The ComPOSTer: Meet the New Team Members!

In 2020 we are excited to welcome three new student assistants to our team. Get to know them below!

Name: Milan Eldridge ’20
Major:  Art & Archaeology 
Hometown:  Dayton, Ohio / Louisville, Kentucky 
Why I was interested in assisting: I have really enjoyed being involved in Pink House [Forbes College’s residential social sustainability living community] what I could do to personally be more sustainable. Among many things, this led me to become more interested in composting on a larger scale and I wanted to help convert our campus’s food waste into a useful material. I am excited to help make our university more environmentally friendly while meeting like-minded peers!

Name: Roy Kim ’22
Major: Anthropology
Hometown: New York City
Why I was interested in assisting: I wanted to help steward the incredible resource of food scraps that we have on campus by turning it to beautiful compost. 

Name  Reese Knopp ’23
Major:  Mechanical Engineering
Hometown:  Northport, NY
Why I was interested in assisting: I’ve always been interested in environmentalism and sustainability, so the S.C.R.A.P. lab has provided me with a great opportunity to participate in practical efforts that make a difference on campus, while also learning a lot about food waste mitigation and composting practices. 

Data: 1/31 – 2/13

The data table now includes a column for POST-CONSUMER material as we continue our effort to collect and compost consumer plate scrapings and compostable serviceware from the food gallery in Frist Campus Center.

The ComPOSTer: PFAS and Volunteer Project

Happy Friday everyone,

This week’s update is a recap from Intersession week. The S.C.R.A.P. Lab was closed and the composting system remained in its auto-digest cycle while Gina attended the U.S. Composting Council’s (U.S.C.C.)’s Annual Conference, COMPOST 2020, where she presented a case study on the S.C.R.A.P. Lab as part of a panel discussing the composting experience on a large(r) college campus. In between her session, Gina also attended other sessions and participated in a volunteer compost bin making project. Read the highlights below:


One of the biggest topics at the conference was a change in the certification standards for compostable serviceware. Starting this year, the Biodegradable Products Institute (BPI) – North America’s leading certifier of compostable products and packaging – will no longer certify compostable serviceware containing intentionally added fluorinated chemicals such as PFAS .

Why does this matter?

PFAS are a group of long-lived chemicals that are used ubiquitously in everyday products for their stain/grease resistant properties. They are found in our clothes, carpets, food packaging, and even Post-It Notes! Because PFAS are water soluble, they enter our waterways and soils, and as a result can accumulate in our bloodstream. In excess amounts, these chemicals may have toxic implications and adverse effects on human health.

What is the impact of the new rule?

About 2,000 or 20% of BPI’s certified products have since lost certification and compostable product vendors are researching and testing new alternatives.

Here at the University, our Campus Dining team will be asking for updated certifications from vendors to limit our procurement of food serviceware and packaging containing PFAS.

Compost Bin Volunteer Project

Several other young compost professionals and I participated in a compost bin-making volunteer project with Charleston (SC)’s Green Heart Project – a non-profit that builds garden-based experiential learning projects and school garden programs to educate students, connect people, and cultivate community through growing, eating, and celebrating food.

We built several 8 cubic feet bins and dropped one off at the recipient school in its urban garden as shown below:

These bins aren’t necessarily large enough to generate hot composting conditions for accelerated organic decomposition, but are small enough to enable school children to engage with them.
The urban school farm incorporates composting into its crop rotation plan.

Data: End of January

With the S.C.R.A.P. Lab closed last week, this week’s data comes from the week prior and represents the to-date statistics at the close of January.

The ComPOSTer: Back at it with baseline post-consumer measurements

Hi all,

The S.C.R.A.P. Lab has been back up and running as of Jan. 6th when students arrived back to campus for Reading Week. In addition to resuming regular loading activities, we have started one of our 2020 action items to expand compostable ware collection in the retail food gallery of Frist Campus Center.

