In this study, green bio-membranes were investigated. Alginate membranes were prepared by crosslinking of sodium alginate in calcium chloride aqueous solution. By fabricating membranes simply using three abundant cheap materials i.e. sodium alginate, salt and water, we have demonstrated membranes with acceptable performance for OSN with excellent chemical stability. Membranes prepared on three different polymeric supports (PAN, crosslinked PAN and Cellulose) showed similar performance. The alginate membranes were also spun coated on glass plate and laminated on alumina support. Great chemical stability was observed towards various solvents including dimethylformamide and dimethylsulfoxide. Characterization tests with FTIR, SEM, AFM and contact angle were carried out. Using same support, many parameters were explored such as the alginate concentration and the post treatment such as drying, crosslinking or precipitating in non-solvent. The range of the membranes permeance was 0.08–1.8 L/m2 h bar depending on conditions used. The nanofiltration experiments revealed a molecular weight cut off of about 1200 g/mol when tested with dyes such as Methyl Orange, Brilliant Blue and vitamin B12 in methanol. We initiated the preparation of fully green organic solvent nanofiltration membranes using green routes by preparing alginate selective layer on top of cellulose support. This study demonstrates that alginate membranes can be a promising candidate for green organic solvent nanofiltration.