Although aeroplanes can fly with batteries, the mass of the battery leaves little room for payload. The only other fuels are hydrogen or oil. Hydrogen is difficult to store, so for the foreseeable future, planes are going to need oil.
However, compared to other oil crops Jathropa has a lower yield and is illegal to plant in Australia because it is rated as a noxious weed. It also has known carcinogenic effects on humans. It also has a wide flowering window and mechanical harvesting will generally result in significant losses in yield (up to 50%).
Introduction to biofuels for jet engines - (ATAG biofuels guide)
Pongamia / Millettia
However the future bio jet fuel future may be dominated by Pongamia/Millettia Pinata.
Pongamia / Millettia represents the best all round sustainable solution for broadacre renewable energy cropping. Because Pongamia is a legume, it produces its own Nitrogen and requires little to no fertilizer. Fertilizers used with competing crops are generally produced from fossil fuels, which can defeat the purpose of using biofuel. It can grow in saline soil similar to a saltbush.
Milletta also has very deep tap roots so is drought resistant and puts carbon into the soil.
Case study of pongamia in an Indian village
The Diesel Tree from South America looks good on the table on the right, but it cannot currently be mechanically harvested and the oil degrades within 1-2 months, making it unuseable as a broadacre solution. Further, it is 14 years before first economic harvest, and requires4000-6000mm of rainfall to achieve good yields. Ref..
Solaris - Energy tobacco
Italian company Sunchem has developed an energy tobacco called Solaris. The strain was developed to push the bulk of the plant’s oils into seed production rather than leaves. It is being trialled in the Limpopo region of South Africa where 3 crops a year is possible.
It produces seed with 40% oil, by cold press we could have 33-34% of raw oil and 65% of protein cake. This is useful as animal feed. The remainder can be fermented to produce methane, CH4.
Major Fatty Acid Composition of Chinese Tallow oil
Lauric acid 0-2.5%
"Trying to substitute 10 per cent of fossil fuels with solid and liquid bioenergy would consume 20 percent of the world's current harvest of all plants and trees, illustrating the need for limits on bioenergy.
That's because the calorific value of fossil fuel consumption is double that of the world's entire harvest of biomass for food, clothing, energy and wood products, show data from European Environment Agency (EEA) experts.
Supercritical water gasification
Supercritical water can be used to decompose biomass via supercritical water gasification of biomass. This type of biomass gasification can be used to produce hydrocarbon fuels for use in an efficient combustion device or to produce hydrogen for use in a fuel cell. In the latter case, hydrogen yield can be much higher than the hydrogen content of the biomass due to steam reforming where water is a hydrogen-providing participant in the overall reaction. Wikipedia
Licella - Biomass to crude oil
Licella are using supercrtical water to convert any form of biomass to a stable Bio-Crude oil. The process breaks down the ether linkages in the polymeric structure of biomass.
Under elevated heat and pressure, water approaches a fourth state of matter called the supercritical state. When water approaches this state it exhibits both acidic and basic properties, and diffusion properties similar to gases.
Their pilot plant is using Pinus Radiata as feed stock, but theoretically, any ligno-cellulosic biomass can be used.
Oil from wood - Wheeler process
The Wheeler process, has two stages:
Yet another exciting idea is to imitate the process nature uses to make oil reserves.
If you take any organic waste, medical waste, tyres, plastic, or sewage sludge, and put it in hot water under pressure for the right time, it will convert to oil, gas and char. The claim is that only 15% of the waste's energy goes into powering the process.
In Missouri 200 tonnes of turkey waste from a food factory is converted to 20 tonnes of oil every day.
Changing World Technologies claim to convert turkey waste costs $0.30 /KG, and tyres cost $0.20/KG of oil produced.
Microbial oleaginous microorganisms
ProBio3 is a French project to convert lignocellulose to oils suitable for jet fuel.
Details are vague.
"Lignocellulose is broken down into sugars through enzymes, then mixed with microorganisms such as yeast, and transformed into lipids through the chemical process of fermentation."
"The fats obtained are then treated with hydrogen to make a type of hydrocarbon with similar properties to fossil fuels."
"large and fatty yeasts, full of synthesized lipids"