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Title: Evaluation of a high-moisture stabilization strategy for harvested microalgae blended with herbaceous biomass: Part II — Techno-economic assessment

Abstract

The seasonal variability in algal biomass production and its susceptibility to rapid degradation increases uncertainty in algal productivity and increases risks to feedstock supply for conversion. During summer months when algal biomass productivity is highest, production could exceed conversion capacity, resulting in delayed processing and risk of biomass degradation. Drying algae for preservation is energy-intensive and can account for over 50% of the total energy demand in algae preprocessing. Anaerobic wet storage – ensiling – is a widely used storage technique for stabilization of high moisture forage. Wet stabilization of algae eliminates the need for drying, and blending with herbaceous biomass allows for the utilization of the silage industry’s existing harvest, handling and storage infrastructure. A storage facility co-located with the algae production and conversion operations was designed to stabilize algal biomass produced in excess of conversion capacity during summer months for use in the winter when algal biomass production is reduced. Techno-economic assessment of the costs associated with ensiling algae and corn stover blends suggest it to be a cost effective approach, compared to drying. In a high algal biomass productivity scenario, costs of wet storage ($/gallon diesel) were only 65% of the cost of drying. When a reducedmore » algal biomass productivity scenario was considered, the stored blend was able to cost-effectively provide sufficient biomass such that winter production in the algal ponds could cease, meanwhile incurring only 91% of the costs of drying; such an approach would facilitate algal biomass production in northern latitudes. Moreover, the wet storage approaches requiring only 8-10% of the total energy consumption and releasing only 20-25% of the greenhouse gasses when compared to a natural-gas based drying approach for microalgae stabilization.« less

Authors:
 [1];  [1];  [1];  [2];  [2];  [2];  [1];  [1]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  2. Harris Group, Seattle, WA (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:
1353124
Alternate Identifier(s):
OSTI ID: 1360915
Report Number(s):
INL/JOU-16-40716
Journal ID: ISSN 2211-9264; PII: S2211926416307676
Grant/Contract Number:
AC07-05ID14517
Resource Type:
Journal Article: Published Article
Journal Name:
Algal Research
Additional Journal Information:
Journal Volume: 25; Journal Issue: C; Journal ID: ISSN 2211-9264
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; algae; blending; corn stover; ensiling; storage; techno-economic analysis

