Life Cycle Assessment and Water Footprint of Diluent and Hydrogen Production via Thermochemical Conversion of Algae Biomass

• Author / Creator

  Nogueira Junior, Edson R

• In recent years, the number of studies exploring the potential of using algae as biomass to produce energy has grown, and biofuels produced from algae could be one of the main alternative sources to fossil fuels in the future. The thermochemical conversion of biomass to bioenergy has been deemed a promising route to produce algae-based products. This study was conducted to evaluate the literature available on the LCA of the thermochemical conversion of algae with a special interest in colder climates like Canada. The focus of the study is on assessments of the life cycle water requirement for the conversion of algae biomass. The review part focuses on the available literature on life cycle assessments of hydrothermal liquefaction, pyrolysis, and gasification, which are the thermochemical conversion pathways explored in depth so far, and on the water footprint related to the steps of the process. The key focus of the study was to examine the life cycle water footprint of conversion of algae biomass to produce diluent and hydrogen via thermochemical conversion. Overall, it takes into consideration two methods of feedstock production: ponds and photobioreactors (PBRs); and four conversion pathways: pyrolysis, hydrothermal liquefaction (HTL), gasification and hydrothermal gasification (HTG). The results obtained confirm the high water requirement for algae production and the necessity for recycling harvested water or adopt the use of alternative water sources. To produce 1 kg of algae through ponds, 1564 L of water are required, and this number decreases to 372 L when PBRs are used, however the energy requirements for PBRs are much higher than for ponds. From a final product perspective, gasification was the thermochemical conversion method that required the highest amount of water per MJ produced (mainly due to its low hydrogen yield), followed by pyrolysis and HTL. On the other hand, HTG presents the lowest water footprint mainly because a large amount of electricity generated as part of the process compensates for the electricity used by the system. The performance for all pathways can be improved through recycling channels.

• Subjects / Keywords

  • Algae Life Cycle Assessment
  • Thermochemical Conversion
  • Water Footprint

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3F47H86M

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.