Renewable fuels are liquid or gaseous fuels produced from biomass. Starting materials are renewable raw materials such as energy crops, cereals, forest biomass, residues and algae.
High quality renewable fuels for aviation
The conventional oil-based aviation fuel is standardized worldwide. It is a kerosene of the denomination Jet A-1. Renewable fuels are designed as so-called drop-in fuels, that means they meet the same specification as conventional petroleum-based aviation fuel. This makes them fully compatible and miscible. Thus, they meet the highest quality requirements and their use requires no changes to the aircraft turbines. Moreover, there are no technical obstacles to mixing alternative fuels with fossil kerosene in the fuel depots of the airports which additionally avoids infrastructure costs.
Sustainability as the ultimate goal
Sustainability must be a top priority in the production and use of alternative fuels. Rising food prices, competition for water and negative land use changes in the context of sustainable fuel production must be avoided.
Under this condition, the production of raw materials for renewable fuels offers clear advantages: The emergence of a new agricultural branch in developing countries can serve as a catalyst for the further development of the cultivation region - a sustainable agricultural practice creates jobs, promotes the development of local infrastructure and counteracts the rural exodus.
National and international sustainability regulations for the production of fuels from renewable resources already exist today. These initiatives and regulations need to be aligned to achieve global sustainability standards for alternative energy fuels for aviation.
Need for further manufacturing processes
So far, five different production processes for renewable aircraft fuels made from sustainable raw materials have been approved and a number of other technologies are currently in the approval process. The more technologies are approved, the broader the selection of possible raw materials becomes. As a result, numerous regional supply chains can be created which additionally supports the reduction of CO2 emissions.
|Fischer-Tropsch||2009||Flexible||Velocys, Sasol, Shell, UOP|
|HEFA||2011||Fatty acids and oils||UOP, Neste Oil|
|AtJ w/o aromatics||2016||Sugar, lignocellulose||Gevo, Cobalt|
|AtJ with aromatics||-||Sugar / ethanol||Byogy/ Lanzatech|
|Catal. Thermolysis||-||Fatty acids and oils||ARA|
|HDO-SK/ HDO-SAK||-||Sugar, lignocellulose||Virent/ Shell|
|FT with aromatics||-||-||Virent/ Shell|
|Renewable Diesel||-||Fatty acids and oils||Neste, Diamond|
Energy crops are agricultural crops grown with the main objective of producing energy. These include, for example, sugar-rich or starch-containing plants, such as sugarcane or cereals, as well as oil plants such as oilseed rape and oil palm. Of particular importance are varieties such as Camelina and Jatropha which are not used for food production. They provide an oil that is particularly easy to process.
For decades, various oil plants have been grown successfully on a large scale globally and research is constantly being conducted to establish "new" oil plants. The oil produced is used in a variety of areas: In addition to the use for energy, the oil can be used for the production of food, animal feed or for the production of chemicals and cosmetics.
In order to exclude competition with the food market and thereby increase the acceptance of the energetic use of the oils, aireg relies primarily on the use of non-consumable raw materials for the production of kerosene from sustainable resources. Basically, large quantities of vegetable oil, primarily produced for the food and feed market or the chemical industry, are available on the market for potential sustainable kerosene production. However, the costs are comparatively high. Targeted plant breeding of energy crops with the aim of realizing higher yields, however, is expected to reduce costs in the medium term, especially for the "new" oil crops.
Energy crops belong to the renewable raw materials and supply biomass for power and heat generation as well as for the production of fuels. According to a study by the German Ministry of Transport countries like Russia, Brazil, the USA and Indonesia are expected to be priority countries to produce raw materials for biomass.
Currently under discussion is the prohibition of direct land-use changes such as ploughing up of grassland and clear-cutting of primary forests as well as a legally prescribed conversion of arable land for nature conservation purposes.
Unfortunately, large area potentials for energy crop cultivation can only be considered insufficiently. Here in particular, worth mentioning are so-called ‘degraded areas’ whose soil quality is currently considered insufficient for conventional agriculture. The area estimates range from 600 million to 3.5 billion hectares worldwide. A viable forecast of the biomass potentials of these areas has is difficult because of the different assumptions regarding yield expectations and forms of use. For this reason, a precise consideration of these surface potentials seems very worthwhile.