Hackberry can be used as firewood, but it's not considered one of the best options. It burns relatively well, but it has a lower heat value compared to hardwoods like oak or hickory. Additionally, hackberry may produce more creosote buildup in your chimney, which can be a fire hazard if not properly maintained. If you have access to better firewood options, it's advisable to use those instead of Hackberry for heating purposes.