The use of hydrothermal carbonization to recycle nutrients in algal biofuel production

Robert B. Levine, Christian O.Sambolin Sierra, Ryan Hockstad, Wassim Obeid, Patrick G. Hatcher, Phillip E. Savage

Research output: Contribution to journalArticlepeer-review

59 Scopus citations


The high fertilizer demand for biodiesel production from microalgae is a significant challenge facing the commercialization of this promising technology. We investigated a processing strategy called hydrothermal carbonization (HTC) to convert wet algal biomass into a lipid-rich hydrochar and aqueous phase (AP) co-product. By reacting biomass at 200°C for 15 min, about 50% of the algae biomass became a solid hydrochar and roughly 40-70% of the C, N, and P in the reactant material dissolved into the AP. For the first time, an AP co-product of this nature was analyzed by HPLC, GC-MS and FT-ICR-MS to identify and characterize the dissolved organic matter. Using a unique marine bi-culture suspected to contain a green algae (Nannochloris) and a cyanobacteria (Synechocystis), we demonstrated that this AP co-product can support biomass growth better than a medium containing only inorganic nutrients. To manage unwanted contamination and optimize AP utilization, we employed a two-stage growth process and fed-batch additions of the AP co-product. The effect of media recycling and nutrient supplementation, as well as a production model for a large-scale facility, are discussed. Our work suggests that HTC can play a critical role in making algal biorefineries more sustainable by obviating biomass drying for fuel processing and recycling nutrients. © 2013 American Institute of Chemical Engineers Environ Prog, 32: 962-975, 2013

Original languageEnglish (US)
Pages (from-to)962-975
Number of pages14
JournalEnvironmental Progress and Sustainable Energy
Issue number4
StatePublished - Dec 2013

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Environmental Chemistry
  • General Chemical Engineering
  • Renewable Energy, Sustainability and the Environment
  • Water Science and Technology
  • Waste Management and Disposal
  • General Environmental Science


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