If stools and urine (human or animal) can't be used for fertilizer, what will be the ruling if these impurities are used to produce gas for vehicles a

Answer

The vapour, smoke and ash realized after burning an impurity are not impure. Thus, the gas which has been prepared will be permissible for use in vehicles although Muslims should not deliberately embark on operations to produce gas from impurities. Allah Ta'ala has created more than ample pure substances for our sojourn on earth. Rasulullah (sallallahu alayhi wasallam) said: "Verily, the world has been created for you (i.e. for your temporary stay here) while you have been created for the Aakhirah." Nabi-e-Kareem (sallallahu alayhi wasallam) also said: "Allah has not created the cure for my Ummah in substances which have been made haraam for them." But the brains of kuffaar being impregnated with kufr always first incline to najaasat (faeces, urine, liquor, blood, and other impurities). The same mentality prevails in the medical world. Their brains overlook the billions of pure substances Allah Ta'ala has created for medicine. Kufr is spiritual filth, hence the kuffaar always incline towards physical filth and impurities.