A2MExperimental and modeling approaches to optimize

an algae-to-methane coupled bioreactor system

Ruby An – 2015 SURF Metcalf StudentPrincipal Investigators : Joe Vallino & Zoe Cardon

The University of Chicago – Chicago – IL – MA – Woods Hole – Marine Biological Laboratory

Algae-to-methane (A2M) has potential as an efficient and practical renewable energy strategy

• Algal biomass: minimal land & water usage• Methane: efficiently stored & energy on demand

www.prx.orgwww.wageningenur.nl

A2M Research Aims

1. Experimental – Develop closed system with 100% nutrient recycling– Maximize methane production

2. Modeling – Develop accurate description of system– Predict system performance to achieve experimental

objectives

A2M Design

Temperature: 25 °C

A2M Design

Aerobic Algal Reactor

Inputs:• Air • CO2

• Light – Diel 12h Cycle

Temperature: 25 °C

Chlamydomonas rienhardtii CW15

25 μm

Green algae mutant lacking a cell wall

A2M Design

Temperature: 25 °C

Anaerobic Microbial Digester

Output: • CO2 and methane gas• Digested algae as nutrients & detritus

Aim 1: Experimental Set-upA2M IRL

Liquid Volume:• pH• Dissolved oxygen (DO)

Headspace:• Oxygen (O2 ) • Carbon Dioxide (CO2 )• Methane (CH4)

Data Monitoringin both reactors

Key Features of the Data

Lights on Lights off

Lights on Lights off

CO2 + H2O CH2O + O2 light

algae

Key Features of Data

Installed spargers

Doubled light levels

Elevated CO2 input0.039% => 2%

Key Features of Data

Day 1 Yesterday

Aim 2a: Algal Reactor Mass Balance Model

rate of change = gain - loss

State Variables:1. CAlgae

2. CDIC(aq)

3. CO2(aq)

4. pCO2(g)

5. pO2(g)

Inflow & Outflow

Inflow & Outflow

MassTransfer

Inflow & Outflow

MassTransfer

Algal Growth & Respiration

CO2 + H2O CH2O + O2lightalgae

Algal Growth Equation

Light Limitation CO2 Limitation

Adjustable Parameters

Model & Data Comparison

Model fit to days 57-60

ModelData

Model & Data ComparisonModel predictions for days 30-33

Data

Model

In Summary:

• Experimentally - achieved high algal growth • Accurately modeled algal reactor dynamics

• Establish and maximize methane production• Develop the full coupled bioreactor model to

simulate methanogenisis

Next Steps:

Acknowledgements

Joe VallinoZoe Cardon

Suzanne Thomas

Anonymous DonorKen Foreman & Wyntin Goodman

Zeiss Microscopy StaffJim & Joey

Questions/Discussion

Supplementary Info

Anaerobic Microbial Community

www.oceanscience.com

Inoculated Day 71

Methane

• Microscopic analysis of algal cellular disintegration

• Jumpstart methanogenic pathway : new inoculum

• Genomic analysis of microbial community?

Methane Production Strategies