As with all data collection efforts, our first step is to obtain a baseline of current quantity and quality of the items that are placed in the S.C.R.A.P. Lab bin by diners for composting. Under the current procurement practices, these include all food scraps, napkins, burrito bowls and molded fiber (paper) plates as indicated by the signage on the temporary bin:

To limit contamination of non-acceptable items, the S.C.R.A.P. Lab bin has a lid and is placed at the end of the line so only the most well-intended consumers use the bin. We find that many people just discard their items in the first bin that they see without even looking at the signage. So we might not capture the greatest amount of viable material, but the risk of contamination is lower.

The S.C.R.AP. Lab bin is placed at the far end of the materials sorting line to limit contamination.

Over the last 6 days of measurement, we’ve noticed the following trends:

  • The amount of post-consumer material collected is about 30 lbs/day
  • Contamination levels hover around 15% (by volume), you can think of that as a B to B+ which is good but not great
  • The most common contaminants have been polymer-based materials such as cups and utensils made with PLA (see below) which can only be composted in facilities that keep these materials at a high temperature for an extended (or repeated) number of times unlike our composting system which has a short residency period of 5-7 days.
PLA-based cup and utensils that were incorrectly placed in the S.C.R.A.P. Lab bin

Next Steps:

  • We will continue to collect and monitor the “front of house” bin this week to confirm the above trends
  • We will test a “Report Card” sign to bring awareness to the level of contamination and the most common culprits
  • Meanwhile, our Campus Dining team is hard at work at reviewing their disposable product line and trying to replace certain items with ‘SCRAPPY-friendly” items

Weekly Data: 1/3 – 1/16

Over the last two weeks, we resumed loading activities. This week when the composting vessel reaches capacity (about 75% full), we will resume off-loading.

Looking back on 2019

Dear composting friends,

Thank you for being loyal followers and supporters of the S.C.R.A.P. lab in its first full calendar year of composting operations! With the New Year (and Decade) just a few hours away, the ComPOSTer takes a moment to look back on the highlights of 2019 as well as the next steps to look forward to in 2020. See you in the New Year!


Over the last year, the S.C.R.A.P. Lab…

  • Converted 62 tons of food scraps into nutrient-rich compost that is now being tested on the campus grounds in a variety of forms
  • Avoided 37 metric tons of CO2-equivalent emissions
  • Engaged 18 students as operational assistants
  • Expanded food scraps collection partnerships with the Coffee Club and 4 campus departments (McGraw Center, Geosciences, Ecology & Evolutionary Biology, Psychology)
  • Partnered with several major campus events to divert both food scraps and serviceware for compostability testing
  • Featured in and engaged many more people in 30 presentations and tours
  • Contributed to Campus as Lab projects:
    • Student course projects: 3
    • Faculty-sponsored research projects: 3 active
    • Junior papers/senior theses: 2 active


  • Expanded compostables collection in the food gallery of Frist Campus Center
  • Integration of research efforts with operational testing of different carbon feedstocks, beginning with wood pellets
  • Testing of different food scraps collection and drop-off systems to expand reach across campus
  • Begin the study of compost applications on campus farmland
  • A new video highlighting the behind the scenes processes and the people involved in the journey from food scrap to compost
  • Facility Relocation: “SCRAPPY” will be moved to a permanent home on campus in spring 2020.

The ComPOSTer: Meet this semester’s new assistants

Good evening all,

As we head into Thanksgiving, I just wanted to convey my gratitude to the team of student assistants who make the daily to weekly cross-campus trek to participate in the food scraps composting demonstration project.

Composting can be a very labor intensive process, so having a hardworking and dedicated team is key to success! This semester we are lucky to have 8 regular student assistants, 3 of whom are new to the project.

