Wood that has a moisture content of less than _____% burns hotter and cleaner than freshly cut wood.

Wood that has a moisture content of less than 20% burns hotter and cleaner than freshly cut wood due to the reduced amount of water present in the wood fibers. When wood has high moisture content, a significant amount of energy is used to evaporate the water before the wood can ignite and burn effectively. As the moisture content decreases, the energy utilized for drying the wood also decreases, leading to more efficient combustion. This results in a hotter fire and the production of less smoke and particulate matter, which contributes to cleaner burning.

Moisture content above this threshold can lead to inefficient burning, increased creosote buildup in chimneys, and more air pollution. Thus, the optimal burning efficiency is achieved with wood that has been seasoned to have a moisture content below 20%. This understanding is crucial for practices related to efficient wood burning, either in stoves or fireplaces, making it a key concept in fire safety and efficiency.