This is cut and pasted from a guide put out by the State of Nebraska. The formatting is confusing, but read the row of headings and you can figure it out. Maybe South Carolina's State Forestry Service has one for you. I couldn't find SweetGum. What's it most similar to? Maple? Sycamore?

Good luck. -- Marie

Heating With Wood
I. Species Characteristics and Volumes
Heat content, burning characteristics and overall quality of woods commonly burned in Nebraska, as well as information on buying firewood, are included here.

Mike Kuhns, State Extension Forester
Tom Schmidt, Forester

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 Species Characteristics
 Firewood Volume
 Buying Firewood
 For More Information

Wood is a source of heat currently used by many Nebraskans, and more firewood likely will be burned as the cost of other energy sources, such as gas and electricity, rises. In order to use firewood effectively, an understanding of species' characteristics and firewood volumes is needed.
Species Characteristics
Firewood from different species or types of trees varies widely in heat content, burning characteristics and overall quality. Table I below presents several important burning characteristics for most species used in Nebraska.
Green weight is the weight of a cord of freshly cut wood before drying. Dry weight is the weight of a cord after air drying. Green firewood may contain 50 percent or more water by weight. Green wood produces less heat because heat must be used to boil off this water before combustion can occur. Green wood also produces more smoke and creosote than dry wood. Firewood always should be purchased dry or allowed to dry before burning.
Dry wood may cost more than green wood because it produces more heat and is easier to handle.
A wood's dry weight per volume, or density, is important because denser or heavier wood contains more heat per volume. Osage-orange is the densest firewood available in Nebraska. It contains almost twice the heat by volume as cottonwood, one of our lightest woods. It is best to buy or gather dense woods such as oak, ash or mulberry.
Hardwoods, or woods from broadleaved trees, tend to be denser than softwoods, or woods from conifers. Some firewood dealers sell "mixed hardwood" firewood. This may or may not be desirable, depending on the proportion of low-density hardwoods, such as cottonwood, that are included.
The amount of heat per cord of dry wood is presented in Table I. Heat content is shown as a percent of dry green ash, a common Nebraska firewood. Values above 100 signify a higher heat content than green ash and values below 100 a lower heat content.
Table I also contains information on other characteristics that determine firewood quality. Ease of splitting is important because larger pieces of wood usually must be split for good drying and burning.
Fragrance and tendency to smoke and spark are most important when wood is burned in a fireplace. Woods that spark or pop can throw embers out of an open fireplace and cause a fire danger. Conifers tend to do this more because of their high resin content.
Woods that form coals are good to use in wood stoves because they allow a fire to be carried overnight effectively.
TABLE I. Firewood Facts
Species Weight (lbs./Cord) Heat/ Cord (1,000 BTU'S) % Green Ash Ease of Splitting Smoke Sparks Coals Fragrance Overall Quality
Green Dry
Apple 4850 3888 27.0 135 Medium Low Few Good Excellent Excellent
Ash, Green 4184 2880 20.0 100 Easy Low Few Good Slight Excellent
Ash, White 3952 3472 24.2 121 Medium Low Few Good Slight Excellent
Basswood (Linden) 4404 1984 13.8 69 Easy Medium Few Poor Good Fair
Birch, Paper 4312 2992 20.8 104 Medium Medium Few Good Slight Fair
Boxelder 3589 2632 18.3 92 Difficult Medium Few Poor Slight Fair
Buckeye, Ohio 4210 1984 13.8 69 Medium Low Few Poor Slight Fair
Catalpa 4560 2360 16.4 82 Difficult Medium Few Good Bad Fair
Cherry, Black 3696 2928 20.4 102 Easy Low Few Excellent Excellent Good
Coffeetree, Kentucky 3872 3112 21.6 108 Medium Low Few Good Good Good
Cottonwood 4640 2272 15.8 79 Easy Medium Few Good Slight Fair
Douglas-Fir 3319 2970 20.7 103 Easy High Few Fair Slight Good
Elm, American 4456 2872 20.0 100 Difficult Medium Few Excellent Good Fair
Elm, Red 4800 3112 21.6 108 Easy Medium Few Excellent Good Good
Elm, Siberian 3800 3020 20.9 105 Difficult Medium Few Good Fair Fair
Fir, Concolor 3585 2104 14.6 73 Easy Medium Few Poor Slight Fair
Hackberry 3984 3048 21.2 106 Easy Low Few Good Slight Good
Hickory, Bitternut 5032 3832 26.7 134 Medium Low Few Excellent Excellent Excellent
Hickory, Shagbark 5104 3952 27.5 138 Difficult Low Few Excellent Excellent Excellent
Honeylocust 4640 3832 26.7 133 Easy Low Few Excellent Slight Excellent
Ironwood 4590 4016 27.9 140 Difficult Medium Few Excellent Slight Excellent
Juniper, Rocky Mountain 3535 3150 21.8 109 Medium Medium Many Poor Excellent Fair
Locust, Black 4616 4016 27.9 140 Difficult Low Few Excellent Slight Excellent
Maple, Other 4685 3680 25.5 128 Easy Low Few Excellent Good Excellent
Maple, Silver 3904 2752 19.0 95 Medium Low Few Excellent Good Fair
Mulberry 4712 3712 25.8 129 Easy Medium Many Excellent Good Excellent
Oak, Bur 4960 3768 26.2 131 Easy Low Few Excellent Good Excellent
Oak, Red 4888 3528 24.6 123 Medium Low Few Excellent Good Excellent
Oak, White 5573 4200 29.1 146 Medium Low Few Excellent Good Excellent
Osage-Orange 5120 4728 32.9 165 Easy Low Many Excellent Excellent Excellent
Pine, Eastern White 2780 2250 15.6 78 Medium Medium Few Poor Good Fair
Pine, Jack 3200 2488 17.2 86 Difficult Low Many Poor Good Fair
Pine, Ponderosa 3600 2336 16.2 81 Easy Medium Many Fair Good Fair
Redcedar, Eastern 2950 2632 18.2 91 Medium Medium Many Poor Excellent Fair
Spruce 2800 2240 15.5 78 Easy Medium Many Poor Slight Fair
Sycamore 5096 2808 19.5 98 Difficult Medium Few Good Slight Good
Walnut, Black 4584 3192 22.2 111 Easy Low Few Good Good Excellent
Willow 4320 2540 17.6 88 Easy Low Few Poor Slight Poor
Firewood Volume
Though firewood dry weight is important for determining heat content, firewood is normally bought and sold by volume.

