Search

Shrub willow (Salix spp.) is capable of producing commercially attractive amounts of biomass in short rotations, but harvesting costs and logistics remain a concern. There is a particular need for information about harvesting operations on larger, commercial short‐rotation woody crop systems. Another recent issue on commercial fields in northern New York is commercial growers conducting harvests during the growing season rather than the recommended dormant season when fields may be too wet to harvest. This study evaluated and modeled the in‐field performance of a cut‐and‐chip harvester for almost 700 wagonloads of chips operating in commercial willow fields in a wider array of crop and field conditions than have been previously reported. Analysis indicated that the time of harvest (leaf‐on or leaf‐off) and whether site conditions were wet or dry affected the harvester's material capacity. Mean material capacity was greatest for leaf‐off, dry conditions (71.8 Mg/hr) and lowest for leaf‐on harvests, which were similar for wet (30.4 Mg/hr) and dry conditions (29.7 Mg/hr). Mean crop specific fuel consumption ranged between 1.3 and 3.3 L/Mg, but can get considerably higher for standing biomasses below 40 Mg/ha. Wet ground conditions and leaf‐on harvests tend to decrease material capacity and increase fuel consumption as the harvester has to divert power to forward movement and material processing. Relationships for material capacity and fuel consumption based on standing biomass, time of harvest and ground conditions will be essential for evaluating and modeling the economic and environmental impacts of commercial‐scale willow operations. [ABSTRACT FROM AUTHOR]

Landscape design has been embraced as a promising approach to holistically balance multiple goals related to environmental and resource management processes to meet future provisioning and regulating ecosystem services needs. In the agricultural context, growing bioenergy crops in specific landscape positions instead of dedicated fields has the potential to improve their sustainability, provide ecosystem services, and minimize competition with other land uses. However, growing bioenergy crops in sub-productive or environmentally vulnerable parts of a field implies more complex logistics as small amounts of biomass are generated in a distributed way across the landscape. We present a novel assessment of the differences in production and logistic costs between business as usual (BAU, dedicated fields), and distributed landscape production of shrub, or short-rotation willow for bioenergy within a US Midwestern landscape. Our findings show that regardless of the mode of cropping, BAU or landscape design, growing shrub willows is unlikely to provide positive revenues (−$67 to -$303 ha−1 yr−1 at a biomass price of $46.30 Mgwet−1) because of high land rental costs in this agricultural region. However, when translated into a practice cost per unit of N removed at the watershed scale (range: $1.8-37.0 kg N−1 yr−1), the net costs are comparable to other conservation practices. The projected opportunity cost of growing willows instead of corn on underproductive areas varied between -$14 and $49 Mgwet−1. This highlights the potential for willows to be a cost effective choice depending on the intra-field grain productivity, biomass price and desirable concurrent ecosystem services. © 2016 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Commercial and research scale plantings of short-rotation woody crops require reliable and efficient estimations of biomass yield before time of harvest. Biomass equations currently exist but the accuracy and efficiency of estimation procedures at the level of specificity needs to be quantified for clones being used in North America. Diameter-based allometric equations for aboveground biomass for four clones of willow (Salix discolor, Salix alba, Salix dasyclados, and Salix sachalinensis), between two sites (Canastota and Tully, NY), and across four years (1998–2001), were developed using ordinary least-squares regression (OLSR) on log-transformed variables, weighted least squares regression (WLSR) on log-transformed variables, and nonlinear regression (NLR) methods and validated using independent data sets. Biomass estimations derived from clone, age, and site (Specific) using OLSR equations had highest R 2 and lowest percent bias (<2.3%) allowing for accurate estimations of standing biomass. Values for specific equations using WLSR were similar, but bias was higher for NLR (0.7–12.5%). However, the amount of time and effort required to develop specific equations, is large and in many situations prohibitive. Biomass estimates derived from clone and age, regardless of site (Intermediate), resulted in small increases in prediction error and a small increase in percent bias using OLSR (<0.4%) and WLSR (<1.7%). The increase in percent bias was larger (1.1–5.7%) for NLR equations. Intermediate models correspond to the loss of only a small amount of accuracy while gaining more efficiency in estimating standing biomass. Estimates of biomass derived from clone alone (general) equations, considering neither age nor site, had the weakest prediction abilities that may lead to large errors for biomass estimations using OLSR (7.0–9.5%), WLSR (1.1–21.7%) or NLR (31.9–143.4%). [Copyright &y& Elsevier]

Short-rotation woody crops (SRWC) have the potential to make substantial contributions to the supply of biomass feedstock for the production of biofuels and bioproducts. This study evaluated changes in the fuel quality (moisture, ash, and heating value) of stored spring harvested shrub willow (Salix spp.) and hybrid poplar (Populus spp.) chips with respect to pile protection treatments, location within the storage piles, and length of storage. Leaf-on willow and poplar were harvested in the spring, and wood chips and foliage with moisture content in the range of 42.1% to 49.9% (w.b.) were stored in piles for five months, from May to October 2016. Three protection treatments were randomly assigned to the piles. The control treatment had no cover (NC), so piles were exposed to direct solar radiation and rainfall. The second treatment had a canopy (C) installed above the piles to limit direct rainfall. The final treatment had a canopy plus a dome aeration system (CD) installed over the piles. Covering piles reduced and maintained the low moisture content in wood chip piles. Within 30 days of establishment, the moisture content in the core of the C pile decreased to less than 30%, and was maintained between 24%–26% until the end of the storage period. Conversely, the moisture content in the NC piles decreased in the first two months, but then increased to the original moisture content in the core (>45 cm deep) and up to 70% of the original moisture content in the shell (<45 cm deep). For all the treatments in the tested conditions, the core material dried faster than the shell material. The higher heating value (HHV) across all the treatments increased slightly from 18.31 ± 0.06 MJ/kg at harvest to 18.76 ± 0.21 MJ/kg at the end of the storage period. The lower heating value (LHV) increased by about 50% in the C and CD piles by the end of the storage period. However, in the NC piles, the LHV decreased by 3% in the core and 52% in the shell. Leaf-on SRWC biomass stored in piles created in late spring under climatic conditions in central and northern New York showed differing moisture contents when stored for over 60–90 days. Overhead protection could be used to preserve or improve the fuel quality in terms of the moisture content and heating value if more than two months of storage are required. However, the implementation of such management practice will depend on whether the end users are willing to pay a higher price for dryer biomass and biomass with a higher LHV. [ABSTRACT FROM AUTHOR]