Hear in their own words why each wanted to join the S.C.R.A.P. Lab team:

Name and Class Year: Christian Hernandez ’22
Concentration: Molecular Biology
Hometown: Manvel, TX
Why you decided to join the team: As a small farmer and composter myself, I want to participate in how composting can work at a larger scale as well as just maintain some fitness through physical labor.
Name and Class Year: Julia Herrle, ’19*23
Concentration: MPA, International Relations
Hometown: Wexford, PA
Why you decided to join the team: I’m passionate about improving food security and sustainability of food systems. Reducing food waste is an important part of this, and I’m excited to learn more about composting at Princeton!
Name and Class Year: Chloé Vettier, GS
Concentration: French Literature
Hometown: Paris, France
Why you decided to join the team: because I want to support sustainable initiatives on campus – and I really miss my composter in Paris!

Weekly Data: 11/8 – 11/21

Happy Thanksgiving!


The ComPOSTer: Welcome Back & Compostable Coffee Pod Testing

Hi all,

The S.C.R.A.P. Lab has been back up and running for the past week since everyone returned from Fall Break.

One of the latest efforts we are testing is collecting and composting spent compostable coffee pods and their packages from departments making the switch from single-use disposable coffee cups. Made popular by Keurig about 15 years ago, these “K-Cups” have contributed to society’s growing plastic waste problem. In 2014, Keurig sold enough K-Cups that if placed end-to-end, would circumnavigate the globe 10.5 times. The majority of these ended up in landfills.

Since then Keurig has responded by creating recyclable K-Cups, but these are still energy intensive to make and there is no guarantee that the cups will actually be recycled. Consumers have to place them in recycling bins and not all recycling centers have the correct sorting technology to properly recycle them. Furthermore, more and more recycling centers across the U.S. have stopped accepting the type of plastic (#5) used to make these K-cups due to China’s import ban on plastic waste.

So… where composting facilities exist, the more sustainable option is a coffee pod made of compostable* materials and packaging like these from Wolfgang Puck Co.

These compostable pods are used in coffee machines such as NEWCO’s CX Touch.

Carola Gerbick removes a bin of spent coffee pods from the coffee machine.

The S.C.R.A.P. Lab is currently partnering with the Psychology and Geosciences departments to test the compostability of different types of  branded pods and packages claiming to be “100% compostable” inside of the in-vessel composting system.

If all goes well, we will try to advance this best practice across other campus departments.

*Look for “compostable”, not “biodegradable”, to ensure that the materials break down in a reasonable amount of time and don’t release metal residues. For assurance, pursue products that have been certified by the Biodegradable Products Institute (BPI). 

Weekly Data: 11/1 – 11/7

Last week we started to gradually re-fill the composting system so there wasn’t any compost to off-load. We expect to begin off-loading again at the end of this week.

Total Food Academic


/Event Collection

Campus Center/Cafes Wood Shavings (BA/CS) % BA/CS Compost Off-Loaded GHG Emissions Saved (MTCO2-eq)
11/1 – 11/7 2,967 333 2,634 1,026 35% 0
Cumulative (lbs) 142,250 3,718 138,532 46,162 32% 136,200 42

The ComPOSTer: Fall Break Plans

Hi all,

Leaves are turning on campus, midterms are over, and students have started to depart campus for Fall Break.  Which means that the S.C.R.A.P. Lab will also be getting a rest and will be temporarily shut down during this time. In preparation, the team focused on gradually emptying the compost from the system’s vessel over the last week.

During Fall Break, Gina will be attending the Association for the Advancement of Sustainability in Higher Education (AASHE)’s annual conference and will be co-presenting with several other higher education institutions on a session titled, On-Site Composting: How to Start, Evolve, and Overcome Challenges.

With on-site composting becoming an increasingly important and recognized food waste diversion strategy to meet institutional sustainability goals,  the session will provide useful information and resources so other colleges/universities can assess which processes are best suited to start or grow their own campus composting programs. The S.C.R.A.P. Lab will be featured as one of several case studies that will provide session participants with a better understanding of different composting systems and their associated operations.


