Biodegradable Bag Manufacturing Process: Complete Guide

Traditional plastic bags are a major contributor to global pollution. Every year, over 8 million tons of plastic bags end up in oceans, taking hundreds of years to decompose. We urgently need better solutions. Biodegradable plastic bags have emerged to address this challenge. These bags are made from plant-based materials such as corn starch, PLA, and PBAT and can naturally decompose within months instead of centuries.

The production process of biodegradable plastic bags involves a series of specialized techniques, including raw material preparation, polymerization, extrusion, and quality testing. Whether you are a manufacturer looking to expand your product line or a company seeking sustainable packaging solutions, understanding this process is the first step toward contributing to a cleaner planet.

Understanding Biodegradable Bags

What Makes a Bag Biodegradable?

The concept of biodegradable plastic bags is to allow natural decomposition through the action of microorganisms such as bacteria and fungi. Unlike traditional plastics, these bags contain polymers derived from renewable resources that microorganisms can metabolize.

The key lies in their molecular structure—biodegradable plastics have chemical bonds that can be broken down by natural processes, turning the material into water, carbon dioxide, and biomass.

Biodegradable plastic bags decompose naturally within months, not centuries.

Differences Between Biodegradable and Traditional Plastic Bags

The main difference between biodegradable and conventional plastic bags is in their composition and final degradation. Traditional bags are made from petroleum-based polymers that are difficult to degrade naturally.

Biodegradable bags, on the other hand, are usually made from plant-based materials and may contain additives that accelerate decomposition.

They also differ in durability—the shelf life may be shorter, and their physical properties vary.

Decomposition Timeline

Most biodegradable bags can decompose within 3–6 months under suitable composting conditions, whereas traditional plastic bags may take over 500 years.

Environmental factors such as temperature, humidity, and microbial presence affect decomposition speed.

Types of Biodegradable Bags

Several types of biodegradable bags are available in the market:

• PLA (Polylactic Acid): Suitable for industrial composting, offering good transparency and printability.
• PBAT (Polybutylene Adipate Terephthalate): Highly flexible, often used in shopping bags.
• PHA (Polyhydroxyalkanoates): Fully biodegradable even in home compost and marine environments.
• Starch-based plastics: Affordable and easy to compost, though moisture resistance may be limited.

Raw Materials for Biodegradable Bags

Plant-Based Materials (Corn Starch, Sugarcane, Potato)

The journey of a biodegradable plastic bag starts with renewable plant resources. Corn starch is the most widely used due to its abundance and low cost. Manufacturers extract starch from corn kernels and process it into polymers.

Sugarcane bagasse, the fibrous residue after juice extraction, is another excellent source, especially in regions rich in sugarcane.

Potato starch works similarly to corn starch but produces slightly different material properties.

Polylactic Acid (PLA)

PLA is derived from fermenting plant sugars, mainly from corn or sugarcane. The process involves extracting starch, converting it into sugar, fermenting it into lactic acid, and polymerizing it into PLA pellets.

PLA offers excellent tensile strength and transparency, making it ideal for bags requiring good visual quality. Its main advantage is complete decomposition in industrial composting within 3–6 months under specific temperature and humidity conditions.

Polybutylene Adipate Terephthalate (PBAT)

PBAT is a flexible biodegradable polymer that provides elasticity and strength to bags. Unlike PLA, PBAT is partially petroleum-based and combined with biodegradable components, including butanediol, adipic acid, and terephthalic acid.

Polyhydroxyalkanoates (PHA)

PHA production is different from other biodegradable plastics. Instead of directly processing plant materials, specific bacteria produce PHA inside their cells by fermenting sugars or plant oils. The polymer is then extracted and purified.

PHA can fully biodegrade in home composting and even marine environments, making it one of the most environmentally friendly options, though production costs are currently higher.

Additives for Performance and Durability

Even biodegradable plastics require additives for bag production. Additives enhance strength, flexibility, and durability without affecting biodegradability. Common additives include:

• Natural plasticizers for flexibility
• Mineral fillers like calcium carbonate to reduce cost and improve performance
• Processing aids used in manufacturing
• UV stabilizers to prevent premature degradation
• Natural colorants for branding and visual appeal

Modern biodegradable bag formulations balance performance and environmental benefits, ensuring optimal function during use and complete decomposition afterward.

Core Manufacturing Steps of Biodegradable Bags

Step 1: Raw Material Preparation

Raw materials are usually in powder or pellet form and must be dried to remove moisture. Excess moisture can cause issues in later production steps. High-quality materials at this stage are critical for producing high-quality bags.

