Climate & flying
What moves us? What can we move? These are questions we have been asking ourselves since long before the current social debate on climate action. Moreover, we have been pursuing a roadmap for sustainable product development for years. This guides the hard work we are doing to minimize aircraft engines’ fuel consumption and CO2 and pollutant emissions in several stages. Now we want to go one step further and are aiming for emissions-free flight.
Aviation is an important backbone of the economy. It ensures worldwide mobility, contributes to growth and prosperity and also connects people and cultures with each other. Today’s globally connected industries cannot function without it. However, flying has an impact on the environment and in particular on the climate and has recently seen strong growth rates. This is a major challenge that we are addressing as a responsible company: we are actively involved in shaping the change towards sustainable aviation with innovative, low-emission propulsion concepts. Our activities focus on climate action and the reduction of in-flight CO2 emissions, with the ultimate goal of achieving fully emissions-free aviation. The only way we can do this is if the entire industry pulls together and policymakers implement the appropriate framework. For that reason, we are involved in numerous aviation initiatives.
Our contribution to the SDGs
Our sustainable product development contributes to the Sustainable Development Goals (SDGs) of the UN’s 2030 Agenda. We see our greatest impact as being in the areas of SDG 13 on “Climate action” and SDG 9 on “Industry, innovation and infrastructure.” In addition, our ecologically efficient engines support SDG 12 on “Sustainable consumption and production.” The SDGs are to be achieved by 2030, which is why UN Secretary-General Antonio Guterres has proclaimed the new decade the “Decade of action.” Our approach is longer-term, extending to 2050 and beyond, as aviation is characterized by very long development and operating cycles.
Pioneering: Our approach to climate action
We are working on solutions to make flying more environmentally friendly, with a focus on reducing fuel consumption and hence the CO2 emissions of engines. Given our expertise in the development and manufacture of high-pressure compressors and low-pressure turbines, this is something we can directly influence. We are also conducting research into new propulsion concepts that will pave the way for aviation to become emissions-free. Sustainable product development with reduced fuel consumption is contained in the MTU Principles. We have also formulated guidelines on product development according to environmental criteria in our MTU Code of Conduct. Fuel consumption and CO2 emissions are directly proportional and are a major factor in how aviation affects the climate. This is why improving fuel efficiency is very important to us, as it reduces both resource consumption and the impact on the climate. In addition, the use of alternative fuels, known as sustainable aviation fuels (SAFs), can significantly reduce CO2 emissions both from the aircraft fleet already in service and from our new engines. This is why we are calling for the use of SAFs. They are absolutely essential for climate-friendly aviation.
We are committed to meeting the goal set out in the Paris Agreement of 2015 of limiting global warming to less than two degrees Celsius. This target far exceeds the goals defined by the European aviation industry and research sector’s Strategic Research and Innovation Agenda (SRIA) and extends beyond the worldwide targets set out by the International Air Transport Association (IATA). In our “Technology roadmap toward emission free flying,” we present a possible path to long-term emissions-free aviation. We are currently revising our Clean Air Engine agenda to redefine targets and ensure we help achieve the overarching Paris target.
We have a climate strategy and are pursuing a clear goal
Climate change is one of the greatest global challenges of our time. There is broad consensus in society on limiting climate change to a maximum temperature increase of two degrees Celsius by 2050 (Paris target). To achieve this, global emissions of greenhouse gases must be drastically reduced. According to the International Energy Agency, global air traffic is responsible for some 2.7% of CO2 emissions around the world (data from 2015). MTU has made climate action a key focus of its sustainability strategy and pursues specific goals, particularly for products, as the vast majority of CO2 emissions over an aircraft engine’s entire lifecycle occur in flight, in other words during the service life of our products. We actively support decarbonization, i.e. the shift to a long-term carbon-free economy, and include our own business activities in our climate action. → Learn more about this commitment under Climate protection in production.
