ABSTRACT Afforestation of former agricultural land is increasingly prioritized as a natural climate solution, yet tree establishment is inhibited by herbaceous competition, browsing pressure, limited seed dispersal, and planting costs. Short‐rotation willow (Salix spp.) crops could provide renewable biomass for multiple rotations and subsequently transition to forest by facilitating hardwood establishment through rapid canopy closure, suppression of competing vegetation, and improvement of site conditions. This potential, hardwood regeneration within nine willow fields in New York State was assessed using two sequential studies. In study 1, a rapid point‐quarter survey quantified seedling density, height, and spatial gradients relative to seed sources. In a follow‐up study, fixed‐area plots were established across these gradients to quantify seedling densities and evaluate stand, soil, and seed‐source proximity attributes. Hardwood regeneration was dominated by wind‐disseminated species, primarily Fraxinus and Acer spp., with mean densities reaching 30,000 seedlings ha−1 in some locations. Regeneration was spatially structured, declining with increasing distance from seed sources; densities typically fell below 2500 seedlings ha−1 beyond 40–75 m from forest edges. The point‐quarter method underestimated fixed‐plot densities but reliably distinguished areas of high and low regeneration. Logistic regression indicated that regeneration exceeding thresholds associated with successful forest establishment (1500 and 2500 seedlings ha−1) was positively related to proximity to seed sources and higher willow survival, whereas other soil and stand properties were not associated with seedling density. These findings suggest that short‐rotation willow systems could function as a hardwood nurse crop and integrate biomass production with afforestation.

Shrub willow (Salix spp.) is a promising candidate for evapotranspiration (ET) covers due to its rapid growth and high water use. This study assessed 30 willow clones over two three-year rotations on a former industrial waste site in Solvay, NY, with alkaline, low-organic substrates and intermittent hardpan. Survival was high after the first rotation (87.9% ± 1.7 SE), but yield was lower and more variable (6.55 Mg ha−1 y−1 ± 0.25 SE) than on mineral soils. In the second rotation, both survival (42.6% ± 3.0 SE) and yield (5.08 Mg ha−1 y−1 ± 0.38 SE) declined. Clone rankings shifted between rotations (Spearman ρ = 0.13, p = 0.48), suggesting that short-term trials poorly predict long-term performance on degraded sites. Survival emerged as the primary driver of yield, with a smaller interaction from hardpan. Clone 05X-295-014 showed notable resilience, maintaining strong performance despite widespread hardpan. Five clones from S. miyabeana and S. purpurea x S. miyabeana groups demonstrated sustained or increasing yield and survival above 60%. These findings emphasize the importance of selecting for survival alongside yield in multi-rotation trials to ensure effective long-term deployment for biomass and phytoremediation in challenging sites.

This study reveals patterns of yield and survival of short-rotation coppice (SRC) willow cultivars over eight rotations (1993–2019). Cultivars fell into four broad categories: commercial, released, stable, and decline. SV1, the singular cultivar that advanced to commercial deployments, had first-rotation yields of 8.9 Mg ha−1 a−1, peaking at 15.2 Mg ha−1 a−1 by the fourth. Mean yields from rotations 2–8 were still 36% above first-rotation yields, confirming the commercial potential for this cultivar over 26 years. The released group (four cultivars) had stable yields over six rotations (approximately 3 to 7 Mg ha−1 a−1), rising to match commercial yields (10 Mg ha−1 a−1) between the sixth and eighth rotation. Most of the cultivars were in the stable group that had relatively consistent yields over time. First-rotation yields in this group were approximately 5 Mg ha−1 a−1, and average yield increased by 23% for rotations 2–8. The two cultivars in the decline group were impacted by disease and browsing that lowered survival and growth. These findings are crucial for understanding willow systems’ potential over their full lifespan as a bioenergy crop, which is a crucial input into yield, economic, and environmental models.

