This document describes a biomass gasification system developed by Prof. Dr. Krishna Raj Shrestha and his team at the Research Centre for Applied Science and Technology (RECAST) in Nepal. The system was tested at loads of 3 kW and 6 kW, achieving overall efficiencies of 9.45% and 15.36% respectively when using producer gas and diesel in dual mode. In single gasification mode, the system achieved efficiencies of 79.13% and 84.03% at the two loads. The document provides details on the gasification process, equipment used, types of biomass available in Nepal as feedstock, and test results for temperature, pressure and emissions.

1. Biomass Gasification System
for Rural Electrification
Prof. Dr. Krishna Raj Shrestha
Research Centre for Applied Science and
Technology (RECAST)
Tribhuvan University
Kathmandu, Nepal

2. Project Team
• Prof.Dr.Krishna Raj Shrestha-TeamLeader
• Uttara Bajracharya -Sociologist
• Rajib Thakur- Energy Engineer
• Bijay Raj Subedee- Biotechnologist
• Roshan Kumar Amatya -Senior Mechanics
• Sushil Karmacharya - Senior Mechanics
• Dambar Bahadur Ale - Helper

3. Introduction
• Biomass refers to all forms of organic matter produced
as products of photosynthesis. Biomass has long served
as one of the primary energy forms utilized by human
being for essential activities aside from nutrition.
Different forms of biomass are
• Forest based products
• Timber, fuel wood, wood chips/shavings, saw dust, a
milling residue, forest waste like leaves, twigs, shrubs,
herbs herbal products, etc.
• Agriculture based products
• Aquatic plants
• Animal dung and human waste.

4. Energy Consumption Situation by fuel
type
79.6%
2.8%
3.9%
12.3%
1.2%
0.1%
376.3 MGJ
Biomass
Grid electricity
Coal
Petroleum
Renewable
Others
Source :WECS Survey
,2011

5. Gasification
Biomass gasification is basically conversion of solid
biomass (i.e. wood/ wood wastes, agro-residues and
organic industrial wastes) into a combustible gas
mixture. It is carried out in an enclosed reactor
operating at about 900oC where in a part of the
biomass is combusted by air to provide the heat. The
resulting gas known as producer gas contains CO(15
-29 %), CO2 (5 -15 %), H2 (5 -12 %), N2 (50 –65 %) and
small amounts of hydrocarbon gases. The calorific
value of the gas ranges from 1200-1500 kcal/m3.

6. Gasification Reactions
Devolatilization C+heat CH4+ condensible -
hydrocarbons+char
Steam-Carbon C + H2O + heat CO + H2
Reverse Boudouard C + CO2 + heat 2CO
Oxidation C+O2 CO2 +heat
Hydrogasification C+2H2 CH4+ heat
Water Gas shift H2O + CO CO2+ H2 + heat
Methanation 3H2 + CO CH4 + H2O + heat
4H2 + CO2 CH4 + 2H2O + heat

8. Why Gasification?
• Biomass covers 80 percent of the energy needs
of Nepal (WECS 2011).
• The biomass mostly used for fuel is firewood (68
percent) followed by agricultural residue and
animal dung, which are generally of low grade
and burnt in traditional stoves. (WECS 2010)
• Due to smoke and particulate matters created by
unscientific combustion, the indoor air in houses
gets polluted causing respiratory and eye-
related health problem to users, especially
women and children.

9. Different waste biomass
Lantana camera Mugwort – Tite pati
Banmara Mikania Macrantha
- Banmasa
Pine needles

10. Agro residues
Crop type Area
[Ha]
Crop Prod
[MT]
Residue
type
RPR* Total Residue
Prod [MT]
Paddy 1,531,493 5,072,248 Total
residue
1.68 8,521,376
Husk 0.267 1,354,290
Maize 871387 2179414 Total
residue
5,389,691
stalk 2 4,358,828
cob 0.273 594,980
husk 0.2 435,883
Millet 278030 315067 stalk 1.08 340,272
Wheat 765317 1846142 straw 1.75 3,230,748
Buckwheat 10339 10021 Straw 1 10,021
Barley 27966 34829.8 straw 1.75 60,952

