11 9 The development of viable lignocellulosic-biofuel industries in the United States will require dependable delivery of supplies of feedstocks logistically available to conversion facilities. The selection of feedstocks ultimately will vary with geogra p­­ hical region across the United States. Dedicated bioenergy crops as sources of lignocellulose are likely to be most productive in the southern regions of the United States due to more abundant sunlight and longer growing seasons. O f course, dedicated bioenergy crops in the southwest must tolerate heat and drought, whereas species grown along the Gulf Coast must tolerate heat as well as variable soil moisture and variable soil-oxygen environments associated with different soil types. Dedicated energy crops for the panhandle of T exas and the Midwest will have shorter growing seasons and will need to be more cold tolerant.


### Crop Selection E conomically viable bioenergy-production facilities will require the appropriate selection of crops to ensure year-round availability of feedstock tailored to local climatic, biotic, and soil stresses. F rom a facility manager’s perspective, a complement of crops that allows year-round delivery of feedstock is paramount and, in this regard, is a contrast to regional monoculture systems that are predominant across much of the nation. F urthermore, bio

mass-crop production and management systems must be developed and tailored to each crop and each climatic region to ensure optimal biomass yields. These actions will require a coordinated effort focused on the development of multiple crop-production systems. 

# High-Tonnage Dedicated Energy Crops: The Potential of Sorghum and Energy Cane

Bill F . McCutchen and R obert V

. A vant Jr. Texas AgriLife Research College Station, TX



### David Baltensperger Texas A&M University College Station, TX12 0 R eshaping A merican A griculture to Meet its Biofuel and Biopolymer R oles The primary limiting factors for sustainable lignocellulosic- and biodiesel-fuel indus

tries in the United States are the reliable supply of economically priced feedstocks and the logistics of the harvesting, transport, storage, and overall supply chain. The current model for ethanol production from feed grains can be significantly augmented by the production technologies associated with high-yielding biomass crops, specifically sorghum, switchgrass, and energy cane. A key to sustaining and enhancing growth of the biofuels industry (combined with environmentally sustainable production systems) is the devel

opment of adequate acreage of dedicated feedstocks that produce high tonnage at prices that give producers and biorefineries acceptable profit margins. 

### Sorghum Sorghum offers considerable potential as a dedicated lignocellulosic biomass crop. The broad genetic diversity within the genus provides plant breeders the opportunity to de

velop biomass sorghum adapted to diverse climates with low, and possibly high, water availability, to include many different biotic and abiotic stresses. The development and production of photoperiod-sensitive sorghum will facilitate full-season production of biomass, to maximize yield for significant tonnage. Yields in the range of 1 5 dry tons per acre have been achieved on the T exas A &M F arm at College Station. E ven greater yields are anticipated under optimum conditions. Sorghum is of particular interest because it is the only annual, high-tonnage dedicated energy crop with the potential for being produced on large acreages, and it already has an existing agronomic ( e.g. seed) infrastructure. 

### Energy Cane Sugarcane, particularly the high-tonnage varieties ( i.e. energy cane), offers the greatest potential as a bioenergy crop for production in much of E ast T exas and the US Gulf Coast. Sugarcane has a proven track record of producing exceptionally high yields on heavy clay soils in which many other crops are unable to grow well. F or the past century, sugarcane varieties have been developed primarily for accumulation of high levels of sucrose. Com

mercially grown varieties can produce up to 40 dry tons per acre under optimal conditions. Biomass productivity probably could be increased even more if sucrose accumulation were no longer a constraint on breeding programs. Several other grass species have the potential to produce exceptional biomass yields, including Arundo, Miscanthus
, and Miscanthus crossed with sugarcane hybrids, known as Miscane and developed at T exas A &M A griLife. The seasonal diversity of biomass production that these species afford may play an important role in ensuring year-round production of feedstock supplies.


