Conventional soil stabilizers such as lime and cement have now proven to cause detrimental impacts on the environment. Thus the usage of natural biopolymers in soils reinforcement seems to be an essentially engineered effort. On the other hand, industrial agriculture wastes propose stability potential in geotechnical engineering. Vinasse biopolymer is a waste material produced from ethanol during sugarcane processing. In this study effectiveness of vinasse to stabilize sand was investigated through laboratory tests. The treatment of sandy soil by using an environmentally-friendly material, i.e. vinasse biopolymer, seems to be economical, pollution controlling, and an appropriate solution of the wastes disposal. The effect of biopolymer content, curing time, and percentage of soil compaction were studied by compaction tests, direct shear tests and unconfined compressive strength tests. The amounts of biopolymer used in the experiments ranged from 2% to 6%. In a number of samples, a small amount of cement has been added to investigate the stability of samples exposed to moisture. Compaction tests have been conducted to study the effect of adding biopolymer on the soil density. The results of this experiment showed that adding the resin to the soil samples may have a typical role of lubrication and facilitate the soil compaction process. Using the vinasse resin up to 6%, instead of adding water to soil, increases the maximum dry density. Also, direct shear tests were done to investigate the effect of adding the vinasse biopolymer on the shear strength and shear strength parameters of the soil samples. Various factors such as the amount of biopolymer and cement, curing time, density as well as the effect of moisture on the strength of treated and untreated soil samples were also investigated. The results of these experiments indicate that the soil shear strength has increased steadily by adding the biopolymer up to 5%. Moreover, adding 5% the biopolymer to soil samples cured for 14 days and direct sheared under 100 kPa normal stress, showed shear strength increment up to 9.5 times and internal friction angle 1.8 times in comparison to that of untreated soil. The soil cohesion was also enhanced to the significant value of 476 kPa. Moreover the test results showed that by adding cement as well as increasing curing time and density, the soil shear strength increases steadily. The amount of %5 vinasse and %0.5 cement were found to be optimal values ??for which the soil shear strength increased up to 10 times in 14-day curing time under 100 kPa normal stress in comparison to that of untreated soil. The effect of moisture on soil samples showed that shear strength of treated sample was reduced in wet conditions. But with subsequent drying, the sample gains its initial shear strength again. Therefore, the presence of water has a significant effect on the strength of treated soil samples. Coating the surface of the treated soil samples with silane can make the samples to be waterproof, by which the sample strength may be maintained at moisture exposure conditions. Making direct shear tests on saturated samples showed that the strength of the treated samples reduced nearly to that of original untreated soil due to saturation. To improve the performance of the stabilized soil under saturated conditions, the efficiency of various additives such as bentonite, superabsorbent polymer, and water-resistant adhesives was investigated. It was concluded that adding a polyester adhesive can maintain the treated sample strength in saturated conditions to some extent. Moreover, the results of unconfined compressive strength test showed that the compressive strength of treated soil with Vinasse biopolymer increased significantly. Finally, microscope observation was performed on both treated and untreated soil samples by scanning electron microscopy (SEM) images to evaluate the resin stabilizing process. The SEM images showed that there is no bond between soil particles in the untreated soil samples. The Vinasse, however, binds the soil particles by coating the particles surface which in turn, increases the soil strength. Adding a small amount of cement along with vinasse leads to a greater increase in the binding of soil particles. The image of treated soil sample with vinasse in saturated condition showed that vinasse biopolymer is still present between soil particles although shows no evident adhesive effect.