Zero Emissions: Net Zero vs. True Zero

At the moment, much of the discussion surrounding sustainable aviation is centred on Net Zero targets. The specific roadmaps differ from country to country but on the whole, they are predominately set on reducing carbon dioxide (CO₂) emissions by 2050.

Many argue that these measures do not go far enough and that the real goal should be focused on True Zero. How the industry plans to reach these targets, through alternative technologies and addressing the non-CO₂ effects, will be introduced in this blog and further discussed at the Sustainable Skies World Summit in May 2024.

What is the difference between Net Zero and True Zero?

Net Zero quite simply is the target of negating the amount of greenhouse gases produced by human activity by reducing emissions and removing carbon dioxide already in the atmosphere. The UK Government has set out strategies to decarbonise all sectors of the UK economy in order to meet Net Zero targets by 2050.

In comparison, True Zero considers both CO₂ and non-CO₂ effects and is what many in the industry believe should be regarded as the true goalpost in sustainable aviation.

What are the Non-CO₂ Effects?

Although carbon dioxide emissions are the most frequently talked about, they only make up a small percentage of the issue. Emissions from aviation specifically also include nitrogen oxides (NOx), water vapour and contrails, particulates, carbon monoxide, unburned hydrocarbons, and sulphur oxides (SOx). These could potentially have a 2–3 times greater climate change impact than CO₂ alone (Roland Berger).

Non-CO₂ emissions have frequently been overlooked with much of the attention being placed on carbon emissions alone, but as the industry looks beyond Net Zero 2050 targets it must broaden its scope and truly address how we can achieve zero emission flight.

What is Zero Emission Flight?

Flying without producing any emissions is a difficult challenge. Zero emission flight ultimately requires an alternative source of power to conventional jet fuel and the industry is working tirelessly to research and develop new solutions that utilise hydrogen, electric, solar and hybrid technologies all with the hope of delivering truly zero emission flight.

The leading technologies showing potential at the moment are electric and hydrogen. Electric vertical take-off and landing aircraft (eVTOLs) could offer a zero emission solution but currently only for short distance flights. Learn more about the role of eVTOLs here.

Hydrogen on the other hand, could provide the answer to truly zero emission flight, with many leading aerospace companies paving the way with research and development.

Hydrogen in Focus

Hydrogen has been safely used in the industry for many years and could play a major role in the future of sustainable flying. Firstly, hydrogen can be combusted to create electrical power for battery-powered aircraft such as eVTOLs. Secondly, hydrogen can be used as a fuel itself, replacing the need for conventional jet fuel and sustainable aviation fuel in the long run.

The latter option, whilst boasting the most potential, also creates the biggest challenge. There are numerous engineering challenges to consider with hydrogen technology but by far the most pressing is the fuel density of hydrogen. Simply put, to use hydrogen as a direct fuel you would need much bigger fuel tanks than what is currently used on commercial airliners. This will require a fundamental shift in how aircraft are designed.

To compare this with the use of Sustainable Aviation Fuels (SAF), which currently require no change to the aircraft itself, hydrogen is a huge long-term investment and something not everyone is yet fully behind. With numerous technologies being developed and tested, it has become difficult for investors to know which path to back.

Short-Term vs. Long-Term Investment

To achieve Net Zero targets and ultimately True Zero, there will likely not be a single solution, but instead a combination of changes to technology, fuels and operations. The short-term measures we make will play just as important role and these include maximising the usage of SAF, minimising fuel burn through operation efficiency and carbon removal measures. SAF is one of the leading developments and currently can cut carbon emissions by 65% (source: IATA). Learn more about SAF here.

However, to achieve absolute zero emission flight we must go further. A revolution in either sustainable fuels or technology will have the greatest impact and these long-term measures will likely require a shift in how we view flying and perhaps lead to a big change in aircraft design.

As it stands, many of the short-term measures only concern reducing CO₂ emissions to meet Net Zero targets. To take this further, considering non-CO₂ emissions and reaching True Zero, longer-term strategies and bigger changes will be required.

Going Beyond Flight

To reach True Zero, zero emissions in the skies also need to be reflected on the roads and other forms of transport. To achieve this across the industry, we must go beyond the actual flight and consider operational and airport emissions too. This includes collaborating with other transport industries and analysing the full supply chain. Read more about Operation Efficiency.

Leading Voices

ZeroAvia, ‘Hydrogen-electric is the best option for long-term transition to clean aviation’

Airbus’ ZEROe Project, ‘Airbus’ ambition is to bring to market the world’s first hydrogen-powered commercial aircraft by 2035’

Rolls-Royce, ‘Pioneering hydrogen engine combustion’

Roland Berger, ‘The Roadmap to True Zero’

IATA, ‘Liquid hydrogen as a potential low-carbon fuel for aviation’

What to expect at SSWS24

The conference programme at this year’s Sustainable Skies World Summit will feature sessions dedicated to zero emissions, this includes the exploration of non-CO₂ effects and the impact of zero emission aircraft.

Hear from the leading experts about what projects and technologies are worth investing in and how collaboration across the sector is performing. Join the conversation at SSWS24!

The conversation will also continue at this summer’s Farnborough International Airshow, with many of the sessions from SSWS24 feeding directly into the sustainability theme at FIA2024.