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

Abstract

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.

Life cycle greenhouse gas emissions of ethanol produced via fermentation of sugars derived from shrub willow (Salix ssp.) hot water extraction in the Northeast United States

“…The GHG emissions associated with the processes of site preparation and maintenance, harvesting, transportation, and storage of the biomass are higher for summer than winter harvest and storage for both grassland and cropland. This is the case, because the fuel consumption per unit of harvested willow biomass (L Mg −1 ) during winter harvest is 45% lower than summer harvest and dry matter loss in winter storage piles is 13.8% less than in summer storage piles after 3 months [ 24 , 30 ]. Thus, the higher dry matter loss and fuel consumption during the summer season contribute higher emissions than during winter by 34% for cropland and 21% for grassland for these processes.…”

“…Storage duration has the greatest influence on the net GHG emissions for scenarios that incorporate summer harvest of willow biomass due to the higher rate of dry matter loss in summer storage piles than winter storage piles [ 30 ]. Longer storage duration, i.e., higher dry matter loss, results in decreased net GHG emissions compared to the baseline values for all cropland scenarios, but it results in increased net GHG emissions for grassland scenarios.…”

“…Previous modeling studies have shown that changes in soil carbon are different when cropland and grassland are converted to willow, and suitable areas of grassland and cropland that can be converted into willow production have been identified for a five-county region in northern New York state [ 17 , 23 ]. Summer and winter harvests are studied as separate scenarios in this LCA, because they show different harvesting and storage dynamics that affect the mass and energy balance of the system [ 24 , 30 ]. Heat and power for HWE and fermentation are cogenerated on site either from the combustion of HWE willow biomass or natural gas.…”

“…Furthermore, it is assumed that harvested willow chips will be stored in outdoor piles for a period ranging from zero to 6 months with an average storage period of 3 months as the baseline value. Changes in dry matter loss (DML) and quality changes during the summer and winter storage are from recent storage trial studies of willow [ 30 , 45 ]. After 3 months in storage, the average DML is estimated at 18.9% for summer storage and 5.2% for winter storage (Eq.…”

The US bioeconomy at the intersection of technology, policy, and education

“…To overcome seasonal dependencies, biomass can be stored under controlled conditions to maintain the quality of the biomass and reduce the amount of dry matter lost during the storage period. 33,34 Some R&D also focuses on new conversion processes that can utilize different types of feedstocks concurrently, thus lowering the economic vulnerability of conversion facilities and resulting in a more consistent production throughout the year. 35 Crop development techniques (including conventional and biotechnological) are also being used to develop higher quality crops with suitable chemical composition.…”