Harvesting systems are an essential component of woody biomass supply chains and are a major cost and source of environmental impacts associated with the delivered biomass. Short rotation woody crops have the potential to supply large amounts of biomass over small areas due to their high yields and short rotation lengths. The development of harvesting systems that can effectively cut and chip high yielding woody crops and produce consistent quality material has been a barrier to the deployment of woody crops. Over the past two decades, efforts have focused on developing systems that are based on forage harvesters, typically used in agricultural operations, fitted with headers specifically designed for the high yield and large stem density found in woody crops. Research and development resulted in dramatic improvements in the performance of these harvesters with effective material capacity exceeding 80 Mgdry/h during the dormant season with good ground conditions. The chips produced are of consistent quality that meet recognized international standards. With the expansion of woody crops across the landscape the period for harvesting has expanded into the growing season and to times of the year when ground conditions are wetter. This has resulted in reductions in effective material capacity by 50% and presents challenges for the year-round supply of biomass to end users. Future research and development work will focus on improving harvester performance in a wider range of conditions while maintaining the quality of the biomass produced.

In any short-rotation coppice (SRC) operation, a certain percentage of harvestable material is unrecovered, which contributes to harvesting system losses. This material may be in the form of merchantable and non-merchantable components. These losses affect economics but also influence yield, nutrient cycling, and carbon sequestration. There are very few estimates for harvesting losses available in the literature, and they are limited by small sample sizes. The objective of this work was to provide a broad overview of harvesting losses in willow SRC over a wide range of standing biomass and harvesting conditions. The average total harvesting losses were between 3 and 4 Mg ha−1, which is between 6 and 7 percent of the standing biomass. Losses can spike to nearly 40% on less than 3% of the area. Harvesting losses are significantly, but weakly, correlated with increased standing biomass. These results highlight the complexity and variability in harvesting losses as well as which aspects of harvesting systems might be targeted to reduce or partition material losses. These results have implications for designing machinery and economic modeling of these systems.

Belowground biomass is an important but less studied component of energy crop systems that is essential in understanding the greenhouse gas benefits of these systems. In this study, a complete above- and belowground biomass inventory (foliage, stems, stools, coarse and fine roots) was performed on three cultivars of short-rotation willow biomass crops at two sites. Mixed models were used to analyze the proportion of biomass allocated to each component and the ratios between different components. The root:shoot (R:S) ratio, defined here as the stable unharvested biomass (stool and coarse roots) divided by the shoot biomass, averaged 0.63 (SE: +0.04). Though the portion of the plant where the willows distributed their belowground biomass varied, the R:S ratio was not significantly different across sites (p = 0.8970), cultivars (p = 0.2834), nor in the site × cultivar interaction (p = 0.8481). These results may be associated with the consistently good growth across sites and limited differences in site conditions. However, the R:S ratios were affected by the overall productivity of the stand (p = 0.0978), with higher producing stands having moderately lower ratios. This information on biomass allocation between components is essential for understanding and estimating the carbon balance of these systems and breeding and selection programs.

New York State's (NYS) Climate Leadership and Community Protection Act (CLCPA) requires that 100% of the state's electricity supply be greenhouse gas emissions-free by 2040 and that 6000 megawatts (MW) of solar energy must be installed in NYS by 2025. This study aims to evaluate the environmental impact of electricity generation from New York State distributed solar photovoltaic systems. This cradle-to-grave life cycle assessment (LCA) follows the International Standardization Organization (ISO) framework for LCA, including the goal and scope definition, inventory analysis, impact assessment, and interpretation. The study is based on operational data from 120 existing solar installations. Global Warming Potential varies substantially by site, with the minimum and maximum impact values varying from 25.2 to 88.5 gCO(2eq)/kWh, and with a mean of 45.6 gCO(2eq)/kWh. Regression analysis shows this range is attributable to differences in site location, capacity factor, and system design (i.e., monocrystalline and polycrystalline panels, area power ratio). Based on absolute percentage, the inclusion of the end-of-life process reduces the total environmental impact from 2% in Ozone Depletion to 16% in Acidification, indicating a positive impact of engaging in end-of-life management across all categories. This analysis can help policymakers understand the implications of the solar PV installation mandate.

