Thank you for your mention.
if you can only supply 50 HU per machine
This is the point.
Actually, simple oil only can provide 16HU/t and the biogas provides only 32HU/t.
Because there is no Buildcraft currently, this is the maximum of oil based heat generator.
Recently I realized that the easiest way is using Radioisotope Heat Generator by putting Pellets of RTG Fuel.
Hmmm... It is easy way but less interesting for me.
Anyway now I implemented 50EU/40mb simple oil based steam generator.
Thank you for your supports, all of you.