How to improve the environment, realize a virtuous cycle of ecology, develop clean energy to replace traditional energy and build a conservation-oriented society is a problem worthy of our attention.

(1) Biomass energy, wind energy, water energy, geothermal energy and solar energy belong to renewable energy, while fossil energy and nuclear energy belong to non-renewable energy.

(2)① When the straw is burned, the chemical energy in plants is converted into internal energy;

② Main hazards: First, it pollutes the environment; The second is to cause a fire; Third, it causes traffic accidents and affects road traffic and aviation safety;

3 Suggestions: First, it is used as coarse grains; The second is straw gasification, popularizing biogas digesters and straw gasifiers. Third, the use of straw to develop mushroom industry;

So the answer is: (1) fossil energy and nuclear energy; (2) Within ①; (2) polluting the environment; ③ Used as roughage.