Original Article Source:
CURRENT SCIENCE, VOL. 118, NO. 11, 10 JUNE 2020
SANDIP MANDAL, ICAR-Central Institute of Agricultural Engineering, Nabibagh, Bhopal 462 038, India e-mail: firstname.lastname@example.org
Cooking is the major energy-intensive activity in many households of rural India 1 . A significant number of rural households still depend on biomass for cooking fuel due to easy access, sociopolitical situation, age-old cultural practice and low income 2 . The Ujjala Yojana of the Government of India had provided LPG connection to 80 million households, but the second and consecutive filings are less common3 . Use of fuel wood for cooking has serious health implications especially for women and children due to indoor pollution4 . On an average a woman spends 3 to 4 h per day for collecting firewood from the forest, which she could otherwise have spent on more productive activities. Considering this fact, efforts have been made to introduce improved cookstoves as an alternative to LPG, but the transition is not satisfactory 2 . Hence, there is an option for alternate cooking fuel using biomass available in the near vicinity. Beehive briquettes are charcoal briquettes made from char and clay mud mixed in certain proportion (Figure 1).
Mud acts mainly as a binding agent and reduces the rate of burning. These briquettes are circular in shape having a diameter of 150 mm and height of 85 mm with around 21 holes of 10 mm diameter. Due to the holes it looks like a beehive; thus the name ‘beehive briquette’. Dried beehive briquette produces smokeless blue flame during burning for 2.5–3 h. It can be burnt in a simple metal stove generally used for biomass burning with an efficiency of approximately 25– 35%. The briquette is ignited by a small fire below by using dried woodchips. Once the briquette catches fire at the base, the fire spreads uniformly and propagates upward. It can be used for cooking and space heating of rooms.
This is an eco-friendly, alternative clean source of household fuel to save electricity and fuel wood. Emission of harmful gases from burring briquette is very low compared to wood and woody biomass. The calorific value of this briquette is approximately 18–20 MJ/kg, and emission of CO, CO2, CH4, NO and NOx ranges between 0.05–0.1%, 0.1–0.5%, 100–200 ppm, 0.5–3.0 ppm and 0.5– 3.5 ppm respectively, which is well within the permissible limits5 . The primary raw material required for this briquette is charcoal, which can be made from crop residues or any biomass grown in nearby fields and rural houses. Charcoal can be prepared by partial carbonization of biomass residues like wood, saw-mill waste, forest biomass like leaves, twigs and agricultural residues like maize stalk, pigeon-pea stalk and weeds. A 200 l used oil drum can be utilized as a charring drum after incorporating a gas-sealing lid and a chimney. The cheapest binding agent used for this briquette is soft mud. Dry soil dominant in clay content can also be used after mixing it with water.
The beehive briquetting mould is made of mild steel. The mould consists of a base plate of 5 mm thickness with 21 iron pegs of 12 mm diameter, a perforated pressure plate and a cylinder of 85 mm diameter. It is simple to fabricate and easy to use. With available crop residues from the farmers’ fields, this briquette can be made in the rural households at almost negligible expenses. Equal amount of crop residues is produced in crops like cotton, maize, soybean, pigeon pea, chickpea, etc. These crop residues can be converted to char with a recovery rate of 25–35% depending on the process employed6 . For making one briquette, 300 g of char is needed and one briquette is sufficient for making one meal for a family of four members. Thus, beehive briquettes can cater to the need of rural women to some extent by providing clean cooking fuel.
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