The Princeton
Biodigester Project
By: Kevin Griffin
Outline
 Background Information
 Explanation of the Princeton Biodigester Project
 Details of Progress this Summer
 Future Plans
What Is a Biodigester?
 Anaerobic Digestion-C6H12O6 → 3CO2 + 3CH4
 Main byproducts are CO2, methane, and compost
Motivation
 Energy Independence
 Import 45% of transportation and
heating fuels in 2011 (EIA)
 Waste Management
 65% increase from 1980
 28% compostable (MSU)
 Environmental Impact
 Methane would otherwise
escape or be burned
 CH4 is a 20 times more potent
green house gas than CO2 (EPA)
Project Summary
 Biodigester at the
Forbes Garden
 Food waste from the
Forbes Dining Hall
 Pilot project to
determine viability of
Mid-Atlantic climate and
evaluate quality of
compost produced
Benefits to the University
 Reduce methane emissions
 Eliminate emissions from transporting
food waste
 Reduce food waste collection costs
 Supply the Garden Project with
compost
 Provide nitrogen rich compost to the
community, decreasing the
community’s need for nitrate fertilizers
that pollute the water supply
 Produce natural gas for heating and
cooking
Implementation
Construction of the Biodigester
Circuit for System Monitoring
and Data Logging
Challenges
 Two stages of digestion.
 Acidogenic bacteria break sugars and amino acids
into organic acids.
 Methanogenic bacteria then convert acids into CO2
and CH4
 Methanogenic bacteria are sensitive to pH and
temperatures
 The composition of waste stream can greatly affect
the balance of these bacteria groups
Future Research
 Response to




Changes in temperature
Changes in pressure
The introduction of bacterial cultures
The use of different waste materials
and how these changes affect the
system pH and the health of essential
bacteria.
Acknowledgements
 I would like to thank Dr. Shana Weber from the
Office of Sustainability for all of her help and
support.
 Thank you to Professor Justin Sheffield for technical
advice.
 Thank you to Sean Gallagher and his team for
constructing the biodigester and donating materials.
 Thank you to Dean Caddeau and the Forbes
College Office for their support and advice.
Sources of Data
 http://www.eia.gov/tools/faqs/faq.cfm?id=32&t=6
 http://css.snre.umich.edu/css_doc/CSS04-15.pdf
 http://epa.gov/climatechange/ghgemissions/gases/c
h4.html
 http://www.wcasfmra.org/biogas_docs/6%20Biodige
ster%20manual.pdf