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Home , Softwood, Wood fuel

facts & figures

by James E. Houck and Brian N. Eagle or Softwood? H ow much could a wo o d c h u ck chuck ? It depends on whether he’s chucking hard wood or softwo o d .

he relative merits of various from the various species within the Some people argue that wood are the subject of broad classifications of hardwood and burn cleaner that softwoods, i.e., pro- T considerable lore, old wives’ softwood. However, in general, hard- duce less air emissions and less cre- tales and personal preferences. Hard- wood provides longer burning , osote, while others claim the opposite. wood and softwood are the two major is denser, dries (seasons) slower, and Perhaps both claims are true, with hard- divisions in wood types. The term contains more total heat per volume wood performing better in some appli- hardwood is used synonymously with () but less total heat per unit of ances and scenarios, and mass compared to softwood. vice-versa. Or perhaps the difference in Because hardwood seasons slower, opinions is due to differences in mois- it is often burned when it is wetter ture contents commonly encountered than softwood. Softwood has a higher because of the different drying rates. wood fires are bright and clear, heat content per unit of mass because “Depending on the type of wood If the logs are kept a year. it contains more resin than hardwood, and the climate, wood seasoning (air ’s only good, they say, and resin has about twice the heat con- drying) can take from three to 12 If for long it’s laid away. tent as the other two most common months for . The optimal and logs burn too fast, components making up wood – cellu- moisture content in terms of minimiz- Blaze up bright and do not last. lose and . Softwoods make bet- ing particulate emissions during wood wood burns like a church yard mold, ter kindling and, because of resin is between 20 and 30 per- Ev’n the very flames are cold. pockets, tend to crackle more than cent. If the moisture content is too Poplar gives a bitter , hardwoods, which makes softwoods high, an appreciable amount of Fills your eyes and makes you choke. valued by some for their aesthetic use is necessary to vaporize the water, Apple wood will scent your room in . reducing the heating value of the wood With incense like perfume. and , if dry and old, Keep away the winter cold. But ash wood wet and ash wood dry A king shall warm his slippers by.

— Anonymous

wood from deciduous , i.e., trees that, with some uncommon exceptions such as western live oak species, lose their leaves every autumn. Oak, maple, and birch are examples of deciduous trees. The term softwood is used synony- mously with wood from coniferous trees, i.e., evergreens. (A few do lose their needles and by defini- tion are not “evergreen.”) Pine, , and are examples of conifers. Another way to look at it is that hardwood trees generally have leaves and softwood trees generally have needles and cones. Not all hard- are really harder than all soft- woods, and vice-versa. There is considerable variability in the burning characteristics among wood Cordwood pile in .

JANUARY 2007 HEARTH & HOME 4 9 hearth facts & figures as well as decreasing combustion effi- he easiest and best for either a or ciency, which in turn increases par- f i replace is achieved with a mixture of softwoods ticulate smoke formation. T “On the other hand, wood with a mois- and hardwoods – combining softwoods for easy ture content that is too low burns too igniting with hardwoods for longer burning and fast; that (can) cause oxygen-limited con- good coaling qualities. ditions, which lead to incomplete com- bustion with increased wood smoke Percent Hardwood and Softwood Use particulate formation.” (E n v i r o n m e n t a l Science & Technology, 1998, 32, 13-22.) for Residential Wood Fuel by Selected States Rapid combustion caused by dry wood can also cause organic vapors U.S. CENSUS DIVISION STATE HARDWOOD S O F T W O O D to be volatilized and escape before New England Connecticut 87% 13% they are completely combusted. A western softwood, , Maine 44% 56% is specified for the U.S. EPA certifi- Massachusetts 75% 25% cation test of wood heaters for low emissions; it is also used for the UL New Hampshire 64% 36% safety standard for solid-fuel room Rhode Island 84% 16% heaters and factory-built fireplaces. Vermont 71% 29% Would results be different if a hard- wood were used? Middle Atlantic New Jersey 70% 30% While some people are very choosy New York 82% 18% about the type of wood they burn, on Pennsylvania 93% 7% average what is most readily available ends up as fuel. For that reason hard- South Atlantic Delaware 86% 14% wood use is dominant in most of the Florida 68% 32% East and Midwest, while hardwood and Georgia 74% 26% softwood usage is mixed in the West. The two most common species Maryland 86% 14% groups with similar availability for res- North Carolina 75% 25% idential fuel in the are pine and oak. When the usual prefer- South Carolina 81% 19% ence for hardwood is taken into con- Virginia 68% 32% sideration the balance tips toward oak. West Virginia 75% 25% White oak, northern red oak, black oak and chestnut oak are the most common East South Central Alabama 84% 16% oak species used for fuel. Among , Kentucky 77% 23% loblolly pine, ponderosa pine, eastern Mississippi 83% 17% white pine and shortleaf pine are the most common species used for fuel. Tennessee 90% 10% Interestingly, red maple is the sin- East North Central Indiana 98% 2% gle most common wood species used Michigan 97% 3% for fuel in the East due to its wide geo- graphic range. Similarly, Douglas fir is Wisconsin 96% 4% a commonly used fuel in the West due West South Central Arkansas 84% 16% to its wide geographic range there. In addition to the , pines, red maple Louisiana 84% 16% and Douglas fir, yellow poplar and sugar West North Central Kansas 99% 1% maple are also in the top 10 species Minnesota 98% 2% used for fuel. Many minor hardwood species, when taken in aggregate along Missouri 99% 1% with oak and maple, make hardwood, Nebraska 96% 4% as a group, the most common fuel type North Dakota 96% 4% in the United States. South Dakota 80% 20% Mountain Colorado 27% 73% James E. Houck and Brian N. Eagle can Pacific 69% 31% be reached at OMNI Environmental Services; e-mail [email protected] and [email protected], Data from U.S. Service and reports to Tennessee Valley phone (503) 643-3788. Authority and U.S. EPA.

5 0 HEARTH & HOME JANUARY 2007