S.C.R.A.P. lab

As Academic Year 2025–26 came to a close earlier this month, the ComPOSTer is using this time to reflect on where things stand at the S.C.R.A.P. Lab and share where we see opportunities emerging in the months and years ahead.

If you’ve been following along, much of our operational landscape remains unchanged from the update we shared in September 2025, with budget limitations at the University continuing to constrain the scale of activities we can support. Despite this reality, we were able to keep our coffee grounds diversion partnership with Coffee Club running smoothly.

A huge amount of credit goes to our Compost Concierge student team, Cade and Tarun, who picked up several hundred pounds of coffee grounds every week to ensure that this organic material continued finding a productive end-of-life pathway instead of heading to disposal.

Additionally, staff and students supported organics diversion at several campus events, including the Facilities’ Annual Cookout & Bring Your Child to Work Day, and the TASA Night Market.

In total, just under 8,000 pounds—nearly 4 tons—of compostable material was recovered and transformed into compost over the course of the academic year. We also continued connecting with students, staff, visitors, and the broader organics recycling community around composting and sustainable materials management through course visits, site tours, presentations and other outreach activities.

Meanwhile, we’ve been actively pursuing grant opportunities and partnerships that could support future projects, research initiatives, and infrastructure development. While some federal funding opportunities have disappeared, others at the state and national level remain available—and in some cases have expanded.

New Jersey Organics Recycling Is Gaining Momentum

One reason for optimism is the rapidly evolving policy landscape around food waste and organics recycling. Earlier this year, New Jersey enacted S2426/A2090, one of the state’s most significant food waste reduction laws to date. The legislation requires Solid Waste Management Districts to develop strategies for reducing food waste and directs the NJ Department of Environmental Protection (NJDEP) to create a tiered permitting structure for food waste composting and recycling facilities.

Taken together, these provisions signal a growing commitment to expanding organics recycling infrastructure and making composting more accessible across the state. While details will be worked out through future planning and rulemaking, the law has the potential to create new opportunities for municipalities, institutions, businesses, and community-scale composting operations. Read more on WasteDive

Looking Ahead

At the S.C.R.A.P. Lab, we view these developments as an encouraging sign that organics recycling is receiving increasing attention. Although budget constraints continue to shape what is possible in the near term, the broader landscape is evolving in ways that could create new opportunities for research, education, infrastructure development, and community partnerships. As counties begin developing food waste reduction strategies and NJDEP advances work on tiered composting permits, we’ll be following closely and looking for ways to contribute our experience and perspective.

For now, we’re grateful to everyone on campus who helped divert nearly 4 tons of compostable material this year and kept the work moving forward.

The budget may not have changed, but the momentum certainly has.

And for organics recycling in New Jersey, things are just starting to heat up.

It has been a difficult time in higher education, specifically here at Princeton with sudden cuts to federal research funding and an increase in the endowment tax. While Princeton is more well-positioned than other universities, we have been planning for reduced budgets across the board, including in Facilities.

Since 2018, the Sustainable Composting Research at Princeton (S.C.R.A.P.) Lab has served as a meaningful Campus as Lab and campus engagement resource while converting a portion of the campus’s wasted food into a nutrient-rich soil amendment for campus grounds. Key highlights of the project so far have been:

1. Diverting and recycling over 355,000 lbs. of wasted food into compost
2. Receiving $100k in grant funding from both internal and external sources that have supported student and faculty research and teaching, while also working toward advancing industry knowledge in the circular materials economy.
3. Dr. Xinning Zhang’s FRS 115: Decomposing the Science of Composting: How to Turn Waste into Resource course and several other Campus as Lab projects.
4. Employing dozens of students who have gained real-world skills in sustainable event planning and materials management as compost operational assistants and bin monitors

After the Spring 2025 semester we finished our pilot period of the campus demonstration operations and successfully advocated for the S.C.R.A.P. Lab to become a permanent part of Facilities Operations due to the benefits to both campus sustainability and to the university’s core research and teaching mission.

Unfortunately, due to the recent hiring freeze, we haven’t been able to hire the necessary staff to help us continue and grow our on-site composting efforts. Until we can hire more personnel, we will have to sadly pause our composting operations. It’s disappointing and a shock that external forces beyond our control are impacting our ability to continue this successful project.

