Agro Waste Potential
Posted June 23, 2008on:
The agricultural waste is a low-density biomass, scattered all over the country. Also, it is available in a wide variety of forms having a wide variety of physical and chemical properties. As a result, in spite of its tremendous potential as a renewable source of energy, it has remained more or less neglected by the energy planners as well as technocrats. Also, almost all attempts at finding economically feasible ways of using biomass as a source of energy on a wide scale have proved unsuccessful and unsustainable. We however, believe that it is techno economically feasible to use biomass as a source of energy.
An excellent example of the right approach to use of biomass energy is a chain of technologies developed and successfully commercialized by Appropriate Rural Technology Institute.
Every year, farmers in Maharashtra state alone are simply burning off millions of tons of sugarcane trash (dried leaves of sugarcane left in the field after harvesting of the cane). In 2005, the government undertook a project that attempted to explore means of converting this biomass into a value added fuel, namely char briquettes. Under the project an oven-and-retort type charring kiln was developed. It converted sugarcane trash into powdery char. The charring kiln can be easily dismantled and transferred from one location to other, thereby eliminating the need to transport large quantities of loose biomass. Operated as a continuous batch process, it consumes about 250 kg of trash to generate about 50 kg of char powder every day. Three unskilled labourers can operate two kilns simultaneously to produce 100 kg char powder per day. The powder can then be briquetted by using a briquetting machine. The production cost of the briquettes is about Rs. 8 per kg.
Kerosene, which is the preferred cooking fuel for of the urban poor, is getting costlier and costlier as the government is gradually withdrawing the subsidy on it. We felt that the char briquettes made from agricultural waste could be a suitable low cost alternative fuel for the urban poor. However, switching from one form of fuel to other also requires a switch over from one type of cooking stove to other. It was, therefore, necessary to develop a cooking stove that was designed to suit the combustion characteristics of the char briquettes. Therefore Sarai cooker was developed. The cooker combines the principle of a hotbox, with the principle of a fuel-efficient stove. The result is so energy efficient that it requires just about 100 gm of char briquettes to cook vegetables, rice and dal for a family of five, and another 50 gm or so for roasting rotis on the charcoal burning stove which is part of the cooker assembly. Even if the briquettes are available in the urban market at the rate of Rs.10 per kg, the Sarai system requires fuel worth just about Re.1 per meal. No other fuel-stove system has such a low operating cost.
The concept has taken off very well among urban as well as rural households in rice eating localities in Maharashtra. The reason for it is its practical feasibility which is as follow:
1. Conventional thinking had always focused on producing tons of briquettes in a centrally located factory. This involves collection and transportation of widely scattered and low density raw material, and the transportation cost itself renders the entire project impractical. Our approach of decentralized production of char, and transportation of the char to a centrally located briquetting facility makes more economic sense.
2. The Sarai cooker is assembled using components already available in the utensils market. Thus, the production of the cooker does not involve any dedicated machinery or infrastructure. As a result, the cooker can be produced at a relatively low cost of about Rs.350-500 (depending mainly on the cost of stainless steel) making it affordable for the target users and profitable for the producer and retailers.
3. Because of the efficient design of the stove, the quantity of fuel required per meal is very less, keeping the cost of fuel per meal cooked at the lowest possible level for the consumer. This allows the per kg cost of the briquettes to be high enough to provide sufficient net income to the char producers, the briquetters, as well as the retailers. This example clearly demonstrates that it is possible to find ways of using biomass energy in techno economically feasible ways. Considering the huge amount of agrowaste produced annually in India, it can be easily seen that the chain of technologies described here can have a tremendous positive impact on the rural economy of the country.