11. Agro residues (cont)
Crop type Area
[Ha]
Crop Prod
[MT]
Residue type RPR Total Residue
Prod [MT]
Oil Seed 214835 179145 Stalk 4.01 71,837
Sugarcane 64472 2930047 Bagasse 0.29 849,714
tops/leaves 0.3 879,014
Total 1,728,728
Jute 10540 14424 Stick 2 28,848
Soybean 29281.8 28269.8 Total 98,944.3
Straw 2.5 70,674.5
Pods 1 28,269.8
Black Gram 27496.2 22482.4 Straw/stick 1.66 37,320
Cotton 135 133 Sticks 2.75 365.75
Coconut Husk 0.419 NA
Shell 0.12 NA
Coffee 1780 425000 Husk 2.1 892,500
Ground nut 2736 3869 Husk 0.477 1,845
Straw 2.30 8,899

12. Saw Dust

13. Twigs and branches

14. Different Forest waste
• Banmara - 1.78 kg/m2 (17 tons/ha)
• Pine needles - 4.5 million tons (382,944.80
ha pine forest area)
• Besarmi jhar - 5-6 kgs/m2
• Saal leaves - 2,019,600 tons of leaf litter per
year
- 5 tons of waste materials/month
• Mikania micrantha - ~ 600,000 tons of dried
Mikania (20 districts)

15. Besarmi jhar, Saal leaves
and leaf litter

16. Estimates of Mikania as raw
materials

17. Municipal Solid waste
No. Type of waste 1976 1981 1985 1988 1995 1999 2000 2004 2008
1 Organic 67.8 60.0 67.5 58.1 65.0 67.5 69.84 67 68.0
2 Paper 6.5 19.3 6.0 6.2 4.0 8.8 8.5 10 10.0
3 Rubber 0.0 0.0 0.0 0.4 1.0 0.3 0.54 0.24 mix1
4 Leather - - - - - - 0.12 - -
5 Wood 2.7 1.6 0.0 0.5 3.0 0.6 0.73 - -
6 Plastic 0.3 3.6 2.6 2.0 5.0 11.4 9.17 16 13.0
7 Bone - - - - - - 0.23 - -
8 Textile 6.5 5.3 2.7 2.0 3.0 3.6 3.02 4 2.0
9 Ferrous metal 4.9 3.4 2.2 0.4 1.0 0.9 0.87 1 -
10 Aluminium - - - - - - 0.05 - -
11 Metal - - - - - - - - 1.0
12 Sand dust - - - - - - - - 1.0
12 Glass 1.3 3.4 4.0 1.6 1.0 1.6 2.5 1 4.0
13 Construction
debris/Others
10.0 3.4 15.0 28.9 17.0 5.3 4.33 1.24 1.0
From simple calculations, this gives about 181 tons of plastics, 186 tons of
paper, 36 tons of textiles and 15 tons of woody matter on a daily basis
58 municipalities in Nepal and the amount of waste generated by these
municipalities per day comes to 2813.13 tons. Out of this amount of generated
waste, 2164.49 tons are collected.

18. Industrial waste
• Waste from veneer industries
• Furniture, handicraft (wooden frames), etc.
– Bira Furniture in Patan - 10-15 tons of wood
waste per month
– Lalitkaltmak Kastha Udyog - (~0.5 tons) of Saw
dust and 1-1.5 tons of wooden strips are
generated per week
Subject Amount in Cu.ft.
processed per
day
Waste per day
(taking 50%)
Density of
soft wood
Total Amount
waste per day
Waste from Sri Om
Veneer
400 cft.
(300-500cft)
200 cft. =
5.66 m3
53lb/cft*
(670kg/m3)
3792kg or
3.8 tons
Total Amount of waste generated from 200 industries from all over Nepal 758.440 tons
Current use by local people and boilers and tea drying = 25% 189.610 tons
Unutilized waste that can be used for briquetting = 75% 568.830 tons

20. RECAST’s involvement in Gasification (1985)

21. Biomass Gasification for Electricity
Generation (1999)

22. Biomass Gasification for Electricity Generation(2011)

23. Schematic Diagram of biomass gasifier and its measuring
points during testing
T1 Ambient temperature T4 Temperature at orifice meter
T2 Temperature at outlet of cyclone separator T5 Temperature inside the gasifier
T3 Temperature at outlet of cooler Pd Pressure difference at orifice
meter

24. Gasifier

25. Flaring of Producer gas

26. Design of Biomass gasifier

27. Cyclone separator

28. Filter Tank

29. Air Heater (9 kW capacity) to
test the real output of the plant

30. Measuring Instruments used
during the testing
Multi channel temperature scanner
K type thermo couple
Orifice flow meter
True RMS clamp on meter
Balance up to 100 kg.
Portable gas analyzer ( For Co measurement
of producer gas)
Stop watch
burette 1000 ml