For the next academic year, this means that we will no longer be collecting food scraps and compostable diningware at the Frist Food Gallery or at small department events. However, to keep the composting system from shutting down completely, we will be processing coffee grounds only from campus cafes like the Coffee Club. This amount will be substantially less than the 15 tons of wasted food and other compostable material we diverted and recycled into compost in the 2024-2025 academic year. Rest assured, that all leftover food from Frist, as well as plate scrapings and leftover food from dining halls will still be picked up by our organics recycling hauler for repurposing as animal feed or used to produce biogas at the Trenton Renewables anaerobic digestor facility.

At this point we will enter a data analysis phase to package all the project’s data, results, and accomplishments to date, including a successful NJ Department of Environmental Protection compostables grant research project in which we demonstrated that in-vessel composting technology can help address the infrastructure gap for processing compostable food serviceware. Read our latest blog post, “Are compostable products actually compostable?” to learn more.

Despite the external challenges facing Princeton, we are still committed to leveraging Princeton’s unique position to lead by example and drive positive change for people and planet. Thank you to all the organizations, departments, and individuals who have contributed to the S.C.R.A.P. Lab’s success since 2018. We appreciate your efforts to drive sustainability action through composting operations, and we look forward to a time in the future when we can reintroduce SCRAPPY at full capacity.

Research on understanding compostable product decomposition in a University setting

Left: Off-loading of low wood compost from composter. Right: Low wood treatment pile in outdoor compost.

In our last post, we discussed improvements made in the Frist Food Gallery designed to keep food waste and certified compostable products (compostables) out of landfills and instead redirect them to the S.C.R.A.P. Lab. In this post, we will dive deeper into the composting impacts from the integration of compostables from Eco-Products based on research findings from Dr. Xinning Zhang’s First-Year Seminar (FRS 115): Decomposing the Science of Composting: How to Turn Waste into Resource (2023 and 2024) and her Geoscience student, Isabella Sibaja ‘26.  

In 2023, the FRS class identified a longer curing time was required for compost to reach suitable maturation when compostables were added. This result led to an adjustment in the unloading cycle to occur once every 6 to 7 weeks in 2024, rather than the previously tested 7 to 10 days. At the same time, the FRS class tested “low(er) wood” (40% compostables, 5% wood) and “high(er) wood” (30% compostables, 20% wood) input scenarios by weight. For both scenarios, the longer residency time allowed the temperature inside of the vessel to reach thermophilic levels (>104˚F; Figure 1), enabling faster feedstock decomposition and allowing compost to mature quickly and effectively.

[1] Average temperatures at the beginning (Port 1), middle (Port 2), and end (Port 3) of the composting vessel reached the Thermophilic Stage (>104˚F) in 2024. 

Isabella Sibaja continued this investigation on the composts’ maturity under the guidance of Dr. Zhang and support from Gina Talt. She used 16s ribosomal DNA analysis to identify the diversity of microbial populations found in both the “low wood” and “high wood” treatments in the different ports of the in-vessel composter. 

Sibaja interestingly identified the presence of microbes such as Bacillaceae and Actinomarinales which are correlated with high temperatures.  Below Figure 2 identifies Port 3 as having increased microbial diversity and maturation compared to Ports 1 and 2. This finding is reasonable since compost spends the most time in Port 3 in the in-vessel composting system  as it waits to be unloaded. Yet, these results may be due to the increased presence of compostables, increased material in the system, prior microbial activity, or another confounding factor. Regardless, they imply prolonged thermophilic stages, indicating that more time would be needed for the compost to reach maturity in both treatments. 

[2] Microbiome diversity identified from Ports 1, 2, and 3 between 9/18/24 and 11/13/24, measured weekly; Produced by Isabella Sibaja, Geosciences ‘26 

Therefore, the composts were tested again once off-loaded from the composter and spent 3-4 months in outdoor curing piles. The “low wood” treatment was found to contain more mature and stable compost compared to the “high wood” treatment after analysis by the class and commercial lab testing as shown in Figure 3 comparing metrics of the treatments to the recommended values of finished compost. 

