Biodegradable Packaging

From corn to resin

What you need to know about Biodegradable Packaging

For the past five decades, the packaging industry has witnessed several generations of plastics that have evolved into a variety of packaging materials such as polystyrene, polyethylene and polypropylene. However, these materials are made from fossil fuels. With the increasing push to “Go Green,” and not waste non-renewable resources, the packaging industry continues to look for the renewable solution to their packaging problems.

The following is a brief overview of the various production methods employed in the packaging industry today. We feel that, through understanding these production options, you will be able to better appreciate the superior aspects of the Nviroplast line of packaging solutions and their positive impact on our environment, when compared to the petrochemical based product widely used in today's marketplace.

Types of Biodegradable Plastics

Normal plastics derived from petroleum are made from synthetic polymers. However, polymer chains are also found in nature. Common naturally occurring polymers include cellulose, lignin, and starch. Cellulose is abundant in all plants, although some plants produce more than others. Lignin is typically found in wood, and starch is common in plants such as corn, potatoes, and wheat.

The reason traditional plastics are not biodegradable is because their long polymer molecules are too large and too tightly bound together to be broken apart by decomposer organisms. However, plastics based on natural plant polymers derived from wheat or corn starch have molecules that are readily attacked and broken down by microbes.

There are two main types of biopolymers: those that come from living organisms, and those which need to be polymerized but come from renewable resources. Both types are used in the production of bio-plastics.

1) Biopolymers from Living Organisms

These biopolymers are present in, or created by, living organisms. These include carbohydrates and proteins and can be used in the production of plastic for commercial purposes. Following are examples:

Cellulose- Wood, cotton, corn, wheat, and others: This polymer is made up of glucose. It is the main component of plant cell walls. This polymer is much stronger than Starch, another biopolymer made up of glucose units.

Soy Protein- Soybeans: Protein which naturally occurs in the soy plant.

Starch- Corn, potatoes, wheat, tapioca, and others: This polymer is one way carbohydrates are stored in plant tissue. It is a polymer made up of glucose. It is not found in animal tissues.

Polyesters- Bacteria: These polyesters are made by capturing and polymerizing the natural byproducts of bacterial respiration. Examples are PLA, PHA, etc.

2) Polymerizable Molecules

These molecules come from renewable natural resources, and can be polymerized to be used in the manufacture of biodegradable plastics.

Following are examples:

Lactic Acid- Beets, corn, potatoes, and others: Produced through fermentation of sugar feedstock's, such as beets, and by converting starch in corn, potatoes, or other starch sources. It is polymerized to produce polylactic acid -- a polymer that is used to produce plastic.

Triglycerides- Vegetable oils: These form a large part of the storage lipids found in plant and animal cells. Vegetable oils are one possible source of triglycerides that can be polymerized into plastics.

How are Biopolymers and Bio-plastics Made?

There are two methods being researched and used to produce plastics from plants. The first uses fermentation while the second relies on the plant to produce the polymers. These two methods are outlined below.

1. Using Fermentation to Produce Plastics

Fermentation, used for hundreds of years by humans, is even more powerful when coupled with new biotechnology techniques. Fermentation is the use of microorganisms to break down organic substances. Today, fermentation can be carried out with genetically engineered microorganisms, specially designed for the conditions under which fermentation takes place, and for the specific substance that is being broken down by the micro-organism. There are two ways fermentation can be used to create biopolymers and bio-plastics:

      A). Bacterial Fermentation with No polymerization

- Bacteria are one group of microorganisms that can be used in the fermentation process. Fermentation, in fact, is the process by which bacteria can be used to create polyesters. Bacteria called Ralstonia eutropha are used to do this. The bacteria use the sugar of harvested plants, such as corn, to fuel their cellular processes. The by-product of these cellular processes is the polymer. The polymers are then separated from the bacterial cells.

      B). Bacterial Fermentation that requires subsequent polymerization

- Lactic acid is fermented from sugar, much like the process used to directly manufacture polymers by bacteria. However, in this fermentation process, the final product of fermentation is lactic acid, rather than a polymer. After the lactic acid is produced, it is converted to polylactic acid using traditional polymerization processes.

2. Growing Plastics in Plants

Plants are becoming factories for the production of plastics. Through genetic engineering, researchers have created a plant based on the Arabidopsis Thaliana plant of Asia that is being used to make polymers. The plant contains the enzymes used by bacteria to create plastics. Researchers have transferred the gene that codes for this enzyme into the plant. As a result, the plant produces plastic through its cellular processes. The plant is harvested and the plastic is extracted from it using a solvent. The liquid resulting from this process is distilled to separate the solvent from the plastic.

Application of Biodegradable plastics

As with conventional plastics, bio-plastics have a very broad application spectrum. Initial applications have already established themselves successfully in important markets. When particular properties can be transformed to useful values, then true commercial success can be had.

Many bio-plastics products are still being used in areas where compostability represents a significant benefit. This is particularly the case for segments which are closely linked to biological recycling e.g. collection bags for compost, agricultural foils, or nursery products. Other applications such as packaging and technical applications are gaining importance. This is an area where functionality factors influence the decision for bio-plastics.

Processing of Bioplastic

Bio-plastics can be processed into a vast number of products using conventional plastics processing technologies. The process parameters of the equipment have to be adjusted to specifications unique to each polymer. This is usually not a complex procedure. Machine and plant manufacturers are also getting involved in processing bio-plastics on their equipment. They are searching for optimization possibilities.

Numerous individual production steps are often necessary prior to achieving the finished product. Depending on the requirements, basic materials are modified through compounding, with resulting formulations being tailored for specific applications such as film or injection molding. If it is important that the biodegradability or compostability is maintained, this must be taken into account during the selection of the type of processing and materials. This concerns not only polymers and all additives, but also colorants, labels and stickers on the final product, as well as the contents in the case of packaging. There are strict certification criteria that must be met and validated by approved labs in order for something to be labeled, “compostable.”

Compostable Standards

Many international organizations have established standards and testing methods for compostability, namely:

The ASTM, CEN and DIN standards specify the criteria for biodegradation, disintegration and eco-toxicity for a plastic to be called compostable.

Certification of compostable Biodegradable Products

Certification standards such as the ASTM D6400 or EN 13432 requirements to the protected quality label that allows the identification and proper handling of compostable plastic products on the market. It ensures that the product can be composted. Product certification guarantees that not only the plastic is compostable but also all other components of the product, e.g. colors, labels, glues and - in case of packaging products - residuals of the content. The protected "compostability label" (called "seedling") may only be used for certified products. The logo as well as the number of the certificate printed on the product allows the producer to identify the product and show proof of conformity: The product marketed must match the product tested.

It is recommended to commercial users or retailers of compostable bio-plastic products to ask distributors about their product certification and to demand the certification number. Even if it is not intended to compose the product, certification guarantees a high product safety. Certification, moreover, distinguishes between bio-plastic and conventional plastic and offers marketing and communication possibilities.

Reference: www.european-bioplastics.org