An integrated approach for utilizing waste products of 2G bio-refineries to fractionate the lignin of high purity. The present invention also provides a method of recycling of two waste products (2-G ethanol residue as the substrate (LRBR) and fusel oil/synthetic fusel oil (SFO) as one of the solvent) of the biorefineries in a beneficial manner to fractionate the lignin of high purity. The present method of separating high purity lignin comprises fractioning extractive-free lignin rich residue with a solvent, wherein the solvent is a mixture of SFO/Fusel oil and Formic acid. An optimized ratio of waste fusel oil and formic acid gave more than >85% yields of high purity lignin.