Do you mean biogas residues? If yes, there are many approaches that can be adopted. One of such is to use the residues for making compost for application in crop production. Good luck and best regards.
Anoop Kumar Srivastava thanks for interest, the question was that how can and which approaches we can use to produce hight quality organic fertilizer? which sources and which approaches while keeping in point biogas
I have personally used slary from biogas digestor to make compost with mixture of mosses (by products of sugar), baking yeast, maize brain. the result was overwhelming and Mazabuka Sugar here in Zambia has adopted the technology. The company is adding this compost to cane field at 5tones per hectare.