NOVELTY - Producing a monomer component from a genetically modified polyhydroxyalkanoate (PHA) biomass comprises heating the biomass in the presence of a catalyst to release a monomer component from the PHA, where the monomer component yield is 70% based on one gram of monomer component per gram of polyhydroxyalkanoate.    USE - The methods are used for producing a monomer component from a genetically modified PHA biomass, for producing acrylic acid from a PHA biomass using a multiple tandem catalysis reaction protocol, for producing acrylic acid from a genetically engineered PHA, and for producing 5-hydroxyvalerolactone from a genetically engineered PHA biomass (all claimed).    ADVANTAGE - The biobased chemicals (monomer components and derivatives) are produced simply and cost effectively while overcoming the problems of cell toxicity and purity. The method is used for producing high purity, high yield, biobased monomer components from renewable carbon resources. The advantages of this biorefinery process are that it uses a renewable carbon source as the feedstock material, the genetically engineered hosts produce PHAs in high yield without adverse toxicity effects to the host cell (which could limit process efficiency) and when combined with catalysts and heated is capable of producing biobased monomer components and their derivatives in high yield with high purity.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are:    (1) a continuous biorefinery process for production of acrylic acid from a PHA biomass using a multiple tandem catalysis reaction protocol by (a) culturing a genetically engineered PHA biomass to produce poly-3-hydroxybutyrate, (b) pyrolyzing the poly-3-hydroxybutyrate to produce crotonic acid, (c) reacting the crotonic acid to form a lower alkyl crotonate ester in the presence of a transesterification catalyst, and (d) reacting the lower alkyl crotonate ester under suitable conditions to form a lower alkyl acrylate and a lower alkene via cross-metathesis in the presence of a first metathesis catalyst with a sufficient amount of proplylene, where the propylene is formed from a metathesis reaction of ethylene and 2-butene in the presence of a second metathesis catalyst and excess propylene is continuously removed;    (2) a continuous biorefinery process for the production of acrylic acid from a genetically engineered PHA biomass by (a) culturing the genetically engineered PHA biomass to produce polyhydroxypropionate, (b) heating the polyhydroxypropionate with a catalyst to produce acrylic acid, and (c) recovering the acrylic acid;    (3) a continuous biorefinery process for the production of glycolide from a genetically engineered PHA biomass by (a) culturing the genetically engineered PHA biomass to produce polyglycolide, (b) heating the polyglycolide with a catalyst to produce a glycolide monomer component, and (c) recovering the glycolide monomer; and    (4) a continuous biorefinery process for the production of 5-hydroxyvalerolactone from a genetically engineered PHA biomass by (a) culturing the genetically engineered PHA biomass to produce poly-5-hydroxyvalerolactone, (b) heating the poly-5-hydroxyvalerolactone with a catalyst to produce a 5-hydroxyvalerolactone monomer, and (c) recovering the 5-hydroxyvalerolactone monomer.