[3] Average of three composite samples. All data analyzed by a commercial lab. Pile curing data for 2023 composts not included due to poor in-vessel results. *Per guidelines from the CCREF Compost Operations Training Course (2019) and certified compost standards in the Seal of Testing Assurance program

This significance can be attributed to the Eco-Products’ carbon-rich fibrous and starchy composition, enough to provide adequate carbon needs and sustain microbial activity in decomposition. In other words, the compostables contain less lignin and thus more “bioavailable carbon” than the traditionally-used bulking agent of wood chips, indicating less required breakdown steps, and leading to more mature compost. 

In conclusion, compostable products can successfully decompose in a reasonable timeframe and create mature and stable compost. They can even substitute for traditional carbon, however, there are still several factors to consider.

One of the drawbacks stemming from compostables is their particle size compared to wood chips. After shredding, the compostables’ smaller particle size increased compactness within the vessel, producing more anaerobic (oxygen-depleted) pockets which led to significantly increased methane production. However, the total GHG emissions produced by composting during the in-vessel stage was still 85% less than that of a landfill, continuing to prove composting’s positive environmental impact.

Amongst this collected data there does appear to be some slight differences with the addition of compostables regarding maturity, microbial diversity, and gas emissions. However, since these differences appear to be subtle and do not impede the system’s functionality, these compostables can be considered a suitable alternative bulking agent. Specific to Princeton, this compost can best be used as a soil amendment for Grounds’ landscaping, an ideal goal as we strive closer towards a circular economy as a campus.

Pardon the delay! Over the past year and a half, we wrapped up our second year of research into compostable product collection and processing. We’re excited to share final results-starting with Part I: Upstream collection – featuring audit data from our education campaign and infrastructure upgrades at the point of toss

As we shared in our last post, a baseline audit of the Frist Food Gallery showed that over 60% of landfill waste could be composted—mostly food scraps and compostable dining products.

In response, our Dining team partnered with procurement and suppliers to streamline product offerings and switch to certified compostables. We also redesigned the toss zone, adding a compostables bin and deploying student and staff ambassadors to guide diners. Once the ambassadors stepped back, we reinforced sorting with signage featuring real item examples above each bin.

The results? A third-party audit showed that landfill waste was cut by more than half! Our overall waste diversion percentage jumped from 4% to 56% as shown in the data charts below:

Additionally, over 50% of the compostable stream was diningware—proof that packaging swaps matter.

Contamination in the compost stream started at 20%, but we’ve since halved that to 10% thanks to further improvements: motion-sensor compactor bins, a large banner advertising the collective impact, and permanent 3D wall signage:

Still, our goal is 5% contamination or less. This spring, we surveyed diners to understand sorting pain points. One big insight? The condiment station near the toss zone was causing congestion. So, with guidance from the Kahneman-Treisman Center for Behavioral Science, we’re relocating it and redesigning the area with a “decision tree” layout—compost on one side, landfill on the other—to encourage more mindful sorting.

While we wait for these changes, stay tuned for the next post in our series where we’ll dive into the composting process itself and what we learned about compost quality.

Happy New Year everyone!

In today’s post, the comPOSTer takes a look back at the fall semester happenings at the S.C.R.A.P. Lab:

In the Fall we received the results from our spring baseline audit of everything consumers were putting in trash and recycling at retail dining. We selected the largest venue – Frist Gallery – and one of the smaller cafes (Shultz) on campus as representative locations. Over the course of two days in mid-April, our Campus Dining and Sanitation staff helped us collect and transport the waste materials so they could be audited by our contractor, MSW Consultants.

Figure 4-2 (shown below) compares the recoverability of refuse from the Frist Campus Center and the Shultz Café. Key takeaways include:

• Most of the food waste (average of ~35%) from each location was loose, this amounted to 100 lbs. over two days (“Food Waste/Compostable” columns)
• Another ~30% of items across the two locations consisted of items “Eligible for Conversion to Compostable Alternatives” Uncertified paper items such as commercial soft drink cups, french fry “boats,” and uncoated paper plates were the biggest culprits.

In sum, over 60% of items going to the landfill have the potential to be diverted to composting in the two retail dining locations.

