In a composite material, the reinforcing agent and the matrix must adhere well at the interface; any effect can reduce the strengthening effect. Using components composed of the same material, as in all-cellulose composites, the adhesion at the interface is expected to be improved. In addition, this construction would improve the recyclability of the material.In her thesis, Helena Halonen presents a production method that entails more advantages including low cost, simplicity and relatively predictability. The method involves the use of existing raw materials, i.e. pulps that are already available from the pulp mills. Biocomposites based on chemical pulp or dissolving pulp are processed via compression moulding, a commonly used technique found in nearly all industrial sectors. It would therefore be relatively easy to implement the method in an industrial installation.The experiments show that the optimum press temperature would be 170 °C in order to achieve fast drying without the material being broken down thermally, while still having excellent mechanical properties.The thesis also describes a method for producing biocomposites based on bacterial cellulose fibril aggregates from Gluconacetobacter xylinusprocessed through a biosynthesis. The formation of cellulose fibrils was affected by the addition of hydroxyetylcellulose (HEC) which resulted in a biocomposite with remarkable mechanical properties including improved strength, modulus and toughness. The HEC coating improved the fibril dispersion and prevented fractures.(Innventia)