Anaerobic Algae Digestor for Biogas Production

The goal of this project is to construct a four-stage, rumen-derived anaerobic digester for research in optimizing parameters for biogas production from algae.

=Problem Definition= Microalgae are an increasingly attractive replacement for current fossil fuel use. Production of biogas from anaerobic digestion remains unfeasible for large scale production due to technical restraints. Currently, most lab-scale anaerobic digesters used in research use a two-phase approach. We will be designing a four-phase anaerobic digester based on a compound stomach and the steps of anaerobic digestion to control and monitor the following parameters: temperature, pH, retention time, pump flow rate, electric conductivity, water level, and pressure to optimize the production of oxygen, carbon dioxide, and methane gases. Our digester will produce biogas with 50% methane content by the Spring 2019 and will allow the University of Idaho Biological Engineering department to continue to perform research on these important parameters for biogas production.

Background
Microalgae are an increasingly attractive replacement for current fossil fuel use. Production of biogas from anaerobic digestion remains unfeasible for large scale production due to technical restraints. Currently, most lab-scale anaerobic digesters used in research use a two-phase approach.

Deliverables
 Users will be able to inoculate the system via an inoculation port in the top cap of each chamber    Users will be able to monitor O2, CO2, and CH4 gas concentrations in each chamber via a touchscreen user interface  Users will be able to monitor pH, temperature, electric conductivity, mixing time, pump flow rate, water level, and pressure using this system.   Using water level output and individual gas concentrations, users will be able to calculate total gas produced in the system   The system will be retrofitted to the photobioreactor designed by a previous capstone team   The chambers will be easy to disassemble for cleaning   By the end of the semester, we will have produced biogas 

Specifications
 Functional:   Each chamber will have a one gallon working volume   The chambers will be easy to disassemble and clean </li>

 User Interface:   Operator shall be able to view temperature, pH, electrical conductivity, pump flow rate, water level, and mixing time using a touchscreen device powered by Raspberry Pi. </li>  Mixing, temperature and pump flow rate will be controlled automatically by the system based on user inputs </li>  Operator will be able to view oxygen, carbon dioxide, and methane gas composition </li>  Users will be able to view data taken by the sensors on two minute increment. </li>

 Mechanical:   Digester will be airtight and withstand pressure produced from anaerobic digestion </li>  The main section of the digester will be transparent for viewing of the project </li>  An inoculation port will be included for each chamber for additions of microbes and sampling </li>

 Electrical:   </li>

 Software:   We will be using a raspberry pi and arduino to control the system </li>  It will be coded in Python </li>  It should be able to export data to an Excel sheet </li>

 Environmental:   The chambers will withstand internal, water temperatures from 25 to 60 degrees Celsius </li>  The chambers will be free from oxygen </li>

 Production:   We will produce 50% methane concentration biogas by the end of the semester </li>  The cost will not exceed $4000 </li>

=Design Considerations= <li> Temperature</li> <li> Mixing</li> <li> Pumps</li> <li> Retention Time</li>

<li> </li> =Project Learning= <li> Literature - Anaerobic Digestor, and process parameters therein. </li> <li> Communication – Understanding project as a team by communicating problems </li> <li> Teamwork - Working together on solutions </li> <li> Biweekly Meetings – satisfy bullets above: Communication and Teamwork </li> <li> Troubleshooting – Foreseen troubleshooting with wiring and integrating the system. Keep moving forward, meet in a lab. </li> <li> Time Management – Being efficient with personal time so team can regularly meet. </li> <li> Resources – Getting advice from advisors, professors, peers, and forums (for electrical/software troubleshooting) </li> <li> Modeling, 3D Printing (pumps), Anaerobic Digestion, Microcontrollers, Choosing sensors, one chamber Prototype </li>

=Final Design= <li> Four Chamber Anaerobic Digester </li> <li> Airtight, use PVC caps and fabricate the caps to screw onto column chambers (top bottom) </li> <li> 24-hour retention time (All four) </li> <li> Arduino and raspberry pi for digitizing sensor data </li> <li> Data acquisition using computer </li> <li> Peristaltic Pumps (3D Printed) </li> <li> Mixing slurry (stepper motor and roto blade) </li> <li> Compartmentalized sensors with extra 3D printed coverings to maintain seal </li>

=Validation= <li> Analyzing gas content to prove successful anaerobic digestion process </li> <li> Airtight seals – Compare gas sensor data (o2 content) with atmospheric O2 </li> <li> Retention time/velocity of fluid: validated using time interval with water level data (from water level sensor) </li> <li> Microcontroller – Using multimeter and checking outputs at computer (Arduino) we will slowly validate until final implementation. </li> <li> Software – Proved by running Program </li> =Team Members=

=Additional Documentation=

Project Schedule



Meeting Minutes We are using the OneDrive platform to store and organize our meeting minutes. Follow the link to view the minutes. Minutes

Presentations

Agenda Likewise, follow the link below to view our agendas. Agenda