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  Greenhouse Gases From Small-Scale Combustion Devices in Developing Countries: Charcoal-Making Kilns in Thailand (EPA/600/R-99/109) December 1999

Airborne emissions from charcoal-making kilns commonly used in the developing world were measured during typical operating conditions. Five types of kilns were tested: brick beehive, mud beehive, earth mound, rice husk mound, and single (oil) drum.

The experiments were conducted in Thailand, which produces per year about 7.2 million of the estimated 26–100 million tons of charcoal produced globally. Emission factors for the production of charcoal were determined for the direct greenhouse gases carbon dioxide, methane, and nitrous oxide; the indirect greenhouse gases carbon monoxide and total nonmethane hydrocarbons; and total suspended particulates. Charcoal production efficiency (yield) and charcoal and fuelwood composition were determined as well.

As is generally known to be the case for charcoal making, the conversion of wood carbon to charcoal carbon was fairly inefficient, ranging from a low of 48 percent for the earth mound kilns to a maximum of 57 percent for the brick beehive kilns. Average emission factors, expressed as grams of pollutant per kilogram of charcoal produced, for the three runs of each of the five kiln types ranged from:

  • 970 to 1600 for carbon dioxide
  • 13 to 58 for methane
  • 0.017 to 0.084 for nitrous oxide
  • 110 to 340 for carbon monoxide
  • 9 to 95 for total nonmethane hydrocarbons
  • 0.7 to 4.2 for total suspended particulates

A substantial fraction of the original fuel carbon was lost as carbon dioxide and other products of incomplete combustion (PIC). On average, fuelwood carbon is diverted approximately as follows: 52 percent to charcoal, 24 percent to carbon dioxide, and 10 percent to PIC. Thus, due to the higher global warming potentials of PIC relative to carbon dioxide, such kilns can produce rather large net greenhouse gas emissions, even when the wood is harvested renewably.


Susan Thorneloe

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