The goals of the fall semester were to:

1. Replace traditional petroleum-based plastic packaging with certified compostable packaging
2. Provide collection receptacles for compostable items and change the behavior of diners to encourage proper sorting
3. Investigate how adding the compostable products affects the composting process

First, our Campus Dining team worked with our food supplier to streamline the number of disposables that are offered in retail dining while also swapping out products for the compostable alternatives. Working mainly with Eco-Products, we identified two different types of certified compostable products:

• Molded fiber (consisting of paper or sugarcane) – typically plates, “clamshell” containers, and bowls like the tan ones shown below
• Polylactic acid (“PLA”) – which is a plastic substitute made from fermented plant starch (usually corn) – typically utensils and cold cup lids
• Or a combination of both (e.g. hot coffee cups or soup containers that are fiber-based but have PLA coatings)

In October, we began to transition some of the single-use packaging to the compostable alternatives and began collecting them during meal hours with the help of bin monitors to ensure a contaminant-free stream.

For two weeks we loaded the food scraps and compostables using the standard way (shredded by the composter’s built in shredder). We had a transition week during fall break and then two weeks after that we pre-shred the compostables through a chipper prior to being loaded in the hopper as part of the exercise on investigating the impact of size reduction. Throughout the Zhang lab researchers and students in the first year seminar course monitored exhausts gases and compost quality.

In mid-December the students presented their posters with preliminary findings on how adding the compostable products affected the exhaust gas profiles and nutrient (particularly nitrogen) cycling.

Meanwhile, we transitioned most packaging products to compostable alternatives and rolled-out 24/7 collection containers for consumers in the Frist Gallery. We took an agile approach and tinkered with the space based on direct feedback from diners and their observed behaviors. See our evolution below:

MSW Consultants came back to campus to perform the follow-up audit. Results are pending but quick observations included:

• About a 10% contamination rate (by weight)
• 30% loose food
• The remaining ~60% are certified compostable products that were loaded into SCRAPPY and treated as a carbon or “brown” source for the system (consistent with earlier audit results)

We will continue to modify and enhance the sorting area to improve diversion and lower contamination rates, but so far we are okay with the level of contamination.

Happy first week of classes to the Princeton community!

In celebration of the start of the ’23-24 academic year, we look back at the summer happenings at the S.C.R.A.P. Lab:

OPERATIONS

After a taking a break from mid-May through June, the S.C.R.A.P. Lab was back in operation on a limited schedule after July 4th through the end of August. We processed on average a half of a ton per week (about half of what we process during the busier academic semesters).

RESEARCH

The rest of the time was focused on research and course planning tied to our DEP compostables testing grant. The next phase of our grant studying bioplastic composting will happen this fall in conjunction with FRS 115: Decomposing the Science of Composting: How To Turn Waste into Resource. In preparation, we met with Prof. Zhang and her lab team to test out the sampling protocol for the class:

ENGAGEMENT

We also had a tour with the US Composting Council and engaged a group of first-year students for a work day.

IN THE NEWS

Waste360 recently profiled the S.C.R.A.P. Lab in a piece about broader efforts happening in the Garden State to advance organics recycling: How Princeton is Taking Compost to the Next Level

ON TAP

Stay tuned for more research updates later this month!

For our final post of ICAW, we share updates on our DEP grant project to study and test innovate new methods for using, collecting, and recycling compostable plastic products.

As part of our assessment on how well several types of compostable plastic products break down in our composting systems (SCRAPPY followed by piles or windrows), we first need to better understand our post-consumer retail waste stream. Our goals are to:

• streamline and cut down on the number of single-use serviceware items (The fewer kinds of serviceware, the easier it is to encourage proper recycling)
• pick better product alternatives that are certified compostable (preferably PFAS free too) so we can test them in our systems

So our first step in this journey was to conduct a waste audit of everything consumers were putting in trash and recycling at retail dining. We selected the largest venue – Frist Gallery – and one of the smaller cafes on campus as representative locations. Over the course of two days in mid-April, our Campus Dining and Sanitation staff helped us collect and transport the waste materials so they could be audited by our contractor, MSW Consultants.

While we are still waiting for the full audit results, we share some details and preliminary findings in the photo essay below (trigger warning for anyone who doesn’t want to see the food waste):

Overall we captured a lot of waste – 250 lbs alone of organics (wasted food & molded fiber compostable serviceware that we know composts well) went to SCRAPPY directly after the sort across both days.

