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Testing shows Virent SAK bio-jet provides more than 50% reduction in PM emissions while maintaining engine performance

Bio-jet emissions testing by Rolls-Royce, supported by the Federal Aviation Administration (FAA) under the Continuous Lower Energy, Emissions, and Noise (CLEEN) program, has confirmed that jet fuels containing Virent’s BioForm Synthesized Aromatic Kerosene (SAK) fuel blend produced a greater than 50% reduction in particulate matter emissions compared to conventional jet fuel.

The testing thus verified the potential for the SAK fuel to reduce the adverse environmental impact and health effects resulting from jet fuel combustion. The emissions data and other successfully completed test results have been summarized in a report released by Rolls-Royce, British Airways, and the FAA.

Virent was chosen to participate in the initial Rolls-Royce Laboratory Test program, and was then selected by Rolls-Royce to proceed to the more advanced Rig Testing portion of the program.

Virent’s SAK fuel blend met all test requirements and the report concluded that the fuel “…offers the potential to be [a] drop-in fuel and hence achieve approval for use for the aviation industry”.

Virent is developing two bio-derived jet fuel products using its Bioforming process (catalytic conversion of carbohydrates in a water solution): Hydrodeoxygenated Synthesized Kerosene (SK) consisting of C9-C16 paraffins and naphthenes and Hydrodeoxygenated Synthesized Aromatic Kerosene (SAK) consisting of C9-C11 aromatics.

Virent’s SAK fuel is a mixture of clean burning aromatics that are missing from other alternative jet fuels; blending with SAK eliminates low density and materials compatibility issues that limit the allowable blend levels of these alternatives. SAK can be combined with Virent SK or other alternative blendstocks to enable a 100% alternative jet fuel blend that meets all ASTM D7566 requirements.

The Rolls-Royce testing of the SAK fuel blends demonstrated this capability with a 50% to 80% reduction in particulate matter emissions depending on engine operating conditions.

Key properties of SAK include:

  • Aromatics and Naphthalenes. SAK can satisfy the minimum aromatic levels in jet fuel without naphthalenes, offering lower emissions and better combustion properties than conventional jet fuel.

  • Sulfur. The BioForming Process removes sulfur and other ash contaminants to below detectable levels, which reduces emissions and fuel systems wear.

  • Boiling Point Distribution. Flash point and end point are controlled by distillation, similar to conventional petroleum refinery processing. SAK blends have a broad boiling point range containing C8-C16 hydrocarbons, comparable to conventional jet fuel.

  • Thermal Stability Breakpoint. A higher breakpoint than conventional jet fuel reduces fouling and deposit formation potential.

  • Freeze Point. A superior freeze point allows expanded operational boundaries on flight pattern and altitude.

  • Acid Number. A low acid number ensures reactive oxygenated species have been removed to prevent corrosion.

  • Density and Heating Value. Blending SAK with Virent SK or other alternative fuels provides an option to meet the minimum density spec while still providing good overall energy content.

Virent produced the renewable SAK fuel in its pilot demonstration plant in Madison, Wisconsin.

The International Civil Aviation Organization (ICAO), a specialized agency within the United Nations, is leading international policy making efforts to control particulate matter and greenhouse gas emissions from the aviation sector. Virent’s SAK fuel can reduce both particulate matter and greenhouse gas emissions without compromising engine performance, and when fully commercialized will support the growth of the aviation industry while addressing anticipated ICAO regulations.

Virent will progress additional testing of the SAK fuel in collaboration with external parties as part of the ASTM certification process.



Synthetic and bio synthetic fuels are cleaner.


And particulates rather than greenhouse gases per se are the real key to dealing with adverse climate change and adverse changes to the upper atmosphere.

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