Main features
- biogas can be produced from manure, sewage, municipal waste, plant material, grass and food waste. Biogas is mostly methane, which can be used as fuel. https://en.wikipedia.org/wiki/Biogas
- hydropower is potential energy of falling water. Small commercial hydro power plants also exist in the market today. https://en.wikipedia.org/wiki/Hydropower
- wave power uses energy of ocean waves. Wave power plants are under development. https://en.wikipedia.org/wiki/Wave_power
- geothermal energy plants utilise heat energy from earth’s core. Geothermal energy is large-scale energy production. https://en.wikipedia.org/wiki/Geothermal_energy
