Woody Bioenergy Crops for the Southeastern United States
Woody Bioenergy Crops for the Southeastern United States Mark 1 Coleman and Keith 2 Kline 1 USDA-Forest Service, 241 Gateway Drive, Aiken, SC 29803; coleman. m@earthlink. net 2 Oak Ridge National Lab, Oak Ridge, TN 37831 -6038; klinekl@ornl. gov Introduction Short-Rotation Woody Crops Production Systems Biomass is an important alternative energy resource that can offset greenhouse gas emissions from fossil fuels, provide crop options for marginal farmlands and improve rural economies. Forests cover nearly 60% of the southeastern US. Woody energy crops include fast growing native species that have shown large productivity gains from improved genetic resources and cultural practices. Woody feedstocks offer many advantages compared to other types of biomass and options for conversion to various types of energy (liquid fuels, electric power, and other bio-products) are possible. Here we summarize accumulated learning from southeastern practitioners’ experiences with woody cropping systems and discuss examples of many of the most promising woody energy crop species. • Southern Pines • Hardwoods • Coppice Pine Process Benefits • Adaptability of species to regional areas • Lower ash content • Year-round availability • Stable, consistent feedstock supply • High density products • Easy to store • Easy to handle • Mix with the other woody feedstocks Sampling soil sweetgum Hardwood Enhanced Pine Production Potential • Poplar, Eucalyptus, Sycamore, Sweetgum • Large growth potential • Forest operations equipment • Genomic resources • Relatively low input crops • Genomic Resources • Multiple market options Environmental Benefits • Protect soil, water and air • • • quality Sustainable production systems Sequester carbon Create wildlife habitat Increase diversity Ø landscape Ø biological Ø soil microbial and mesofauna Improve productivity of marginal farmland Energy Conversion of Woody Biomass • Combustion boilers • Gasification Ø Synthesis gas: 20% H 2, 20% C 0, 5% CH 3 • Pyrolysis: Bio-oil & Char Ø Bio-Oil is a crude containing high value chemicals • Biofuels • Biochemical processes requiring: Ø Cellulosic enzymes Ø Distillation energy • Thermochemical process Ø Catalytic conversion of synthesis gas Ø Alcohols and diesel Cuttings for planting • Elite genetic selections • Adapted to wide range of sites • Variety of selective herbicides • Developed operations Advantages of Using Woody Crops for Bioenergy • Provide diversity of feedstocks • Location and geographic distributive advantages Coppice After cut Willow • Vegetative propagation • High density planting (6000 trees/acre) • Cut every 3 to 4 years • Replanting required after 25 years • Efficient harvesting equipment • Experience to date has been with northern temperate culture • Willow native to southern US, merits research • Sycamore coppice yields twice that of seedlings Late in year 2 Year 3 Harvester Eucalyptus Range Positive Response to culture treatments Herbicides Orlando, FL • 2 ½-year-old Eucalyptus Grandis • Growth Rates of 2 to 3” diameter/year • 7. 2 dry tons/acre/year Bainbridge, GA • 4. 5 -year-old • survived > 150 freezing nights • 1. 7 – 2. 7 diameter per year • 7 dry tons/acre/year Fertilization Practitioners Survey Eucalyptus E. amplifolia E. viminalis E. nova-anglica E. macarthurii E. camphora • Numerous forestry practitioners were interviewed about the potential for woody energy crops in the southeastern US. • In total, over 250 person-years of southeastern forestry research experience. • Each was asked to name potential crop species, management requirements, expected productivity rates and factors impacting yields. • The table summarizes results. Table 1. Summary of practitioner survey of potential for woody energy crop species for southeastern US. Woody Plantation Crop Expected Production (dry Mg/hectare-yr) Low Avg. High Production Costs ($dry/Mg) Cottonwood and Hybrid Poplars Sycamore 6 9 12 15 -95 • Broad genetic resources 7 9 11 15 -95 • Rapid early growth Sweetgum 4 6 8 15 -65 Eucalyptus 18 22 25 15 -65 Hybrid Aspen 9 10 12 no data • Broad site requirement • Disease resistance • Broad site requirement • High growth • Broad site requirement Loblolly Pine 8 9 10 10 -40 Advantages • Operational infrastructure • Broad genetic resources Sycamore Disadvantages • Narrow site requirements • Disease susceptible • Relatively slow growth • Restricted by frost • Undeveloped genetic material Pine & Sweetgum trials - year 12 Conclusions • Several woody crops offer high growth potential in the southeastern US under proper silviculture but costs for hardwood plantations may be prohibitive. • Loblolly pine has the most developed infrastructure. It can be grown at lower cost and at higher rates on the largest variety of sites. • Bottomland hardwoods such as cottonwood and sycamore are limited by site and soil requirements and disease. • Eucalyptus out performs other species in biomass output/year but is limited by frost to Florida and a narrow band along the gulf coast. • Coppice crops offer potential to rapidly expand production but require research to identify the best species and cultivars for a given locale and to develop appropriate cultural practices and operational equipment. • Extensive natural hardwood and mixed forest resources in the southeast also merit further study for potential contributions to bioenergy.
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