How biodegradable bags are made today?

Here the process breakdown

Granules of biodegradable material are loaded into an extruder, melted into a viscous-flowing mass, passed through a filter, and shaped into a sleeve by extruding the melt through an opening.

The sleeve is inflated with air, adjusting the thickness and size of the film. At this stage, side folds for future "T-shirt" bags are also made.

The film is wound into rolls.

The next stage involves treatment with a corona discharge to improve paint adhesion, which will later be used to apply images.

On flexographic machines, using flexographic printing, designs (logos, text, or photographic images) are applied to the material. Special flexographic plates are used to transfer the paint onto the fabric. This method allows for up to six colors and produces beautiful, multicolor images with many shades.

Bag-making machines seal the blanks by welding the seams on the handles and bottoms. Then, the handles of “T-shirt” and “banana” bags are cut out.

Extruder for Biodegradable Film Production

What is the cornerstone of the new bioplastic production technologies? No suspense here—the production technology has not fundamentally changed. The key point in the production of biodegradable polymers is obtaining material from plant-based raw materials with the required properties and characteristics.

What Raw Materials Are Used to Produce Eco-Bags from Corn Starch

In the quest for eco-friendly materials, researchers focused on studying biodegradable polyesters. The goal was to find bio-based raw materials that could be converted into a monomer and subsequently polymerized into biodegradable plastic.

Corn and its starch turned out to be the most promising raw material, forming the basis of modern eco-bag production. Starch is widely available since corn is relatively easy to grow. Moreover, it possesses near-ideal properties: high hydrophilicity (absorbs water well), resistance to organic solvents, and rapid biodegradability, converting into a substrate. Additionally, chemically modified starch can be used to produce composites and copolymers.

How Corn Starch Becomes Durable Packaging from Edible Sweet Corn

Through the fermentation of corn starch sugars, a monomer—lactic acid—is first obtained using various fermenting microorganisms such as acetic and lactic acid bacteria, yeasts, and their combinations. The lactic acid is then polymerized into polylactide (PLA), a thermoplastic aliphatic polyester. Granules of this material can be loaded into an extruder to make film or, for example, filaments for 3D printing.

PLA biobags are not as durable, transparent, or shiny as polyethylene bags but are a worthy alternative to “eternal” plastic. Moreover, PLA eco-bags with logos are excellent advertising carriers and effective marketing tools.

Properties and Advantages of PLA

• Fully biodegrades during composting.

• Resistant to ultraviolet light.

• Low flammability, emits no acrid black smoke when burned.

• The most affordable and inexpensive bioplastic available.

• Approved for use in Ukraine.

Another technology allows the production of biobags from a starch-pectin blend with added plasticizers (e.g., glycerin).
Granules are made from the composite blend, and film is produced from the granules using the extrusion method. The extrusion of "starch-based" sleeves is similar to the process for synthetic polyethylene sleeves.

Example of Oxo-Biodegradable Plastic Decomposition at an intermediate stage

What Other Raw Materials, Besides Starch, Can Be Used to Make Biodegradable Bags?

Biodegradable bags can be made from various plant and animal polysaccharides. These materials are subject to controlled biodegradation into carbon dioxide and water and are replenishable in nature. It’s worth remembering that fossil fuel reserves, including oil, are limited, and the day when they run out is approaching.

The properties of polysaccharides depend on the composition and spatial structure of their macromolecules. Therefore, not all raw materials are suitable for making bio-bags. Some technologies are currently impractical, while others are too costly. However, in the future, bio-bags with logos might be made from soybeans, mushrooms, or seaweed.

Types of Natural Raw Materials for Biodegradable Plastics

• Polyhydroxyalkanoates (PHAs)
  Natural biodegradable polymers derived from poly-β-hydroxybutyric acid. The most promising is poly-3-hydroxybutyrate, which is already used to make biodegradable bags with logos. It is synthesized by certain microorganisms in nature, and its production is waste-free and environmentally friendly. Currently, it is primarily used to produce surgical sutures, dressing materials, and orthopedic implants but is entering the commercial market as 100% bio-based and biodegradable material for compostable plastic production.

• Cellulose
  The most important polysaccharide and a polymer of glucose, primarily derived from wood. Cellulose can be used to produce bioplastics, cellophane, and viscose. However, the raw material must first be chemically modified into a liquid (viscous) state, and the material obtained from forming (hot pressing) is no longer 100% natural.

• Chitin
  A nitrogen-containing polysaccharide mainly derived from crustacean shells. It is expensive and valuable, making its use for eco-bags impractical. Chitin is used to make surgical threads, various medications, and dietary supplements.

• Chitosan
  A derivative of chitin, naturally found only in termite queens and zygomycete fungi. A promising use is producing nanofiber wound dressings for extensive burns and wounds.

• Protein
  Can be used to produce so-called protein plastics from animal and plant sources. Suitable raw materials include soybeans, but the technology for producing soy-based films is still under development.

• Natural Rubber
  A natural polymer found in the milky sap of tropical plants. Used to produce latex gloves, various coatings, rubber, footwear, and tires.

Biodegradable T-Shirt Bag with Logo

There are more exciting developments in the field of biodegradable materials

• In Israel, eco-friendly polyethylene is produced from Ulva lactuca algae with the help of Haloferax mediterranei microorganisms. These halobacteria feed on algae and produce polyhydroxyalkanoates.

• Avani Eco Hub (Bali, Indonesia) has long been producing biobags from cassava tubers.

• In Chile, successful experiments have been conducted using limestone sedimentary rocks.

In Japan, a technology was developed using nut shells and protists. The reserve carbohydrate of these eukaryotic organisms, paramylon, is similar in composition and properties to starch.