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Composition of Wood


Wood’s Substances

Wood is composed of dry matter and water. Dry matter is the part of wood that does not contain water. The dry matter contains a certain amount of elements: 50 % carbon (C), 41 % oxygen (O), and 6 % hydrogen (H). The rest are different substances, mainly nitrogen (N), sulphur (S) and ash.  

Because there are many vaporizable elements, such as oxygen and hydrogen in the wood’s dry matter, the flame is long. Hydrogen burns with a high flame, ash with a short flame.

  • carbon (C) 50 %
  • oxygen (O) 41 %
  • hydrogen (H) 6 %
  • other substances

Wood’s Flammable Substances

Carbon and hydrogen are the substances in wood which burn and give out heat energy. Of the flammable substances the share of carbon is 88 %, and that of hydrogen 12 %. The oxygen and ash that wood contains do not give out heat energy. Ash contains sand and clay which the tree has absorbed from soil.

  • carbon (C) 88 %
  • hydrogen (H) 12 %

Heat Distribution

Hydrogen and carbon produce heat in the burning process. The heat energy produced by these elements is divided so that carbon gives out 67 % of the energy, and hydrogen 33 %.

Hydrogen is relatively more efficient as a heat producer. The share of hydrogen of the wood’s flammable substances is only 12 %, and of the total wood only 6 %. Still, hydrogen produces about third of the total heat energy of the wood.

Heat distribution of the flammable substances

  • carbon (C) 67 %
  • hydrogen (H) 33 %



EUBCEBiofuels-2015Bioenergia 2015Agritechnica 2015RENEXPO BucharestACERC
Power & Energy Africa 2015 Kenya
Power & Energy Africa 2015 in Dar-es-Salaam, Tanzania.RENEXPO® BiHtcbiomass2015: Technology for the Bioeconomy