Biorefinery was used to transform two organic wastes, i.e. urban park & garden green waste and porcine plasma (PPP), into raw materials for biocomposite production. The effect of the nature, size and content of the filler on the final performance of biocomposites was assessed. Two fractions stemming from an urban park and garden green waste, i.e. a representative fraction of the total waste (RF) and a branches-rich fraction (B), were considered as fillers of a PPP bioplastic. PPP-RF/B biocomposites were obtained by compression-moulding and then characterised by tensile tests, dynamic mechanical analysis, water uptake, and water vapour permeability. Using a filler size around 28 mu m at 30 wt%, the Young's Modulus of samples including B fraction was double the value of that including RF, due to the presence of grass in the overall urban waste. Moreover, a greater strengthening was perceived when using larger particle sizes (around 140 mu m) of the B fraction, highlighting the importance of the grinding stage. The loss tangent evolution with temperature from dynamic mechanical tests denoted an antiplasticizing effect of the urban biowastes, which should be considered in future applications as a certain exudation degree would be expected. Regarding barrier properties, water permeability increased at higher filler contents (i.e., 30 wt%), while oxygen permeability decreased. Generally, composites from plasma and urban biowaste could be considered in future applications (e.g., packaging), as they showed great reinforcement and stability during water immersion, apart from a darker to-nality and decreased oxygen permeability.