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

Abstract

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.

Cut‐and‐chip harvester material capacity and fuel performance on commercial‐scale willow fields for varying ground and crop conditions

“…This is especially true when willow occupies lower quality land with somewhat poorly to very poorly drained soil. In addition, difficulties securing and mobilizing equipment on short notice have caused some commercial growers to start harvesting in the late summer or early fall (Eisenbies, Volk, Therasme, & Hallen, 2019; Therasme, Eisenbies, & Volk, 2019). In other words, they are placing more importance on ground conditions and being able to complete harvests than on concerns about potential impacts of harvesting during the growing season.…”

Hot Water Extracted and Non-extracted Willow Biomass Storage Performance: Fuel Quality Changes and Dry Matter Losses

“…The sampling points were placed at 1.5-2.5 m apart of each other along the length of the pile. A total of eight temperatures probes connected to two data loggers (HOBO U12-008) were inserted in the shell and core of the piles following the description provided by Eisenbies et al (2016) and Therasme et al (2019). Data loggers inserted in this storage pile automatically recorded the pile temperature every 30 min.…”

“…But, moisture content increases during autumn and winter storage (Filbakk et al, 2011). The moisture content of uncovered willow chip storage piles harvested in late spring with a moisture content of 46% decreased to 37-26% after 60 days of storage and increased thereafter until the end of the storage trial in mid-autumn (Therasme et al, 2019). However, Eisenbies et al (2016) reported an increase of moisture from 42% at harvest in February to 49% in May and 44% in July.…”

“…Dry matter loss (DML) can occur at multiple places along the supply chain such as during harvesting, loading and unloading of vehicles, transportation, and storage. DML is an important factor as it can translate into loss of revenue (Routa et al, 2018;Therasme et al, 2019), waste of resources, higher greenhouse gas emissions per unit of energy delivered, and challenges at conversion facilities. A DML of 10% during the storage of willow biomass for heat production would result in 6% increase of greenhouse gas emissions per unit of delivered heat and 9% decrease of the net energy yield per unit of land (Whittaker et al, 2016).…”

“…Most recent SRWC storage studies in the United States do not report the amount of DML in outdoor storage pile of wood chips (Ergül and Ayrilmis, 2014;Lin and Pan, 2015;Eisenbies et al, 2016;Therasme et al, 2019). However, DML reported in European studies ranges from 0.9 to 4.5% per month and total DML can reach up to 47% after 18 months of storage in open outdoor piles (Table 1).…”