I might get my dual fuel running within this year, but we'll see. I made some preliminary calculations, and I save some 20-25% on fuel costs. First I wasn't too impressed about the numbers (€/100km), but after I added up the whole year, savings were quite impressive. Some calculate that how long it takes to system to pay itself back, in my case it's about 18 months. But I don't care to make that kind of calculations. Those numbers are made with CNG, CBG is just a little bit more expensive so I guess it's about 20-22%.
One thing I didn't even consider, but EWS claims that dual fuel system increase power as much as 25%
www.ewsews.com FATMAN, were you talking about ews kit?
Biodiesel would be way to go, if it were readily available. I don't have time to mess with it, nor I don't have place for it. Not to mention that I would have to pay tax of it, too. At the moment, to me, biodiesel would be waste of time.