Biomass Energy

Source: http://bioenergy.ornl.gov/papers/misc/energy_conv.html

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 is 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
    • Energy content of wood fuel (air dry, 20% moisture) = about 15 GJ/t
  • Energy content of agricultural residues (range due to moisture content) = 10-17 GJ/t
  • Metric tonne charcoal = 30 GJ (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) = 26.7 GJ/t = 21.1 MJ/liter. HHV for ethanol = 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 , equivalent to 1,700 kWh. 7.2 barrels oil are equivalent to one tonne of oil (metric) = 42-45 GJ.
  • Gasoline:LHV= 32 MJ/liter. HHV =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 = 36.4 MJ/liter or 42.8 GJ/t
    • petro-diesel density (average) = 0.84
  • Note that the energy content (heating value) of petroleum products per unit mass is fairly constant, but their density differs significantly
  • Metric tonne coal = 27-30 GJ (bituminous/anthracite); 15-19 GJ (lignite/sub-bituminous)
    • 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 = 38.3 MJ/m3; LHV = 34.6 MJ/m3

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
  • 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 residues

Locally grown biomass

The PollutionTaxAssociation (See http://pollutiontaxassociation.org.uk) has asked the Fishergate Environmenta lPanel to look into the possibilities of enhancing the carbon sequestration of locally grown biomass when used as a heat source for public buildings. Biomas (such as cropped wood coppice) can actually be Carbon Negative because the roots keep growing when the wood is cropped as fuel.

Topics to discuss:

  • What are the economic parameters for users and growers?
  • Can waste biomass and cropped biomass be combined?
  • How does biomass use fit into a regional framework?
  • Is wood burning combined heat and power viable?
  • Is carbon capture from flues gasses economic on a small scale?
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