Showing papers by "Patrick D. Keyser published in 2014"
TL;DR: In this article, the authors investigated the characteristics of switchgrass biochar produced via carbonization and explored its potential use as a solid fuel in existing power plants that were built to accommodate coal and peat.
Abstract: Switchgrass is a high yielding, low-input intensive, native perennial grass that has been promoted as a major second-generation bioenergy crop. Raw switchgrass is not a readily acceptable feedstock in existing power plants that were built to accommodate coal and peat. The objective of this research was to elucidate some of the characteristics of switchgrass biochar produced via carbonization and to explore its potential use as a solid fuel. Samples were carbonized in a batch reactor under reactor temperatures of 300, 350 and 400 °C for 1, 2 and 3 h residence times. Biochar mass yield and volatile solids decreased from 82.6% to 35.2% and from 72.1% to 43.9%, respectively, by increasing carbonization temperatures from 300 °C to 400 °C and residence times from 1 h to 3 h. Conversely, biochar heating value (HV) and fixed carbon content increased from 17.6 MJ kg−1 to 21.9 MJ kg−1 and from 22.5% to 44.9%, respectively, under the same conditions. A biomass discoloration index (BDI) was created to quantify changes in biochar colors as affected by the two tested parameters. The maximum BDI of 77% was achieved at a carbonization temperature of 400 °C and a residence time of 3 h. The use of this index could be expanded to quantify biochar characteristics as affected by thermochemical treatments. Carbonized biochar could be considered a high quality solid fuel based on its energy content.
132 citations
TL;DR: Overall, the results suggest that harvests within 10–20 m 2 ha −1 RBA yield the largest increases in Cerulean Warblers, benefit additional disturbance-dependent species, and may retain closed-canopy species but at reduced levels.
31 citations
TL;DR: In this article, the authors aim at characterizing switchgrass (Panicum virgatum L.)-biochar morphology, estimating water-holding capacity under increasing ratios of char: soil, and determining nutrient profile variation as a function of pyrolysis conversion methodologies.
Abstract: Biochars form recalcitrant carbon and increase water and nutrient retention in soils; however, the magnitude is contingent upon production conditions and thermo-chemical conversion processes. Herein we aim at (i) characterizing switchgrass (Panicum virgatum L.)-biochar morphology, (ii) estimating water-holding capacity under increasing ratios of char: soil; and, (iii) determining nutrient profile variation as a function of pyrolysis conversion methodologies (i.e. continuous, auger pyrolysis system versus batch pyrolysis systems) for terminal use as a soil amendment. Auger system chars produced at 600°C had the greatest lignin portion by weight among the biochars produced from the continuous system. On the other hand, a batch pyrolysis system (400 °C – 3h) yielded biochar with 73.10% lignin (12 fold increases), indicating higher recalcitrance, whereas lower production temperatures (400 °C) yielded greater hemicellulose (i.e. greater mineralization promoting substrate). Under both pyrolysis methods, increasing biochar soil application rates resulted in linear decreases in bulk density (g cm-3). Increases in auger-char (400 °C) applications increased soil water-holding capacities; however, application rates of >2 Mt ha-1 are required. Pyrolysis batch chars did not influence water-holding abilities (P>0.05). Biochar macro and micronutrients increased, as the pyrolysis temperature increased in the auger system from 400 to 600 °C, and the residence time increased in the batch pyrolysis system from 1 to 3 h. Conversely, nitrogen levels tended to decrease under the two previously mentioned conditions. Consequently, not all chars are inherently equal, in that varying operation systems, residence times, and production conditions greatly affect uses as a soil amendment and overall rate of efficacy.
28 citations
TL;DR: Despite evidence of reliable signaling in this species, it is found that there are no strong relationships between plumage and reproductive performance, potentially because factors other than individual differences more strongly influenced fecundity.
Abstract: Colorful plumage traits in birds may convey multiple, redundant, or unreliable messages about an individual. Plumage may reliably convey information about disparate qualities such as age, condition, and parental ability because discrete tracts of feathers may cause individuals to incur different intrinsic or extrinsic costs. Few studies have examined the information content of plumage in a species that inhabits forest canopies, a habitat with unique light environments and selective pressures. We investigated the information content of four plumage patches (blue-green crown and rump, tail white, and black breast band) in a canopy-dwelling species, the Cerulean Warbler (Setophaga cerulea), in relation to age, condition, provisioning, and reproduction. We found that older males displayed wider breast bands, greater tail white, and crown and rump feathers with greater blue-green (435–534 nm) chroma and hue than males in their first potential breeding season. In turn, older birds were in better condit...
15 citations
TL;DR: Although NWSG did not show strong responses to season of burn, Switchgrass cover appeared to be increased by spring burns when compared to the control plots, and forb cover was sparse throughout the study, therefore, in high-rainfall environments, soil disturbance may be necessary to reduce grass cover and stimulate forb cover in dense stands of planted N WSG.
Abstract: State and federal agencies have promoted native grass/forb plantings to increase and enhance habitat for Colinus virginianus (Northern Bobwhite). However, many plantings have resulted in dense stands of grass that do not provide suitable structure for Northern Bobwhite. Prescribed fire is an important tool for managing succession in southeastern grasslands, and previous research has suggested that the timing of prescribed bums can influence plant community composition and structure. We examined the response of planted, native warmseason grasses (NWSG) at three sites in Tennessee to the timing of annual burns conducted 2008–2011 during March, April, May, and September. The grasses included Andropogon gerardii (Big Bluestem), Sorghastrum nutans (Indiangrass), Panicum virgatum (Switchgrass), Schizachyrium scoparium (Little Bluestem), and Bouteloua curtipendula (Sideoats Grama). We monitored vegetation response once each summer during July or August). We used mixedmodel ANOVAs to analyze the effect o...
9 citations