Russell W Jessup* | ||
Department of Soil and Crop Sciences, Texas A&M University, College Station, USA | ||
Corresponding Author : | Russell W Jessup Department of Soil and Crop Sciences Texas A&M University, College Station, USA Tel: +979-315-4242 E-mail: rjessup@tamu.edu |
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Received May 10, 2013; Accepted May 13, 2013; Published May 18, 2013 | ||
Citation: Jessup RW (2013) Seeded-Yet-Sterile’ Perennial Biofuel Feedstocks. Adv Crop Sci Tech 1:e102. doi:10.4172/2329-8863.1000e102 | ||
Copyright: © 2013 Jessup RW. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. | ||
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Acceptance and deployment of leading candidate cellulosic energy crops has been significantly inhibited by their lack of providing both inexpensive seeded establishment options and high first-year biomass production in perennial feedstocks with mitigated risk of crop invasiveness. Pearl Millet-Napier grass (‘PMN’; Pennisetum glaucum R. Br. x P. purpureum Schumach) and King grass (‘KG’; P. purpureum x P. glaucum), in comparison, are perennial biomass crops with immense potential to combine both the high yields of tropical perennial grasses such as energy cane (Saccharum spp.) and the integrated agronomics of large-seeded annual grasses such as sorghum (S. bicolor [L.] Moench). PMN and KG are further unique among energy grasses as ‘seeded-yetsterile’ (SYS) feedstocks, in which fertile parents allow seeded production of hybrids that are subsequently sterile in biomass production fields [1,2]. PMN yields can equal or exceed that of sugarcane in tropical environments (20 Mg ha-1) [3] and more than double that of switch grass (Panicum virgatum L.) in semiarid environments (10-15 Mg ha-1) [1,4]. PMN seeds are comparatively large, and hybrid seed production can approach that of commercial forage sorghum [5]. PMN therefore provide comparatively inexpensive seed units, with seed:feedstock production acre ratios (2-400:1; direct seeded) versus energy cane (10:1; vegetative billets), switchgrass (40:1; broadcast seed), or M. x giganteus (10:1; vegetative rhizomes). Hybrid PMN and KG are polycultures, reducing risks of crop failure and environmental impacts due to monoculture. The presence of a common subgenome further provides a mechanism for capturing heterosis in PMN and KG hybrids [6]. Previous evidence of climbing legume intercrops’ capacity to provide surplus nitrogen and increased overall biomass yields in napier grass [7,8] indicate a similar potential as a renewable source of nitrogen for PMN and KG. Within the genus Pennisetum, PMN and KG have several closely-related, apomictic species that provide potential to introgress this valuable trait [9]. Advantages of PMN and KG can be summarized upon comparison with current leading candidate energy grass feedstocks for desirable traits in biofuel ideotypes (Table 1). | |
PMN and KG possess a diverse natural range of carbohydrate composition [10,11], providing advantages towards optimizing biofuel yields. Biomass fractions not utilized by conversion platforms subsequently offer opportunities for biorefining high-value coproducts. Napier grass, for example, possesses the highest leaf protein content among perennial grasses [12] and offers potential for largescale production of plant protein-derived bioplastics [13]. Plant-based bioplastics have been commercially developed utilizing geneticallymodified crops [14], and similar platforms based on non-transgenic plants would offer alternative technologies with vastly reduced developmental and regulatory costs. Further, incomplete hydrolysis derivatives of lignocellulosic material are common and provide a further process-based platform for production of xylo- (‘XOS’) & cellooligisaccharides (‘COS’) with utility as functional foods, prebiotics, feed additives, and specialty chemicals [15]. XOS and COS commodity markets are expanding rapidly, providing additional economic incentives for PMN and KG producers and positive health impacts for society [16]. | |
Through their highly efficient use of water and nutrients [17], perennial grasses such as PMN and KG are particularly promising crops with which the more than 1.1 billion acres of marginal, globally abandoned agricultural lands [18] could be brought into biomass production [19,20]. Such innovative application of perennial grasses in land use systems would enhance: 1) erosion mitigation, soil restoration, and carbon sequestration [21,22], 2) wildlife habitat [23], and 3) conservation agricultural practices [24]. As a result of such endeavors, sustainable strategies for biofuel systems with high energetic efficiencies, low food security trade-off risks, and significant environmental conservation impacts could be achieved. PMN and KG, moreover, therefore offer seed companies enhanced product ownership and control, growers inexpensive crop establishment costs and high biomass yields, feedstock customers economically viable value chains, co-product customers high-value commodities, and governments ecologically-optimized systems with little or no risk of crop invasiveness. | |
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