See below for the cumulative to-date data going into Fall Break:

Total Food Academic/Residential Buildings Campus Center/Cafes Wood Shavings (BA/CS) % BA/CS Compost Off-Loaded GHG Emissions Saved (MTCO2-eq)
Cumulative (lbs) 139,283 3,385 135,898 45,136 32% 136,200 41

The ComPOSTer: Event Partnerships!

Good evening all,

With the Fall semester in full swing, activity at the S.C.R.A.P. Lab has been heating up. In the last month, we were busy processing an extra 579 lbs. of food scraps and compostable items from 3 major events on campus serving a combined total of around 1,750 people. They were: the First Year Pre-Rade (1,000 people), Graduate College BBQ (250 people), and the Facilities Appreciation Picnic (500 people).

A summary of the event logistics, successes, and lessons learned are below:

At all events, student EcoReps bin monitored Resource Recovery areas to encourage proper sorting and a clean stream of compostable items

  • 0.33 lbs/person  – average weight of compostable material per attendee (range from 0.25 to 0.4 lbs/attendee).
  • The majority of the material – about two-thirds – was compostable serviceware rather than food scraps.  Because of this the volume of the total material recovered was more significant than the weight. The 579 lbs. of recovered material took up the space of about 35 full, large garbage bags!
  • At large events, where attendees have freedom to move around, more material was collected at the permanent outdoor bins rather than the dedicated resource recovery tents, prompting us to shift our strategy mid-event and send more bin monitors to the tentless permanent bins
  • Expect the unexpected: there will likely be materials generated at the event that you didn’t expect to have (e.g. condiment packets brought by caterers). Make sure to inform the bin monitors on where these materials should be placed so they don’t end up in the incorrect stream.
  • Like the bamboo utensils tested earlier this year, the birch utensils also tended to only partially shred and did not compost fully (although they will eventually biodegrade)
  • The paper plates and wood based products should be loaded gradually into the composting system. Loading too many at once can jam the system so it is best to alternate or combine with food scraps when possible
  • Paper plates shouldn’t completely substitute for wood shavings as the bulking agent/carbon source (BA/CS) because they tend to lose their form and mat together under high moisture conditions. When adding one part paper plates per each food and wood bucket pair (equivalent to substituting around 15% of the BA/CS total with the paper plates), we found that the bulk density and free air space of the resulting compost increased and decreased respectively from baseline conditions, indicating a reduction in air flow potential throughout the compost pile. Next time we receive a large load of paper plates, we will reduce their contribution to closer to 10% or lower of the BA/CS.

Lastly, at the Facilities Picnic, we also promoted waste reduction and reuse efforts which should always precede any recycling/composting efforts:

  • Attendees were encouraged to bring their own cup (or were provided with a reusable one)
  • Reusable sporks were also handed out this year. Cleaning stations were provided so that attendees could reuse the sporks throughout the event and take them back for future use. If attendees didn’t want to keep their spork, there were also drop-off containers so that the sporks could be recovered for reuse (see photos below):

Weekly Data (9/13 – 10/10)

Weekly data from the last 4 weeks are below. You’ll notice that the % BA/CS was higher early on and has gradually returned to the usual range of ~33%. In the summer months we were receiving a higher than average moisture content so we needed to compensate with more carbon/wood shavings. Now that the academic year has started, the moisture content has returned to previous levels due to menu changes.

Total Food Academic/Residential Buildings Campus Center/Cafes Wood Shavings (BA/CS) % BA/CS Compost Off-Loaded GHG Emissions Saved (MTCO2-eq)
9/13 – 9/19 3,158 119 3,039 1,296 41% 3,400
9/20 – 9/26 3,433 201 3,232 1,265 37% 2,200
9/27 – 10/3 3,775 233 3,542 1,357 36% 3,600
10/4 – 10/10 3,324 182 3,142 1,055 32% 4,800
Cumulative (lbs) 136,433 3,157 133,276 44,193 32% 125,600 40

The ComPOSTer: S.C.R.A.P. Lab Turns 1!