The UN Intergovernmental Panel on Climate Change (IPCC) reports that the climate impact of air traffic is due mainly to CO2 emissions, ozone production as a consequence of NOx (nitrogen oxide) emissions, and the formation of contrails and cirrus clouds. Since CO2 emissions have the greatest effect on the climate, the greatest potential for us to have an impact lies in cutting down on this greenhouse gas by developing energy-efficient engines. New combustor concepts can significantly reduce NOx emissions, Since the combustor is not one of the components in our commercial aviation portfolio, we can make only an indirect contribution to avoiding nitrogen oxides by improving efficiency. Contrails and cirrus clouds also have an impact on the climate; they are generated under certain temperature and humidity conditions in the atmosphere triggered by particle and water emissions. Clever selection of flight routes and altitudes can greatly reduce contrails and cirrus clouds or even avoid them. Contrails can also be reduced with the help of sustainable fuels, as these produce fewer particulate emissions due to a lower proportion of aromatics. New propulsion concepts developed by MTU promise major reductions in the long term, both in terms of NOx emissions and in the formation of contrails.
The first generation of the GTF Engine Family already powers 744 aircraft through the air, helping reduce CO2 emissions by more than three million metric tons. (Source: Pratt & Whitney, May 2020)
The aviation industry is characterized by long product cycles, with aircraft engines as a rule spending 30 years in service before they are decommissioned. Goals to produce more eco-efficient engines must therefore have a long-term perspective and are established in memoranda of understanding by the aviation stakeholders (airlines, aviation industry, research, aviation authorities). In Europe, goals aimed at cutting fuel consumption and CO2 emissions are defined in the SRIA since 2012. However, since these are not sufficient to meet the target set out in the Paris Agreement, we have undertaken to accelerate and broaden our activities in this regard. We believe that aviation must become emissions-free in the long term, which is why we are currently revising our Clean Air Engine agenda and the specific goals it pursues for the coming decades up to 2050—to make this a reality.
We have already achieved a great deal: The geared turbofan engine
With the first generation of the GTF Engine Family, which we are developing and manufacturing together with our partner Pratt & Whitney, we have not only achieved but in fact exceeded our first climate target of a 15% reduction in CO2 emissions (16% for the PW1100G-JM that powers the A320neo, for example). Since 2016, this engine family has been successively introduced in various models for a total of five aircraft applications. With almost 10,000 orders and options, it has become a major business success and measurably reduces the burden on the environment: this first generation has already enabled airlines to avoid more than three million metric tons of CO2 in flight. It also brings significant improvements in terms of airborne pollutants: the geared turbofan’s NOx emissions are 50% lower than those of its predecessor model.
Our Clean Air Engine agenda: Paving the way for emissions-free flight
Following the promising launch of the new geared turbofan engine, we now want to reduce fuel consumption and CO2 emissions even further. To achieve this, we are taking an evolutionary approach based on the geared turbofan, which still offers huge potential for improvement. In the next generation, we want to develop its technology and turn it into an ultra-high bypass engine. Running the new engines on sustainable fuels (SAFs) will largely avoid CO2 emissions altogether. Our engineers are already busy working on preliminary designs and technologies for the new generation. Within the German government’s LuFo aeronautics research program and European technology initiatives such as Clean Sky 2, we are driving development to get the engine ready for full-scale production; for example, we opened a new component test center at our headquarters in Munich in 2019 to test new materials and designs. This technology development work could be completed by 2027.
As part of our Clean Air Engine agenda, we’re exploring different approaches to reducing fuel consumption and CO2 emissions; our ultimate goal is to make aviation emissions-free. In our pursuit of this goal, we have completely new propulsion concepts on our agenda, which must surpass today’s technology by a long way. After all, these revolutionary engine architectures hold great potential and open the door to emissions-free flight. We are pursuing several promising concepts, which our experts are already working on together with universities: one is known as the composite cycle concept, in which an additional piston compressor and piston engine significantly increase air compression. In turn, this further reduces fuel consumption and CO2 emissions. The advantage of this approach is that the design of the aircraft would not have to be changed to accommodate such an engine. However, it brings with it another great challenge: the high pressure and temperature ratios in the engine increase NOx emissions.
