website developed by
Dtex Consulting
Copyright 2007,
R D Associates Ltd.
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Biomass Fuels
Biomass Fuel Types
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Wood pellets are produced out of waste products from the
timber industry. Wood shavings and sawdust
pressed together to form pellets. 22Kg of wood pellets replaces 1 litre of fuel oil. |
Grain and similar fuel crops may also be be used as fuel,
stored in a silo. Grain tends to
clinker, however this may be reduced by adding lime to the silo. 2.5Kg of grain replaces 1 litre of
fuel oil. |
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Wood Chip size varies from 5 to 50mm. The water contents
of the woodchip should not exceed 20-25%
by volume. About 15m3 of chipped conifer wood is needed to replace 1000 litres of fuel
oil, and about 11m3 if chipped hard wood. |
Rapeseed cake is produced as a by-product of rapeseed
oil production. Produced by cold pressing rapeseed, the cake can be either in the form of a
meal or actual pellets (as shown). 1kg of cake (about 11% oil content) has an energy value
of approximately 5.4 kWh/kg |
Biomass Fuel Sources
- Energy Crops – robinia, willow, poplar, eucalyptus, miscanthus, sweet sorghum etc.
- Clean Residues from Industry – furniture manufacturers, sawmills, timber processors, recycled
timber.
- Wood Wastes & Forest Residues – forest residues, primary wood processing, straw,
secondary wood and textile wastes.
Biomass & Fossil Fuel Relative Costs
Fuel comparison data
|
Fuel Type |
Gross Calorific Value
(MJ/kg) |
Thermal Value
(kWh/kg) |
Density
(kg/m3) |
Cost
(£/litre or £/Tonne) |
Cost
(p/kWh) |
Quanitity Used per 100kW
(Litres or kg) |
Kerosene 28sec |
46.20 |
12.83 |
817.15 |
£0.38 |
3.05 |
9.54 Litres |
Gas/Diesel Oil 35sec |
45.60 |
12.67 |
890 |
£0.27 |
2.20 |
8.87 Litres |
Fuel Oil |
43.40 |
12.06 |
890.13 |
£0.25 |
2.10 |
9.32 Litres |
Liquid Petroleum Gas (LPG) Butane |
49.40 |
13.72 |
- |
n/a |
3.50 |
- |
Natural Gas |
39.80 |
11.06 |
- |
n/a |
2.50 |
- |
Oilseed cake (10.9% oil) |
19.30 |
5.36 |
654.00 |
£110 |
2.05 |
18.66 kg |
Oilseed oil |
39.20 |
10.89 |
920 |
£40 |
0.37 |
9.98 Litres |
Glycerine |
20.00 |
5.56 |
1259.37 |
- |
- |
- |
Barley |
18.6 |
5.17 |
609 |
£100 |
1.93 |
19.34 |
Wheat |
17.00 |
4.72 |
746 |
£100.00 |
2.12 |
21.17 kg |
Oilseed Grain |
26.5 |
7.36 |
774 |
£150.00 |
2.04 |
13.58 kg |
Woodchip (30% MC) |
12.24 |
3.40 |
250 - 200 |
£60.00 |
1.76 |
29.41 kg |
Woodpellet (6% MC) |
17.64 |
4.90 |
650 - 705 |
£160.00 |
3.3 |
20.41 kg |
1 MJ = 0.2778 kWh
Useful Conversion Factors
The SI unit for heat energy ( in fact all forms of energy ) is the Joule (J).
- 1 thermal calorie (cal) = 4.184 J
- 1 British thermal unit (Btu) = 1055.056 J
- 1 therm = 100 000 Btu = 105.5 MJ
Heat flowrate is also defined as power, with the SI unit of Watts (W)
- 1 W = 3.41214 Btu/h = 0.238846 cal/s
- 1 kWh = 3412.14 Btu/h
- 1,000,000 Btu/h = 293 kWh
Fuel |
kWh |
MJ |
1 kg Wood pellets (8%) |
4,72 |
17,00 |
1 l fuel oil |
10,0 |
36,00 |
Fuel oil <---> Bio fuels (calculated from thermal values)
1 kg wood pellets (8%) |
0,47 litre oil |
1,62 kg wood chips (40%) |
1,13 kg straw (15%) |
1 litre fuel oil |
3,42 kg wood chips (40%) |
2,12 kg wood pellets (8%) |
2,4 kg straw (15%) |
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