, electrification offers the most efficient and scalable path to cutting emissions. But some forms of transport — especially long-distance aviation, shipping, and other high-energy applications — remain difficult or impractical to electrify with today’s battery densities.
In the meantime, for these hardest-to-abate segments, sustainable fuels play a crucial complementary role, enabling emissions reductions where direct electrification can’t yet deliver. McKinsey estimates sustainable fuels could abate 0.6–1.2 Gt CO₂ annually by 2050.
To understand what sustainable fuels need to deliver to achieve success at a material scale, it’s important to understand a bit about the chemistry of liquid hydrocarbons.
What are liquid hydrocarbons — and where do they come from?
Crude oil is basically a messy soup of hydrocarbon chains — molecules made from carbon and hydrogen atoms in different lengths. Short chains, like methane (one carbon, four hydrogens), are light gases. Mid-length chains become liquids like gasoline, diesel, and jet fuel. Very long chains are heavy, sticky substances like tar or asphalt. In a refinery, crude oil is heated and separated so each chain length can be collected for its best use — a process called fractional distillation, often followed by chemical tweaking to improve performance. Our entire transportation system runs on the liquid middle of this spectrum.
A New Way Forward
Fueling change for heavy transport
To unlock the potential of sustainable fuels, the challenge is to rebuild hydrocarbon molecules — with the same chain lengths and properties — but with clean sources of hydrogen and carbon. That means finding sustainable ways to get the required atoms, plus the energy needed to assemble them, so they can drop into today’s engines, pipelines, and fueling infrastructure.
Turning that chemistry into cleaner transport requires rapid innovation on several fronts — from how we source carbon and hydrogen to how we synthesize, scale, and deploy new fuels.
Innovation Imperatives
Establish low-emissions manufacturing methods for sustainable aviation fuel (SAF), ammonia, methanol, aromatics, olefins, and other fuels
There are three pathways for sustainable fuels to fully decarbonize heavy industry and transport. We must find ways to produce existing fuels without emissions; create drop-in, low-carbon replacements for current fuels; and develop new fuels, along with the engines and infrastructure they’ll need. In addition to electrifying industrial processes (in particular, heat), we need to pioneer novel routes (e.g., catalytic, electrochemical, or biological) that can efficiently build these high-value molecules from clean carbon and hydrogen. Mastering these advanced synthesis methods is critical to creating clean replacements for the foundational components of high-performance fuels and industrial chemicals — and for tackling some of our economy’s most stubborn sources of emissions.
Develop clean, low-cost, and scalable sources of carbon and hydrogen
Fossil fuels are hydrocarbons, meaning they’re a combination of hydrogen and carbon. The sustainable fuels that replace them will be made up of the same dynamic building blocks. Creating sustainable fuels depends on abundant, low-emissions sources of both carbon and hydrogen — but today, clean supply is constrained and costly. Innovations in biomass aggregation, CO₂ capture, electrolysis, and the exploration of natural hydrogen reserves could unlock the feedstocks necessary for the large-scale production of e-fuels, biofuels, and hydrogen-based fuels. Achieving a low-cost, scalable supply of carbon and hydrogen is critical to making sustainable fuels competitive and deployable across aviation, shipping, and heavy transport.
Advance cost-competitive production methods that don't compete with food production
Biofuels can help cut emissions in hard-to-electrify transport, but challenges remain: in particular, finding pathways that can cost-effectively scale to meet a meaningful share of global fuel demand. High-productivity, non-food sources — such as algae cultivation and other advanced feedstocks — offer potential routes forward. Breakthroughs in process efficiency, feedstock aggregation, and cost will be critical for biofuels to scale sustainably, enabling them to decarbonize aviation, shipping, and long-haul trucking without straining food, land, or water resources.
Utilize waste streams to create synthetic hydrocarbons
Our economy generates vast streams of carbon-based waste — from agricultural residues to municipal trash — that typically end up in landfills, while we simultaneously extract fossil fuels to produce the hydrocarbons for our fuels and chemicals. But what if we could leverage those waste streams? The key technical need is to scale up advanced conversion processes (like gasification and pyrolysis), which can break down diverse waste streams and chemically reassemble them into high-value synthetic hydrocarbons, such as sustainable aviation fuel or the building blocks for plastics. This transforms a costly waste-disposal problem into a useful feedstock, simultaneously cutting landfill emissions and displacing the need for fossil fuel extraction.
The most viable solutions will:
To displace ~3.8 billion tons of crude oil per year, solutions must draw from feedstocks that can expand to meaningful volumes without triggering land-use change, deforestation, food displacement, or other negative externalities — while also approaching cost parity with fossil fuels at scale. This means prioritizing lower-risk feedstocks such as agricultural and forestry residues, waste streams, algae, captured CO₂, and limited energy crops grown on degraded land — sources that can scale without major environmental harm and whose costs can realistically fall as volumes increase. Scarce and higher-cost biogenic carbon should be reserved for applications that truly require it, such as aviation and certain industrial uses.
Fossil fuels arrive as energy-dense hydrocarbons, with nature having already done much of the conversion work. Sustainable fuels must recreate that chemistry — requiring capital-intensive facilities to convert new feedstocks into usable fuels. The most viable solutions will dramatically reduce the cost, complexity, and scale requirements of these conversion systems, and limit the need for new pipelines, storage, and distribution infrastructure by leveraging or adapting what already exists.
Fossil fuels are like batteries pre-charged with energy from the sun over geological time, delivering exceptionally high energy density. In contrast, sustainable fuels must be produced using supplied energy — ideally renewable electricity. Winning solutions will therefore need to recreate fuels with comparable energy density while dramatically reducing the energy intensity of fuel production or accessing ultra-low-cost clean power in order to compete with fossil fuels.
To make a material impact on transport emissions within the lifetime of today’s vehicle fleets, sustainable fuels must be usable in existing engines with minimal modification. Solutions that require new engine architectures, extensive retrofits, or long replacement cycles face significant adoption and timing barriers — particularly in aviation, shipping, and long-haul transport, where assets are long-lived and capital-intensive. Engine-level compatibility enables faster deployment, lower transition costs, and immediate emissions reductions.
