UW Anaerobic Digester: Food Waste, Renewable Energy & Public Health: Feasibility

Executive Summary:

This project is seeking CSF funding for a feasibility phase trial to test whether there is capacity to build a 160 square foot anaerobic digester on the UW Seattle Campus. The anaerobic digester costs ~$95,000 and would utilize food waste from the Husky Union Building (HUB) to create compost and Renewable Natural Gas. This feasibility study would finalize: 1) Site Location 2) Gas Usage 3) Compost Usage

1) Site Location: the current proposed site for the anaerobic digester is adjacent to the Southwest doors of the HUB. Paul Zuchowski, HUB Associate Director, proposed this location because of: a) Proximity to the HUB kitchen (food waste source) b) High degree of visibility with many students passing through these doors c) Accessible electricity and water hookups. We considered other locations on campus, but none of those locations have all three of the above features of this proposed site near the HUB. The SW doors of the HUB is currently the best available option, but we need to finalize several details: a) Cost estimate of water/electricity hookup to HUB building b) Permission to clear plants/shrubs that are currently occupying this space.

2) Gas Usage: The anaerobic digester uses microbes to break down food waste and produce Renewable Natural Gas (RNG), which is chemically equivalent to methane gas. We could use the RNG in many ways, and we need to finalize what we would do with the gas. The current options are: a) Power a small generator to charge batteries for the UW Mail Services electric bicycles. We are discussing this option with Douglas Stevens, Program Support Supervisor at UW Mail Services b) Compress the natural gas into small tanks that can be used at UW student/staff/faculty barbeques, or sold to food trucks on campus or at the U-District Farmer's Market c) Clean the natural gas and plug it into the UW natural gas pipelines. Currently, charging the electric bicycle batteries seems to be the best option, but we need to finalize the following details: a) Discuss feasibility of having a battery charging station at the HUB (i.e. is it too far away from Mail Services?) b) How would the batteries be stored/secured? c) What regulations/procedures need to be in place to ensure safety of gas storage/usage?

3) Compost Usage: The anaerobic digester produces compost, which can be directly applied to plants. We are collaborating with Howard Nakase and Grounds Management to provide them with this compost free-of-charge. We need to finalize these details: a) How much compost would be used by Grounds Management (i.e. would there be surplus compost?) b) Would the UW Farm be able to use any compost? C) How would the compost be transported from the digester to Grounds Management/UW Farm?


Students/Staff/Faculty Involved:

Dr. Heidi Gough, PhD, Department of Civil & Environmental Engineering

Dr. Sally Brown, PhD, School of Forest Resources

Dr. Marilyn Ostergren, PhD, UW Renewable Energy Liaison

JR Fulton, Housing & Food Services Capitol Planning/Sustainability Manager

Aaron Flaster, BA, Research Coordinator, Department of Psychology

Global Sustainability Initiative (RSO)

Student Involvement:

This project would involve 1 part-time staff position, and 15-20 student volunteer positions. The part-time paid staff would be responsible for maintaining the digester (e.g. monitoring temperature, monitoring pH, monitoring odor control, bringing food waste to the digester 1x per day, etc.). The volunteer positions would be undergraduate/graduate students that want to conduct research projects on any aspect of the digester (e.g. gas composition, compost, engineering, business, etc.). These volunteers would be responsible for carrying out research their own papers/projects that are supervised by a UW faculty member. The volunteers could also be trained to lead tours of the digester for other UW students.  

Student involvement and interest in this project would also come from a UW Registered Student Organization (RSO), called Global Sustainability Initiative (GSI). The undergraduate members include: Caelan Wisont, Zhaoyi Fang, Yushan Tong, and Kyler Jobe. GSI focuses on promoting sustainability on a global scale, emphasizing household-scale anaerobic digestion projects to create methane gas for stoves. GSI grew out of SafeFlame LLC, which was started by a UW MBA graduate (Kevin Cussen), and received a CSF grant in 2015-2016. GSI also connects interested students to anaerobic digestion projects and gets students excited about working with anaerobic digestion, renewable energy, and public health.

Education & Outreach:

We will publicize our project in three ways:

1) GSI: GSI will advertise this project to other RSOs, and will publicize this digester project during their tabling events. GSI is the undergraduate student group that is helping to push this project forward, and their current network with other RSOs will help raise awareness about our project on campus.

2) Signage: If the digester is built, we will create signage on/around the digester with educational information about anaerobic digestion. For instance, the signage will explain how anaerobic digestion works, how the gas/compost is being used, statistics/scale of the current project, how the project could be scaled up, other digester projects currently happening in Seattle, etc. These signs would be located on the outside of the digester and available for anyone to read.

