What's the difference between compostable and biodegradable?
Compostable versus degradable. Here we are providing the terms and definitions frequently used in marketing communications so we can better identify these materials ensuring these products are disposed of correctly.
Degradable
Capable of being degraded. The term means any material capable of being decomposed chemically or biologically. Most materials degrade over time. Plastic degrades to microplastic, for example.
Biodegradable
An extension of degrading. Materials with the ability to be broken down into non-harmful substances through living micro-organisms, a natural process. The time frame taken for materials with this capacity varies depending on the perishability of the material itself.
Compostable
Often wrongly considered to be the same as biodegradability, compostable materials require specific conditions in order to decompose back to their natural elements.
Compostability of materials according to the European Standard EN 13432
Compostable products are designed for organic recycling. Industrial composting is an established process with commonly agreed requirements concerning temperature and timeframe for biodegradable waste to metabolise to stable, sanitised products (biomass) to be used in agriculture (humus/fertiliser). This process takes place under controlled conditions—temperatures, humidity, aeration, et cetera in industrial or municipal composting plants.
The criteria for the industrial compostability of packaging are set out in the European standard EN 13432. EN 13432 requires compostable products to
— disintegrate after 12 weeks
— and completely biodegrade after six months.
That means 90 per cent or more of the plastic material will have been converted to CO2. The remaining share is converted into water and biomass – i.e. valuable compost. Materials and products complying with this standard can be certified and labelled accordingly.
Home compostability certifications based on EN 13432
Currently, there are several national standards for home compostability of compostable materials and corresponding certification schemes, which are mainly based on the European Standard EN 13432.
To confirm compliance with these standards and schemes, compostable products are tested according to the conditions found in home composting systems, in particular, lower temperatures and longer dwell times compared to conditions in industrial composting facilities. Materials or products compliant with these standards can be recognised by a conformity mark stating their home compostability.
OK compost HOME certification details all the technical requirements that a product must meet in order to obtain the certification. Defined in 2003, the requirements of the OK compost HOME programme still today serve as the basis for the drafting of several standards such as:
Australia: AS 5810 (2010) – Biodegradable plastics - Biodegradable plastics suitable for home composting
France: NF T 51800 (2015) – Plastics - Specifications for plastics suitable for home composting
Europe: prEN 17427 (2020) - Packaging — Requirements and test scheme for carrier bags suitable for treatment in well-managed home composting installations
International Organisation for Standardisation criteria
Under the International Organization for Standardization (IOS), there are standards for both home and commercial composting. The main standards are from Europe, the US, and Australia. Most commercial composting standards require a product to:
— 100% biodegrade,
— biodegrade into completely non-toxic by-products, and
— biodegrade within 90 days.
The Australian Standard AS 5810-2010 for home composting requires a product to:
— 100% biodegrade,
— biodegrade into completely non-toxic by-products, and
— biodegrade within 180 days.
The specified requirements for home and commercial composting standards differ in the time frame. Materials break down faster in a commercial compost facility due to the controlled environment and this is largely a condition of heat.
Microbial activity during hot composting
Temperature rise within a compost system results from microbial activity. As microorganisms work to decompose materials, their metabolic activity generates heat, raising the temperature of the compost. The microbes involved in the aerobic composting process ( Compost Microbes) fall into two groups:
— Mesophilic those that are active in temperatures of (10 °C to 45 °C) and
— Thermophilic active at 45°C to 70°C.
Temperatures between 32°C (90°F) and 60°C (140°F) indicate rapid decomposition is taking place within the compost.
Industrial composting is an established process for transforming biodegradable waste of biological origin into stable, sanitised products to be used in agriculture. Different technologies are available, but the general process of composting remains the same. It is a controlled process that can be divided into two distinct phases: active composting followed by curing. The active composting phase lasts a minimum of 21 days. Under these conditions, microorganisms grow on organic waste, breaking it down to CO2 and water and using it as a nutrient. Part of the energy is released into the surrounding environment as heat.
During composting, organic waste is amassed in piles, and, as a consequence, the total production of heat can be high. When the temperature of the composting pile increases, microbial populations shift: microbes adapted to ambient temperature (mesophiles) reduce their activity levels or die and are then replaced by microbes adapted to survive at higher temperatures (thermophiles).
In industrial composting facilities, temperatures in the compost heaps range between 50°C and 60°C. For hygienisation purposes, temperatures need to remain above 60°C for at least one week in order to eliminate pathogenic microorganisms. During the curing phase, the rate of decomposition declines to a slow and steady pace, and the compost matures at temperatures in the lower mesophilic range (< 40°C) with the synthesis of humic substances.
Composting and circular economy
Composting is part of the waste-to-value system, and it is where we must focus our efforts if we want to reach the ambitious targets set by our government that commits Aotearoa, New Zealand, to becoming a low-emissions, low-waste circular economy by 2050. We’ve been here for over a decade, developing industry-leading, compostable packaging that works towards accelerating the circular economy in Aotearoa, New Zealand.
Our products are designed to offer solutions to help tackle plastic pollution, keeping fossil fuels in the ground and minimising the environmental impact of convenience culture. If your business is still using plastic, use the links below to explore our service further. For custom branding enquiries, please email us at hello@ecoware.co.nz.
