Biomass and solid fuels

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Biomass boilers
         For warm water

  • BIO
    Automated, pellet, wood chips,

  • Farmer
    Automated, pellet,wood chips,
    wood logs, multifuel

  • Automat
    Self-loading, automated,
    pellet, wood chips, multifuel

Steam boilers    

  • Low pressure steam (0,5bar) automated boilers for biomass, pellet, wood chips, multifuel        

Coal boilers

  • Automated brown coal boilers
    For warm water or low pressure steam

Fuel feeder systems

The fuel spectrum for the CARBOROBOT boilers

The CARBOROBOT is a multifuel technique boiler with a wide fuel spectrum, from the different quality biomass materials to the fossile coal to .

Renewable biofuels (biomass) use is usually in the form of combustible solids, either wood, the biogenic portion of municipal solid waste or combustible field crops. Field crops may be grown specifically for combustion or may be used for other purposes, and the processed plant waste then used for combustion.

Fossil fuel is a fuel formed from the remains of organic materials. Fossil fuels include coal, oil, and natural gas.

Major traded forms of solid biofuels
EN ISO 17225 part 1 is a very general standard that explains how to classify the biomass to be used for energy purposes and lists the major traded forms of solid biofuels, see table.

Fuel name
Common preparation method
Whole tree
< 500mm
No preparation or delimbed
Wood chips
BIO / Farmer
5 -100mm
Cutting with sharp tools
Hog fuel
BIO / Farmer
Crushing with blunt tools
Log wood/firewood
100 -1000mm
Cutting with sharp tools
Can be shredded or unshredded
Lengthways oriented & bound
Fuel powder
< 1mm
Cutting with sharp tools
Planing with sharp tools
> 25mm
Mechanical compression
BIO / Farmer
< 25mm
Mechanical compression
Small square
0.1m 3
Compressed and bound to squares
Big square
3,7m 3
Compressed and bound to squares
Round bales
2,1m 3
Compressed and bound to cylinders
Chopped straw
10 -200mm
Chopped during harvesting or before combustion
Grain or seed
BIO / Farmer
No preparation or drying except for process operations necessary for storage for cereal grain
Fruit stones or kernel
BIO / Farmer
5 - 15mm
No preparation or pressing and extraction by chemicals
Fibre cake
Prepared from fibrous waste by dewatering
BIO = Classic, Automat, Steam type CARBOROBOT boilers


Wood pellet, Agripellet

The pellet is biomass renewable material. The term pelletting means the compressing of agricultural and forestry materials. Pellets are compressed products manufactured on circular cell roller presses, ranging from 6 to 25 millimetres in size. More condensed pellets used for heating range from 6 and 12 millimetres in size.

Further informations Pellet

Wood chips

Wood chip fuel is increasingly seen as an important element in reducing our CO2 emissions. Wood provides the greatest amount of renewable energy across Europe, though this is over looked as most is used in small heating projects. The wood chip good for the fuel mixing.

Further informations Wood chip


Wood is now recognised as good value, at least as cost effective as other renewables. The traditional form of wood fuel which can be easily stored, air dried and burnt in a wide range of appliances from open fires to modern automated boilers.

Further informations Wood

Corn, grain

The corn and many other grains, too: wheat, rice, sorghums, millets, oats, rye, barley, rye, triticale, buckwheat, fonio, cherry pits, olive pits and grains is what fuels our stoves. Fuel mixing

Further informations Corn & grain

Fuel mixing (Co-firing)

The fuel mixing is the most important use direction of CARBOROBOT boilers. This special designed boilers are able to burn mixes of different biomass and fossile fuels. multi-fuel combustion.

Further informations Fuel mixing

Residues & waste

Agricultural crop residues and waste are the plant parts, primarily stalks and leaves, not removed from the fields with the primary food or fiber product. Examples include corn stover (stalks, leaves, husks, and cobs); wheat straw; and rice straw. . Fuel mixing

Further informations Residues & waste


Coal is fossil fuel. Coal is classified as a nonrenewable energy source because it takes millions of years to form. Coal is cheap and high energy dense fuel. In CARBOROBOT may use alone or ideal carrier for the biomass co-firing in mixes. The coal industry has found several ways to reduce sulfur, nitrogen oxides, and other impurities from coal. They have found more effective ways of cleaning coal before it leaves the mine, and coal companies look for low-sulfur coal to mne.