Citation Formats

Wendt, Lynn M., Wahlen, Bradley D., Li, Chenlin, Ross, Jeffrey A., Sexton, Danielle M., Lukas, John C., Hartley, Damon S., and Murphy, J. Austin. Evaluation of a high-moisture stabilization strategy for harvested microalgae blended with herbaceous biomass: Part II — Techno-economic assessment. United States: N. p., 2017. Web. doi:10.1016/j.algal.2017.04.015.
Wendt, Lynn M., Wahlen, Bradley D., Li, Chenlin, Ross, Jeffrey A., Sexton, Danielle M., Lukas, John C., Hartley, Damon S., & Murphy, J. Austin. Evaluation of a high-moisture stabilization strategy for harvested microalgae blended with herbaceous biomass: Part II — Techno-economic assessment. United States. doi:10.1016/j.algal.2017.04.015.
Wendt, Lynn M., Wahlen, Bradley D., Li, Chenlin, Ross, Jeffrey A., Sexton, Danielle M., Lukas, John C., Hartley, Damon S., and Murphy, J. Austin. Wed . "Evaluation of a high-moisture stabilization strategy for harvested microalgae blended with herbaceous biomass: Part II — Techno-economic assessment". United States. doi:10.1016/j.algal.2017.04.015.
@article{osti_1353124,
title = {Evaluation of a high-moisture stabilization strategy for harvested microalgae blended with herbaceous biomass: Part II — Techno-economic assessment},
author = {Wendt, Lynn M. and Wahlen, Bradley D. and Li, Chenlin and Ross, Jeffrey A. and Sexton, Danielle M. and Lukas, John C. and Hartley, Damon S. and Murphy, J. Austin},
abstractNote = {The seasonal variability in algal biomass production and its susceptibility to rapid degradation increases uncertainty in algal productivity and increases risks to feedstock supply for conversion. During summer months when algal biomass productivity is highest, production could exceed conversion capacity, resulting in delayed processing and risk of biomass degradation. Drying algae for preservation is energy-intensive and can account for over 50% of the total energy demand in algae preprocessing. Anaerobic wet storage – ensiling – is a widely used storage technique for stabilization of high moisture forage. Wet stabilization of algae eliminates the need for drying, and blending with herbaceous biomass allows for the utilization of the silage industry’s existing harvest, handling and storage infrastructure. A storage facility co-located with the algae production and conversion operations was designed to stabilize algal biomass produced in excess of conversion capacity during summer months for use in the winter when algal biomass production is reduced. Techno-economic assessment of the costs associated with ensiling algae and corn stover blends suggest it to be a cost effective approach, compared to drying. In a high algal biomass productivity scenario, costs of wet storage ($/gallon diesel) were only 65% of the cost of drying. When a reduced algal biomass productivity scenario was considered, the stored blend was able to cost-effectively provide sufficient biomass such that winter production in the algal ponds could cease, meanwhile incurring only 91% of the costs of drying; such an approach would facilitate algal biomass production in northern latitudes. Moreover, the wet storage approaches requiring only 8-10% of the total energy consumption and releasing only 20-25% of the greenhouse gasses when compared to a natural-gas based drying approach for microalgae stabilization.},
doi = {10.1016/j.algal.2017.04.015},
journal = {Algal Research},
number = C,
volume = 25,
place = {United States},
year = {Wed Apr 26 00:00:00 EDT 2017},
month = {Wed Apr 26 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.algal.2017.04.015

