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Here’s a detailed white paper on the use of biomass gasification for the Indian silk industry. The white paper details the case study of a project that was implemented during the period 1995-2002.

I present excerpts from the white paper. The full white paper can be accessed from here

Mulberry silk production, which accounts for about 90 per cent of Indian silkworm breeding (sericulture), is concentrated in the States of Andhra Pradesh, Karnataka and Tamil Nadu in the south of the country. States towards the northeast produce such non-mulberry silks as tassar, muga and eri. Sericulture
has spread over the years and now provides employment for more than 5 million people living in 59,000 villages and covers an area of 282,000 hectares. An efficiency survey of 236 cooking ovens found that charkhas consume between 2.44 and 3.20 kilograms of wood per kilogram of cocoons processed, while cottage basin ovens consume 1.5 to 2.0 kilograms. It was then calculated that charkhas need about 1,300 kilocalories of energy to process one kilogram of cocoons and that cottage basins require about 875 kilocalories. This difference in energy needs can be explained by the longer operating periods and larger cooking vessel areas of charkhas. The main drawbacks of the traditional ovens are that they do not allow fuel consumption to be controlled and that large fluctuations occur in such process parameters as water level and temperature.

There was plenty of scope, therefore, for improving the efficiency and design of the ovens. As a first step, existing ovens were retrofitted to control their burning rates, maximize their flue gas heat recovery and reduce other losses. Retrofitted ovens allowed modest energy savings of about 25 per cent, but this was not enough to encourage silk reelers to face the inconvenience and expense of retrofitting their ovens. To be economically viable, the project had to come up with an alternative design that was capable of meeting the energy needs of silk-reeling units while generating substantial fuel savings.

Faced with the challenges of evaporation losses and the need for controlled burning, a gasifier system appeared to be the best option, and TERI started to
develop a suitable gasifier-based silkreeling oven. A downdraft, throatless gasifier was selected because less tar and particulate matter are produced in its raw
producer gas and it allows the use of relatively large wood chips and other fuels compared with updraft and cross-draft gasifiers. A water seal tank is placed under the gasifier to collect ash and cinders.

The main goal of the project was to improve the productivity and profitability of post-cocoon processing in the silk industry, including reeling and dyeing. Project activities fell into five main categories: technology and system development, economic assessment, market development, entrepreneur development, and human resource development. The final product — the SERI-2000 oven — evolved from a process of prototype development and testing, which included inputs from silk
experts, engineering consultants and manufacturers. The oven is now commercially marketed by two licensed manufacturers. The entire process, from laboratory prototype to final commercial model, was completed in just over three years (May 1995 to June 1998).

During the system development, fieldtesting and marketing phases of the project, the team entered into partnership with the following individuals and public- and private-sector institutions and organizations:
• private manufacturers — 2M Industries of Bombay and Silktex Industries of Kanakapura;
• silk experts — D. Mahadevappa and T.S. Nagaraja;
• design consultants — the Industrial Design Center, IIT of Bombay and Kvaerner Powergas of Bombay;
• numerous potential users of the new technology;
• international experts — Sorane SA (Switzerland) and Ashton Court Consultants (United Kingdom);
• the donor — the Swiss Agency for Development and Cooperation; and
• Departments of Sericulture in Andhra Pradesh, Karnataka and Tamil Nadu.

To date, about 35 gasifier-based systems have been installed in the silk industry for reeling and dyeing. Long-term testing of these systems has found that their use
leads to savings of 745 rupees a day: 90 rupees from reduced wood consumption, 455 rupees from increased silk production and 200 rupees from improved silk
quality. Overall, the systems are saving about 822 tons of fuel wood a year and generating an extra 2,490 kilograms of silk. In addition, pollution and water requirements have also been reduced considerably.

The long-term impact of the project is to increase the competitiveness of the Indian silk industry in international markets by improving productivity, profitability and environmental quality through the introduction of biomass gasification technology.

While what has been described above appears to be a project with a limited impact, I think the case study (I urge you to read the full white paper too) exhibits what can be achieved with the right mindset, a scientific approach based on discussions and partnerships