Further informations Coal

The ash melting

Straw contain potassium and sodium compounds. These alkali compounds are present in all annual crops and crop residues in particular. During combustion, alkali combines with silica and causes slagging and fouling problems in conventional combustion equipment designed for burning wood at higher temperatures. Volatile alkali also lowers the fusion temperature of ash: in conventional combustion equipment having furnace gas exit temperatures above 800C, combustion of agricultural residue causes slagging.

Further informations Ash

Fuel characteristics and autonomy of the boiler

Conversion factors

This is a quick-reference list of conversion factors used by the BIOenergy Feedstock Development Programs at ORNL. It was compiled from a wide range of sources, and is designed to be concise and convenient rather than all-inclusive. Most conversion factors and data are given to only 3 significant figures. Users are encouraged to consult other original sources for independent verification of these numbers. The following are links to Web sites we have found useful (many universities worldwide maintain good guid+es and conversion calculator pages):

Energy contents are expressed here as Lower Heating Value (LHV) unless otherwise stated (this is closest to the actual energy yield in most cases). Higher Heating Value (HHV, including condensation of combustion products) is greater by between 5% (in the case of coal) and 10% (for natural gas), depending mainly on the hydrogen content of the fuel. For most biomass feedstocks this difference appears to be 6-7%. The appropriateness of using LHV or HHV when comparing fuels, calculating thermal efficiencies, etc. really depends upon the application. For stationary combustion where exhaust gases are cooled before discharging (e.g. power stations), HHV is more appropriate. Where no attempt is made to extract useful work from hot exhaust gases (e.g. motor vehicles), the LHV is more suitable. In practice, many European publications report LHV, whereas North American publications use HHV.

Energy units


  • 1.0 joule (J) = one Newton applied over a distance of one meter (= 1 kg m2/s2).
  • 1.0 joule = 0.239 calories (cal)
  • 1.0 calorie = 4.187 J
  • 1.0 gigajoule (GJ) = 109 joules = 0.948 million Btu = 239 million calories = 278 kWh
  • 1.0 British thermal unit (Btu) = 1055 joules (1.055 kJ)
  • 1.0 Quad = One quadrillion Btu (1015 Btu) = 1.055 exajoules (EJ), or approximately 172 million barrels of oil equivalent (boe)
  • 1000 Btu/lb = 2.33 gigajoules per tonne (GJ/t)
  • 1000 Btu/US gallon = 0.279 megajoules per liter (MJ/l)


  • 1.0 watt = 1.0 joule/second = 3.413 Btu/hr
  • 1.0 kilowatt (kW) = 3413 Btu/hr = 1.341 horsepower
  • 1.0 kilowatt-hour (kWh) = 3.6 MJ = 3413 Btu
  • 1.0 horsepower (hp) = 550 foot-pounds per second = 2545 Btu per hour = 745.7 watts = 0.746 kW

Energy Costs

  • $1.00 per million Btu = $0.948/GJ
  • $1.00/GJ = $1.055 per million Btu

Some common units of measure

  • 1.0 U.S. ton (short ton) = 2000 pounds
  • 1.0 imperial ton (long ton or shipping ton) = 2240 pounds
  • 1.0 metric tonne (tonne) = 1000 kilograms = 2205 pounds
  • 1.0 US gallon = 3.79 liter = 0.833 Imperial gallon
  • 1.0 imperial gallon = 4.55 liter = 1.20 US gallon
  • 1.0 liter = 0.264 US gallon = 0.220 imperial gallon
  • 1.0 US bushel = 0.0352 m3 = 0.97 UK bushel = 56 lb, 25 kg (corn or sorghum) = 60 lb, 27 kg (wheat or soybeans) = 40 lb, 18 kg (barley)

Areas and crop yields

  • 1.0 hectare = 10,000 m2 (an area 100 m x 100 m, or 328 x 328 ft) = 2.47 acres
  • 1.0 km2 = 100 hectares = 247 acres
  • 1.0 acre = 0.405 hectares
  • 1.0 US ton/acre = 2.24 t/ha
  • 1 metric tonne/hectare = 0.446 ton/acre
  • 100 g/m2 = 1.0 tonne/hectare = 892 lb/acre
    • for example, a "target" bioenergy crop yield might be: 5.0 US tons/acre (10,000 lb/acre) = 11.2 tonnes/hectare (1120 g/m2)

