Plastics made from renewable resources are often referred to as bioplastics or biopolymers. The term "bioplastics" is not precisely defined. It is usually used to describe a variety of materials that consist, at least partially, of bio-based (renewable) feedstock and/or are biodegradable.
Bio-based: The term ‘bio-based’ means that a material or product is (partly) derived from biomass. Biomass is organic material of biological origin (excluding material embedded in geological formations and/or fossilized). Examples of biomass are plants, trees, algae, marine organisms, micro-organisms, animals, etc. "Bio-based" can also mean that the feedstock derives from any form of organic waste.
Biodegradable: Materials are biodegradable if they can be converted into natural substances such as water, carbon dioxide and compost by different naturally occurring organisms. In most cases, microbiological biodegradation is the most important process. Biodegradation is strongly dependent on the conditions for the microorganisms in water and soil. Furthermore, the biodegradation process is dependent on the presence or absence of oxygen. The property of biodegradation does not depend on the resource basis of a material but is rather linked to its chemical structure. The term "biodegradable" does not specify neither the time frame nor the environmental conditions which are necessary for the natural degradation of the material.
‘Bio-based’ does not equal ‘biodegradable’
The biomass which can be used to produce bio-based plastic, can be obtained from different feedstocks. Carbohydrate-rich food plants, such as corn or sugarcane, or oily plants are the most commonly used raw materials for producing bio-based plastics today. These traditional agrocultural crops are called the first generation feedstock. It is currently the most resource-efficient and cost-efficient way to produce bio-based plastics. However, the impacts caused by these first generation feedstocks on the environment and on people's lives have drawn criticism. Issues such as the competition between food production and animal feed, land consumption, water use and pesticides must be taken under consideration when talking about sustainable bio-based plastics. In addition, these raw materials are often extracted under precarious conditions for both workers and local inhabitants. Raw materials obtained from agriculture and forestry are indeed renewable, but their supply is neither unlimited nor available at all times. There is no doubt that intensive agriculture and forestry have negative effects on the climate and the environment; therefore, a sustainable and resource-saving use of biogenic resources is necessary.
In the mean time, second and third generation feedstocks for bio-based plastics are being developed. Progress is being made on procedures for using cellulosic raw material and non-edible by-products of food crops such as straw, corn stover, bagasse or organic waste (second generation feedstock). Second generation feedstocks are still linked to “food” crop market dynamics. Third generation feedstock are algae or non-agricultural waste which can be used to produce bio-based polymers.
Molecule chains with properties comparable to those of petroleum-based polymers are produced from renewable resources through the chemical process of cracking and re-polymerisation. An example thereof is the fermentation of sugars derived from crops such as sugarcane and beets, or the hydrolysis of starch derived from crops such as corn. This produces ethanol, which can be used as raw material for the production of a wide variety of biopolymers. Other products commercially produced through fermentation are, for example, lactic acid, n-butanol, acetone, and polymers such as polyhydroxyalkanoates.
Some of the frequently used materials and their properties are as follows:
PA, PE, PET:
In 2019, bioplastics represented approximately one percent of the more than 359 million tonnes of plastic produced annually.
The bioeconomy as a whole and the market for bio-based and biodegradable plastic are supposed to grow not only because a sustainable & circular bioeconomy is a major European policy priority. According to a market evaluation undertaken by European Bioplastic e.V. in cooperation with the research institute nova-Institute, the global bioplastics production capacity is set to increase from around 2.11 million tonnes in 2019 to approximately 2.43 million tonnes in 2024.
It is essential to talk about sustainable solutions for bio-based plastics the end-of-live options. Following the European waste hierarchy, reuse and recycling are preferred solutions to energy recovery or disposal.
The goal is to close the loop, meaning that the product or the material should be used again after the intended use. For bio-based plastics, there are two preferable ways to close the loop.
The term "recycling" refers to the return of the waste which results from both production and consumption into the economic cycle, i.e. its reuse in the production and use of other products.
As is the case for most conventional plastics, bio-based plastics need to be recycled in separate streams according to material type (e.g. PET-stream). Where a recycling stream for a specific plastic type is established (e.g. PE or PET), the biobased alternatives (bio-PE, bio-PET) can be recycled together with their conventional counterparts. For other materials such as PLA, there is no recycling stream established yet. The main challenge for recycling is sorting the different types of bio-based plastics.
Compostability is the characteristic of a product, packaging or associated component that allows it to biodegrade under specific conditions (e.g. a certain temperature, timeframe, etc). These specific conditions are described in standards, such as the European standard on industrial composting EN 13432 (for packaging) or EN 14995 (for plastic materials in general). Materials and products complying with these standards can be certified and labelled as compostable. In order to make accurate and specific claims about compostability, the location (home, industrial) and timeframe of the process need to be specified. According to the EU standard EN 13432, a product is considered compostable if, among other things, it meets the following criteria under the conditions of an industrial composting plant: