Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Cellulose is an abundant, cheap, renewable, yet recalcitrant, material, which, if dissolved, may be formed into a wide range of materials, composites, and mixtures. Much attention has recently been focused on the use of mixtures of ionic liquids and some solvents (so-called organic electrolyte solutions, OESs) as efficient cellulose dissolution solvents, but many of the cosolvents used lack green credentials a perennial problem where dipolar aprotic solvents are the solvents of choice. We present a rational approach, based on definition of ranges of solvent parameters gathered together in recently published databases, to find "greener" cosolvents for OES formation. Thus, gamma-butyrolactone is identified as a suitable OES former for dissolution of microcrystalline cellulose and biobased gamma-valerolactone as a marginally less efficient, but significantly safer, alternative. Comparison of cosolvent efficiency reveals that previous use of measures of mass, or concentration, of cellulose dissolved may have masked the similarities between 1-methylimidazole, dimethyl sulfoxide (DMSO), N,N-dimethylformamide, N-N'-dimethylimidazolidinone, NN-dimethylacetamide, N-methylpyrrolidinone, and sulfolane (seldom considered), while comparison on a molar basis reveals that the molar volume of the solvent is an important factor. Reference-interaction site model (RISM) calculations for the DMSO/1-ethyl-3-methylimidazolium acetate OES suggest competition between DMSO and the acetate anion and preferential solvation of cellulose by the ionic liquid.41162006207UK Engineering and Physical Sciences Research Council (EPSRC) via the EPSRC Doctoral Training Centre in Sustainable Chemical Technologies, University of Bath [EP/G03768X/1]British CouncilSao Paulo Research Foundation (FAPESP) [CEPID 2013/08293-7, 2014/10448-1, 2015/25031-1]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)