The refereed literature contains few studies that analyze life cycle assessment (LCA) and techno-economic analysis (TEA) methodologies together for lignocellulosic bioenergy systems, using a stochastic modeling approach. This study seeks to address this gap by developing an integrated framework to quantify the environmental and financial impacts of producing and delivering shrub willow in the Northeastern United States. This study analyses four different scenarios from a combination of two different initial land cover types (grassland, cropland) prior to willow establishment, and two harvesting conditions (leaf-on, leaf-off). Monte Carlo simulations were performed to quantify the uncertainty of the results based on a range of financial, logistical, and biophysical variable input parameters (e.g., land rental rates, transportation distance, biomass yield, etc.). Growing willow biomass on croplands resulted in net negative GHG emissions for both leaf on and leaf off scenarios for the baseline. The GHG emissions were lowest for the leaf-off harvest on cropland (−172.50 kg CO2eq Mg−1); this scenario also had the lowest MSP ($76.41 Mg−1). The baseline grassland scenario with leaf-on harvest, results in the highest net GHG emissions (44.83 kg CO2eq Mg−1) and greatest MSP ($92.97 Mg−1). The results of this analysis provide the bioenergy field and other interested stakeholders with both environmental and financial trade-offs of willow biomass to permit informed decisions about the future expansion of willow fields in the landscape, which have the potential to contribute to GHG reduction targets and conversion into fuels, energy, or bioproducts for carbon sequestration and financial benefits.

The commercial establishment of shrub willow (Salix spp.) biomass crops with three- or four-year harvest cycles raises concerns about nutrient removal (NR). In addition, leaf-on harvests outside of the typical harvesting window are becoming more prevalent with a changing climate, and require a better understanding of the potential impact of these changes on biomass production and NR. This study examined the time of harvest effects for six harvest dates on the nutrient and biomass removal of four shrub willow cultivars in central New York State. There were significant differences in biomass in the first-rotation harvest; yields ranged between 77 and 85 Mg ha−1 for the time of harvest treatments during the growing season, and between 93 and 104 Mg ha−1 after dormancy. Harvest timing had significant effects on N and K removal in the combined wood and foliar biomass. Willow harvested in October removed comparatively higher amounts of N (77.1 kg ha−1 year−1) and P (11.2 kg ha−1 year−1) than other harvests. Potassium removal was greater for plants harvested in June (51.2 kg ha−1 year−1) and August (52.5 kg ha−1 year−1). Harvest timing and cultivar interactions suggest that targeted cultivar selection and deployment could maintain yields and limit excess nutrient losses.

Background The amount of carbon dioxide in the atmosphere has been on the rise for more than a century. Bioenergy crops are seen by the Intergovernmental Panel on Climate Change as an essential part of the solution to addressing climate change. To understand the potential impact of shrub willow ( Salix spp . ) crop in the northeast United States, effective and transparent life cycle assessment of these systems needs to occur. Results Here we show, ethanol produced from the fermentation of sugars from hot water extract of willow grown on cropland can sequester 0.012 ± 0.003 kg CO 2eq MJ −1 for a supply system incorporating summer harvest and storage. Despite decreases in soil organic carbon when willow is instead grown on grassland, the produced fuel still can provide significant climate benefits compared to gasoline. Conclusions Shrub willow converted to ethanol can be a carbon negative source of transportation fuel when the electricity and heat required for the conversion process are generated from renewable biomass. The sequestration of carbon in the belowground portion of the plants is essential for the negative GHG balance for cropland and low GHG emissions in grassland.

