Environmental Engineering Reference
In-Depth Information
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Large-scale biofuels production, in the long run, will require other resources, includ-
ing dedicated energy crops. Dedicated feedstocks are perennial grasses and trees
grown as crops specifically to provide the required raw materials to bioenergy pro-
ducers. A steady supply of low-cost, uniform, and consistent-quality biomass feed-
stock will be critical for the economic viability of cellulosic ethanol production.
During the late 1980s, the Department of Energy sponsored research on perennial
herbaceous (grassy) biomass crops, particularly switchgrass, which is considered a
model energy crop because of its many perceived advantages: (1) native to North
America, (2) high biomass yield per acre, (3) wide regional coverage, and (4) adapt-
ability to marginal land conditions. An extensive research program on switchgrass
in the 1990s generated a wealth of information on high-yielding varieties, regional
adaptability, and management practices. Preliminary field trials show that the eco-
nomic viability of switchgrass cultivation depends critically on the initial establish-
ment success. During this phase, seed dormancy and seedling sensitivity to soil and
weed conditions require that recommended practices be closely followed by growers.
Viable yields require fertilization rates at about half the average for corn.
Switchgrass (
Panicum virgatum
) is a hardy, deep-rooted, perennial, rhizomatous,
warm-season grass native to North America. It is believed to be most suitable for
cultivation in marginal lands, low-moisture lands, and lands with lower opportunity
costs such as pastures, including lands under the Conservation Reserve Program
(CRP) where the federal government pays landowners annual rent for keeping land
out of production (McLaughlin and Kzos, 2005). Additionally, a large amount of
highly erodible land in the Corn Belt is unsuitable for straw or stover removal but is
potentially viable for dedicated energy crops such as switchgrass. Factors favoring
adoption of switchgrass include selection of suitable lands, environmental benefits
(carbon balances, improved soil nutrients and quality), and the use of existing hay
production techniques to grow the crop. Where switchgrass is grown on CRP lands,
payments help to offset production costs. Factors discouraging switchgrass adoption
include no possibility for crop rotation; farmers' risk aversion for producing a new
crop because of lack of information, skills, and know-how; potential conflict with
on-farm and off-farm scheduling activities; and a lack of compatibility with long-
term land tenure. Overall, production budget and delivery cost assessments suggest
that switchgrass is a high-cost crop (undercurrent technology and price conditions)
and may not compete with established crops, except in areas with low opportunity
costs (e.g., pasture land, marginal lands).
Substantial variability is apparent in the economics of switchgrass production
and assessments of production budgets and delivered costs. Factors at play include
methods for storage and handling, transport distances, yields, and types of land
used (cropland vs. grassland). When delivered costs of switchgrass are translated
into break-even prices (compared with conventional crops), it becomes apparent that
cellulosic ethanol or biopower plants would have to offer relatively high prices for
switchgrass to induce farmer to grow it (Rinehart, 2006). However, the economics
of switchgrass could improve if growers benefited from CRP payments and other
payments tied to environmental services (such as carbon credits). In the long run,
