Plastics from renewable resources are often referred to as bioplastics or biopolymers. "Bioplastics" is not a precisely defined term. This term is usually used to describe various 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). Biomass could be 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 could be converted into natural substances such as water, carbon dioxid 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. The biodegradation is furthermore 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 specifying neither the time frame nor the necessary environmental conditions.
‘Bio-based’ does not equal ‘biodegradable’
The biomass, that can be used for the production of bio-based plastics, can be obtained from different feedstocks. Carbohydrate-rich food plants like corn or sugar cane or oily plants are the most used raw materials for bio-based plastics today. This traditional agrocultural crops are called the first generation feedstock. It is the most resource and cost efficient way to produce bio-based plastics in the moment. On the other hand the impacts of these first generation feedstocks on environment and people have drawn criticism. Competition to food and animal feed, land consumption, water use and use of pesticides have to be taken under consideration, when talking about sustainable bio-based plastics. In addition, these raw materials are often extracted under precarious conditions for workers and local inhabitants. Raw materials obtained from agriculture and forestry are renewable, but not unlimited and available at all times. Intensive agriculture and forestry has undoubtedly negative effects on climate and environment, so that 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 developed. Procedures for using cellulosic raw material and non-edible by-products of food crops like straw, corn stover, bagasse or organic waste are developed (second generation feedstock). Second generation feedstock is still linked to “food” crop market dynamics. Third generation feedstock uses algae or non-agricultural waste to produce bio-based polymers.
Through the chemical process of cracking and re-polymerisation, molecule chains with properties comparable to those of petroleum-based polymers are produced from renewable resources.
A way to produce materials is for example the fermentation of sugars derived from crops such as sugarcane and beets, or the hydrolysis of starch derived from crops such as corn. It produces ethanol, which can be used as raw material for the production of a wide variety of biopolymers. Other products are commercially produced by fermentation are, for example, lactic acid, n-butanol, acetone, and even polymers such as polyhydroxyalkanoates.
Some of the frequently used materials and their properties are as follows:
PA, PE, PET:
In 2019, bioplastics represented about one percent of the more than 359 million tonnes of plastic produced annually.
Bioeconomy as a whole and the market for bio-based and biodegradable plastic is supposed to grow not only because a sustainable & circular bioeconomy is a major European policy priority. According to a market evaluation done by European Bioplastic e.V. in cooperation with the research institute nova-Institute, global bioplastics production capacity is set to increase from around 2.11 million tonnes in 2019 to approximately 2.43 million tonnes in 2024.
Talking about sustainable solutions for bio-based plastics the end-of-live options are essential. Following the European waste hierarchy reuse and recycling are solutions prefered to energy recovery or disposal.
The goal is to close the loop meaning after the intended use the product or the material should be used again. For biobased plastics there are two preferable ways to close the loop.
The term recycling refers to the return of waste from production and of consumer waste. However, it is essential that this waste is reintegrated into the economic cycle, i.e. that it is reused for the production and use of other products.
As most conventional plastics, biobased plastics need to be recycled in separate streams for each 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 like for example PLA there is no recycling stream established yet. The challenge is the sorting of some sorts of bio-based plastics.
Compostability is a 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 this standards can be certified and labelled accordingly. In order to make accurate and specific claims about compostability the location (home, industrial) and timeframe need to be specified. According to the EU standard EN 13432, a product is considered to be compostable if, among other things, it meets the following criteria under the conditions of an industrial composting plant: