The nature of emissions from wood and charcoal fired ovens
There are two different sources of fumes from solid-fuel cooking appliances – the cooking of the food and the combustion of the fuel.
Cooking is a complex process involving several different types of reaction including oxidation, pyrolysis and the Maillard reaction which is associated with browning. Cooking also leads to phase-changes, where solids become liquids and liquids become gases. Phase-changes differ from reactions in that they are reversible e.g. if animal fat turns from the solid phase to the liquid phase due to an increase in temperature, it will revert back to the solid phase when it cools down.The type of fumes released during cooking also depends on what is being cooked, with fats, proteins and carbohydrates emitting different chemical compounds.
The fumes produced from combustion also vary depending on what type of fuel is used. Wood or wood pellets largely consist of carbon and hydrogen, and therefore can theoretically be burned to produce only carbon dioxide and water. However, in reality they also produce toxic substances which are the result of incomplete combustion such as carbon monoxide and wood-tar compounds.
Charcoal differs from wood in that the wood-tar has been driven off during manufacture, however there is still a significant problem with emissions of carbon monoxide.