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  • The seasonal variability in algal biomass production and its susceptibility to rapid degradation increases uncertainty in algal productivity and increases risks to feedstock supply for conversion. During summer months when algal biomass productivity is highest, production could exceed conversion capacity, resulting in delayed processing and risk of biomass degradation. Drying algae for preservation is energy-intensive and can account for over 50% of the total energy demand in algae preprocessing. Anaerobic wet storage – ensiling – is a widely used storage technique for stabilization of high moisture forage. Wet stabilization of algae eliminates the need for drying, and blending with herbaceousmore » biomass allows for the utilization of the silage industry’s existing harvest, handling and storage infrastructure. A storage facility co-located with the algae production and conversion operations was designed to stabilize algal biomass produced in excess of conversion capacity during summer months for use in the winter when algal biomass production is reduced. Techno-economic assessment of the costs associated with ensiling algae and corn stover blends suggest it to be a cost effective approach, compared to drying. In a high algal biomass productivity scenario, costs of wet storage ($/gallon diesel) were only 65% of the cost of drying. When a reduced algal biomass productivity scenario was considered, the stored blend was able to cost-effectively provide sufficient biomass such that winter production in the algal ponds could cease, meanwhile incurring only 91% of the costs of drying; such an approach would facilitate algal biomass production in northern latitudes. Moreover, the wet storage approaches requiring only 8-10% of the total energy consumption and releasing only 20-25% of the greenhouse gasses when compared to a natural-gas based drying approach for microalgae stabilization.« less
  • Here, algal biomass is becoming increasingly attractive as a feedstock for biofuel production. However, the swing in algal biomass production between summer and winter months poses a challenge for delivering predictable, constant feedstock supply to a conversion facility. Drying is one approach for stabilizing algal biomass produced in excess during high productivity summer months for utilization during low productivity months, yet drying is energy intensive and thus costly. Wet, anaerobic storage, or ensiling, is a low-cost approach that is commonly used to preserve high moisture herbaceous feedstock. The potential for microalgae stabilization without the need for drying was investigated inmore » this study by simulating ensiling, in which oxygen limitation drives anaerobic fermentation of soluble sugars to organic acids, dropping the pH and thereby stabilizing the material. Algal biomass, Scenedesmus obliquus, was blended with corn stover and stored in acidic, anaerobic conditions at 60% moisture (wet basis) to simulate wet storage by means of ensiling. Results demonstrate that algae and corn stover blends were successfully preserved in anaerobic, acidic conditions for 30 days with < 2% dry matter loss occurring during storage compared to 21% loss in aerobic, non-acidified conditions. Likewise, Scenedesmus obliquus stored alone at 80% moisture (wet basis) in acidified, anaerobic conditions for 30 days, resulted in dry matter losses of 6–14%, compared to 44% loss in neutral pH, anaerobic storage and 37% loss in a neutral pH, aerobically stored condition. Additional experiments were performed at a larger scale in which an algae and corn stover blend was subject to mechanical oxygen exclusion and a Lactobacillus acidophilus inoculum, resulting in 8% loss over 35 days and further indicating that acidic, anaerobic conditions can stabilize microalgae biomass. In summary, the stabilization of harvested algae can be achieved through anaerobic storage, securing a feedstock that is labile yet of high value.« less
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  • It is generally recognized that the front-end (pretreatment, fractionation, enzymatic hydrolysis) steps of a lignocellulose-to-ethanol process are both technologically immature and represent a large component ({approximately}60%) of the total product cost. In the past, we have tried to itemize the process steps and equipment for a complete plant. It was evident that, owing to the complexity and interrelated nature of this process, it was difficult to determine the influence of even minor changes to the process on the overall production cost of the product. We had originally developed a techno-economic model, based on spreadsheets, as a computational and assessment tool.more » However, our more recent work, which has looked at various process options such as hardwood vs softwoods, SO{sub 2} pretreatment of softwoods, and enzyme recycling, indicated that the model required greater flexibility if it was to assess a {open_quotes}generic{close_quotes} biomass-to-ethanol process. The model is currently being modified to address both the flexibility issues, through the incorporation of flowsheeting concepts, as well as including the most recent work on the various process options. In this article, we have described some of the pretreatment and fractionation issues that are being addressed in the updated model. 78 refs., 10 figs., 1 tab.« less
  • Ex situ catalytic fast pyrolysis of biomass is a promising route for the production of fungible liquid biofuels. There is significant ongoing research on the design and development of catalysts for this process. However, there are a limited number of studies investigating process configurations and their effects on biorefinery economics. Herein we present a conceptual process design with techno-economic assessment; it includes the production of upgraded bio-oil via fixed bed ex situ catalytic fast pyrolysis followed by final hydroprocessing to hydrocarbon fuel blendstocks. This study builds upon previous work using fluidized bed systems, as detailed in a recent design reportmore » led by the National Renewable Energy Laboratory (NREL/TP-5100-62455); overall yields are assumed to be similar, and are based on enabling future feasibility. Assuming similar yields provides a basis for easy comparison and for studying the impacts of areas of focus in this study, namely, fixed bed reactor configurations and their catalyst development requirements, and the impacts of an inline hot gas filter. A comparison with the fluidized bed system shows that there is potential for higher capital costs and lower catalyst costs in the fixed bed system, leading to comparable overall costs. The key catalyst requirement is to enable the effective transformation of highly oxygenated biomass into hydrocarbons products with properties suitable for blending into current fuels. Potential catalyst materials are discussed, along with their suitability for deoxygenation, hydrogenation and C–C coupling chemistry. This chemistry is necessary during pyrolysis vapor upgrading for improved bio-oil quality, which enables efficient downstream hydroprocessing; C–C coupling helps increase the proportion of diesel/jet fuel range product. One potential benefit of fixed bed upgrading over fluidized bed upgrading is catalyst flexibility, providing greater control over chemistry and product composition. Since this study is based on future projections, the impacts of uncertainties in the underlying assumptions are quantified via sensitivity analysis. As a result, this analysis indicates that catalyst researchers should prioritize by: carbon efficiency > catalyst cost > catalyst lifetime, after initially testing for basic operational feasibility.« less