31. Test results
`
Load
(kW)
Ambient
Temperatu
re
T1(o
C)
T2
(oC) T3(oC)
T4
(oC) T5(oC)
Pressure
difference
( cm of
water)
Gas
quantity
(m3
/secon
d
Gas
quantity
(m3
/Hour
Time
taken to
consume
100ml
Diesel
consumpt
ion per
hour
(liter) Mode
Diesel/
Producr
e gas
ratio
Charcole
consump
tion (Kg)
12.30 6.00 24.00 2.53 2.37 Diesel 100.00 0.00
1.00 6.00 24.00 79.00 19.00 84.00 457.00 8.00 0.00 14.15 4.23 1.42 Duel 59.81
1.30 6.00 27.00 156.00 62.00 164.00 525.00 7.00 0.00 13.00 3.19 1.88 Duel 79.31
2.00 6.00 30.00 203.00 84.00 208.00 530.00 8.50 0.00 14.58 5.06 1.19 Duel 50.00
2.30 6.00 33.00 265.00 112.00 247.00 560.00 7.00 0.00 13.00 5.13 1.17 Duel 49.32
3.00 6.00 33.00 192.00 84.00 196.00 459.00 8.50 0.00 14.20 5.06 1.19 Duel 50.00
Average 6.00 30.75 204.00 85.50 203.75 518.50 8.00 0.00 13.70 4.53 1.32 57.69 2.80
7.00
Time
Load
(kW)
Ambient
Temperatu
re
T1(o
C)
T2
(oC) T3(oC)
T4
(oC) T5(oC)
Pressure
difference
(cmof
water)
Gas
quantity
(m3
/second
Gas
quantity
(m3
/Hour)
Time
takento
consume
100
ml(minut
Diesel
consumpt
ionper
hour
(liter) Mode
Diesel/P
roducre
gasratio
Charcole
consump
tion(Kg)
12.30 3.00 28.00 28.00 28.00 28.00 28.00 3.96 1.52 Diesel 100.00 0.00
1.00 3.00 28.00 142.00 94.00 140.00 1052.00 3.00 0.00 8.92 5.05 1.19 Duel 78.42
1.30 3.00 29.00 168.00 94.00 178.00 1293.00 4.00 0.00 10.10 5.93 1.01 Duel 66.78
2.00 3.00 32.00 253.00 127.00 269.00 1440.00 3.00 0.00 8.92 4.40 1.36 Duel 90.00
2.30 3.00 34.00 238.00 119.00 215.00 1440.00 3.00 0.00 8.92 5.08 1.18 Duel 77.91
Average 3.00 30.75 200.25 108.50 200.50 1306.25 3.25 0.00 9.21 5.12 1.17 78.28 2kg/hour
4.00

32. Efficiency Calculation
Mass flowrate of
producergas
(m3/hour) (mg)
Calorificvalue of
producergas
(Kcal/m3)(cg)
Output
(mg*cg)
(Kcal/hour)
Mass flow
rate of Solid
fule
(Kg/hour)
(ms)
Calorificvalue of
Solidfuel
(Kcal/Kg) (cs)
Input
(ms*cs)
(Kcal/hour)
Efficiency
(%)
9.21 1167.15 10752.37 2.00 6794.00 13588.00 79.13
13.70 1167.15 15984.94 2.80 6794.00 19023.20 84.03
Efficiency of Biomasss gasifier at diffferent load condition
Powerproduce
fromgenerator
(KW)
Tharmalenergy
required(Kcal/hour
)
Diesel
consumed
(liter/hour)
Calorific
valueof
diesel(Kcal/
lit)
Thermelenergy
imputsfrom
diesel
(Kcal/hour)
Producer
Gas
consumpti
on(m3/h)
Calorific
valueof
producer
gas
(Kcal/m3)
Thermel
energy
imputs
from
producer
Total
Energy
imputs Efficiency
3.00 2580.00 1.17 9281.00 10858.77 9.21 1167.15 10752.37 21611.14 11.94
6.00 5160.00 1.32 9281.00 12250.92 13.70 1167.15 15984.94 28235.86 18.27
Efficiency DualMode