Abstract: The leaf cuticular waxes of six Salix clones (one Salix miyabeana, one Salix dasyclados, one Salix eriocephala, two Salix purpurea, and one interspecific hybrid of Salix eriocephala × interior) with different biomass productivities were characterized by gas chromatography–mass spectrometry. Total wax content ranged from 6.3 to 16.8μg cm−2, and two distinct patterns of wax were measured. The wax from leaves of S. dasyclados ‘SV1’ differed from all other clones and was dominated by fatty acids (42%), high concentrations of n-alkanes (25%) and n-alcohols (28%), with low n-aldehyde content (4%). All other clones produced cuticular wax dominated by n-alcohols (32–51%), particularly 1-hexacosanol, with fatty acids (14–37%) and n-aldehydes (19–26%) present in lower abundances. Clones of Salix grown under identical environmental conditions produce noticeably different amounts of cuticular wax. In contrast to previous studies of Salix, total wax content was independent of biomass productivity, measured as basal area, suggesting that wax production is not directly linked with woody biomass production by shrub willows under these site conditions. [Copyright &y& Elsevier]

In this study, we tested the effect of hot water extraction (HWE) as a biomass pretreatment on the pyrolysis of three cultivars of shrub willow via both conventional heating (using a micropyrolyzer, Py-GC/MS) and microwave-assisted heating (using a laboratory scale microwave reactor and activated charcoal as an added microwave absorber). The py-GC/MS experiments revealed that there was little difference in pyrolysis behavior among the cultivars for raw or HWE pretreated samples. Using either heating method, pyrolysis of the HWE pretreated samples produced less acetic acid and CO 2 than did the untreated biomass; conversely there was an increase in levoglucosan yield with HWE pretreatment. The difference in levoglucosan yield was particularly large (4 fold increase) for the py-GC/MS experiments and was attributable in large part to the demineralization of the HWE samples. The decreased mineral content appeared to have a larger effect on conventional heating than in the microwave assisted heating. The pyrolysis of HWE pretreated biomass also led to more rapid temperature increases during microwave-assisted pyrolysis performed at 1000 W. Therefore the microwave-assisted pyrolysis of HWE was studied at two different microwave power settings to compare the effect of HWE on both processes at similar temperatures. At similar temperature conditions the yield of bio-oil, bio-char and non-condensable gases from microwave-assisted pyrolysis were similar between the pretreated and raw willow but the bio-oil contained higher concentrations of aromatic hydrocarbons and less acetic acid and levoglucosan. Overall, the HWE pretreatment had a greater effect on bio-oil composition than bio-oil yield. [ABSTRACT FROM AUTHOR]

Recently, there has been interest in shifting to carbon-neutral sources of energy, including bioenergy from short rotation woody crops. This study looked at the growth and yields of short rotation willow in an agroforestry intercropping system compared to a conventional single variety plot system used as a control. Three willow clones (Salix dasyclados SV1, Salix miyabeana SX67 and Salix purpurea 9882-41) were established in each field setup, where in the agroforestry field willow plots were located between 15m wide rows of 20-year-old mixed tree species. Differences in photosynthetic photon flux density (PPFD), soil temperature, soil moisture and soil/foliar nitrogen between the two field setups were investigated from 2006 to 2007. Willow yields were significantly higher in the agroforestry fields during both years of the study, with 0.8 and 0.5odtha−1 for the agroforestry and control fields, respectively, in 2006, and 3.0 and 1.1odtha−1 respectively, in 2007. There were opposite trends in clonal yields between the two field setups in 2006, but in 2007, clonal yields were in the same order across fields with averages of 2.8, 2.2 and 1.2odtha−1 for SV1, SX67 and 9882-41, respectively. Daily average photosynthetic photon flux density was 210μmolm−2 s−1 (16%) lower in the agroforestry system, and PPFD was correlated with soil temperatures that were on average 0.4°C and 2.7°C lower in the agroforestry field in 2006 and 2007, respectively (r =0.82 and 0.93). Soil temperatures were negatively correlated with soil moisture levels that were on average 1.4% and 1.9% higher in the agroforestry field in 2006 and 2007, respectively (r =−0.54 and −0.41), and soil moisture content was positively correlated with willow yields (r =0.49 and 0.72). There was less soil available nitrogen in the agroforestry field, but no difference in foliar nitrogen between fields. An experiment excluding root competition in the top 1 m of soil between intercropped trees and willows in the agroforestry field found no significant competition for soil moisture or nitrogen in the first two years of growth. Results of this study suggest that moderate shading in an intercropping setup can result in a buffering effect on microclimate conditions, where there is less variation in soil moisture content and soil temperature across a range of weather conditions. [Copyright &y& Elsevier]