Thermochemical biomass conversion

Heat breaks biomass down into gas, oil or char.

Capture · Bioenergy · No. 42

• Capture
• Output: Gas, oil, char

Heat dry wood to about 500 C for a second or two without oxygen, and up to 75% of it turns liquid.

Chart: Illustration: Thermochemical biomass conversion

Where it comes from

Chart: Map of where it comes from

Starve hot biomass of oxygen and it falls apart: fast pyrolysis at about 500 C gives mostly oil, slow heating at 400 C mostly char, gasification at 800 C mostly gas.

Three things to know

1. Bio-oil is not crude oil: it is about 25% water and holds roughly 40% of fuel oil's energy by weight.
2. Torrefaction roasts biomass at 200-350 C into a dry, water-resistant bio-coal that keeps about 82% of its mass.
3. Making one tonne of Fischer-Tropsch fuel takes about 5.6-7.1 t of crop or forest residue.

The journey

1. 1 BiomassWood, crop residues, sludge or algae
2. 2 HeatingLittle or no oxygen, 200-800 C
3. 3 SplittingGas, oil and char in varying shares
4. 4 UpgradingTars cleaned; hydrogen strips oxygen from oils
5. 5 ProductsPower, heating oil, bio-coal, jet fuel

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