33. Power (kW)
Efficiency of
Gasifier
Efficiency of
CI engin and
Overall
efficiency
3.00 79.13 11.94 9.45
6.00 84.03 18.27 15.36
Overall efficiency of the Gasification
Powerproduce
fromgenerator
(KW)
Tharmal energy
required
(Kcal/hour)
Diesel
consumed
(liter/hour)
Calorific
value of
diesel(Kcal/
lit)
Thermel energy
imputs from
diesel
(Kcal/hour) Efficiency
3.00 2580.00 1.52 9281.00 14107.12 18.29
6.00 5160.00 2.27 9281.00 21067.87 24.49
9.00 7740.00 2.57 9281.00 23852.17 32.45
Efficieny Diesel mode

36. Gasification Plant at Sarlahi
• Capacity 11 kW
• Equipment cost Rs 20 Lacs
• Power supplied to 100 houses
• Funded by RERL, through AEPC
• Biomass used- Dhaincha (Sesbania sp.)

38. Rice Husk Gasification Plant
• 32 K.W Plant at Suhapur sohari, Parsa Dist.
• Husk Power System (P) Ltd., Bihar
• Plant Cost Rs 52 Lacs.
• Funded by Poverty Alleviation Fund and DDC Parsa
• Fuel consumption- 50 kg RH per hour
• Power supplied to 209 houses in the community
• Run by community-earns Rs 70,000/- by supplying
power and Rice milling
• Charges Rs 80/- per family per months per CFL bulb
• Rice Sheller mill- 12 Quintal Paddy produces 350 kg
of Rice Husk.

40. Further developments in this area…..
• Alternative Energy Promotion Centre(AEPC) has conducted
feasibility study in the Terai region of Nepal to install Biomass
Gasification Plant for Rural Electrification. Such a unit has
been tested in Sarlahi district aiming to pilot a site in the
district.
• There are more than 40 gasification plants that are
successfully operating in India and overseas for heat and
power applications. (TERI 2010)
• Renewable Nepal Program of Kathmandu University (KU) is
also working on a Project namely “Design, fabrication and
testing of a biomass gasifier for small size petrol and diesel
engines” since August, 2010.(KU 2010)
• China is expected to achieve the most rapid growth in
gasification worldwide. Since 2004, 29 new gasification plants
have been licensed or built in China.

41. Biomass Power Plant
• Narayani –Shanker Biomass Power Plant
to be established in Lumbini, Rupandehi District
• Technology & equipments is based on Indian
Institute of Science specifications
• Installed capacity of the BPP is 700 Kwe which
will be fed to the NEA sub-station at Lumbini.
PPA already done with NEA.
• undertaken by TMB-ENERGIETECHNIK
Chhetrapati, Kathmandu, Nepal.
Tel# 4256056/ 4257627
Email: cbari@info.com.np
URL:http://reeep.org/groups/TMB.energie

42. • Biomass contributes nearly 80 % of the total energy demand in Nepal. Its
efficient utilization coupled with co-generation of value added products
can provide a dependable and economic route.
• Use of partially pyrolyzed biomass materials eliminates the problem
relating to tar formation.
• The performance evaluation of the gasification plant showed that this
unit is capable of generating producer gas of 1167 kcal/Nm3 energy to
power 20 H.P engine generator on dual fuel mode with 51% replacement
of diesel oil. This shows that the gasification plant could be used for
generating electricity in the rural areas as a decentralized power unit
after carrying out some field tests.
• Biomass gasification can offer an attractive alternative renewable
energy system especially in rural areas where biomass fuel is available.
Thus can provide community based small-scale independent power
plants.
Conclusion and recommendation

43. Recommendation
• Proper training on the Fabrication and use of the
biomass gasification plant for electricity generation
should be given to the rural communities before the
technology is disseminated in the field.
• There should be Policy support from the government like
providing subsidies for the promotion and development
of this technology.
• The technology of the gasification system is simple in
construction and requires negligible maintenance during
its operation.

44. • Field trials and demonstrations should be done in order to
convince the rural communities for generating electricity
through biomass gasification.
• Elaborate testing of the gasification plant on various partially
pyrolyzed biomass materials should be done.
• Various biomass residues should be characterized to establish
their suitability for gasification.
• Different biomass material such as forest residues like pine
needles, agricultural waste, briquettes, etc. should also be tried
as feeding materials in the gasifier in order to save forest.
• Scope for other industrial application should be ventured.
Scope for Further Studies

45. Acknowledgements
• University Grant Commission
• Executive Director, RECAST, T.U.
• Kathmandu University
• TERI and IIT-Delhi, India.
• AEPC