What is Sustainable Aviation Fuel?

Sustainable Aviation Fuel, often referred to as SAF, is a liquid fuel used in commercial aviation that reduces carbon dioxide emissions by up to 80 percent over its lifecycle compared to traditional jet fuel. It is produced from sustainable feedstocks rather than being refined from petroleum. These feedstocks include used cooking oils, municipal solid waste, woody biomass, and even captured carbon dioxide.

The most important characteristic of SAF for any founder to understand is that it is a drop-in fuel. This means it is chemically almost identical to the conventional Jet A or Jet A-1 fuel used today. It does not require changes to aircraft engines or airport fueling infrastructure. For a startup, this is a critical distinction because it removes the need to reinvent the entire aviation hardware ecosystem.

Building in this space requires a deep understanding of the chemistry and the supply chain. You are not just building a product. You are building a complex logistical network that sources waste and converts it into a high-performance energy source.

There is no single way to make SAF. Instead, there are several approved pathways that startups and established energy companies use to create the final product. One common method is the Hydroprocessed Esters and Fatty Acids process, known as HEFA. This involves refining vegetable oils or waste fats. It is currently the most commercially mature pathway.

Another method is the Alcohol-to-Jet pathway. This takes alcohols like ethanol or isobutanol and converts them into synthetic kerosene. This is particularly interesting for founders who have access to agricultural residues or specialized fermentation technologies.

There is also the Gasification and Fischer-Tropsch process. This takes solid waste and turns it into a synthesis gas before refining it into fuel. This pathway allows for the use of municipal trash, which solves two problems at once: waste management and fuel production.

Finally, there is Power-to-Liquid or e-fuels. This uses renewable electricity to split water into hydrogen and then combines that hydrogen with captured carbon dioxide. This is often considered the gold standard for long term sustainability, though it is currently the most expensive to produce.

When you look at conventional jet fuel, you are looking at carbon that has been trapped underground for millions of years. When it is burned, that carbon is added to the atmosphere. This is a one way trip for carbon.

SAF works differently because it relies on a circular carbon cycle. The plants used for feedstock absorbed carbon dioxide from the atmosphere while they grew. When the fuel is burned in a jet engine, that same carbon is released back into the air. This results in a much lower net addition of carbon to the environment.

Beyond carbon, SAF also tends to have fewer impurities like sulfur. This can lead to a reduction in particulate matter emissions and contrail formation. For a business owner, this means the value proposition of your product is not just carbon reduction, but overall air quality improvement.

However, the energy density of SAF must match conventional fuel exactly. Aviation is a weight-sensitive industry. If your fuel has lower energy density than fossil fuels, planes cannot fly as far or carry as much cargo. This is why the chemical specifications for SAF are so rigid.

Many people ask why we do not just switch to electric planes. For short hops and small aircraft, batteries are a viable solution. But for long haul flights across oceans, batteries are far too heavy.

Hydrogen is another alternative being explored by many startups. Hydrogen has excellent energy density by mass, but it requires massive, pressurized tanks that take up a lot of space. It also requires entirely new aircraft designs and airport infrastructure.

This is where the business case for SAF becomes strongest. It bridges the gap between our current infrastructure and a zero-emission future. It allows the existing fleet of thousands of aircraft to continue operating while still meeting climate goals.

As a founder, you have to decide if you want to bet on the fuel of today or the airframe of tomorrow. SAF represents the most immediate and scalable path for the industry because it works with what we already have.

The most obvious role for a startup is in the production of the fuel itself. This is a capital-intensive path. It requires building refineries and securing massive amounts of feedstock. This is the heavy lifting of the energy transition.

Another scenario is focusing on the feedstock supply chain. Startups can build technologies to collect used cooking oil more efficiently or to process municipal waste into a cleaner format for refineries. There is significant value in the logistics of trash.

There are also opportunities in software and verification. Airlines need to prove to regulators and customers that the fuel they are using is actually sustainable. This creates a need for transparent tracking systems that follow a gallon of fuel from the farm or the waste bin to the airplane wing.

Finally, some founders are looking at modular production. Instead of building one massive billion dollar refinery, they are building smaller, containerized units that can be placed near waste sources. This reduces the cost of transporting heavy feedstock over long distances.

While the potential is massive, there are many unknowns that a founder must think through. The biggest is the Green Premium. SAF is currently much more expensive than fossil jet fuel. How long will customers or governments be willing to pay that extra cost?

Another question is the limit of feedstock. Is there enough used cooking oil in the world to power every flight? Most experts say no. This means the industry must move toward more complex feedstocks like agricultural waste or carbon capture, which are harder to process.

Policy is another major variable. Many countries are introducing mandates that require a certain percentage of SAF to be used by a specific date. If those mandates change or are delayed, the market for your product could shift overnight.

Founders should also ask how the scaling of SAF will impact other industries. If we use all our waste fats for planes, what happens to the industries that currently use those fats for soap or animal feed? These interconnected markets create risks that are hard to see from the outside.

Finally, we have to consider the long term technical viability. If a breakthrough in battery energy density happens sooner than expected, will the demand for SAF for short haul flights disappear? Navigating these questions is the real work of an entrepreneur in this field.

Building a company in the SAF space is not for the faint of heart. It requires a mix of chemical engineering, complex logistics, and an understanding of global policy. But for those willing to put in the work, it offers a chance to solve one of the hardest problems in modern transportation.