Slaughterhouse/tannery wastes such as fleshings, hair which are made up of proteins are not utilized properly even though they are rich in amino acids. Proteins are hydrolysed to amino acids and separation of amino acids involves several process steps. In most of the processes reported, all the amino acids were not totally separated. Supercritical solvents are having special properties, which are absent in conventional liquid based solvents however, they are not suitable for polar substances. Amino acids solubility in supercritical carbon dioxide is very low, hence a study has been made to measure solubility of modified amino acids (N-CBZ amino acids). This modification showed increased solubility. By suitable derivatisation and by means of blocking both the polar groups (COOH, NH2) the solubility of these amino acids can be increased further and supercritical fluid extraction technique can be used for separation of amino acids. (C) 2003 Elsevier B.V. All rights reserved.