Biomass energy

  • Cord: a stack of wood comprising 128 cubic feet (3.62 m3); standard dimensions are 4 x 4 x 8 feet, including air space and bark. One cord contains approx. 1.2 U.S. tons (oven-dry) = 2400 pounds = 1089 kg
    • 1.0 metric tonne wood = 1.4 cubic meters (solid wood, not stacked)
    • Energy content of wood fuel (HHV, bone dry) = 18-22 GJ/t (7,600-9,600 Btu/lb)
    • Energy content of wood fuel (air dry, 20% moisture) = about 15 GJ/t (6,400 Btu/lb)
  • Energy content of agricultural residues (range due to moisture content) = 10-17 GJ/t (4,300-7,300 Btu/lb)
  • Metric tonne charcoal = 30 GJ (= 12,800 Btu/lb) (but usually derived from 6-12 t air-dry wood, i.e. 90-180 GJ original energy content)
  • Metric tonne ethanol = 7.94 petroleum barrels = 1262 liters
    • ethanol energy content (LHV) = 11,500 Btu/lb = 75,700 Btu/gallon = 26.7 GJ/t = 21.1 MJ/liter. HHV for ethanol = 84,000 Btu/gallon = 89 MJ/gallon = 23.4 MJ/liter
    • ethanol density (average) = 0.79 g/ml ( = metric tonnes/m3)
  • Metric tonne biodiesel = 37.8 GJ (33.3 - 35.7 MJ/liter)
    • biodiesel density (average) = 0.88 g/ml ( = metric tonnes/m3)

Fossil fuels

  • Barrel of oil equivalent (boe) = approx. 6.1 GJ (5.8 million Btu), equivalent to 1,700 kWh. "Petroleum barrel" is a liquid measure equal to 42 U.S. gallons (35 Imperial gallons or 159 liters); about 7.2 barrels oil are equivalent to one tonne of oil (metric) = 42-45 GJ.
  • Gasoline: US gallon = 115,000 Btu = 121 MJ = 32 MJ/liter (LHV). HHV = 125,000 Btu/gallon = 132 MJ/gallon = 35 MJ/liter
    • Metric tonne gasoline = 8.53 barrels = 1356 liter = 43.5 GJ/t (LHV); 47.3 GJ/t (HHV)
    • gasoline density (average) = 0.73 g/ml ( = metric tonnes/m3)
  • Petro-diesel = 130,500 Btu/gallon (36.4 MJ/liter or 42.8 GJ/t)
    • petro-diesel density (average) = 0.84 g/ml ( = metric tonnes/m3)
  • Note that the energy content (heating value) of petroleum products per unit mass is fairly constant, but their density differs significantly hence the energy content of a liter, gallon, etc. varies between gasoline, diesel, kerosene.
  • Metric tonne coal = 27-30 GJ (bituminous/anthracite); 15-19 GJ (lignite/sub-bituminous) (the above ranges are equivalent to 11,500-13,000 Btu/lb and 6,500-8,200 Btu/lb).
    • Note that the energy content (heating value) per unit mass varies greatly between different "ranks" of coal. "Typical" coal (rank not specified) usually means bituminous coal, the most common fuel for power plants (27 GJ/t).
  • Natural gas: HHV = 1027 Btu/ft3 = 38.3 MJ/m3; LHV = 930 Btu/ft3 = 34.6 MJ/m3
    • Therm (used for natural gas, methane) = 100,000 Btu (= 105.5 MJ)

Carbon content of fossil fuels and bioenergy feedstocks

  • coal (average) = 25.4 metric tonnes carbon per terajoule (TJ)
    • 1.0 metric tonne coal = 746 kg carbon
  • oil (average) = 19.9 metric tonnes carbon / TJ
  • 1.0 US gallon gasoline (0.833 Imperial gallon, 3.79 liter) = 2.42 kg carbon
  • 1.0 US gallon diesel/fuel oil (0.833 Imperial gallon, 3.79 liter) = 2.77 kg carbon
  • natural gas (methane) = 14.4 metric tonnes carbon / TJ
  • 1.0 cubic meter natural gas (methane) = 0.49 kg carbon
  • carbon content of bioenergy feedstocks: approx. 50% for woody crops or wood waste; approx. 45% for graminaceous (grass) crops or agricultural residue


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