Switchgrass Biofuel Production on Reclaimed Surface Mines: I. Soil Quality and Dry Matter Yield

Abstract

Growing food crops for biofuel on productive agricultural lands may become less viable as requirements to feed a growing human population increase. This has increased interest in growing cellulosic biofuel feedstocks on marginal lands. Switchgrass (Panicum virgatum L.), a warm-season perennial, is a viable bioenergy crop candidate because it produces high yields on marginal lands under low fertility conditions. In other studies, switchgrass dry matter (DM) yields on marginal croplands varied from 5.0 to 10.0 Mg ha −1 annually. West Virginia contains immense areas of reclaimed surface mined lands that could support a switchgrass-based biofuel industry, but yield data on these lands are lacking. Field experiments were established in 2008 to determine yields of three switchgrass cultivars on two West Virginia mine sites. One site reclaimed with topsoil and municipal sludge produced biomass yields of 19.0 Mg DM ha −1 for Cave-inRock switchgrass after the sixth year, almost double the varieties Shawnee and Carthage, at 10.0 and 5.7 Mg ha −1 , respectively. Switchgrass yields on another site with no topsoil were 1.0 Mg ha −1 after the sixth year, with little variation among cultivars. A second experiment was conducted at two other mine sites with a layer of topsoil over gray overburden. Cavein-Rock was seeded with fertilizer applications of 0, 34, and 68 kg N-P 2 O 5 -K 2 O ha −1 . After the third year, the no fertilizer treatment averaged biomass yields of 0.3 Mg ha −1 , while responses to the other two rates averaged 1.1 and 2.0 Mg ha −1 , respectively. Fertilization significantly increased yields on reclaimed mine soils. Where mine soil fertility was good, yields were similar to those reported on agricultural soils in the Northeastern USA.

Switchgrass and Giant Miscanthus Biomass and Theoretical Ethanol Production from Reclaimed Mine Lands

“…Switchgrass and giant miscanthus (hereafter, miscanthus) are warm-season (C 4 ) perennial grasses with promising biofuel production capabilities due to their productivity on marginal land such as reclaimed mine lands [14][15][16][17][18][19][20]. This is consistent with the emerging view that cellulosic bioenergy feedstock production should be based on perennials grown on marginal lands that are unsuitable for annual cropping [9,15,21,22].…”

“…On marginal land, annual yields with < 67 kg N ha −1 have ranged from 2.0 to 19.0 Mg DM ha −1 for switchgrass [5,6,11,15,16,49,54,55]. On fertile WV mine soils, DM production in the seventh year of growth was 10.0 and 19.0 Mg DM ha −1 , respectively, for switchgrass cultivars Shawnee and Cave-In-Rock [14]. No published studies have reported miscanthus yields on reclaimed mine land in the eastern USA.…”

“…Another potential agricultural use for reclaimed lands in this region is the production of dedicated bioenergy feedstocks for transportation fuels and for direct combustion. Several studies have shown high yields for switchgrass grown on reclaimed mine lands in this region [14,18,19,24]. Studies in Europe and the USA have shown miscanthus to be a promising cellulosic bioenergy crop candidate because of its capacity to produce yields double that of the current Bmodel^biofuel crop, switchgrass [25][26][27][28].…”

Soil Quality and Region Influence Performance and Ranking of Switchgrass Genotypes

“…In this context, marginal lands are those that fail to meet local minimum thresholds for economic production of food or feed crops (Shortall, 2013;Richards et al, 2014). For switchgrass, this could include dryland production on nonirrigated pivot corners (Uden et al, 2013), reclaimed surface mines (Brown et al, 2016), buffer strips surrounding sensitive surface waters (Hernandez-Santana et al, 2013;Porter et al, 2015), and highly erosive soils (Hassan et al, 2017). Low-input production conditions will also require the elimination or reduction of N fertilizer, the most expensive of all input factors (Perrin et al, 2008).…”

Assessment of Miscanthus Yield Potential from Strip-Mined Lands (SML) and Its Impacts on Stream Water Quality

“…The experimental studies on the cultivation of miscanthus in SML have also demonstrated that the biomass yield varied widely from 4.9 to 21 dry Mg ha −1 due to the variations in the management/agronomic practices, climate, and soil based on the recently established (3-4 years) miscanthus stands [16]. Similarly, switchgrass yields from SML also varied widely within the experimental plots due to the soil, climate, and land management practices [18]. Therefore, it is important to accommodate these variations while predicting biomass yield potential in a large study area/region.…”