There are three main groups:

Biobased or partially biobased non-biodegradable plastics, such as biobased PE, PP, or PET and biobased technical performance polymers, such as PTT or TPC-ET;
Plastics that are both biobased and biodegradable, such as PLA and PHA or PBS;
Plastics that are based on fossil resources and are biodegradable, such as PBAT.

These plastics are typically produced from sugar derivatives like cellulose and starch. However, it can also be derived from straw, milk, tapioca, sawdust, wood chips, food waste, vegetable oils and fats, etc.

Bio-based plastics have properties similar to plastics derived form non-renewable sources. For example, biopolyethylene is made from sugar cane, but its physical properties are similar to polyethylene which is made from petroleum.

Although bioplastics are "bio-based", not all of them are biodegradable.

Biodegradation is a process wherein the microorganisms present in the environment converts the materials into a natural substance like carbon dioxide, water, methane, and so on. Also, the material is biodegradable when it degrades in a short period of less than one year. In other words, biodegradation is directly related to the chemical structure of the material rather than its source of origin.

Biobased and biodegradable plastics include blends of starch, polylactic acid (PLA) and polyhydroxyalkanoate (PHA). These are currently the most popular bioplastics. Besides these, there are several other bioplastics such as cellulose-based, and protein-based polymers.

Polylactic acid (PLA)

PLA is derived from sugars found in crops like corn, cassava, or sugarcane. PLA is biodegradable, and non-toxic. When PLA undergoes biodegradation, it releases CO2, water, and decomposed organic matter, which can be used by green plants.

PLA can look and behave like polyethylene (used in plastic films, packing and bottles), polystyrene (Styrofoam and plastic cutlery) or polypropylene (packaging, auto parts, textiles).

Cellulose-based bioplastics

Cellulose plastics are derived from cellulose acetate, nitrocellulose and cellulose esters. These kinds of cellulose are present in plant materials like forestry residue and by-products of agricultural production.

Starch-based materials

Starch plastics are the most common type among bioplastics. It could even be prepared at home by following processes like "gelatinizing starch" and "solution casting".

Starch is abundant, low price, and completely biodegradable. Starch can originate from wheat, corn, rice, and potatoes. Now, starch bioplastics are mainly explored as a sustainable choice for food packaging.

However, it has some disadvantages – for example, it is not waterproof, it is sensitive to moisture and rather brittle. For that reason, starch plastics are sometimes mixed with biodegradable polyesters or filled with nanofillers to make the material stronger.

Protein-based bioplastics

Protein-based plastic can be made from soy, albumin or wheat gluten. Usually, it is strong and elastic, however, it can be water-sensitive and expensive.

Aliphatic polyesters bioplastics

Aliphatic polyester bioplastics are highly biodegradable and biocompatible and usually have a high melting point. Though these kinds of plastics are brittle, blending them with other polymers makes them robust and strong.

Poly 3- HydroxyButyrate (PHB) bioplastics

These aliphatic plastics are derived from a few bacteria processing corn starch, glucose or wastewater.

It is also transparent with a high melting point and does not leave any residue when degraded. However, it usually costs higher than other bioplastics.

Polyhydroxyalkanoates (PHA) plastics

PHA plastics are aliphatic plastics made naturally by microorganisms from lipids and sugar. This kind of plastic is less elastic and malleable as compared to other biodegradable plastics.

Polyhydroxyalkanoate plastics are used in the medical, textile and packaging industry. These plastics are rather costly.

Useful links:

Bioplastic Cook Book

DE-FRAMe