US researchers develop hybrid sweetgum tree to boost bioenergy production

Researchers at the University of Georgia have crossed American sweetgum tree with its Chinese cousin, creating hybrid sweetgum trees that have a potential to boost bioenergy production.

The hybrid sweetgums have a better growth rate and denser wood than native varieties and can produce fibre year-round.

Sweetgum trees thrive under diverse conditions, grow as fast as pine trees and provide the type of fibre desired by paper and bioenergy producers.

Harvesting mature sweetgums can often be too costly or even ill-advised because they typically grow on the edges of swamps and in river bottoms, which are often inaccessible during the wet winter months.

The hybrid sweetgum trees have enormous potential for the production of bioenergy and paper, said Scott Merkle, a professor in UGA's Warnell School of Forestry and Natural Resources.

"The very best hybrid sweetgums are being propagated to produce elite varieties, so that landowners will be able to plant trees that produce more biomass in a shorter time than the top-rated native sweetgum trees," he said.

The new hybrid varieties are already being sold commercially by ArborGen, which began offering rooted cutting seedlings of the new varieties in 2015 after extensive field testing of the trees produced from tissue cultures in Merkle's lab in Georgia, South Carolinam and Alabama.

The tests showed these new hybrids outperform either of the parent species by 20% in both growth rate and wood density.

The new hybrid has been well accepted by forest landowners, particularly in the western areas of the Southeast US, including Texas, Arkansas, and Oklahoma.

ArborGen officials say they produced 300,000 seedlings this year and sold out before the hybrid could even be marketed.

"We were testing the viability of this tree in the marketplace and are pleased to say it was received even better than expected," said John Pait, VP of sales and marketing for ArborGen.

"We are now taking orders for next year with anticipation that we will see the same, if not greater demand, than this year."

A number of other hybrid trees have been produced for forest crops, including hybrid poplars, Eucalyptus and pines, but they have not been popular in the forestry industry.

Merkle said the timing for a new hardwood hybrid lines up with an uptick in prices for hardwood timber.

Referred to as the “wood basket of the world” the southeastern US is home to a thriving forest industry that has typically relied on softwoods like pine trees to supply the bioenergy, paper, timber, and other wood products manufacturers.

Georgia is also a leading exporter of wood pellets to countries using bioenergy in power production.