Ganyeka,
A solution is available that is 100% effective, and that is to mix the fuel with a water dispersant - the best know brand is Prist, but others exist. Prist was designed to stop ice crystals forming in fuel systems, which it achieves by dispersing the water into the fuel so that no ice nuclei form. It has the important side effect that it also completely stops microbial contamination - not, contrary to popular view, because it is a biocide, but by the simple mechanical effect of removing the fuel/water boundary that the bugs need to live on.
You may wonder why Prist is not universally used. Prist costs more than Jet fuel. Even though the concentrations are small (typically 1000:1 mix), by pre-mixing Prist with the fuel you increase the cost by roughly 1 cent per litre. Many small jets and turboprops routinely use Prist in their fuel because they need the anti-ice properties, and they don't use so much fuel that it makes a material difference to their operation. Bulk fuel users - like airlines - find the cost premium to be a problem. Instead they install heat exchangers to solve the ice problem, and rely on utilisation and maintenance programs to solve the bacterial problem.
So if your friend has invented a new additive the target for success is easy - does it cost a lot less than 1c per litre of fuel to deploy it?