Step 2: Polymerization

Polymerization converts raw materials into plastic polymers. Different materials use different techniques:

• PLA: Lactic acid is converted into lactide rings and then polymerized via ring-opening polymerization in large reactors under precise temperature control.
• PBAT: A condensation reaction combines chemical components, releasing water molecules during polymer formation.
• PHA: Polymerization occurs inside bacteria during fermentation, with extraction and purification as the main production steps.

Polymerization determines the final plastic’s strength, flexibility, and biodegradation rate.

Step 3: Extrusion and Film Formation

Once polymers are ready, they are melted and extruded into films. Pellets are fed into an extruder, a long cylinder with a rotating screw.

The screw melts and pushes the polymer forward. The molten plastic passes through a flat die, forming sheets or tubular films.

Many bags use blown film technology, where a tube of molten plastic is inflated like a balloon and cooled by air, then flattened by rollers. Film thickness depends on air inflation and stretching speed.

Step 4: Bag Cutting and Sealing

Films are cut to desired lengths and sealed at the bottom to form bags. For complex designs, films may be folded and sealed at edges.

Sealing uses heat, bonding layers together. Modern machines can produce thousands of bags per hour. Handles or side gussets can be added at this stage.

For printed bags, biodegradable inks are applied before cutting and sealing to avoid affecting decomposition.

Step 5: Quality Control and Testing

Quality checks ensure bags meet standards:

• Thickness and weight consistency
• Seal strength by inflation or filling tests
• Tensile strength measurement
• Tear resistance evaluation
• Biodegradability testing under controlled conditions
• Visual inspection for defects or poor printing

Random sampling ensures only fully tested bags are shipped. This process guarantees functionality during use and complete degradation afterward.

Advanced Manufacturing Technologies

Innovative Extrusion Techniques

Modern extrusion uses twin-screw machines for better mixing and faster processing. They handle different biodegradable materials without major adjustments.

Multi-layer extrusion allows bags with layers having specific properties, such as moisture resistance inside and good printability outside, without adhesives.

Sustainable Manufacturing Practices

Leading manufacturers implement closed-loop water systems and biodegradable lubricants to reduce environmental impact.

Energy Efficiency

Energy is a major production cost. Heat recovery systems capture waste heat, reducing consumption by 15–30%. Variable frequency motors adjust energy use based on demand, lowering power usage up to 40%. Solar panels increasingly supplement factory electricity needs.

These technologies improve product quality, reduce costs, and minimize environmental impact.

Certifications and Standards

Biodegradability Testing

Samples are tested under controlled conditions simulating industrial composting. Materials must degrade at least 90% within 180 days to be considered biodegradable.

Tests may simulate home compost, soil, or marine conditions to verify performance in real-world disposal.

Key Industry Certifications

Recognized certifications include ASTM D6400 (USA) and EN 13432 (Europe). TÜV Austria’s “OK Compost” label and BPI certification are widely trusted.

Global Regulatory Requirements

Europe requires proof for products labeled “biodegradable.” Some US states, like California, have stricter requirements. Several African countries have banned plastic bags, creating opportunities for biodegradable alternatives.

Ensuring Claim Authenticity

• Look for authoritative certification marks
• Avoid vague “green” claims without testing
• Keep detailed records of materials and testing
• Communicate the required composting environment
• Use third-party verification rather than relying solely on suppliers

Guanzhong — Leading Biodegradable Bags Manufacturers

Guanzhong (Fujian Guanzhong Technology Co., Ltd.) is based in Yongchun, Quanzhou, China, with nearly 200,000 m² of industrial park and over 100,000 m² of production facilities.

Specializing in biodegradable and plant-based composite materials, Guanzhong produces biodegradable films, household items, pet waste bags, biodegradable garbage bags, and shopping bags. Key data:

• Patents: 10+
• Production staff: 180
• Annual output: 90,000 tons
• Customization: logos, colors, dimensions, thickness
• OEM/ODM service with minimum order as low as 1 ton of raw materials
• Mold production: 7 days, bag production: 15 days

Guanzhong strictly follows standards such as GB/T 20197, GB/T 19277.1, GB/T 4806.7, ASTM D6400, ASTM D6866, DIN EN 13432, and FDA food contact tests. The company also holds international industrial composting certifications, DIN compost certification, and US BPI biodegradability certifications.

The production process of biodegradable plastic bags marks a key shift toward sustainable packaging. From plant-based raw materials to advanced extrusion techniques, manufacturers now have feasible alternatives to traditional plastics.

Leading biodegradable bags manufacturers and biodegradable garbage bag manufacturers, such as Guanzhong, combine environmental responsibility, advanced technology, and high-quality production to provide solutions that meet market demands while protecting our planet.