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Title: Managing variability in algal biomass production through drying and stabilization of feedstock blends

Abstract

The uncertainty and variability of algal biomass production presents several challenges to the algal biofuel industry including equipment scaling and the ability to provide a consistent feedstock stream for conversion. Blended feedstocks containing both algal and terrestrial biomass may provide a cost-effective method to manage variability of algal biomass production. The hypothesis is that mixing of algae with terrestrial biomass has the potential to create blends with rheologic (flowability) properties similar to terrestrial feedstock and that blends with the consistency of terrestrial biomass can be dried using established low-cost drying systems. To test this hypothesis and its technical feasibility, prototype bench scale simulated drum dyers were designed and tested with blends of algae and ground pine. Scenedesmus dimorphus biomass was used as the algal feedstock, while 2 mm grind pine was used as the terrestrial feedstock. Pine was selected as the representative terrestrial feedstock to leverage independent HTL research using pine feedstock. In these studies, blends up to 60% algae produced drying curves similar to those of pine alone, and reached dryness (2% moisture) much more rapidly than algae alone. Thermogravimetric analyses performed on these feedstocks provided drying curves consistent with the simulated drum dryers. In addition, observable rheologic propertiesmore » at the time of blending served as an indicator of drying performance, as those blends with texture similar to pine also dried similar to the pine control. Logistics analyses performed to determine cost and availability of feedstock materials for blending at production scale further indicate the potential of this approach. Lastly, our results indicate that blending of algae with terrestrial biomass enables the use of low cost dryers and has the potential to improve overall algal biofuel economics by capturing the value of excess biomass produced during periods of high productivity and by decoupling of algal production farms and conversion facilities.« less

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
Publication Date:
Research Org.:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1361414
Alternate Identifier(s):
OSTI ID: 1396632
Report Number(s):
INL/JOU-15-34261
Journal ID: ISSN 2211-9264; PII: S2211926416306348
Grant/Contract Number:
AC07-05ID14517
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Algal Research
Additional Journal Information:
Journal Volume: 24; Journal Issue: PA; Journal ID: ISSN 2211-9264
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; algae; algal logistics; blended feedstocks; algae biofuels; hydrothermal liquefaction; algae biomass storage; blending; economic feasibility; sustainability

Citation Formats

Wahlen, Bradley D., Roni, Mohammad S., Cafferty, Kara G., Wendt, Lynn M., Westover, Tyler L., Stevens, Dan M., and Newby, Deborah T. Managing variability in algal biomass production through drying and stabilization of feedstock blends. United States: N. p., 2017. Web. doi:10.1016/j.algal.2017.03.005.
Wahlen, Bradley D., Roni, Mohammad S., Cafferty, Kara G., Wendt, Lynn M., Westover, Tyler L., Stevens, Dan M., & Newby, Deborah T. Managing variability in algal biomass production through drying and stabilization of feedstock blends. United States. doi:10.1016/j.algal.2017.03.005.
Wahlen, Bradley D., Roni, Mohammad S., Cafferty, Kara G., Wendt, Lynn M., Westover, Tyler L., Stevens, Dan M., and Newby, Deborah T. Wed . "Managing variability in algal biomass production through drying and stabilization of feedstock blends". United States. doi:10.1016/j.algal.2017.03.005. https://www.osti.gov/servlets/purl/1361414.
@article{osti_1361414,
title = {Managing variability in algal biomass production through drying and stabilization of feedstock blends},
author = {Wahlen, Bradley D. and Roni, Mohammad S. and Cafferty, Kara G. and Wendt, Lynn M. and Westover, Tyler L. and Stevens, Dan M. and Newby, Deborah T.},
abstractNote = {The uncertainty and variability of algal biomass production presents several challenges to the algal biofuel industry including equipment scaling and the ability to provide a consistent feedstock stream for conversion. Blended feedstocks containing both algal and terrestrial biomass may provide a cost-effective method to manage variability of algal biomass production. The hypothesis is that mixing of algae with terrestrial biomass has the potential to create blends with rheologic (flowability) properties similar to terrestrial feedstock and that blends with the consistency of terrestrial biomass can be dried using established low-cost drying systems. To test this hypothesis and its technical feasibility, prototype bench scale simulated drum dyers were designed and tested with blends of algae and ground pine. Scenedesmus dimorphus biomass was used as the algal feedstock, while 2 mm grind pine was used as the terrestrial feedstock. Pine was selected as the representative terrestrial feedstock to leverage independent HTL research using pine feedstock. In these studies, blends up to 60% algae produced drying curves similar to those of pine alone, and reached dryness (2% moisture) much more rapidly than algae alone. Thermogravimetric analyses performed on these feedstocks provided drying curves consistent with the simulated drum dryers. In addition, observable rheologic properties at the time of blending served as an indicator of drying performance, as those blends with texture similar to pine also dried similar to the pine control. Logistics analyses performed to determine cost and availability of feedstock materials for blending at production scale further indicate the potential of this approach. Lastly, our results indicate that blending of algae with terrestrial biomass enables the use of low cost dryers and has the potential to improve overall algal biofuel economics by capturing the value of excess biomass produced during periods of high productivity and by decoupling of algal production farms and conversion facilities.},
doi = {10.1016/j.algal.2017.03.005},
journal = {Algal Research},
number = PA,
volume = 24,
place = {United States},
year = {Wed Mar 22 00:00:00 EDT 2017},
month = {Wed Mar 22 00:00:00 EDT 2017}
}

