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Title: Phosphorus and nitrogen recycle following algal bio-crude production via continuous hydrothermal liquefaction

Phosphorus and nitrogen are essential components of microalgal growth media. Critical to a wide range of biochemical processes, they commonly limit primary productivity. Recycling elemental phosphorus and fixed nitrogen after fuel conversion via hydrothermal liquefaction (HTL) of algae biomass reduces the need for mined phosphorus and synthetic nitrogen resources. We used scenedesmus obliquus DOE 0152.Z and Chlorella sorokiniana DOE1412 as test organisms in assessing nutrient recycle of phosphorus from filtered solids collected downstream of the HTL reactor and nitrogen collected from the aqueous phase after gravimetric biocrude separation. Maximum specific growth rates were measured in growth media using HTL waste as the sole source of either phosphorus or nitrogen and were compared to an algal growth medium control (BG-11). The maximum specific growth rate of both organisms in the recycled phosphorus medium were nearly identical to rates observed in the control medium. Both organisms showed significantly reduced growth rates in the recycled nitrogen medium. C. sorokiniana DOE1412 adapted after several days of exposure whereas S. obliquus DOE0152.Z exhibited poor adaptability to the recycled nitrogen medium. After adaptation, growth rates observed with C. sorokiniana DOE1412 in the recycled nitrogen medium were 3.02 (± 0.13) day -1, 89% of the control mediummore » (3.40 ± 0.21). We further tested maximum specific growth rates of C. sorokiniana DOE1412 in a medium derived entirely from HTL byproducts, completely replacing all components including nitrogen and phosphorus. In this medium we observed rates of 2.70 ± 0.05 day -1, 79% of the control. By adding trace metals to this recycled medium we improved growth rates significantly to 3.10 ± 0.10, 91% of the control, which indicates a critical element is lost in the conversion process. Recycling elemental resources such as phosphorus and nitrogen from the HTL biofuel conversion process can provide a significant reduction in media cost and improves the prospects for industrial scale, algae-based biofuels.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [2] ;  [2]
  1. Pacific Northwest National Lab. (PNNL), Sequim, WA (United States). Marine Sciences Lab.
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Chemical and Biological Process Development Group
Publication Date:
Report Number(s):
PNNL-SA-124518
Journal ID: ISSN 2211-9264; PII: S2211926416308384
Grant/Contract Number:
AC05-76RL01830
Type:
Published Article
Journal Name:
Algal Research
Additional Journal Information:
Journal Volume: 26; Journal ID: ISSN 2211-9264
Publisher:
Elsevier
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; Algae biofuel; Nutrient; Resource assessment; Maximum specific growth rates; Sustainability; HTL; algae; biofuel; sustainability; Resource Assessment; Microalgal growth rates
OSTI Identifier:
1372498
Alternate Identifier(s):
OSTI ID: 1390573; OSTI ID: 1398174