Sustainable aviation

The aviation industry is making a huge effort to make aviation emission free. In collaboration with authorities, among others, a number of guidelines have been drawn up which will make it possible for aviation to emission free in 2050.

Sustainable aviation can be approached in many different ways, and there are a myriad of methods that can be used to solve the task (and goal) of CO2 neutral aviation. Here we are talking primarily about SAF, electric, hydrogen and hybrid aircraft, and eVTOL.


You can read more about generel guidelines, starting points of the authorities, sustainable propulsion, progress, providers, companies, developers, etc., find an overview of providers, as well as general information, in the following.

Topics

Guidelines, criteria, political initiatives and general topics, relevant to the development of sustainable aviation

SAF [Sustainable Aviation Fuel]

SAF can be produced in several ways, but the end product must meet at least the same requirements as fossil jet fuel. Once approved, the fuel can be used in existing aircraft, storage tanks and pipelines. The four most obvious methods are 1. HEFA, primarily based on used cooking oil. 2. Fischer Tropsch gasification based on waste as well as wood and residuals. Alcohol to jet (AtJ), mostly based on residual products from sugary raw materials or enzymatic processes. 4. Electrofuels, also called PtX or PtL, produced on electricity, carbon and hydrogen. Common to all those mentioned is that a maximum of 50% may be mixed into the conventional fuel. Efforts are being made to lift or remove this restriction. Airbus and Boeing as well as some airlines have completed successful test flights with 100% SAF.

 

It is crucial that the fuel is sustainable. This is not included in the technical approval but separately by independent organizations that apply a comprehensive set of sustainability criteria for the raw materials, transport and production method used.

 

Today, there are only two producers that can continuously supply SAF. World Energy and Neste. Both with HEFA oil based on used cooking oil. SAF accounts for just half a per mille of aviation fuel consumption globally. 2-3 producers are expected to be on the market during 2022-23, also with SAF produced on used cooking oil, namely Total, Repsol and ENI. In 2023-25, a further number of manufacturers are expected to be ready with the first AtJ, Fischer/Tropsch catalytic or PtX/electrofuel products.

 

Used cooking oil is the dominant SAF raw material. A disadvantage is that there is a natural limit to how much is available. Critics have also pointed out that it is not possible to ensure sustainability all the way back in the supply chain. Limited access to raw materials is a risk for all methods, however to a lesser extend electrofuels, that do not use biogenic raw materials but electricity, hydrogen and carbon. Here, access to renewable energy is a challenge, but is expected to be manageable in an expansion of renewable energy.

 

Electrofuels/PtX is supposed to be the future fuel. Several development projects are underway both in the Nordic region, internationally and in Denmark. The EU and several international analyzes finds that electrofuels will become dominant within the next, or few, decades.

Electric Aircraft

Electric aircraft is powered by 100% electricity. The most common way of operating an electric aircraft is by electric motors, whose driving force is propellers, which in addition are powered by large batteries.


The development of electric aircraft has been underway for a number of years, but the seriousness of climate change in recent years has to that extent been a major driving force for the development of electric aircraft.


Hydrogen Aircraft

Aircraft with hydrogen as the primary power source.

The method of converting hydrogen into hydrogen liquid fuel is one of several promising ways that the aviation sector can meet their climate-neutral targets.


Hydrogen fuel cells produce electricity by combining hydrogen and oxygen atoms. The hydrogen reacts with oxygen across an electrochemical cell similar to that of a battery to produce electricity, water, and small amounts of heat.


Read about companies in the process of developing hydrogen / hydrogen-electric aircraft – also planning long distance passenger aircraft, up to 200 passengers.

eVTOL[Electric Vertical Take Off and Landing]

eVTOL is an electric vertical takeoff and landing plane which uses electricity to hover, take off and land vertically. 

This technology is expected making major advances in electric propulsion. It has a huge potential within future aviation and air mobility, transportation of packages, ambulance and medical transport and passengers.


eVTOL is already a huge industry. Currently over 200 companies are working with eVTOLs.

Exciting to follow this emission free and low noise development.


Hybrid Aircraft 

A hybrid aircraft is a combination of both batteries and ordinary fossil fuels.


The reason for working with a combination of these two fuels is, that for a start it is a good way to solve the big weight problem that fully electric aircraft suffer from, due to very large batteries.


“The research that’s been done in the last few years shows you could probably electrify smaller aircraft, but for big aircraft, it won’t happen anytime soon without pretty major breakthroughs in battery technology,” Barrett says. “So I thought, maybe we can take the electric propulsion part from electric aircraft, and the gas turbines that have been around for a long time and are super reliable and very efficient, and combine that with the emissions-control technology that’s used in automotive and ground power, to at least enable semielectrified planes.”


- https://news.mit.edu