ETHANOL PRODUCTION FROM TWO VARIETIES OF CASSAVA STARCH

ETHANOL PRODUCTION FROM TWO VARIETIES OF CASSAVA STARCH

CHAPTER ONE

 1.0   INTRODUCTION

        The technology for the production of ethanol from starch materials e.g. Cassava involves cooking, liquefaction, saccharification, fermentation and distillation. The basic technology in the process has been well defined but could be improved by introducing systems which require less energy, particularly in the starch conversion and distillation operations (Moorthy and Padmaja, 1990). Application of low-energy requirement systems for the production of ethanol should make it more attractive as liquid fuel (Balagopalan, 1995).

Cassava is one of the richest fermentable substances for the production of ethanol. The fresh roots contain about 30 percent starch and 5 percent sugars, and the dried root contain about 80 percent fermentable substances which are equivalent to rice as a source of ethanol (Moorthy and Padmaja, 1990). In Malaysia and some other countries, many factories are equipped to use cassava roots, starch or molasses (by-product of the sugar industry), the type of product depending on the cost of the raw material (George, 1995). The roots of cassava are washed, crushed into thin pulp and then screened. Saccharification is carried out by adding salphuric acid to the pulp in pressure cookers until total sugars reach 15-17 percent of the content. The pH value is adjusted using sodium carbonate, and the yeast fermentation is allowed for three to four days at suitable temperature for ethanol production (Ray, 1993).

Although the income elasticity of cassava is considered to be low, and in terms of ethanol production, crops like sugar cane enjoy a better competitive position at present, ethanol production in India makes use of cassava as alternate raw material (Balagopalan, 1995). Ethanol production from fresh cassava roots using a low-temperature process is evaluated using a pilot-plant scale (Ray, 1993). The energy saving effect can be analysed. Also the pressurized distillation method could save about 42% of steam consumption against the atmospheric distillation process.

• CASSAVA CULTIVATION AND USES

        The cassava tuber is widely cultivated in tropical areas. Cassava (Manihot spp) require a temperature of 21⁰C – 35⁰C, rainfall of 150cm – 200cm a well drained rich friable loamy soil. It can also grow in poor soil (Iwena, 1995), cassava tubers are valuable food for man and livestock (Padmaja 1995). It is richer than yam in starch. In India, it is believed to have been cultivated for more than a century and account for 90% feed for livestock. The ability of cassava to supply adequate calories at a lower cost encouraged its maximum use among low-income social groups. It was originally a food security crop used to supplement the rice diet during period of food scarcity, but gradually it has become a subsidiary food even in normal years (George, 1995). Cassava flour is widely used as human food e.g. a bread additive. Some of the fibrous residual material with some remaining starch is used as cattle feed or as a raw material for citric acid production (Shigeru and Maeda 1983).

However, cassava is used in varieties of ways in food, pharmaceuticals, and in manufacturing industries. In food industries which remain the largest consumer of starch and starch product. It is used in confectionaries, canned fruits, jams etc (Moorthy 1995) in large scale industries cassava is the raw material for large scale starch extraction in commercial scale. Sago, a processed food starch marketed as small globules or pearls, manufactured in India is from cassava. It can also be used to make biodegradable plastics the starch extracted can be used in wall board, paper and cloth sizing and adhesive, some of the starch is converted to dextrose and used in fruit canning, yeast production for animal feed, human diet and bakery yeast is made from cassava starch (Somachai 1987).

1.2   OBJECTIVES OF STUDY

        The aim of the study is to compare the potentials of two cassava varieties for the production of ethanol.

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