Sustainable aviation fuels (SAFs) are a type of biofuel used to power aircrafts that are produced from renewable sources. Depending on feedstock and production pathway, certified SAFs can have lower lifecycle greenhouse gas emissions than conventional fossil jet fuel. SAFs can be produced from a variety of feedstocks, including agricultural crops, waste oils and fats, and algae. They are chemically similar to traditional jet fuel, and can be used in existing aircraft engines without modification. However, SAF still has to be blended with traditional aviation fuel, which is made from fossil fuels. Current rules state that SAF can make up a maximum of 50% of the mixture, but there are hopes that airlines will be able to use 100% SAF by 2030.
Hydrogen peroxide is used as a rocket propellant in the aerospace industry and decomposes into water and oxygen. Known as "high test peroxide", or HTP, this highly concentrated hydrogen peroxide (up to 98%!) is used as a direct propellant for smaller rockets and launch vehicles, or as an oxidizing agent for turbo pumps in larger launch rockets. HTP is readily available and, unlike some other common propellants, is not classified as carcinogenic.