3) Undergraduate/Graduate Courses: The faculty members collaborating on this project (Dr. Heidi Gough, Department of Civil & Environmental Engineering; Dr. Sally Brown, School of Forest Resources) will encourage their undergraduate and graduate students to conduct research projects on the anaerobic digester. Dr. Gough is primarily interested in the gas production and how changing the inputs (types of food waste) affects the composition of the gas. Dr. Brown is interested in soil science and how the type of food waste affects the chemical makeup of the compost. Additionally, we will do a quarterly presentation for the Sustainability Studio (ENVIR 480) course. This would be a 15-20 minute presentation for the undergraduate students in this course at the beginning of each quarter. ENVIR 480 focuses on sustainability, and a previous group of students from this course conducted a research project on anaerobic digestion. In Fall 2017, Aaron Flaster met with the instructor for ENVIR 480 and the instructor was open to having Aaron present to her students about the anaerobic digester project.

Environmental Impact:
  • Energy Use
  • Food
  • Waste
Project Longevity:

At present, we do not know how this project will be maintained in the long run. We know that too many student projects often fail because students graduate, funds run out, and people forget about past projects. We won’t let that happen with this project. That is precisely why we want to carry out this feasibility phase—to clarify and ensure that we have a clear plan for how to maintain this project in the long run.

To provide ongoing maintenance, we would need to secure funding and create a part-time staff position, or incorporate the ongoing maintenance into an existing UW staff position. We are currently discussing with Howard Nakase whether the UW Sustainability Coordinator position (within Grounds Management) could be responsible for maintaining the digester. We need to finalize: a) Whether this position has enough time to take on these additional responsibilities b) If there needs to be additional ongoing funding, and if so, where that funding will come from.

Environmental Problem:

Food waste is an urgent public health issue. In the U.S., approximately 31% of post-harvest food is wasted (i.e. thrown away or spoiled). This is approximately 133 billion pounds of food annually, costing approximately $161 billion (“USDA | OCE | U.S. Food Waste Challenge | FAQ’s,” n.d.). This is shocking and shameful, given national rates of food insecurity and poverty. In addition, food waste often rots in landfills, creating methane gas, which is nearly 4x as damaging to the ozone layer as CO2 emissions. We have to address food waste at the local, city, and national level.

This anaerobic digester project provides a small-scale model of how to utilize food waste to produce renewable energy and compost. The anaerobic digester that we are proposing to install is pre-fabricated by a Seattle-based business called Impact Bioenergy (http://impactbioenergy.com/). The digester is approximately 160 square feet and can process ~135 pounds of pre-consumer food waste per day. The digester can store ~175 cubic feet of RNG, and when this gas powers a generator, it produces about 360,000 BTU of energy per day, with a 2.5-4kW energy output. This is enough to power a small generator, which can charge batteries for electric cars/bicycles. The gas can also be used directly in pipelines or tanks (if the gas is cleaned/compressed). Although this is a relatively small-scale model, it will show how university campuses and community businesses/organizations can utilize their food waste to produce RNG, which reduces methane emissions, carbon emissions, and pollution associated with hauling food waste to composting facilities/landfills. Other universities in the U.S. have installed anaerobic digesters, but we do not know of any other universities/colleges in the Pacific Northwest Region that have an anaerobic digester that serves as a model for how to utilize food waste.

Explain how the impacts will be measured:

To evaluate the digester’s effectiveness, we will measure:

Food Waste

-        Pounds of food waste diverted to digester from waste-stream (which usually goes to Cedar Grove composting facility),

-        Type of food waste used (X % meat, X% vegetables, etc.)


-        Cubic feet of RNG produced per week

-        Amount of electricity generated per day/week


-        Pounds of compost produced per week


-        Carbon emission reductions of not having to haul away X pounds of food waste

-        Methane emission reductions of preventing food waste from rotting in landfill (for other facilities where food waste is not composted)


-        Cost-savings of diverting waste (cost reductions of not hauling away food waste in garbage trucks)

-        Cost-savings of producing compost (rather than purchasing from a 3rd party)

-        Cost-savings of producing electricity/gas

Total amount requested from the CSF: $10,000
This funding request is a: Grant
If this is a loan, what is the estimated payback period?:


1) Budget Esimate--Impact Bioenergy 2) Cost evaluation of Sustainability Coordinator maintaining digester for 10 days
ItemCost per ItemQuantityTotal Cost
Impact Bioenergy Budget/Engineering Evaluation--Gase Usage800018000
Sustainability Coordinator hourly wage$20/hour10200
UW Facilities Budget Estimate (Electricity/Water)180011800

Non-CSF Sources:

SPU Waste-Free Communities Matching Grant15000
Project Completion Total: $25,000


TaskTimeframeEstimated Completion Date
Site LocationFebruary 1-April1April 1
Gas UsageFebruary 1-April1April 1
Compost UsageFebruary 1-April1April 1
Ongoing MaintenanceFebruary 1-April1April 1