Lignin as co-product of second generation bioethanol production from ligno-cellulosic biomass

To improve the economic viability of the biofuel production from biomass, it is of increasing importance to add value to the lignin produced as a bio-residue. Moreover, to meet the goal to replace 30% of fossil fuel by biofuels by 2030, a huge amount of lignin will soon be produced. The first major step involved to add value to the unconverted lignin is its separation from other biomass constituents to give high purity lignin. In this current work, extraction of lignin from a bio-residue (containing ca. 40% lignin) from second generation bioethanol production is presented. The biomass chosen is Arundo donax L. (or giant reed), which is non-food plant, can tolerate a wide variety of ecological conditions with all types of soils, and has increasingly importance as raw material for industrial purposes as a source of fibers alternative to wood, which availability is decreasing. Slightly different extraction procedures are investigated. Methods used are simple, mild, safe, and avoid destruction of fiber content in the bio-residue, with the final aim to valorize all fractions of the bio-residue, which is an essential step to make biofuel production to be cost effective. Lignins extracted are characterized by morphological analysis, using Scanning Electron Microscopy, SEM, and in terms of thermal behavior -using thermo gravimetric analysis TGA- which is critical for determining suitability of the lignin for polymer composite preparation with improved thermomechanical performance. The method judged as the best of the three leads rapidly to extraction of lignin free from fibers and ash, with thermal behavior suitable for composite preparation.