A black and white hull, or seed shell, encases sunflower seeds, a nutritious snack grown in the center of the bright yellow flower. In addition to food for humans and birds, sunflower byproducts include cooking oil, biodiesel fuel and medicine. Construction and agriculture industries make use of sunflower hulls rather than discarding them. Using a natural, renewable resource such as sunflower seed shells has a lower impact on the environment than depleting slow-forming resources to serve the same purpose.
Sunflower seed shells are allelopathic, which means that they produce a chemical that inhibits the growth of other plants. This property makes sunflower seed shells well-suited for use as mulch in gardens and flower beds because of their ability to suppress weeds. If you have a sunflower seed bird feeder, you no doubt have a stockpile of discarded hulls around the feeder. Add a layer of the seeds around your plants to prevent weed growth, leaving a few inches around plant stalks so the shells don't also inhibit the growth of your flowers. This same property, however, means that sunflower seed shells are not proper candidates for a compost pile. Organic matter in compost piles should break down to support plant growth rather than inhibit growth.
Sunflower seed shells have made their way into the construction trade in the form of Dakota Burl, a natural-fiber wood paneling made from discarded sunflower shells. The wood panels feature a swirled mixture of light and dark colors -- the same colors commonly found in a sunflower shell. The wood presents an environmentally friendly alternative to other wood products because the shells are renewable, recycled waste products instead of wood produced from ancient, harvested trees. The panels, available in 4-by-8-foot sheets that vary in thickness from 1/2 inch, 3/4 inch and 1 inch, are intended for both horizontal and vertical use. Workers cut, sand, stain and paint Dakota Burl in the same manner as other wood products. Common applications include wall paneling, cabinetry, furniture and even award plaques.
Sunflower seed shells provide roughage in feed for ruminants, including cattle and sheep. The hulls are comprised of ash, crude protein, lipid material, reducing sugars and carbohydrates. Although low in protein and nutritional value, the high fiber and carbohydrate content of the hulls make them well-suited for animal feed when mixed with ingredients with higher nutritional value. The hulls absorb liquid ingredients in feed and serve as a filler ingredient. Hulls must be finely ground in the feed for easier digestion. Grind your own hulls for feed if you have a surplus of sunflower seed shells, or sell them to a local ruminant feed manufacturer.
With a heat value of 19.2 megajoules per kilogram, sunflower seed shells are commonly used as a fuel source. Burn the hulls by themselves or pressed into fuel logs with other wood waste products. Renewable resources, such as sunflower hulls, have less impact on the environment than burning wood logs and are generally more affordable than heating with fossil fuels. For example, Barnesville High School in Minnesota uses sunflower hulls to heat the entire school. At the time of publication, the school uses between 450 and 600 tons of sunflower pellets in a single heating season.