A method for producing a manure-derived cellulose acetate at atmospheric pressure, by separating manure into useful components, comprising the steps of: a. flocculation treatment and a filtration treatment where fractions having different particle size are separated by using different mesh sizes to obtain solid fractions having a high lignocellulose content； b. pulping the manure-derived solid fractions with high lignocellulose content at atmospheric pressure with a monocarboxylic acid carrier solution using a bleaching process comprising of ozone or an peroxyacid to produce a dissolving-grade cellulose pulp； c. acetylation the manure-derived dissolving-grade cellulose pulp with acetic anhydride and a catalyst in the monocarboxylic acid carrier solution to produce cellulose acetate； d. extracting fermentable components from the different fractions of the manure to produce monocarboxylic acids for use in the monocarboxylic acid carrier solution.
