Abstract
Meeting the goals set by the Energy Independence and Security Act requires evaluation of all potential feedstock sources including arid and semi-arid portions of the western United States (U.S.). The objective of this study was to assess the lignocellulosic feedstock potential in stream buffers of the inland Pacific Northwest. A 3-yr (2010–2012) experiment was conducted at two sites within each of the three precipitation zones (low, mid, and high). At each site, barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), alfalfa (Medicago sativa L., cultivar Ladak), tall wheatgrass (Agropyron elongatum Podp. cultivar Alkar) (TWG), and a mix of alfalfa and tall wheatgrass (MIX) were planted in a randomized complete block experimental design. Productivity followed precipitation; in the high and mid precipitation zones, the MIX and TWG treatments showed potential production of 3,079 ± 262 l ha−1 and 3,062 ± 235 l ha−1. Productivity in the low zone was inadequate or unreliable as a source of feedstocks. A geographic information system was then used to identify the area available for stream buffers with soil resources that matched the experimental results within each precipitation zone. In 3.7 × 106 ha of dryland cropland, 44 656 ha (1.5%) available within the mid and high precipitation zones is capable of producing 147 million liters of ethanol. This potential contribution is 0.3% of the lignocellulosic ethanol production expected by the year 2022. Though not a substantial contribution, the added benefit of producing energy for on-farm consumption might provide an additional incentive for landowners and managers to install conservation buffers.
Highlights
Commercial scale production of lignocellulosic ethanol was expected to begin in 2014,3 east of the 100th meridian.3 Research and development have concentrated there because of abundant precipitation (!510 mm) per year, fertile soils, highly productive plant communities, and an abundant supply of raw materials
Whereas productive stands of C4 grasses can be grown on millions of hectares east of the 100th meridian including on marginally productive land,11 C3 grass productivity is relatively low across the intermountain west, in land enrolled in various conservation reserve programs
We estimated the areal extent on which these feedstocks could be grown and potential ethanol production based on the potential buffer areas defined by the range productivity mapped in the county level surveys produced by the United States Department of Agriculture–Natural Resource Conservation Service (NRCS)
Summary
Commercial scale production of lignocellulosic ethanol was expected to begin in 2014,3 east of the 100th meridian. Research and development have concentrated there because of abundant precipitation (!510 mm) per year, fertile soils, highly productive plant communities, and an abundant supply of raw materials.. With a Mediterranean climate characterized by fall, winter, and spring precipitations with cool temperatures followed by dry, hot summers, the conditions are ideal for C3 perennial and annual small grain (SG) grasses These conditions, combined with low mean minimum temperatures (8–10 C) during active growth, are limiting for the C4 grasses, e.g., switchgrass (Panicum virgatum L.) or Miscanthus (Miscanthus sp.) typically considered for lignocellulosic feedstock.. Whereas productive stands of C4 grasses can be grown on millions of hectares east of the 100th meridian including on marginally productive land, C3 grass productivity is relatively low across the intermountain west, in land enrolled in various conservation reserve programs These former croplands have soils that are either drought or saline affected, sometimes shallow and rocky, and are often difficult to harvest because of steep terrain.
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