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Biodegradable plastics for sustainable agriculture

The heavy use of plastic of fossil origin in agriculture must be contained by using innovative materials that are far more sustainable. Nowadays, following years of research and experimentation, it is possible to realize technical means biodegradable to the soil, resulting from increasing shares of "biobased" raw materials. We will talk about these opportunities in-depth in EIMA Digital Preview

by Matteo Monni
October - November 2020 | Back

Over the last 50-60 years, we have witnessed a constant and inexorable use of plastics in agriculture, to the point that they have now become a characteristic element of the landscape of many rural areas. Examples of these materials' many uses include greenhouse covers, mulch sheets, nets, irrigation hoses, floriculture jars, silage protection sheets, etc. Therefore, the great versatility of plastics in producing technical means beneficial to farmers is immediately visible. As a matter of fact, the strength of plastics lies in the fact that - at (relatively) low costs - they make it possible to achieve a series of advantages, such as: higher and better quality production, less use of chemical means, and irrigation water, and to modify the crop cycle to respond to the increased demands for food production. On the contrary, however, once their use has been completed, they must be adequately collected and disposed of, a "downside" that affects both operators and the environment.

For some types of manufactured products, these steps can be complicated and thus also very expensive, so much so that even today, much of the plastic coming into the agroecosystems is not recovered correctly. This frequently results in uncontrolled dispersion in the environment. In order to rationally deal with this problem, in particular for all applications of plastics in agriculture "fast-rotating" in the field (mulch) or "disposable" (pheromone supports, mulch for multi-year crops), biodegradable materials are an efficient alternative, environmentally friendly and above all zero-waste production at the end of use. As an example, it is estimated that around 85,000 tons of plastic mulch sheets are annually used in Europe for a total area of 460,000 hectares. Traditional (non-biodegradable) plastic mulching sheets must be removed from the field at the end of the cultivation cycle; they are often contaminated with crop residues that can increase the weight by 65% compared to the new sheet. Removing the sheet also removes soil and organic matter (SOM) contained in the ground; estimating that an amount of 1.2 % of organic matter is removed with this operation in one year, this results in a quantity of 1,800 tons of SOM removed each year. Choosing to use biodegradable agricultural sheets in the soil means fighting its depletion while avoiding contamination with plastics.

The table provides data related to the durability of mulch sheets in bioplastics on different crops. These values result from field trials carried out in over 10 years of experimentation and optimization. For horticultural and floricultural species of high added value, cultivated in the open field or a protected environment, other preventive methods can be used, such as mulching, solarization and/or the use of biodegradable plastic films in soil, possibly derived from biobased raw material (hopefully in progressively increasing shares).

Mulching sheets initially used mainly for medium short-cycle crops, i.e., the main ones for horticultural crops (e.g., zucchini, lettuce, tomatoes, pumpkin, etc.), are now employed, with increased thickness, also for broader cycle crops, such as strawberries and grapevines.

These sheets allow to reduce weeds, provide a more suitable microclimate for the plant, and avoid wasting water while preserving moisture. They also retain heat in the soil, thus limiting the risk of plant roots freezing, especially useful for early crops. As already mentioned, these sheets are made of polyethylene or polyester and must be disposed of at considerable cost at the end of their life.

Research is increasingly encouraged to mitigate the economic and environmental costs generated by the uncontrolled proliferation of plastics on this issue. For instance, the Focus Chimica Verde (Green Chemistry Focus), by CREA PB* for the National Rural Network (2018 - 2020) conducted in strict cooperation with the Green Chemistry Association Bioenet (CVB) and ITABIA, aimed to identify innovative and highly sustainable solutions to solve problems in the production and processing phases of the fruit and vegetable sector and ensure their dissemination to different stakeholders. Between the various activities, the opportunities given today by biobased and biodegradable materials as an alternative to the use of traditional plastics have been thoroughly explored. To this end, a participatory approach has been adopted, thus ensuring farmers' organizations, research representatives, and institutions' involvement in an ongoing dialogue.

Today, after years of research, certified biodegradable soil-based mulch products are finally available on the market, with field performance similar to traditional plastics but which do not have to be removed at the end of the crop as they degrade within a few months. Therefore, these innovative and sustainable sheets provide sufficient protection in the first phase of the cultivation of short-medium-cycle vegetable crops. At the end of the cultivation cycle, they must be put in the best conditions to be attacked by soil microorganisms, i.e., integrated into the soil through different machinery and working techniques (milling, plowing, or other).

Specifically, from a technical-normative point of view, the European Committee for Standardization (CEN) made available on January 24, 2018, the final text of the European Standard (EN 17033:2018) "Plastics - Biodegradable mulching films for use in agriculture and horticulture - Requirements and test methods". This standard defines the specific characteristics and requirements for biodegradable mulching films for agricultural and horticultural applications. The standard is only applied to sheets that prove to exceed the criteria of biodegradability in the soil at room temperature (release of more than 90% relative CO2 in 24 months, at 25 °C) and that, at the same time, do not have negative impacts on the environment. The paper specifies the test methods to evaluate the biodegradability in soil and exclude ecotoxicity effects in the environment and define the mechanical and optical properties of the sheets to ensure a good performance in the field.

 Italy is a leader in this field. In fact, Novamont's MATER-BI bioplastic, used for the production of biodegradable mulch sheets, has also been certified in compliance with the "AIAB Technical Means" regulations. This latter aims to provide professional users with products that, in addition to complying with current laws on the technical means admissible in organic farming, are compatible with the environment and meet technical and ethical requirements of sustainability. This outcome is the result of intensive work carried out by Novamont, AIAB (Italian Association of Organic Agriculture), and Bioagricert (control and certification body for organic production) for the development of a specific standard which requires that mulching sheets for organic farming have the maximum content of renewable raw materials, that come from natural renewable NON-GMO sources and that ensure total biodegradability in soil, in compliance with the European reference standard UNI EN17033 which implies verifying the relevant aspects of use and end of life and the absence of toxic effects on the environment.

To speed up sustainable and plastic-free agriculture, information also has a vital role to play. This is why, during the EIMA Digital Preview, FederUnacoma will host a particular training course entitled "Use of biodegradable materials in agriculture: state of the art and perspectives” organized by the CVB and ITABIA Associations. This course will be addressed in particular to technicians, agricultural organizations, regional public officials, and journalists.

*Note: (Council for Research in Agriculture and Analysis of Agricultural Economics) is the leading Italian public research body dedicated to the agro-food and forestry sector. Its scientific expertise ranges from the main productive sectors (animal husbandry, cereal, and industrial crops, olive and fruit growing, viticulture and enology, horticulture and floriculture, forestry and wood) to the transversal areas of mechanization, defense and certification, environment, politics and bio-economy and human nutrition. It is supervised by the Ministry of Agriculture, Food, and Forestry and Tourism and has full scientific, statutory, organizational, administrative, and financial autonomy.



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