Sunday, December 6, 2009


Indestructibility of plastic materials which are used extensively in almost all activities involving day to day life has become one of the biggest challenges facing the world to day. It takes more than 700 years for some of the plastics to be removed completely from the environment and the pollution potential of millions of tons of plastics discarded after use is mind boggling. Besides, the feedstock used viz, petroleum products, from which most of the plastics are manufactured, is not perennial and can run out in the foreseeable future. The recycling option, if practiced world wide on a large scale, could have reduced the magnitude of the problem of disposal and it would not have been so burdensome as it is to day. Unfortunately not even 5% of the used plastics enter the recycling route, increasing the accumulation of waste plastics every year to astronomical levels.

Present level of technology for making polyethylene uses 1.75 kg of petroleum material to get 1 kg of the end product and the process of conversion entails high energy making plastic truly an energy intensive product, besides contributing to significant green house gas emissions. High Density Polyethylene (HDPE) based packing materials are produced to the extent of 30 million tons annually and the films made from this plastics has unique properties making it a darling of the entire spectrum of industries. Its ability to withstand temperature as high as 120C for limited time and 110C continuously and suitability to blow molding process to manufacture hard bottles and hollow goods, make it a universal choice by food and allied industry. Almost 8 million tons of HDPE are used in making bottles used by dairy, beverage and pharma industries. Though PET bottles have lately come to the fore, HDPE is still preferred by many industries.

Polylactic Acid, claimed to be a green plastic, is made from lactic acid obtained by fermentation but it has become a controversial issue, the claim being contested by some experts. Cellophane, made from regenerated cellulose obtained from wood, cotton, hemp, bagasse etc, could be truly termed a green plastic and it has the advantages such as low air permeability, oil and grease resistance and imperviousness to bacteria and other destructive vectors but suffers from its unsuitability for heat sealing. Besides it may not deserve the green label fully if the CO2 foot print of cellulosic sources used for its production is taken into consideration.

Ethyl alcohol, produced by anaerobic fermentation of sugar sources by yeast is one of the most versatile industrial raw materials man has ever known. Its oxidative product acetic acid is another industrial base from which a number of products are made. Using ethyl alcohol for the manufacture of HDPE is a new route for making polyethylene that can rightly claim to be "green" but commercial production may still be uncertain due to economic factors that still weigh in favor of petrochemical based plastics as long the latter is available cheap. It goes to the credit of an enlightened player like Tetra Pak of Sweden to come forward to start using green plastics made from ethyl alcohol. Ethylene is first produced from alcohol which is then polymerized using special catalysts to prevent branching and yield HDPE.

Brazil, one of the largest producers of sugar from cane, converts a significant portion of its crops into alcohol, mainly to make biofuels either as it is or based on blends with petroleum fractions. Its bold initiative to divert a part of its alcohol production to make HDPE is considered most welcome. In a landmark agreement Tetra Pack, largest producer of cartons for packing milk and beverage products, is supposed to buy about 5000 tons of alcohol derived HDPE per year, 5% of their annual requirement, from the Brazilian petrochemical company Brakem which is slated to start production of the so called green plastics by the end of next year. According to Brakem, alcohol based HDPE production would reduce overall green gas emission significantly compared to traditional process.

What effect such large scale diversion of sugar cane based alcohol to HDPE manufacture, will have on biofuel program or on global sugar prices remains to be seen. Countries like Indonesia, Malaysia and Brazil are being blamed for massive deforestation to reclaim land for cultivation of commercial crops like Oil Palm and Sugarcane and endangering the environment by reducing the extent of carbon sink provided by these forests. How such a dilemma can be addressed must be the concern of the whole world.


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