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Title: Acid-Catalyzed Algal Biomass Pretreatment for Integrated Lipid and Carbohydrate-Based Biofuels Production

Abstract

One of the major challenges associated with algal biofuels production in a biorefinery-type setting is improving biomass utilization in its entirety, increasing the process energetic yields and providing economically viable and scalable co-product concepts. We demonstrate the effectiveness of a novel, integrated technology based on moderate temperatures and low pH to convert the carbohydrates in wet algal biomass to soluble sugars for fermentation, while making lipids more accessible for downstream extraction and leaving a protein-enriched fraction behind. We studied the effect of harvest timing on the conversion yields, using two algal strains; Chlorella and Scenedesmus, generating biomass with distinctive compositional ratios of protein, carbohydrate, and lipids. We found that the late harvest Scenedesmus biomass had the maximum theoretical biofuel potential at 143 gasoline gallon equivalent (GGE) combined fuel yield per dry ton biomass, followed by late harvest Chlorella at 128 GGE per ton. Our experimental data show a clear difference between the two strains, as Scenedesmus was more successfully converted in this process with a demonstrated 97 GGE per ton. Our measurements indicated a release of >90% of the available glucose in the hydrolysate liquors and an extraction and recovery of up to 97% of the fatty acids from wetmore » biomass. Techno-economic analysis for the combined product yields indicates that this process exhibits the potential to improve per-gallon fuel costs by up to 33% compared to a lipids-only process for one strain, Scenedesmus, grown to the mid-point harvest condition.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B)
OSTI Identifier:
1220598
Report Number(s):
NREL/JA-5100-62000
Journal ID: ISSN 1463-9262
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Green Chemistry
Additional Journal Information:
Journal Volume: 17; Journal Issue: 2; Journal ID: ISSN 1463-9262
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; Algae; biorefinery; fractionation; lipids; carbohydrates; bioethanol; renewable diesel; process economics; TEA

Citation Formats

Laurens, L. M. L., Nagle, N., Davis, R., Sweeney, N., Van Wychen, S., Lowell, A., and Pienkos, P. T.. Acid-Catalyzed Algal Biomass Pretreatment for Integrated Lipid and Carbohydrate-Based Biofuels Production. United States: N. p., 2014. Web. doi:10.1039/C4GC01612B.
Laurens, L. M. L., Nagle, N., Davis, R., Sweeney, N., Van Wychen, S., Lowell, A., & Pienkos, P. T.. Acid-Catalyzed Algal Biomass Pretreatment for Integrated Lipid and Carbohydrate-Based Biofuels Production. United States. doi:10.1039/C4GC01612B.
Laurens, L. M. L., Nagle, N., Davis, R., Sweeney, N., Van Wychen, S., Lowell, A., and Pienkos, P. T.. 2014. "Acid-Catalyzed Algal Biomass Pretreatment for Integrated Lipid and Carbohydrate-Based Biofuels Production". United States. doi:10.1039/C4GC01612B. https://www.osti.gov/servlets/purl/1220598.
@article{osti_1220598,
title = {Acid-Catalyzed Algal Biomass Pretreatment for Integrated Lipid and Carbohydrate-Based Biofuels Production},
author = {Laurens, L. M. L. and Nagle, N. and Davis, R. and Sweeney, N. and Van Wychen, S. and Lowell, A. and Pienkos, P. T.},
abstractNote = {One of the major challenges associated with algal biofuels production in a biorefinery-type setting is improving biomass utilization in its entirety, increasing the process energetic yields and providing economically viable and scalable co-product concepts. We demonstrate the effectiveness of a novel, integrated technology based on moderate temperatures and low pH to convert the carbohydrates in wet algal biomass to soluble sugars for fermentation, while making lipids more accessible for downstream extraction and leaving a protein-enriched fraction behind. We studied the effect of harvest timing on the conversion yields, using two algal strains; Chlorella and Scenedesmus, generating biomass with distinctive compositional ratios of protein, carbohydrate, and lipids. We found that the late harvest Scenedesmus biomass had the maximum theoretical biofuel potential at 143 gasoline gallon equivalent (GGE) combined fuel yield per dry ton biomass, followed by late harvest Chlorella at 128 GGE per ton. Our experimental data show a clear difference between the two strains, as Scenedesmus was more successfully converted in this process with a demonstrated 97 GGE per ton. Our measurements indicated a release of >90% of the available glucose in the hydrolysate liquors and an extraction and recovery of up to 97% of the fatty acids from wet biomass. Techno-economic analysis for the combined product yields indicates that this process exhibits the potential to improve per-gallon fuel costs by up to 33% compared to a lipids-only process for one strain, Scenedesmus, grown to the mid-point harvest condition.},
doi = {10.1039/C4GC01612B},
journal = {Green Chemistry},
number = 2,
volume = 17,
place = {United States},
year = 2014,
month =
}

