Biofuels can offer an alternative to fossil fuels in the context climate change and fossil reserves depletion. Plant biomass consists mainly of structural (cell wall) polysaccharides, but contains also reserve polysaccharides (starch, polyfructans) and soluble carbohydrates, that can be converted by micro-organisms. So agricultural residues and herbaceous biomasses offer the opportunity to be converted to second-generation bio-ethanol. In this study, we examined the composition of Lolium perenne, Lolium hybridum, Lolium multiforum, to check their suitability for a dedicated ethanol conversion process. We investigated different varieties (early, intermediate, and late precocity degree; diploid and tetraploïd), different development stages (elongation, heading, flowering), harvest time in the day, and tedding on carbohydrate availability. All harvested samples were either dried at 70°C for biomass composition analysis or frozen for fermentation assays. Soluble carbohydrates were extracted from the dried biomass samples by water at 70°C. Fructose, Glucose, Sucrose and oligofructans to a degree of polymerisation DP11 were analysed by HPLC-ELSD with a Carbohydrate Prevail column. Biomass main components were determined by NIR spectroscopy with special focus on structural polysaccharides cellulose and hemicelluloses. Frozen biomass samples were used to examine the feasibility of a simple ethanol fermentation process directly from crude, not sterilized grasses with the commonly used yeast Saccharomyces cerevisae. Grass was fermented with S. cerevisiae for 40 h at 40°C. Ethanol and volatile fatty acids were analysed by GC-FID. Results show that S. cerevisae can produce ethanol directly from the green biomass but the endogenous microbial flora is responsible for the production of lactic acid and other volatile fatty acids (mainly acetate and butyrate).The soluble carbohydrate conversion yields to ethanol will be presented.