The use of plastic mulch in agriculture has increased dramatically in the last 10 years throughout the world. This increase is due to benefits such as increase in soil temperature, reduced weed pressure, moisture conservation, reduction of certain insect pests, higher crop yields, and more efficient use of soil nutrients. However, disposing of used plastic films, which cause pollution, has led to development of photodegradable and biodegradable mulches. Here we review the use of plastic mulches in agriculture, with special reference to biodegradable mulches. Major topics discussed are (1) history of plastic mulch and impact on crop yield and pest management, (2) limitations of polyethylene mulches and potential alternatives, (3) biodegradable and photodegradable plastic mulches, (4) field performance of biodegradable mulches, and (5) use of biodegradable plastic mulches in organic production. We found that (1) despite multiple benefits, removal and disposal of conventional polyethylene mulches remains a major agronomic, economic, and environmental constraint; (2) early use of photodegradable plastic mulch during the 1970s and 1980s, wrongly named biodegradable mulch films, discouraged adoption of new biodegradable mulch films because they were too expensive and their breakdown was unpredictable; (3) biodegradable plastic films are converted through microbial activity in the soil to carbon dioxide, water, and natural substances; (4) polymers such as poly(lactic acid), poly(butylene adipate-coterephthalate), poly(e-caprolactone), and starch-based polymer blends or copolymers can degrade when exposed to bioactive environments such as soil and compost; (5) with truly biodegradable materials obtained from petroleum and natural resources, opportunity for using biodegradable polymers as agricultural mulch films has become more viable; and (6) the source of polymer and additives may limit use of some biodegradable mulches in organic production. More knowledge is needed on the effect of biodegradable mulches on crop growth, microclimate modifications, soil biota, soil fertility, and yields.

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Polyethylene and biodegradable mulches for agricultural applications: a review

Interest in maintaining food quality while reducing packaging waste has encouraged the exploration of the oxygen and aroma transport properties of edible films. This review article introduces the theoretical basis for oxygen and aroma barrier property determination and presents a brief historical per- spective of the development of barrier polymers. The effects of structure and composition on mass transport in edible films are examined and compared with those of the more thoroughly investigated synthetic polymers. A survey of edible film oxygen and aroma barrier research is presented; areas re- quiring additional investigation are suggested, for applications as well as basic research. The potential of edible films and coatings to provide excellent aroma retention and superior oxygen barrier properties makes this quite a promising area of research for both food and packaging scientists.

Oxygen and aroma barrier properties of edible films: A review

Glass transition and enthalpy relaxation of cross-linked corn starches

Since last few decades the uncontrolled use of plastics for various purposes such as packaging, transportation, industry and agriculture in rural as well as urban areas, has elevated serious issue of plastic waste disposal and its pollution. The efficient decomposition of plastic bags takes about 1000 years.  Plastic causes pollution and global warming not only because of increase in the problem of waste disposal and land filling but also release CO 2 and dioxins due to burning. Commonly used methods for plastic disposal were proved to be inadequate for effective plastic waste management, and hence there is growing concern for use of efficient microorganisms meant for biodegradation of non-degradable synthetic polymer. The biodegradable polymers are designed to degrade fast by microbes due their ability to degrade the most of the organic and inorganic materials, including lignin, starch, cellulose and hemicelluloses.  The present review discusses the current status, mechanisms of biodegradation of plastics, techniques for characterizing degraded plastics and factors affecting their biodegradation.

Aulia Rahmayani

Papers

INTRODUCTION to polymer science and technology