Eucalyptus wood, often found in warmer climates, presents a nuanced answer to the question of its suitability as firewood. The wood itself possesses properties that make it a powerful heat source, similar to traditional hardwoods. However, its effectiveness is entirely dependent on meticulous preparation and careful management.
The Primary Challenge: Moisture and Curing
Freshly cut eucalyptus is notoriously difficult to burn due to its exceptionally high moisture content. Many species, such as River Red Gum, can have a green moisture content ranging from 45% to over 50%. This water must be driven out before the wood can combust efficiently, a process called curing or seasoning. Burning wood with such a high water content means a significant portion of the fire’s energy is wasted simply boiling the internal water away, resulting in a fire that hisses, sputters, and produces excessive smoke.
Achieving a suitable moisture content, ideally below 25%, often requires a protracted seasoning period. While many common firewoods dry in six to nine months, eucalyptus frequently requires 12 to 18 months, and sometimes up to two years, depending on the climate and storage conditions. The wood should be split when green because its dense, twisted grain becomes extremely hard and difficult to process once it begins to dry.
Logs should be stacked off the ground in a single row and covered on top to protect them from rain while allowing air to circulate freely around the sides. Failing to complete this seasoning phase guarantees a poor, low-heat fire that smolders more than it burns.
Heat Output and Density
Once the extensive curing process is complete, eucalyptus wood delivers exceptional performance as a high-quality fuel. Its potential for generating heat is directly tied to its high density, a characteristic it shares with top-tier hardwoods. Wood density determines the amount of combustible material packed into a given volume. Eucalyptus ranks among the highest in density for common firewoods, which translates into a superior British Thermal Unit (BTU) output per cord.
Many eucalyptus species can yield approximately 34.5 million BTUs per cord, placing it just below the highest-ranking woods like Live Oak. This high energy content means the wood burns with intense, sustained heat, making it highly effective for heating homes and maintaining a fire overnight. The density allows the logs to hold heat and form a long-lasting bed of coals.
Safety Concerns and Management
The composition that gives eucalyptus its high heat output also introduces specific safety considerations. The wood contains a high concentration of volatile oils and sap, which become powerful fuel sources during combustion. While these oils contribute to the intense heat, they also increase the production of creosote, a highly flammable residue that condenses on the inner walls of a chimney or flue. Excessive creosote buildup is a significant fire hazard and is the primary cause of chimney fires.
The risk is elevated when burning wood at low temperatures or with restricted airflow, which can happen if the eucalyptus is not fully cured or the fire is intentionally dampened. Therefore, a dedicated maintenance schedule is necessary, requiring more frequent professional chimney inspections and cleaning than might be needed for other woods. The volatile nature of the oils also causes eucalyptus to pop, spark, and throw embers with greater frequency than many other firewoods.
This characteristic is particularly hazardous in open fireplaces where sparks can easily land on nearby flooring or rugs. Using a sturdy, fine-mesh spark screen is a necessary precaution to contain flying embers. Some users manage the intensity and sparking by mixing eucalyptus with a less dense, lower-oil wood to moderate the overall rate and temperature of the burn.