Cost per unit energy production from wind and solar and its maintenance are costly. Whereas biological waste in the from of agricultural waste, municipal solid waste and other waste are not utilised properly for energy generation. A serious thought has to be put into waste conversion to energy.

Thank you Barabara Sawicka,  Fine, Points to be considered are Weed invasion need to checked by intensive crop cultivation. Is that the weeds are biologically rich source that agricultural crops  especially in waste/ barren land. Such studies are to be taken up further in right direction. 

advise: check for Hans Langeveld  in this researchgate-Network, he is working heavily on the Topic.

Dear Bernhard Meier zu Biesen as per your input I explored the contents of  Hans Langeveld work. I may follow his work in future. Thanks a lot for your support.

Please send me ([email protected])  your email and I will forward a bunch of related literature. Have a nice day.

Corn is currently the most widely used energy crop. However,  grasses & trees are likely to become the most popular in the future.

As for grasses, Switch grass appears to be the most promising herbaceous energy crop. It produces high yields & can be harvested annually for several years before replanting. Other varieties that grow quickly, such as big blue stem, reed canary grass, and wheat grass, could also be profitable.

As for trees, Some fast-growing trees make excellent energy crops. Best choices are poplar, willow, sycamore, sweet gum, and cottonwood. Add to them, Euphorbia  tirucalli which was suggested by the Nobel Laureate American biochemist, Melvin Calvin, since this shrub produces energy-rich materials similar to the petroleum hydrocarbons.

Besides the grasses & trees, oil plants(such as soybeans & sunflowers) can be used to make fuel. Like corn, however, these plants require more intensive management than other energy crops.

Dr. Nizar Matar, The content is more informative. It can be understood that bio energy crops can be classified as grass, trees, agricultural crops and oil seed crops. Whereas for grasses and trees farm management of practices are meagre. for agricultural and oil seed crops they are intensive. The crop energy conversion are to looked into for strengthening the component.

Dear Mariappan,

Our investigations of bioenergy in Brazil indicate the cane sugar as a high energy potential culture, particularly in relation to crop residues. The residue can be used as a fuel source to generate heat in furnaces and steam for electricity production or as a source of cellulose for second generation ethanol production. It is also interesting the rice processing residue. Visit my profile and you will have access to many articles on the subject.

Please refer the linkbelow:

http://www.scientificamerican.com/article/how-to-manipulate-plants-to-build-a-better-biofuel/?print=true

Here's a segment of a presentation. Slide 2 shows the average production of oil feedstock per hectare of farm land. It includes food and non-food crops.

This only applies to liquid biofuels, but might be of help.

I am preparing a few manuscript that biohydrogen production from Duckweed.