A method for producing chitosan from naturally occurring chitin-containing raw material, such as crustacean shells, includes an optional pretreatment step to remove non-chitin rich organic material for example, shrimp flesh, from the raw material, e.g., shrimp shells. The optional pretreatment is followed by a demineralization step utilizing a mild hydrochloric acid solution and a deproteination step utilizing a mild sodium hydroxide solution. The deproteination step is followed by a deacetylation step to remove the acetyl group from N-acetylglucosamine (chitin) to form an amine group, yielding d-glucosamine (chitosan). Each step is followed by a washing step and the product is dried, preferably at a temperature not in excess of about 65° C. Known purification and grinding steps may also be used to produce the final chitosan product. The process is carried out in equipment comprising a series of substantially identical or similar tanks (18, 26, 36, etc.) and dryers (62, 62′), suitably interconnected.
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