The invention relates to the separation of manure in fractions and the treatment of said fractions in order to retrieve useful components to produce manure-derived bioplastic and other manure-derived bioproducts. The invention further relates to a method for producing composite (bio)plastic, and to a method for producing fibre from regenerated manure-derived cellulose. The methods include the steps of: flocculation treatment and a filtration treatment; pulping the manure-derived solid fractions; acetylation of the manure-derived dissolving-grade cellulose pulp with acetic anhydride and a catalyst; extracting fermentable components from the different fractions of the manure to produce monocarboxylic acids for use in the monocarboxylic acid carrier solution. Furthermore methods are disclosed for forming composite bioplastics with resin binding agents; and for spinning yarn from cellulose pulp.