There is a need for data on commercial-scale harvesting operations in hybrid poplar short rotation crops to better understand costs and logistics, especially for modeling large scale biorefineries. An investigation was conducted on the in-field performance of a single-pass cut-and-chip harvester operating in commercial fields for over 370 individual wagon loads representing a range of crop and field conditions. Mean material capacity peaked at 70 Mg h-1 in dry conditions in lower biomass (<60 Mg ha- 1), but was only 28 Mg h-1 during wet conditions and often higher standing biomass. Wet ground conditions require the harvester to divert additional power to maintaining forward movement, which results in decreased material capacity and increased fuel consumption. Crops with higher standing biomass had taller trees that do not always feed as smoothly into the harvester, slowing forward progress and lowering material capacity. Mean crop specific fuel consumption, L of fuel per Mg of biomass processed, generally decreased as standing biomass increased. When standing biomass was above 40 Mg ha- 1 mean crop specific fuel consumption (FCC) was 1.69 L Mg-1 in dry conditions and 3.98 L Mg-1 in wet conditions, but when standing biomass was below 40 Mg ha- 1 FCC increased drastically (as high as 5 L Mg- 1) because the harvester is putting more effort into forward speed instead of material processing. Developing relationships between material capacity and fuel consumption based on standing biomass and ground conditions at representative scales are essential for conducting environmental and economic analyses of these systems.

Abstract 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.

A mixed-integer linear programming model was developed to optimize the multiple biomass feedstock supply chains, including feedstock establishment, harvest, storage, transportation, and preprocessing. The model was applied for analyses of multiple biomass feedstocks at county level for 13 states in the northeastern United States. In the base case with a demand of 180,000 dry Mg/year of biomass, the delivered costs ranged from $67.90 to $86.97 per dry Mg with an average of $79.58/dry Mg. The biomass delivered costs by county were from $67.90 to 150.81 per dry Mg across the northeastern U.S. Considered the entire study area, the delivered cost averaged $85.30/dry Mg for forest residues, $84.47/dry Mg for hybrid willow, $99.68 for switchgrass and $97.87 per dry Mg for Miscanthus. Seventy seven out of 387 counties could be able to deliver biomass at $84 per dry Mg or less a target set by US DOE by 2022. A sensitivity analysis was also conducted to evaluate the effects of feedstock availability, feedstock price, moisture content, procurement radius, and facility demand on the delivered cost. Our results showed that procurement radius, facility capacity, and forest residue availability were the most sensitive factors affecting the biomass delivered costs.

Hybrid poplar demonstration-scale farms were managed in Oregon, Washington, Idaho, and California to establish management practices, yields, harvesting methods, and the economics of biomass production. Yield during the 2-year establishment cycle averaged 3.5 dry Mg ha−1 year−1 increasing to 11.6 Mg ha−1 year−1 in the ensuing 3-year coppice cycle. Populus deltoides (Bartram ex Marsh.) × P. maximowiczii (Henry) varieties preformed best in Oregon during the coppice cycle with the best variety producing 18.1 Mg ha−1 year−1, while P. ×generosa (Henry) varieties maximized yields in Washington at 22.1 Mg ha−1 year−1. P. ×canadensis (Moench) varieties excelled in Idaho and California with upper yields of 13.6 Mg ha−1 year−1 and 12.9 Mg ha−1 year−1, respectively. Stands were cut with a single-pass harvester 2 years after planting and a second time after 3 years of coppice growth; material capacity, limited by poor ground conditions, varied between 21.7 to 31.3 green Mg h−1. Chemical composition averaged 1.87% inorganics, 7.74% extractives, 26.90% lignin, 38.07% glucan, 13.66% xylan, 1.61% galactan, 1.14% arabinan, and 2.76% mannan. Production costs (USD) projected over a 20-year rotation of six coppice cycles were $71.81 Mg−1 in Washington, $89.91 Mg−1 in Oregon, $98.76 Mg−1 in Idaho, and $179.07 Mg−1 in California. Land rental, establishment, crop care, harvest, transportation, and land restoration, respectively, accounted for 23%, 5%, 19%, 30%, 17%, and 6% of total feedstock cost. Farms were successfully restored to conditions existing before poplar conversion. In the absence of fertilization, increases in soil pH and decreases in nitrate-nitrogen, zinc, iron, and organic matter were consistently noted but could not be associated with poplar production alone.