Another concept, the water-enhanced turbofan (WET engine), employs a heat exchanger to use the energy from the engine’s exhaust gas stream. It works by evaporatin water in a heat exchanger and injecting the vapor into the combustor for the turbine to generate additional power. A condenser is employed to obtain the requisite water from the exhaust gas. “Wet” combustion of this kind massively reduces nitrogen oxide emissions. This concept also cuts fuel consumption and CO2 emissions by a large degree. In addition, it greatly limits the climate impact of contrails by largely eliminating emissions of water vapor. If this concept proves to be viable, there will be a further challenge to solve together with the aircraft manufacturer: how to integrate the required condenser into the aircraft.
In order to implement our plans, we signed a letter of intent for the EU’s Clean Sky follow-up program Horizon Europe at the Paris Air Show in June 2019. As one of 23 players involved in Horizon Europe—including companies, research institutions and universities—we want to work together to decarbonize aviation in the future.
At the same time as developing these revolutionary new heat engines, we are pushing ahead with the development of electric propulsion systems.
Battery-electric or hybrid-electric propulsion systems? Both are conceivable
Battery-electric propulsion systems enable emissions-free aviation—provided the power is produced sustainably. As things stand, however, battery-electric engines are not technically feasible for existing commercial passenger aircraft. Today’s battery concepts do not come anywhere near the energy density of conventional kerosene. Batteries’ storage capacity is still far too small to power commercial flights. But battery-electric flight is a viable option for air taxis carrying a small number of passengers over short distances.
One possible concept for longer distances would be hybrid propulsion systems combining electric motors, generators, gas turbines and batteries. These open up completely new possibilities in aircraft design and propulsion technology while still using kerosene or SAFs as high energy density fuels for greater range. Disadvantages of hybrid propulsion systems, however, are the significant weight they add and energy conversion losses. We are participating in this future propulsion system through our stake in Silent Air Taxi, which was unveiled to the public in 2019 and is being developed in cooperation with RWTH Aachen University. It will have a parallel hybrid-electric propulsion system.
A true alternative: Sustainable fuels
Our position is clear: aviation must move away from the use of fossil fuels and tap far deeper into renewable energy sources. Because sustainable fuels have the potential to neutralize CO2 emissions generated by aviation, they are an indispensable part of efforts to reach the target of the Paris Agreement.
Sustainable fuels can already be used in today’s infrastructure, which is why MTU is advocating for their adoption. We do this, for instance, through our involvement in the Bauhaus Luftfahrt think tank and the Aviation Initiative for Renewable Energy in Germany (aireg), an association we set up together with airlines, manufacturers and research institutions.
The first synthetic fuels have already been approved for flight operations, having successfully met the stringent quality and safety requirements. The new fuels can be “dropped in” to existing infrastructure, which means there is no need to modify the engine or aircraft. Currently, only biomass-based fuels are available in larger quantities. However, the inputs for their production would otherwise be used for food and these fuels are much more expensive than conventional kerosene.
Experts believe that there is greater potential for non-biogenic processes, in other words for synfuels that are produced using renewable electricity or sunlight. There are two methods suitable for producing electricity- and sunlight-based fuels: power-to-liquid (PtL) and sun-to-liquid (StL). However, the production processes for this artificial kerosene are not yet available on an industrial scale, which means the fuels are still very expensive; at the moment, they cost many times as much as standard kerosene.
Power-to-liquid is a pioneering process for generating kerosene from water and CO2
Does the future belong to the fuel cell?
One very promising propulsion concept is the hydrogen-powered fuel cell as an emerging technology for sustainable aviation. It emits nothing but water, paving the way for climate-neutral and pollutant-free flight. This concept uses hydrogen as its energy source and employs electric motors to drive the propulsors. Hydrogen has a very high energy density, so—in contrast to the electric battery—a fuel cell could conceivably also power long-distance flights. However, the fuel cells available today are not suitable for use in larger aircraft. Nevertheless, in light of their potential, we are pursuing this concept as a long-term solution as part of our Claire Technology Agenda.