“SCRAPPY” – the composting system’s personified nickname

In big news, the S.C.R.A.P. Lab celebrated its 1-year anniversary! We’ve come a long way since that first loading session 365 days ago and want to thank FOR Solutions, our multiple campus partners, and of course our dedicated student assistants in this team effort as we navigated the first year of operations. Now we are in a better place to fine-tune operations in Year 2.

Some of the early highlights of the project over the last year include:

  • 20 students have served as operational assistants (12 currently active), representing 10 different academic disciplines
  • Research
  • 1 Junior Paper, and 1 Senior Thesis planned (so far) for this year
  • 2 Dean for Research Innovation  grants (engaging 6 additional students)
  • 5 courses integrated site visits and/or analysis of the compost
  • High municipal engagement – Many of the town officials, including the Mayor, have toured the facility and have decided to replicate something similar by voting to purchase MetLife Stadium’s unused in-vessel composting system.
  • State government interest: working with Public Affairs we have already had state elected officials visit (with more coming this Fall) so that we can inform the broader legislative process that will incentivize food scraps diversion from landfill for all of New Jersey
  • Partnering with Campus Dining to test different foodservice wares for compostability, and adjusting their procurement practices accordingly
  • Anticipated lawn and grounds maintenance benefits (superior to the existing yard debris composting program), with promising implications for compost “tea”
  • 27 active blog readers – YOU!
  • 5 short videos (see Media page) produced by the Office of Sustainability; 2 videos produced by during the ribbon cutting ceremony in January 2019

Weekly Data (9/6 – 9/12)

See below for last week’s data which can also be viewed in person at the Greenspace in Frist Campus Center (100-level):

Total Food Academic/Residential Buildings Campus Center/Cafes Wood Shavings (BA/CS) % BA/CS Compost Off-Loaded GHG Emissions Saved (MTCO2-eq)
9/6 – 9/12 3,287 123 3,164 1,054 32% 3,600
Cumulative (lbs) 122,743 2,422 120,321 39,220 32% 111,600 36

The ComPOSTer: Welcome Back & Summer Recap

Happy First Day of Fall Semester Classes!

I hope everyone had a relaxing summer! The ComPOSTer will be back on a regular basis with the start of classes, but before we dive into the new academic year, check out what we were up to in the last two months:


Researchers in the Zhang Lab began their “Building Better Compost” study which involves analyzing the gas and microbial profiles along the composting process. The goal of the study is to inform baseline  performance and how it might change by alerting different parameters such as feedstock types and ratios. Stay tuned for results!

Under the guidance of Dr. Jared Wilmoth, Gabby D’Arcangelo ’21 and Calvin Rusley ’20 regularly took feedstock and gas samples along the “compost trail” from when the feedstock first enters the drum, to inside of the drum, and then when it is off-loaded as compost at the end.


I had the opportunity to take a week long compost operations training course with the U.S. Composting Council last month in Ithaca, NY at Cornell University. By engaging in a combination of hands-on activities, lectures, and field trips to different composting operations, I came away with a wealth of knowledge on composting best practices and tools that we will implement and test at the S.C.R.A.P. Lab over the coming year.

Two of the biggest things that we will test to optimize the composting process are 1) pre-mixing carbon into the totes of uneaten food that are especially soupy and 2) adding and/or substituting wood shavings with alternative carbon sources such as straw, wood chips, and soiled food serviceware.

My group’s compost pile that we built using a combination of wood chips, uneaten food, animal manure and bedding (yes you can compost manure!). Left – measuring temperature of the pile on Day 2 ; Right – Steam rising from the pile when it was dissected on the last Day (5)

Field trips to a vermi (worm) composting facility followed by a  facility that composts in 100-ft long aerated static piles.

To-Date Data 

Total Food Academic/Residential Buildings Campus Center/Cafes Wood Shavings (BA/CS) % BA/CS Compost Off-Loaded GHG Emissions Saved (MTCO2-eq)
Cumulative (lbs) 121,540 2,376 119,164 38,830 32% 110,400 36