Dry matter losses (DML) and fuel quality changes occurring in storage piles are important parameters for the management of any biomass supply system. This study evaluates the effect of a hot water extraction pretreatment, harvest season, depth in storage pile and initial moisture content on willow biomass fuel quality [moisture, ash, higher (HHV) heating value and lower (LHV) heating value] during storage, and models DML in storage piles based on experimental data. For the summer storage (SS) pile, mesh bags containing freshly harvested chips (FC) were inserted at 0.5-1 m deep in the pile. For the winter storage pile (WS), the mesh bags were filled with FC and hot water extracted chips (HC) with three different initial moisture contents inserted in the shell (<0.45 cm) and the core (1-1.5 m) of the pile. The ash contents through all sampling periods were in the range of 1.1-2.2% for FC and 0.6-2.1% for HC from both the shell and core of the WS pile. Higher ash contents, in the range of 2.1-3.4%, were observed in SS pile. Moisture contents of the storage piles had differing patterns over time. DML was the highest in the SS pile, reaching up to 33.6% after 140 days in storage; in contrast, there was no significant increase in DML over the first winter season. Although DML of FC and HC were in the same range during the initial storage period, DML of HC was 40% lower than FC after 180 days of storage. Higher DML was observed in the core (e.g., 17.3% for FC) compared to the shell (e.g., 12.1% for FC) at the end of the WS trial. There was no particular trend observed between initial moisture and DML. This study suggests that a linear model is sufficient to estimate DML, but a non-linear model may be needed for chips stored in SS piles for 6 months or longer. It also suggests that DML is reduced in storage piles created in winter, and that willow chips kept in SS should be utilized within 2 months for a DML below a 10% threshold.

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.

The production of short rotation woody crops (SRWCs) such as poplars and willows is a promising component of global bioenergy and phytotechnology portfolios. In addition to the provision of biomass feedstocks and pollution remediation, these trees and shrubs have been sustainably grown to conserve or utilize water in a variety of applications. Growing these woody plants for multiple uses supports many of the United Nation's Sustainable Development Goals (SDGs), especially Clean Water and Sanitation (SDG6) and Affordable and Clean Energy (SDG7). As a result, focusing on ecosystem services such as freshwater and biomass has become an important aspect of deploying these production systems across variable landscapes. The current review consists of an introduction of ecosystem services and the SDGs, as well as SRWCs and their applications. The middle section of the review contains case studies highlighting the positive water linkages of producing short rotation poplars and willows for bioenergy and phytotechnologies. The review concludes with a section that combines the common themes that are consistent among the case studies to address options for integrating new bioenergy feedstock production systems into rural and urban landscapes to promote environmental, social and economic sustainability. This article is categorized under: Bioenergy > Economics and Policy Bioenergy > Climate and Environment

Bulk density is a key attribute of biomass feedstocks that affects both conversion processes and logistics. Reported bulk density for fresh willow chips ranges between 195 and 393 kg m(-3) and it is unknown if standardized methods using several kg of chips scale effectively to collection vehicles that contain several Mg. The objective of this study was to compare three bulk density methods for 53 commercially harvested willow loads and compare bulk density in three different collection wagons. An ISO standard 'bucket' method was compared to actual and effective bulk density measurements. Mean as-received bulk density using the standard ISO method was 262 kg m(-3) (sigma = 25) and was not correlated with wagon load measurements of actual or effective bulk density. The actual bulk density in a small (10 m(3)) collection vehicle was 302 kg m(-3) (sigma = 32), which was significantly greater than the 214 kg m(-3) (sigma = 28) that was measured in two larger (30 m(3)) collection vehicles. In addition, actual bulk density in wagons was higher than the effective bulk density (247 kg m(-3) (sigma = 24)) observed for the truck deliveries. Collection wagon geometry and design impacted these results, which may have implications for modeling these systems. The variation in bulk density values is important to understand and represent in modeling of harvesting and logistics systems in order to capture what is actually occurring in commercial scale operations.