Burning Wood? Caring for the Earth?

As we have moved into the 21^st century, heating with wood has remained popular. Although, some things have changed: wood pellets replaced some “roundwood," stove designs and efficiency have changed, some of the early adopters, now 40 years older, are likely less committed to gathering their own fuel.

Unlike in the 1970s when we were by necessity looking for alternative heating sources to address oil scarcity, the discussion today increasingly is on living more gently on the earth. Evidence of climate change and burgeoning concerns about the long-term impacts of a carbon-based economy is fueling (no pun intended) a resurging interest in alternative energy sources. Among the mix of alternatives is biomass in whatever form (e.g., wood, grass, stover) we can find it. 

Carbon dioxide is one of the principal drivers of climate change. Since the beginning of the industrial revolution, data shows ever-increasing levels of carbon dioxide in our atmosphere, which holds in heat and is evidenced in unprecedented weather changes across the globe. Our reliance on fossil fuel resources underpins these changes in our atmosphere. By using coal, oil, and natural gas, we are returning ancient carbon to the atmosphere and earth's systems for capturing and again storing this carbon influx are not robust enough to address these emissions. Taking steps to reduce increases in atmospheric carbon is the pathway to stabilizing our climate. 

The contrast between using fossil fuels and their long-stored carbon and burning biomass has become a point of contention framed by a debate of long and short carbon cycles. The long cycle is what we are trying to address, which is essentially how do we recapture carbon released by using fossil fuels. The short cycle engages the idea that burning biomass, for example, is releasing “new carbon," that was recently stored. The argument is that this results in a “carbon neutral" cycle that does not increase atmospheric carbon because if it remained in the woods or in the fields, it would just decay and release carbon through that process. So, logically, it gets recaptured in the growth cycle, which is okay? 

Is it really that simple? Unfortunately, no. Among the many challenges of burning wood, there are three primary issues of concern. First, burning trees results in more carbon dioxide emission for a unit of energy output (e.g., BTUs). In fact, some smokestack emission tests show burning wood results in carbon emissions 2.5 times higher than natural gas and 30 percent higher than coal. Second, harvesting trees for fuel leads to more carbon release than if they remained in the forests to grow or, if they are dead, recycle carbon into the soil. Thirdly, there is a question of delay relating to the time-lag as new trees take time to establish and grow large enough to capture the capacity lost through harvesting. If you invest some time reading and learning more about burning wood, this is only the beginning of concerns; others relate to the reflective capacity of black carbon and other harmful gases released in biomass combustion.

While there are concerns about burning wood, individually, those who want to keep the home fires burning should attempt to reduce their potential impact by improving forests while being good environmental stewards. 

Make sure when you burn wood, you burn it efficiently. Those who burn wood know the mantra that dry wood burns best. Simply, wood cut, stacked, and covered, is the best and safest to burn. To properly prepare firewood In Pennsylvania, you should be getting ready to fill the woodshed for next year's season. It is important to cut, split, stack, and cover wood to reduce the moisture content into the range of 20 percent or lower to achieve efficient combustion, a process which takes between 6 months and 2 years depending upon species and moisture contents. For unseasoned wood to burn, the fire must drive off excess moisture as steam before pyrolysis, which is important for efficiency, can happen. That is, the best combustion occurs when there is a flame igniting volatile gases. A smoldering “lazy" fire is not efficient. 

When cutting firewood, choose your trees carefully. It is tempting to remove dead trees with the mistaken idea that they are dry, which is not the case. You can not shortcut the drying cycle with dead trees. As suggested earlier, dead trees decay slowly and return some carbon back into the forest soil for subsequent storage. Second, removing suppressed, crowded, or otherwise struggling trees can benefit those higher quality stems remaining, as they are released by the cutting of their competitors to increase their crown area and grow faster. This in part addresses the lag time as rapidly growing trees are efficient in capturing carbon. 

Finally, as you harvest firewood ensure your woodlot is regenerating. This is a real challenge in Pennsylvania. If you care about your woods and are looking towards its future, it is important to always work toward replacing trees with trees. This does not require planting; rather, think about leaving seed sources for important tree species, use tops and brush to protect seedlings from browse, create canopy openings to bring sunlight to the forest floor, control invasive and competitive plant species, and monitor deer. Again, the goal is to reduce the lag time for the carbon to be recaptured in the growing trees. 

If you burn wood for heating, consider steps to reduce your wood use. Invest in new technology – woodstove design and efficiency has improved much since the 1970s. Consider replacing your woodburner if it dates back to that time period. Second, insulate your house to reduce the amount of wood you need to gather. Insulation pays dividends every year and in all seasons. Gather your wood locally. Doing so limits the movement of some invasive insects (e.g., emerald ash borer, spotted lanternfly), and it also reduces fuel use as you harvest and move next year's fuel. And, finally, get your wood ready for next season now, so it has time to dry. 

The Pennsylvania Forest Stewardship Program provides publications on a variety of topics related to woodland management. For a list of publications, call 800-235-9473 (toll free), send an email to PrivateForests@psu.edu, or write to Forest Stewardship Program, The Pennsylvania State University, 416 Forest Resources Building, University Park, PA 16802. The Pennsylvania DCNR Bureau of Forestry, USDA Forest Service, Penn State Extension, and the Center for Private Forests at Penn State, in Partnership through Penn State's Department of Ecosystem Science and Management, sponsor the Forest Stewardship Program in Pennsylvania.

Written by Jim Finley, Professor Emeritus, Forest Resources Management, Center for Private Forests at Penn State