What is PHA? A complete guide to polyhydroxyalkanoate bioplastics

Most plastics come from fossil fuels and are built in chemical plants. PHA is grown. Bacteria make it inside their own cells as an energy store, much as animals store fat, and it can be harvested and molded into everyday products. That biological origin is the reason microbes in soil, water and compost recognize it as food. This guide explains what PHA is, how it is made, the main types, where it is used, and the challenges that still hold it back.

What PHA is, in plain language

PHA stands for polyhydroxyalkanoate, a family of polyesters made by bacteria. When certain bacteria have plenty of carbon but run short of another nutrient such as nitrogen or phosphorus, they store the extra carbon as PHA granules. Under optimized conditions, PHB, the simplest PHA, can make up 80 to 90% of a cell’s dry weight.

Chemically, PHA is a chain of small building blocks (hydroxyalkanoic acids) linked by ester bonds. Change the side chain on those building blocks and you change the material: some PHAs are stiff, others are rubbery. That range lets one family of materials stand in for several kinds of plastic. A 2025 review counts more than 300 bacteria able to produce PHA, though only a handful are used commercially.

Because microbes make PHA, other microbes carry enzymes to take it apart. A 2025 review in Frontiers in Microbiology lists PHA-degrading bacteria in soils, freshwater and marine ecosystems. That is why PHA as a material biodegrades in soil, freshwater and marine environments, not only in compost.

A short history of PHA

In 1926 the French microbiologist Maurice Lemoigne found polyester granules inside the bacterium Bacillus megaterium. The material was polyhydroxybutyrate (PHB), the first known PHA. For decades it stayed a lab curiosity; petroleum plastics were cheap and new.

According to a 2026 review of PHB, interest grew in the 1970s and 1980s as oil prices swung and plastic pollution became a concern. Imperial Chemical Industries (ICI) in the UK brought out the first commercial PHB-based materials under the name Biopol, adding a second building block (hydroxyvalerate) to make the copolymer PHBV, which is less brittle than pure PHB. Cost kept the market small for years. The same review names high production cost, energy-heavy purification and a narrow processing window as the reasons PHA has taken so long to reach scale.

What changed is demand. Single-use plastic rules, extended producer responsibility (EPR) laws and stricter compostable labeling now reward materials that break down outside an industrial composter. Our EPR compliance guide covers those rules.

How PHA is made

1. Feed: bacteria are grown in large fermentation tanks and fed a carbon source. Producers tightly control temperature, acidity, air and nutrients.
2. Store: when one nutrient is held back, the bacteria switch to storing carbon as PHA granules inside their cells.
3. Extract: the cells are separated from the liquid and opened, and the PHA is recovered and purified.
4. Pelletize and mold: the purified PHA is dried, compounded and formed into pellets, which go through injection molding, extrusion or thermoforming like other plastics.

PlantSwitch runs this whole chain for its own material. CompostZero™ is made through fermentation from renewable feedstocks, and we develop each application and manufacture the finished product ourselves.

The main types of PHA

PHA is a family, not one material. The building blocks decide how stiff, tough or stretchy each type is.

Sources: Materials, 2026 for PHB and PHBV; a review of medical PHAs for PHBHHx and mcl-PHA.

How PHA compares with PLA and conventional plastic

For the detailed head-to-head, read PHA vs PLA: a buyer’s guide.

Where PHA is used beyond foodservice

Cutlery, straws and cups are the most visible uses, but the 2026 PHB review lists a much wider spread:

• Medicine: PHAs have been used to prototype bone scaffolds, nerve conduits and heart patches, and the first FDA-cleared PHA-based absorbable suture is already on the market.
• Farm mulch films, where collecting plastic from a field after harvest is hard.
• Coatings for paper foodservice packaging, where PHA improves water resistance.
• Shopping bags, films and other short-life items where end-of-life matters most.

The challenges PHA still faces

Cost

PHA costs more to make than PLA or conventional plastic. Fermentation and purification are expensive, and researchers point to production cost as the main barrier to wider use. Buyers should expect a premium and weigh it against regulatory exposure and customer expectations. Our total cost guide shows how to build that case.

Processing

Pure PHB has a narrow processing window: it can degrade if held too long at molding temperature. Copolymers, blends and additives widen that window, which is why the material you buy matters as much as the polymer family.

Scale

Global PHA output is still a small fraction of PLA or conventional plastic. For large buyers, supply reliability is a fair question to ask any PHA supplier.

Where PlantSwitch fits, and how to try it

Many PHA producers only sell resin. PlantSwitch is a material science company that makes its own material, CompostZero™, develops the application and manufactures the finished product. PlantSwitch products are certified home compostable, with certifications from TÜV Austria (OK compost HOME), BPI and DIN CERTCO, and they are FDA-compliant for food contact. Our message is simple: No Forever Microplastics.

See the range in the shop, from cutlery kits to straws and stirrers, browse the research in our science library, or request samples and a quote. Hot cups and lids are available by quote. Email sales@plantswitch.com with any questions.