A steam heat generator would be a fairly expensive piece of equipment, it would use a large amount of steam per tick and generate a large amount of heat per tick. There are three good things about this:
1. It would allow biogas production to have a higher tier, more compact, powerful option.
2. it would make more interesting uses for IC2 steam , and by extension 5x5 reactors.
3. Best of all, if this item if allowed to accept universal steam , instead of only IC2 steam , and you work the math cleverly, this device could be integrated in a number of interesting ways with the steam producing machinery of other mods. And i suppose if you're thus enabling the super generation of biogas you may want to create a powerful generator to match that gas production, or speak to other mod makers about including bio gas in their heavy duty generators. BDew for example is a very agreeable fellow