Waste streams are things that other people throw out like waste oil, coffee grounds, left over food, etc. All can be converted to fuel and some to fish food.

No generator or engine is very efficient. A car engine is only about 20% efficient, and a high efficiency power plant is only 40% efficient. An electric motor is about 95% efficient, but couple that to a pump and you lose most of that. It is just the way things work.