From the same site:
U
ranus is composed primarily of rock and various ices, with only about 15% hydrogen and a little helium (in contrast to Jupiter and Saturn which are mostly hydrogen). Uranus (and Neptune) are in many ways similar to the cores of Jupiter and Saturn minus the massive liquid metallic hydrogen envelope. It appears that Uranus does not have a rocky core like Jupiter and Saturn but rather that its material is more or less uniformly distributed.U
ranus' atmosphere is about 83% hydrogen, 15% helium and 2% methane. 83% hydrogen, 15% helium, 2% methane. Seems that there are a lot of hydrocarbons out there. Why the earth's hydrocarbons should be different I don't know. As far as leaf wax is concerned, well, maybe the plant is just using available materials. I don't know, but I agree with the researchers on oil who say it is not a fossil fuel. Coal is another matter.