Advances in shrub-willow crops for bioenergy, renewable products, and environmental benefits

Short-rotation coppice systems like shrub willow are projected to be an important source of biomass in the United States for the production of bioenergy, biofuels, and renewable bio-based products, with the potential for auxiliary environmental benefits and multifunctional systems. Almost three decades of research has focused on the development of shrub willow crops for biomass and ecosystem services. The current expansion of willow in New York State (about 500 ha) for the production of renewable power and heat has been possible because of incentive programs offered by the federal government, commitments by end users, the development of reliable harvesting systems, and extension services offered to growers. Improvements in the economics of the system are expected as willow production expands further, which should help lower establishment costs, enhance crop management options and increase efficiencies in harvesting and logistics. Deploying willow in multifunctional value-added systems provides opportunities for both potential producers and end users to learn about the system and the quality of the biomass feedstock, which in turn will help overcome barriers to expansion

Evaluation of a Single-Pass, Cut and Chip Harvest System on Commercial-Scale, Short-Rotation Shrub Willow Biomass Crops

Harvesting is the single largest cost in the production of short rotation woody crops (SRWC) like shrub 8 willow and previous systems tested in North America have not been effective for the size of material grown. The 9 objective of this study was to evaluate the performance of a single-pass, cut and chip harvester in conjunction with 10 two locally-sourced chip collection systems on 54 ha of coppiced willow harvests in New York State. Harvesting 11 and collection equipment was tracked for 153 loads over 10 days of harvesting using GPS dataloggers. Effective 12 material capacities (Cm) increased linearly with standing biomass up to 40 to 45 Mgwet ha-1 because ground speed 13 was limited by ground conditions. This relationship changed dramatically with standing biomass in the 40 – 90 14 Mgwet ha-1 range, where Cm plateaued between 70 and 90 Mgwet hr-1 and was limited by crop conditions and 15 harvester capacity. The relationship between standing biomass and the harvester’s Cm will probably change under 16 different crop and ground conditions. The size of the harvester and the experience of the operator are other factors. 17 This nonlinear relationship will impact cost and optimization modeling SRWC systems. Improperly sized headland 18 and long haul distances impeded the performance of locally sourced collection systems resulting in a 33% decrease 19 in Cm from the field to the headlands, and 66% from the field to short-term storage as biomass moves through the 20 system

Impacts of land use and land cover change on surface runoff, discharge and low flows: evidence from East Africa

Region: East Africa. Focus: A review of catchment studies (n=37) conducted in East Africa evaluating the impacts of Land Use and Land Cover Changes (LULCC) on discharge, surface runoff, and low flows. New hydrological insights: Forest cover loss is accompanied by increased stream discharges and surface runoff. No significant difference in stream discharge is observed between bamboo and pine plantation catchments, and between cultivated and tea plantation catchments. Trend analyses show that despite forest cover loss, 63% of the watersheds show non-significant changes in annual discharges while 31% show increasing trends. Half of the watersheds show non-significant trends in wet season flows and low flows while 35% reveal decreasing trends in low flows. Modeling studies estimate that forest cover loss increases annual discharges and surface runoff by 16 ± 5.5% and 45 ± 14%, respectively. Peak flows increased by a mean of 10 ± 2.8% while low flows decreased by a mean of 7 ± 5.3%. Increased forest cover decreases annual discharges and surface runoff by 13 ± 1.9% and 25 ± 5%, respectively. Weak correlations between forest cover and runoff (r=0.42, p < 0.05), mean discharge (r=0.63, p < 0.05) and peak discharge (r=0.67, p < 0.05) indicate that forest cover alone is not an accurate predictor of hydrological fluxes in East African catchments. The variability in these results supports the need for long-term field monitoring to better understand catchment responses and to improve the calibration of currently used simulation models

Bioenergy and climate change mitigation: an assessment

Acknowledgements The authors are indebted to Julia Römer for assisting with editing several hundred references. Helmut Haberl gratefully acknowledges funding by the Austrian Academy of Sciences (Global Change Programme), the Austrian Ministry of Science and Research (BMWF, proVision programme) as well as by the EU-FP7 project VOLANTE. Carmenza Robledo-Abad received financial support from the Swiss State Secretariat for Economic Affairs.Peer reviewedPostprin

The Hydrologic Characterization of Three Forested Headwater Riparian Wetlands in East Tennessee

Headwater riparian wetlands form an important hydrologic link between terrestrial and aquatic systems. These wetlands are small and account for only nine percent of the total wetland area in the US, however, they account for nearly half of the upland/wetland edge. Three headwater riparian wetlands were instrumented with flumes, solution samplers and shallow wells to monitor hydrologic and chemical interactions between physiographic positions and streams within the watersheds. The objectives of this study were to examine the general hydrologic and chemical characteristics of such wetlands. Water sampling was conducted in soils and streams during baseflow and stormflow conditions. Cross sections of water tables on wetlands had distinctive differences from those on non-wetlands. Wetland areas had generally level, shallow water tables, while non-wetland bottoms had deeper, more sloping water tables. Calcium concentrations in streams and soils ranged from 2 mg L-1 to 25 mg L-1, and were usually highest on wetland physiographic positions. Magnesium concentrations ranged from 1 mg L-1 to 4 mg L-1 and had similar patterns to those seen for calcium. Dissolved organic carbon concentrations ranged from 5 to 17 mg L-1 and were also highest in wetlands. Total nitrogen concentrations were consistently less than 1 mg L-1 at all positions. Although these wetlands were small, the hydrogeochemical processes occurring were sufficient to alter soil water chemistry. Although wetlands generally had the highest concentrations of the observed solutes, the solute concentrations of non-wetland bottom was closer to wetland values during drier periods on the watersheds

Research Summary: Characteristics of Willow Biomass Chips Produced Using a Single-Pass Cut-and-Chip Harvester

Biomass for bioenergy and/or bioproducts can be sourced from forests, agricultural crops, various residue streams, and dedicated woody or herbaceous bioenergy crops. Despite this wide spectrum of promising feedstocks, no single biomass source can meet the projected demand, or is clearly superior to alternatives in all aspects of cost, quality, and acceptance

Data overhead protection increases fuel quality and natural drying of leaf-on woody biomass storage piles

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 (>45cm 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

Overhead Protection Increases Fuel Quality and Natural Drying of Leaf-On Woody Biomass Storage Piles

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 (&gt;45 cm deep) and up to 70% of the original moisture content in the shell (&lt;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

Research Summary: Development of a Single-Pass Cut-and-Chip Harvesting System for Short Rotation Woody Crops

Many types of specialized machinery for harvesting short rotation woody crops (SRWC) exist, including small and large single-pass cut-and-chip systems, whole stem harvesters, and baling systems. However, due to the limited scale of SRWC deployment, evolving technology, different operational scales, and management objectives, there is presently no dominant harvesting system in use. In New York State, several existing or modified harvesting platforms for SRWC from Europe and North America have been evaluated since 2001 for use in short rotation willow. Technical hurdles encountered on various harvesters that were tested during that time include the durability of equipment, low production rates, irregular feeding of stems into the harvester, limits on maximum stem sizes, and inconsistent size and quality of chips