Charring and briquetting technologies reduce many problems associated
with management and utilization of biomass in domestic and industrial
sectors. Briquetting of some of crop residues has become cost effective
and it is considered as the replacement of firewood in India.
Biomass is widely used for heat and power generation with the latest
combustion and gasification technologies. Same combustion technologies
can be used to burn domestic and commercial waste to obtain energy, which
can present opportunities for improved waste management strategies.
The raw materials needed for making briquettes include biomass derived
from agricultural residue and forest products, shrubs, pieces of fuel
wood trees, saw dust, etc. and sticky clay soil as binder. When briquettes
are produced using charring drum, funnel is inverted first inside the
drum; dried materials are then spread over funnel and burnt. As the dried
biomass materials start burning a little, dried materials are continued
to add and burn. Raw materials should not be burnt completely. Chimney
is attached to the top of the inverted funnel through which white smoke
is ejected. The process of semi burning of biomass is done layer by layer
until the drum is filled two-third. Then the chimney is taken out and
drum is covered and water-sealed to completely extinguish the fire. Once
the fire is extinguished and cooled down then the coal is taken out,
pounded into powder, mixed with the binding sticky clay soil with water
all in appropriate ratio (3 parts of coal: 1 part of binding clay soil).
Then the well-mixed coal is put in the briquette mould and compressed
well with hand or machine. The briquette is then taken out and dried
for 2-3 days under the sun. While drying, briquettes should be kept on
plane and hard surface and should be covered with plastic during the
night to protect from rain and wind. Once the briquette is dried and
made hard, it is ready for burning in the briquette stove. When produced
manually, one person can make about 30 round beehive briquettes with
19 holes through which blue fire-flame comes out when burnt. Depending
on the quality of briquettes, one beehive briquette burns for an hour
to two and half hour. If the semi-burnt charcoal is machine pressed,
it results better fire efficiency. Cost of the briquette piece ranges
from 10-20 rupees (15-30 cents). A normal meal for a nucleus family of
4-5 members can be cooked with one briquette.
- Biomass briquettes are
prominently used in domestic cooking and heating.
- Centralized power
plants based on biomass combustion, pyrolysis or gasification
can provide electricity and heat with generation capacities ranging
from hundreds of kW to hundreds of MW.
Can be used to burn waste
Continuous planned growing
of energy crops absorbs CO2 at same rate as it is produced in the
combustion process, thus leading
to no net increase in atmospheric CO2.
Organized tree planting
contributes to water management, reduction of heat in arid areas
and in prevention
improve soil conditions and prevent severe floods etc.
Easy to convert
to high energy portable fuel (e.g. gas).
- Comparatively cheap.
a large area of land with high initial cost of building power
Burning biomass can result
in air-pollution, if not planned properly.
18.104.22.168 Portable Charring Kiln
Portable charring kiln is a simple unit for converting agricultural
residues to a charred mass. It consists of a M.S.
drum, handle and door. Due to its cylindrical shape, it can
be rolled easily to the site
Waste agricultural mass such as soybean straw,
pigeon pea stalks,
and other material can be
used. A small quantity of residues is fed into the kiln and ignited.
When it gives a white
smoke and starts
properly, additional material
is added to
the kiln. By continuing the process, whole of the kiln gets
Cover is then closed
hot mass is allowed to pyrolysis.
After 6-8 hours, the unit cools down and the charred mass can
be emptied. The char
is used for
smoke free kitchen fuel by
converting them into briquettes.
22.214.171.124 Honeycomb/Beehive Briquettes
The honeycomb/beehive shaped
biomass briquettes is made by using hand mould and it is so simple
that it can be fabricated/manufactured
blacksmiths in rural areas. This hand mould (for honeycomb/beehive briquettes)
consists of 3 parts and is manufactured by local blacksmiths from thick
steel plate (5 mm) and smooth iron concrete reinforcement bars (12 mm).
The mould is 90 mm high and has an internal diameter of 5" (127
mm). 19 holes of 12.5 mm (½ inch) in the bottom allow easy lifting
of the pins and briquette out of the mould. Handles are 10 mm thick.
This mould costs NR (Nepalese Rupees) 5,000 or INR (Indian Rupees) 2,000.
Hand moulding requires 5 kg metal; however, it does not produce a high
briquette density. Estimated moulding pressure may vary between 2-3 kg/cm2.
One person can make 30 briquettes per hour with hand moulding provided
the charcoal-clay mix/paste is ready.
During the manufacturing of new moulds it is recommended to use a precise
welding jig for 19 pins and a drilling jig for the holes. This way the
perforated plate can be placed in any position over 19 pins . The weight
of hand-made, dried briquette is about ½ kg. Average production
cost of dried honeycomb briquettes in Nepal is NRs. 2.50-3.00 per piece,
whereas the briquettes market price is NRs. 4.00 per piece. Local cost
of pure charcoal used by blacksmiths is about NRs. 8.00 per kg.
Calorie Value: Pure woody biomass charcoal produces about 28 mega Joule/kg.
Well-compacted, dried briquette has a weight of about ½ kg. At
high altitudes the briquettes should be adequately dry, while at lower
altitudes it may contain humidity by 15 % or more. Hardwood biomass charcoal
briquettes with 20% clay content produce about 18 MJ/kg or about 9 MJ/briquette.
In practice this may heat 2 litres of water in 15-20 minutes using the
insulated (one briquette) metal stove (from about 20-98 ºC at 1300
m altitude). Burning duration of this briquette is about 1.5 hour.
Forest and agricultural waste charcoal briquettes, also with 20% clay,
produce about 12 MJ/kg or 6 MJ/briquette depending on the composition
of charcoal. In practice, this may heat 2 litres of water in 30-45 minutes
by using the single briquette stove. Burning period of 1 briquette is
about 1 hour.
126.96.36.199 Low Cost Briquetting Machine
briquetting machine designed for converting charred biomass into cylindrical
briquettes is a screw type extruder unit. It has a hopper
for feeding the char and cow dung mixed to predetermined proportion of
water. Feeding is done slowly. Outlet end has a number of openings forming
the die through which the briquettes come out continuously. These are
collected separately in trays and left in the sun for drying. The larger
unit is operated with 2.25 KW motor and produces 60-75 kg of briquettes
per hour. The smaller version produces about 40 kg of briquettes per
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