Now we will be able to better understand our waste composition and how we can divert as much as possible toward recycling/composting over the next few months when we revamp the waste sorting area in Frist over the summer and fall. Stay tuned for more progress updates!

Happy Composting!

For today’s ICAW post we are pleased to share a Q&A about home composting with Tania Althoff who is a Project Manager in the Office of Capital Projects at the University.

Read more about Tania’s journey to composting, her process, and advice to those looking to start:

Why were you interested in starting to compost?

I like to make plant-based meals and salads with different fruits and vegetables, and I realized how much food waste I was throwing in the trash. I wanted to “recycle” these food scraps to make something useful for my garden and yard. Also, I joined an organic community garden this year and this opportunity became a great motivator for starting my own system!

Tell us about your composting system

I have a dual chamber tumbler that sits outside. I turn it occasionally to aerate it and add water to keep it moist. Also, I use a metal bin to collect scraps in the kitchen. I’ve been collecting all plant scraps like pepper stems, potato peels, broccoli or kale stalks, etc. and also egg shells, coffee grounds, newspaper, and leaves. Having just started the system recently, it’s still “brewing” so I don’t have usable compost just yet. It’s a slow process but I’m hopeful I’ll have compost for use later in the growing season!

Any advice for others looking to start composting at home?

Just do your research! There’s so much information out there about how to get started composting at any scale, as well as the different types of home composting options available. Make sure to learn about the balance of nitrogen and carbon that’s required for any system. Good luck!

Thanks Tania!

Don’t forget to visit our Resources pages to learn more about composting basics and find a home composting system suitable for you. For more inspiration, revisit last year’s home composting Q&A with Ted Borer

Tune in for one more post tomorrow for a project update on our DEP grant

During the pandemic, SCRAPPY was relocated from Princeton to West Windsor Township. This March, we held a “relaunch” ribbon cutting ceremony to formally (re)-introduce the West Windsor and greater Princeton University community to our food scraps demonstration composting project. A photo essay of the event is below.

All photos courtesy of Jared Flesher, Communications Specialist with the Office of Sustainability

Following the facility tour, we also raffled off a home composting system. Sarah Williams of the Molecular Biology Department was the lucky winner and the ComPOSTer will follow-up with her to hear about her experience with it.

To learn more about home composting options, visit our Resources page and stay tuned for tomorrow’s post for a home composting Q&A with Facilities staff member, Tania Althoff.

Happy International Compost Awareness Week!

Our first commemorative post highlights project updates from March and April.

During this time we….

1. Reached a big milestone of processing 100 tons of uneaten, non-recoverable food (for the 2 years that scrappy has been operational, not counting offline time during the pandemic)
2. Expanded our team by creating new roles to enable more event and bin pick-ups.
   • Sabrina Fields ‘GS joined the team as a Graduate Compost Coordinator, assisting with food scraps collection efforts in academic departments. Prior to coming to Princeton, Sabrina was at the University of Chicago’s Harris School of Public Policy, where she helped coordinate an effort to reinstitute compost in the Keller Center building as students returned to in-person learning. Being her first experience with composting outside of a residential composting program, she learned a lot about how important the education and behavioral aspects of larger-scale composting programs are. 
   • Victoria Koretsky ’26 joined the team as a Compost Concierge Driver. Victoria drives around campus in our minivan and picks-up smaller buckets and bags of pizza boxes from a few centralized locations on campus, helping to free up time for our operational team
   • We also welcomed three new student team members to the operational crew. Check out their full profiles here

OPERATIONAL UPDATES – MARCH & APRIL

As the weather warmed and we entered the busy part of the spring semester without any pauses in operations, our monthly totals have jumped to the highest they have been since the pandemic.

With Sabrina’s and Victoria’s help, we were able to capture a greater amount of food scraps from non-dining venues by beginning new partnerships with the Center for Policy Research on Energy and the Environment, the Real Food Co-op, as well as working with our student Eco-Rep team to collect compostables at various events across campus.

We estimate that we recovered and composted over 150 gal of food scraps and 200 pizza boxes from events over the last two months.

8,907 lbs.

The total amount of material composted at the S.C.R.A.P. Lab in March

10,128 lbs.

The total amount of material composted at the S.C.R.A.P. Lab in April

Stay tuned for another post tomorrow recapping our re-launch ribbon-cutting ceremony