Cyanobacteria Biorefinery-Production of poly(3-hydroxybutyrate) with Synechocystis salina and utilisation of residual biomass.

•Evaluation of downstream processing on quality of photoautotrophically produced PHB.•Pre-treatment is necessary to achieve PHB with a high molecular weight.•Quality of photoautotrophically produced PHB is comparable to heterotrophically produced PHB.•Using residual biomass to obtain further products and close the nutrient cycle.•CH4 potential of residual biomass (348 mn3 t−1VS) is similar to maize silage.