Figure 1. STANDARD CORD, Total Volume = 128 cu. ft.

Figure 2. FACE CORD, Total Volume = 32 to 48 cu. ft. (Depends on piece length.)

Figure 3. PICKUP LOAD, Approximate Total Volume = 64 cu. ft.
The most common unit of firewood volume is the cord, also known as a standard or full cord. A cord is an evenly stacked pile containing 128 cubic feet of wood and air space.
Though a cord can be piled in any shape, a standard cord is generally thought of as a stack of wood four feet tall, eight feet long, and four feet deep (Figure 1). To figure the number of cords in another size or shape pile, determine the pile's cubic foot volume and divide by 128. A randomly piled stack of wood generally will contain more air and less wood than one neatly piled.
Some dealers sell wood by the face cord or short cord (Figure 2). A face cord is a stack of wood four feet high, eight feet long, and as deep as the pieces are long. Pieces are commonly 12 to 18 inches long, so a face cord may contain 32 to 48 cubic feet of wood and air.
Another common firewood measure is the pickup load (Figure 3). This is an imprecise but common measure. A full-size pickup with a standard bed can hold about 1/2 of a full cord, or 64 cubic feet, when loaded even with the top of the bed. Small pickups hold much less. Random loading will decrease this amount further.
A randomly piled stack or pickup load of wood will contain more air and less wood than one neatly stacked. Crooked, small diameter, and knotty or branchy pieces also reduce the amount of wood in a pile.
Buying Firewood
Species, volume, dryness and need for splitting should be considered when buying firewood. This NebGuide and other publications provide basic information you need to be an informed buyer, but knowing your dealer is the best way to ensure that you are getting what you are paying for.

I've done it. Not nearly so good as oak, hickory, or black locust, but it will burn - once it's seasoned. Be aware, though that it tends to 'pop & snap' - throwing lots of sparks, so if you're burning it in an open-front fireplace, you'd better have a good screen AND be very vigilant about sparks that might make it through the screen.
Larger pieces don't split very well - I've buried several wedges up in big twisty-grained chunks of sweetgum, and had to burn them just to retrieve the wedges.

We have a ton of sweet gum around here but everyone has told us not to burn sweet gum or pine (other than lighter pine) in your fireplace/furnace because of the resins that burn & build up in your pipes. When we've ran out of some of the other stuff we have used a piece or two of the gum, & it does do alot of "popping".

Kathy, I burn absolutely every kind of tree imaginable. The key to burning wood for heat is to be certain it is seasoned: to me that means at least cut and stacked for one year. I do burn sweet gum annually as well as pine (not treated) and as long as it is seasoned I have not had any problems with creosote accumulating in the chimney nor in my cumbustor.

Do what you will, but be careful to screw your chimney pipes together in case you have combustable material in the chimney; it can ignite and "explode" which is the highest cause of house fires.