### Land-Use Changes The development of sorghum, energy cane, and other biomass crops may require changes in land-use management but should include rotational cropping systems. R esearch is req

uisite for identifying which of these species will perform best in each climatic region of the United States. This will include detailed studies on a number of agronomic characteristics necessary to identify optimal performing inbred and hybrid varieties, as well as the iden

-121 tification of best management practices. E ach region will require a management package tailored to its unique climatic and soils environments and its slate of biotic stresses. Unlike most conventional production systems, biomass cropping systems must be developed that incorporate appropriate combinations of high-tonnage crops that provide year-round delivery of feedstock at a price and volume that meet the production and financial needs of both the producers and the owners of bioenergy production facilities.


### Biomass Priorities The US Department of E nergy has suggested that the delivered cost of biomass to con

version facilities should be in the range of $30 to $40 per dry ton, to hold down the cost of biofuels. However, the production costs for dedicated energy crops range from $50 to $ 1 00+ per dry ton. The keys to reducing delivered cost will be high-tonnage crops and highly efficient production systems, but delivering large amounts of biomass (hundreds of millions of tons per year) at rates lower than $50 per dry ton will be difficult; farmers simply will not produce biomass feedstock for returns below what they can receive for current crops. F or agriculture to deliver significant, sustainable supplies of lignocellulose from crop sources, a thorough evaluation must be conducted to assure producer buy-in. T

able 1 shows a comparison of various delivered biomass costs.



### T able 

### 1. P roduc t ivi t y and cos t of delivered biomass


### . Residue Woody Switch- Forage Bioenergy biomass grass sorghum sorghum
Biomass per acre per year (dry tons) 2 5–0 8 0 5–0 5– 10 8 0 5–0 8

0 5–0 10

5–0 1 2

E stimated cost delivered to converter $ 6 0 + $50–75 $0–90+ $5 $50–0 $50–7 5 $0–90+ $5 $50–0 $ 6 0–90 + $5 $50–0 $ 65 $50–0 6 (per dry ton)

A

successful, sustainable biofuels economy must be based on diverse biomass resources available consistently throughout the year that will include appropriate storage measures. F orest resources, municipal solid waste, urban construction residue, energy cane, switch

grass, energy sorghums, and algae will be important in a diversified portfolio. T o develop this bioenergy portfolio several guiding principles should apply:

• protect the environment,

• assure economic viability,

• minimize water demand,

• minimize competition for food and feed production, and

• minimize disruptions in the marketplace.

McCutchen, A vant, and Baltensperger122 R eshaping A merican A griculture to Meet its Biofuel and Biopolymer R oles 

### T

exas A griLife R esearch T

exas A griLife R esearch has funding exceeding $ 26 million for more than thirty projects supported by the T exas legislature, the federal government, and corporate partners to develop sustainable bioenergy production that addresses diverse feedstock development, agronomic practices, logistics, production modeling, and conversion technologies, as well as economic, policy and environmental assessments. Key faculty members with inter

national experience in plant science, agronomy, agricultural engineering, biochemistry, biophysics, and economics are leading these research initiatives.



### Since A pril 2 00 6 , Bill McCutchen has served as associate director of T exas A griLife R esearch, within the T exas A &M University System. His mission includes developing and implementing strategic research initiatives across the biological sciences, with facilitation of university-industry relationships. He also assists in developing intellectual property from R &D. He earned BS and MS degrees in entomology from T exas A &M, where he was recipient of the Distinguished Graduate Student R esearch A ward in 1 989. He received his PhD from the University of California Davis in 1 993, having won the Young Scientist A ward from the A merican Chemical Society in 1 99 2

. Dr. McCutchen joined T exas A griLife R esearch from DuPont A griculture & N utrition, where his responsibilities included crop-protection R &D across agricultural biotechnology and chemistry programs. He was named a DuPont R

esearch F ellow in 2 00 2 . In 2 007, he was presented with the Henry W allace A gricultural R evolution Impact A ward, DuPont’s and Pioneer’s most prestigious research award for agriculture. He has more than thirty patents and pending

-­ patent applications. McCutchen provided the vision, innovation, and leadership that propelled a new generation of dual-herbicide-tolerant transgenic crops—corn, soybean, and cotton—and a new-generation weed-management solution, trade

marked as O ptimum G AT T M



### .