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  • In this study, terrestrial lignocellulosic biomass has the potential to be a carbon neutral and domestic source of fuels and chemicals. However, the innate variability of biomass resources, such as herbaceous and woody materials, and the inconsistency within a single resource due to disparate growth and harvesting conditions, presents challenges for downstream processes which often require materials that are physically and chemically consistent. Intrinsic biomass characteristics, including moisture content, carbohydrate and ash compositions, bulk density, and particle size/shape distributions are highly variable and can impact the economics of transforming biomass into value-added products. For instance, ash content increases by anmore » order of magnitude between woody and herbaceous feedstocks (from ~0.5 to 5 %, respectively) while lignin content drops by a factor of two (from ~30 to 15 %, respectively). This increase in ash and reduction in lignin leads to biofuel conversion consequences, such as reduced pyrolysis oil yields for herbaceous products as compared to woody material. In this review, the sources of variability for key biomass characteristics are presented for multiple types of biomass. Additionally, this review investigates the major impacts of the variability in biomass composition on four conversion processes: fermentation, hydrothermal liquefaction, pyrolysis, and direct combustion. Finally, future research processes aimed at reducing the detrimental impacts of biomass variability on conversion to fuels and chemicals are proposed.« less
  • In this work, we examined the behavior of feedstock blends and the effect of a specific feedstock densification strategy (pelleting) on the release and yield of structural carbohydrates in a laboratory-scale dilute acid pretreatment (PT) and enzymatic hydrolysis (EH) assay. We report overall carbohydrate release and yield from the two-stage PT-EH assay for five single feedstocks (two corn stovers, miscanthus, switchgrass, and hybrid poplar) and three feedstock blends (corn stover-switchgrass, corn stover-switchgrass-miscanthus, and corn stover-switchgrass-hybrid poplar). We first examined the experimental results over time to establish the robustness of the PT-EH assay, which limits the precision of the experimental results.more » The use of two different control samples in the assay enabled us to identify (and correct for) a small bias in the EH portion of the combined assay for some runs. We then examined the effect of variable pretreatment reaction conditions (residence time, acid loading, and reactor temperature) on the conversion of a single feedstock (single-pass corn stover, CS-SP) in order to establish the range of pretreatment reaction conditions likely to provide optimal conversion data. Finally, we applied the assay to the 16 materials (8 feedstocks in 2 formats, loose and pelleted) over a more limited range of pretreatment experimental conditions. The four herbaceous feedstocks behaved similarly, while the hybrid poplar feedstock required higher pretreatment temperatures for optimal results. As expected, the yield data for three blended feedstocks were the average of the yield data for the individual feedstocks. As a result, the pelleting process appears to provide a slightly positive effect on overall total sugar yield.« less
  • In this work, we examined the behavior of feedstock blends and the effect of a specific feedstock densification strategy (pelleting) on the release and yield of structural carbohydrates in a laboratory-scale dilute acid pretreatment (PT) and enzymatic hydrolysis (EH) assay. We report overall carbohydrate release and yield from the two-stage PT-EH assay for five single feedstocks (two corn stovers, miscanthus, switchgrass, and hybrid poplar) and three feedstock blends (corn stover-switchgrass, corn stover-switchgrass-miscanthus, and corn stover-switchgrass-hybrid poplar). We first examined the experimental results over time to establish the robustness of the PT-EH assay, which limits the precision of the experimental results.more » The use of two different control samples in the assay enabled us to identify (and correct for) a small bias in the EH portion of the combined assay for some runs. We then examined the effect of variable pretreatment reaction conditions (residence time, acid loading, and reactor temperature) on the conversion of a single feedstock (single-pass corn stover, CS-SP) in order to establish the range of pretreatment reaction conditions likely to provide optimal conversion data. Finally, we applied the assay to the 16 materials (8 feedstocks in 2 formats, loose and pelleted) over a more limited range of pretreatment experimental conditions. The four herbaceous feedstocks behaved similarly, while the hybrid poplar feedstock required higher pretreatment temperatures for optimal results. As expected, the yield data for three blended feedstocks were the average of the yield data for the individual feedstocks. As a result, the pelleting process appears to provide a slightly positive effect on overall total sugar yield.« less
  • In this work examine the behavior of feedstock blends and the effect of specific feedstock densification strategy (pelleting) and on the release and yield of structural carbohydrates in a laboratory-scale dilute acid pretreatment (PT) and enzymatic hydrolysis (EH) assay. We report overall carbohydrate release and yield from the two-stage PT-EH assay for five single feedstocks (2 corn stovers, miscanthus, switchgrass, and hybrid poplar) and three feedstock blends (corn stover-switchgrass, corn stover-switchgrass-miscanthus, and corn stover-switchgrass-hybrid poplar). We first examined the experimental results over time to establish the robustness of the PT-EH assay, which limits the precision of the experimental results. Themore » use of two different control samples in the assay enabled us to identify (and correct for) a small bias in the EH portion of the combined assay for some runs. We then examined the effect of variable pretreatment reaction conditions (residence time, acid loading, and reactor temperature) on the conversion of a single feedstock (single-pass corn stover, CS-SP) in order to establish the range of pretreatment reaction conditions likely to provide optimal conversion data. Finally, we applied the assay to the sixteen materials (8 feedstocks in 2 formats, loose and pelleted) over a more limited range of pretreatment experimental conditions. The four herbaceous feedstocks behaved similarly, while the hybrid poplar feedstock required higher pretreatment temperatures for optimal results. As expected, the yield data for three blended feedstocks were the average of the yield data for the individual feedstocks. The pelleting process appears to provide a slightly positive effect on overall total sugar yield.« less