Journal Article:
Free Publicly Available Full Text
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Citation Metrics:
Cited by: 23works
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  • One of the major challenges associated with algal biofuels production in a biorefinery-type setting is improving biomass utilization in its entirety, increasing the process energetic yields and providing economically viable and scalable co-product concepts. We focus on the impact of compositional characteristics of biomass on the susceptibility to pretreatment in order to maximize the valorization of algal biomass conversion for biofuels and bioproducts. The release of monomeric carbohydrates in the aqueous phase and extractability of the lipid fraction was measured based a response surface methodology to find significant explanatory variables and interaction terms. We studied the effect of harvest timingmore » on the conversion yields, using three algal strains; Chlorella vulgaris and Scenedesmus acutus and Nannochloropsis granulata representing three different nutritional metabolic phases. Four cultivation conditions of high (≥ 90 gallon gasoline equivalent/ton biomass) value for a combined sugar- and lipid-based biofuels process were identified. These four conditions represent either mid or late stage harvest cultivation regimes. Lastly, the results indicate that acid pretreatment has potential to be applicable for a vast range of biomass samples to obtain high energy yields, but that the exact conditions and optima are dependent on the strain and likely the starting composition of the biomass.« less
    Cited by 1
  • One of the major challenges associated with algal biofuels production in a biorefinery-type setting is improving biomass utilization in its entirety, increasing the process energetic yields and providing economically viable and scalable co-product concepts. We focus on the impact of compositional characteristics of biomass on the susceptibility to pretreatment in order to maximize the valorization of algal biomass conversion for biofuels and bioproducts. The release of monomeric carbohydrates in the aqueous phase and extractability of the lipid fraction was measured based a response surface methodology to find significant explanatory variables and interaction terms. We studied the effect of harvest timingmore » on the conversion yields, using three algal strains; Chlorella vulgaris and Scenedesmus acutus and Nannochloropsis granulata representing three different nutritional metabolic phases. Four cultivation conditions of high (≥ 90 gallon gasoline equivalent/ton biomass) value for a combined sugar- and lipid-based biofuels process were identified. These four conditions represent either mid or late stage harvest cultivation regimes. Lastly, the results indicate that acid pretreatment has potential to be applicable for a vast range of biomass samples to obtain high energy yields, but that the exact conditions and optima are dependent on the strain and likely the starting composition of the biomass.« less
  • Beginning in 2013, NREL began transitioning from the singular focus on ethanol to a broad slate of products and conversion pathways, ultimately to establish similar benchmarking and targeting efforts. One of these pathways is the conversion of algal biomass to fuels via extraction of lipids (and potentially other components), termed the 'algal lipid upgrading' or ALU pathway. This report describes in detail one potential ALU approach based on a biochemical processing strategy to selectively recover and convert select algal biomass components to fuels, namely carbohydrates to ethanol and lipids to a renewable diesel blendstock (RDB) product. The overarching process designmore » converts algal biomass delivered from upstream cultivation and dewatering (outside the present scope) to ethanol, RDB, and minor coproducts, using dilute-acid pretreatment, fermentation, lipid extraction, and hydrotreating.« less
  • The U.S. Department of Energy (DOE) promotes the production of a range of liquid fuels and fuel blendstocks from biomass feedstocks by funding fundamental and applied research that advances the state of technology in biomass production, conversion, and sustainability. As part of its involvement in this program, the National Renewable Energy Laboratory (NREL) investigates the conceptual production economics of these fuels. This includes fuel pathways from lignocellulosic (terrestrial) biomass, as well as from algal (aquatic) biomass systems.