Apr 9, 2015

Project addresses barriers to biodegradable plastic mulch

Biodegradable plastic mulches (biodegradable mulches) are an alternative to polyethylene plastic mulches (plastic mulches) which are widely used in vegetable production. Ideally, they provide the same benefits for growing crops as plastic mulches with the additional benefit of completely breaking down. Breakdown of these mulches is by native soil microorganisms and mulch remaining at the end of the growing season can be tilled into the soil or composted.

Biodegradable mulches have been available since the 1980s, but they are not widely used. Recently, through a survey and focus groups, commercial growers, agricultural educators and industry members were asked about the bridges and barriers to adoption of biodegradable mulches.

Bridges or opportunities identified were:

• Waste reduction, because the mulch biodegrades
• Environmental benefits of not using petroleum-based mulch including disposal issues
• A desire to learn more about biodegradable mulches

Barriers included:

• Insufficient knowledge of their long-term use
• A perceived high cost which is not offset by use of these mulches
• Unpredictable breakdown

To address these barriers, a group of 22 researchers and Extension specialists from multiple universities are conducting research trials and Extension activities.

Since the rate of degradation of biodegradable mulches is highly dependent on their composition and the environment, the group is studying the breakdown of several biodegradable mulches over a five-year project in Washington, Tennessee and Montana in the field and laboratory. They will investigate how the mulches affect crop production including weed populations, diseases and insect pests. They will also study the effects of the mulch as it breaks down on soil ecology.

Some evidence shows that even though biodegradable mulches cost more than plastic mulches, they may be cheaper to use when factoring in the cost of removal and disposal of the plastic mulch. The project team will conduct an economic analysis to compare biodegradable mulches and plastic mulches including costs for retrieval and disposal.

A website has been developed as part of the project. The site will serve as a warehouse for information as the project develops. Information currently on the site includes a glossary of terms for biodegradable mulches which includes “biobased mulch”, “biodegradable mulch” and “bioplastics” among many other terms.

The site also has fact sheets on biodegradable mulch including one on their use in organic production systems. In 2012, the National Organic Standards Board passed a motion allowing the use of 'biodegradable biobased mulch film' providing that the mulch is 'produced without organisms or feedstocks derived from excluded methods' and meet certain degradation standards (at least 90% degraded in 2 years or less). At present, no biodegradable mulch has been approved.

– Elsa Sanchez, Penn State University