PLA versus PHA: What’s the difference?

What are PLA and PHA?

PLA (polylactic acid) and PHA (polyhydroxyalkanoate) are both bio-based, compostable polymers commonly used in foodservice and other packaging formats such as mailers.

These polymers are often grouped together, but they behave quite differently, not because one is “better,” but because they were designed for different composting realities.

Understanding the difference requires looking beyond the material itself and toward how our current composting systems actually operate.

READ MORE: Materials shaping the future. What is PLA?

What is PLA?

Polylactic acid (PLA), is produced by bacterial fermentation under controlled conditions of a carbohydrate source like corn starch, cassava or sugarcane. PLA is the second most produced bioplastic (after thermoplastic starch) and has similar characteristics to polypropylene (PP), polyethylene (PE), or polystyrene (PS), as well as being biodegradable.

However PLA is a chemically modified material that has to be industrially composted at high temperatures at the end of its life. So

PLA is not rejected from composters because it “doesn’t compost.”

It is rejected because many composting systems are not configured to process it. PLA typically requires:

• sustained temperatures around 55–60°C
  

• consistent heat, moisture and pH profiles, and

• longer composting cycles, beyond six months

Many industrial composting standards were developed around European composting models, which tend to operate with longer retention times and tightly controlled conditions. In contrast, many composting facilities in places like New Zealand and Australia:

• operate shorter cycles to cut operating costs
  

• experience fluctuating temperatures, and
  

• are not optimised for packaging breakdown.

Under these conditions, PLA may not disintegrate fully within the composting timeframes, resulting in facilities to exclude it to reduce additional processing times and costs. PLA is not failing, the infrastructure has not developed sufficiently to take advantage of processing it. This mismatch is where most real-world composting challenges emerge.

READ MORE: Compostable materials in the real world: Scion x WasteMINZ

What is PHA?

PHAs are bio polyesters produced in nature by microorganisms via bacterial fermentation of sugars or lipids, where microorganisms create the polymer as an energy storage material. PHA is comparable to polypropylene in function but bio-derived. 

When PHA was studied in soil environments it was found that:

• PHA breaks down at lower temperatures,
  

• biodegrades much faster in variable conditions, and
  

• performs better in shorter composting cycles

PHA’s biodegradability rate depends on microbial activity, moisture levels, temperature, and pH. Within the agreeable environment, PHA’s can biodegrade within seven weeks. Because of this, PHA is often more compatible with today’s commercial composting systems, particularly those focused on food waste rather than packaging.

Is PLA or PHA “better”?

Neither material is inherently better, but rather, only better aligned to different systems. The real question is, what material is better suited to the organics services I can access?

• PLA is widely recognised as industrially compostable and can meet EU standards such as EN 13432 under certified test conditions. In practice, however, many composting facilities do not operate under the sustained temperatures or cycle times required for PLA to reliably biodegrade.

• PHA is likewise recognised as industrially compostable and can be certified to standards such as EN 13432 and ASTM D6400. Because it biodegrades at lower temperatures and in more variable conditions, it tends to perform more reliably within today’s shorter-cycle, food-waste–driven composting systems.

The challenge is not material innovation. It is infrastructure lag.

Why this matters for compostable packaging

PLA didn’t become problematic. Composting systems have historically focused on processing garden and food waste and understanding that distinction is vital. Choosing compostable packaging requires selecting materials that work within current composting systems. This requires considering:

• how composting operates in your region,
  

• whether packaging is accepted by local facilities, and
  

• how long materials are actually given to break down in those facilities

Until composting systems evolve, materials that biodegrade at lower temperatures will continue to see greater acceptance.

READ MORE: Home versus industrial composting

What does a viable way forward look like?

Composting infrastructure is in the middle of transitioning from processing majority yard waste to accepting more types of inputs, including post-consumer food waste and compostable mailers and packaging. 

It will be possible to recover compostable packaging at far greater rates than today, not to mention all the food scraps attached to this packaging when the central government, industry groups and composters align to harmonise policies. A functional system requires:

• clear national compost input guidelines,
  

• enforceable packaging design and labelling rules, and
  

• alignment between what is placed on the market and what composting systems can reliably process
  

• nationwide bans on problematic look-a-like products
  

• national advertising campaigns to educate the public on compostable plastics

Australia is beginning to move in this direction, and in the process of developing national packaging reforms towards a circular economy, including:

• bans on problematic materials and chemicals to improve recycling and composting rates
  

• material compatibility with end-of-life systems. Look to the Australian Recycling Label (ARL), evidence backed (what is actually recyclable and % of access to kerbside collections)
  

• mandatory PFAS testing to create opportunities for compostable packaging to play a role in aiding food recovery through kerbside FOGO collections
  

• consistent labelling aligned with actual recovery pathways
  

• a proposed national extended producer responsibility scheme (EPR) 

These reforms acknowledge an important reality that the transition to a circular economy for compostable packaging requires systems change to recover, identify and process these materials. Compostable packaging was designed to be recoverable with food waste, to divert these materials from landfill where they produce methane and other greenhouse gases (GHGs).

Packaging designed to compost at lower temperatures, within shorter cycles, verified through third party certification—such as PHA, when supported by clear labelling stands a better chance of being recovered and transformed via organics recycling and delivering reliable outcomes.

If a transition to PHA is on your radar for 2026, email us at hello@ecoware.co.nz to start the conversation and explore custom branded options.