Techno-economic analysis of algal lipid fuels

144 Pages·2013·1.68 MB·English

AN ABSTRACT OF THE THESIS OF

Xuwen Xiang for the degree of Master of Science in Chemical Engineering presented on
December 3, 2013

Title: Techno-Economic Analysis of Algal Lipid Fuels

Abstract approved: ________________________________________________________
Christine Kelly

A techno-economic analysis (TEA) was performed to evaluate the technology, cost, and resource
use for algal biofuel production based on today’s economics and technology. The basic goal of
this study is to develop a model to calculate the mass and energy balances and costs to produce 10
million gal of lipid per year from microalgae. There are previous studies that estimate these
parameters, but the detailed assumptions and calculations are not published. This analysis
considers two algal growth pathways, e.g. open pond and photobioreactor (PBR) cultivation. This
study demonstrated that large-scale PBRs costs are much more than open pond systems for the
production of biofuel from algae. Lipid production costs are highly sensitive to the assumption of
algae productivity and lipid content. Currently, the economics of producing biofuel from algae is
not competitive with petroleum fuels. In future, several strategies can be performed for potential
enhancement algal biofuel economics, includes the production of high value co-products from
algae, integrating wastewater treatment, and improvement of algal biofuel technology.
©Copyright by Xuwen Xiang
December 3, 2013
All Rights Reserved
Techno-Economic Analysis of Algal Lipid Fuels

by
Xuwen Xiang

A THESIS
Submitted to
Oregon State University

in partial fulfillment of
the requirements for the
degree of

Master of Science

Presented December 3, 2013
Commencement June 2014
Master of Science thesis of Xuwen Xiang presented on December 3, 2013.

APPROVED:

____________________________________________________________________
Major Professor, representing Chemical Engineering

____________________________________________________________________
Head of the School of Chemical, Biological and. Environmental Engineering

____________________________________________________________________
Dean of the Graduate School

I understand that my thesis will become part of the permanent collection of Oregon State
University libraries. My signature below authorizes release of my thesis to any reader upon
request.

____________________________________________________________________
Xuwen Xiang, Author
ACKNOWLEDGEMENTS

The author expresses sincere gratitude to advisor Dr. Christine Kelly for her patients, motivation
and advising. Her guidance helped me to develop my interests and ideas about engineering
research, in addition to helping me proceed through the master program and complete the thesis.
The author would also like to thank Bryan Kirby, Megan Shadlow, and Tal Sharf for their help
and encouragement.
CONTRIBUTION OF AUTHORS

Dr. Christine Kelly reviewed and modified the manuscript and helped the author to design the
study. She also helped the author analyze the economic values for the lipid price.
TABLE OF CONTENTS
Page
1 INTRODUCTION ........................................................................................................................ 1
2 ALGAL BIOFUELS TECHNOLOGY REVIEW ........................................................................ 2
2.1 Microalgae ............................................................................................................................. 2
2.2 Potential of Microalgal Biodiesel .......................................................................................... 2
2.3 Strain Isolation and Selection ................................................................................................ 2
2.4 Chemical Composition and Lipid .......................................................................................... 4
2.5 Algae Cultivation .................................................................................................................. 5
2.5.1 Sunlight .......................................................................................................................... 6
2.5.2 Temperature ................................................................................................................... 7
2.5.3 Salinity ........................................................................................................................... 7
2.5.4 pH ................................................................................................................................... 8
2.5.5 Contamination ................................................................................................................ 8
2.5.6 Scale-up cultivation ........................................................................................................ 9
2.6 Nutrients, CO and Water ...................................................................................................... 9
2
2.6.1 Nutrients for algae cultivation ...................................................................................... 10
2.6.2 Effect of Nutrients ........................................................................................................ 11
2.6.3 Nutrients recycle .......................................................................................................... 12
2.6.4 CO ............................................................................................................................... 12
2
2.6.5 Water ............................................................................................................................ 14
2.7 Algae Cultivation Pathways ................................................................................................ 14
2.7.1 Open pond .................................................................................................................... 15
2.7.2 Photobioreactor ............................................................................................................ 19
TABLE OF CONTENTS (Continued)
Page
2.8 Downstream Processing: Harvesting and Dewatering ........................................................ 22
2.8.1 Flocculation and sedimentation .................................................................................... 23
2.8.2 DAF .............................................................................................................................. 25
2.8.3 Filtration and screening ................................................................................................ 26
2.8.4 Centrifugation .............................................................................................................. 27
2.8.5 Drying .......................................................................................................................... 29
2.9 Extraction of Lipid from Algae ........................................................................................... 29
2.9.1 Cell disruption .............................................................................................................. 29
2.9.2 Extraction and purification process .............................................................................. 30
2.10 Conversion of Algal Extracts ............................................................................................ 32
2.11 Other Biofuel Conversion Technologies ........................................................................... 33
2.11.1 Biofuels from heterotrophic algae .............................................................................. 33
2.11.2 Pyrolysis ..................................................................................................................... 34
2.11.3 Gasification ................................................................................................................ 34
2.11.4 Liquefaction ............................................................................................................... 35
2.11.5 Anaerobic digestion ................................................................................................... 35
2.12 Non-fuel Valuable Products .............................................................................................. 38
2.13 Algae Biodiesel Economic Review ................................................................................... 40
3 TECHNO-ECONOMIC ANALYSIS RESULTS ....................................................................... 41
3.1 Baseline Algal Biofuel Pathway Overview for TEA ........................................................... 41
3.2 Open Ponds .......................................................................................................................... 42
3.3 PBR ..................................................................................................................................... 45
TABLE OF CONTENTS (Continued)
Page
3.4 Nutrients, Water, and CO ................................................................................................... 47
2
3.4.1 Phosphorus ................................................................................................................... 47
3.4.2 Nitrogen........................................................................................................................ 48
3.4.3 Water Demand ............................................................................................................. 49
3.4.4 CO Demand ................................................................................................................ 51
2
3.5 Downstream Processing: Harvesting and Dewatering ........................................................ 53
3.5.1 Flocculation and Sedimentation ................................................................................... 53
3.5.2 DAF .............................................................................................................................. 54
3.5.3 Centrifugation .............................................................................................................. 55
3.6 Extraction of Lipid from Algae ........................................................................................... 56
3.6.1 Cell disruption .............................................................................................................. 56
3.6.2 Extraction and purification process .............................................................................. 57
3.7 Anaerobic Digestion ............................................................................................................ 59
3.7.1 Anaerobic Digestion ..................................................................................................... 59
3.7.2 CHP systems ................................................................................................................ 61
3.7.3 Extraction and anaerobic digestion process flow. ........................................................ 62
3.8 Baseline Algal Biofuel Model and Mass Flows .................................................................. 63
3.8.1 TEA baseline model ..................................................................................................... 63
3.8.2 Algae Process Flow Diagram ....................................................................................... 65
3.9 Aspen Plus Simulation Development .................................................................................. 73
3.9.1 Introduction to Aspen Plus simulation ......................................................................... 73
3.9.2 Aspen Plus simulation for algal biofuel ....................................................................... 75