Potential of Loblolly Pine (Pinus taeda L.) as a Biofuel Feedstock

Woody biomass can be an alternative energy source in the Southeastern U.S. due to its wide availability and ability to grow on marginal sites. Loblolly pine, as the most productive forest tree species in the region, is of logical interest for biofuel production. Volume yield was analyzed across nine test series to assess genetic variation in profitability of young-age biomass harvesting and the effects of family on volume production in young plantations. At age eight, the top 10% of families averaged 17.2% more volume growth than the local mixture of first-generation families. Full-sib family mean heritabilities for height and volume were moderate to high at all ages (age eight broad-sense full-sib family mean heritabilities ranged from 0.61 to 0.93), reaffirming that gain in biomass yield is possible through selection. Economic analysis of the data indicated that biomass-only harvests would not be profitable at current prices. If biomass prices increased in response to the development of a bioenergy industry, young-age biomass harvesting may become profitable, but soil expectation values would not be maximized at very young ages.;Loblolly pine biomass presents a challenge for producing ethanol; enzymatic hydrolysis of polysaccharides from softwood pulp typically produces lower yields of fermentable sugars relative to hardwood pulp. Since many chemical and physical wood properties in loblolly pine are subject to genetic control, variation in some of these properties will likely affect the efficiency of ethanol production.;Wood samples were collected from a series of 8-year-old clonal trials in South Carolina and Georgia. Clonal varieties of loblolly pine were divided into groups using a cluster analysis based on near-infrared (NIR) spectra of ground wood samples from multiple individual trees, or ramets, of each of the clonal genotypes. These clusters were used to select a subset of clones for chemical analysis that would encompass most of the natural variation in the clonal population. Wood samples from three pooled ramets of each clone in this set were tested, using enzymatic hydrolysis after a dilute acid or alkaline pretreatment to produce sugar yields for each clone. The lowest yielding treatment, a dilute acid pretreatment followed by enzymatic hydrolysis using 20 filter paper units (FPU) of enzyme, produced an average of 0.21 mg sugar/mg wood. The highest yielding treatment, an alkaline pretreatment followed by enzymatic hydrolysis using 40 FPU as well as mechanical beating, produced 0.52 mg sugar/mg wood. NIR clustering and a number of wet chemistry-determined wood properties were significant predictors of sugar yield. Economic analysis of these sugar yields using a biorefinery process model indicates that ethanol from loblolly biomass is not cost-competitive with gasoline. However, if oil prices go up or bioconversion technology improves, making ethanol from biomass may become a profitable venture.;In order to characterize genetic variation in sugar yield from loblolly pine wood, 300 powdered wood samples from a clonal test series were tested using a high-throughput enzymatic hydrolysis process with a dilute acid pretreatment. The mean sugar yield was 0.21 mg sugar/mg wood, and ranged from 0.10 to 0.29 mg sugar/mg wood. Clonal genetic values indicate that yields can be improved ∼4-5% over the mean through the use of the best clones. Clone mean repeatability for sugar yields ranged from 0.29 to 0.44. For NIR-predicted lignin and cellulose contents, clone mean repeatabilities were 0.81 and 0.78, respectively. A calibration model was developed to predict sugar yields using NIR spectra, but the overall R2 was relatively low (= 0.30). The ratio of performance to deviation (RPD) was 1.54 for the calibration model and indicates that the model may at best be accurate enough for a rough initial screening of families.