The Weekly ComPOSTer: New Project Name!

Hi all,

Our project has a new name!

As hinted at earlier, we decided to change the name of our project after learning that the term “biodigester” may refer to decomposition processes that create different forms of soil amendments other than the one produced by the FOR Solutions system (i.e. compost). Hence, to make the connection with composting clearer, we will be referring to the system as a composter or composting system, and will call the demonstration project:  “S.C.R.A.P.” Lab or Sustainable Composting Research at Princeton Lab. Our goal is to investigate the sustainability of repurposing uneaten campus food into a soil amendment using aerobic in-vessel rotary drum composting technology.

Note: The URL for this blog is now: (although anyone who uses the old URL will automatically be re-directed).

We understand that there may be a negative association with the word “scrap,” but our intent is to change conventional thinking that [food] scraps are a form of “waste,” but rather nutrients that can be returned to the environment to enrich the soils that we all depend on for food and key ecosystem services. Help us spread the word!

In other news, we had a productive brainstorming session with staff and students on ideas for a new resource recovery station at the Frist Campus Center. Sarah Bavuso, Campus Dining Sustainability Manager, led us through a great session filled with colored sharpies and sticky notes.

Earlier today and over the rest of this week, we will be off-loading the composting system until it is nearly empty to prepare for a temporary shut-down of operations over Spring Break next week. But don’t worry – the uneaten food that we would normally process won’t go to the landfill. Organic Diversion, the University’s contracted hauler that picks up uneaten food at the campus dining halls, will be assisting us during this time. When we return from Spring Break we will provide more information about the differences between Organic Diversion and the S.C.R.A.P Lab.

See you in two weeks!

Weekly Data: 3/2 – 3/8

We again continued to load roughly 3,000 lbs. of food scraps and off-loaded a similar amount in compost. 

Food Wood shavings (BA/CS) %
Compost Off-loaded
Week Totals (lbs.) 3,029 995 33% 3,000
CUMULATIVE (lbs) 58,763 17,947 31% 47,500

The Weekly BioDIGESTer (2/28): Re-imagining the Frist post-consumer compost bin

Good evening compost subscribers,

We need your help!

If you are on campus or even following along from afar, we would love to hear any thoughts you might have for re-imaging the resource recovery station in the campus center where we receive some of our uneaten food.

Currently our system is only accepting pre-consumer kitchen scraps and leftover food from Frist Campus Center, but it would also be great if we can capture and divert post-consumer food scraps.

How should the new area and compost bin be designed so that they simultaneously limit contamination while educating the campus community and visitors about our food scraps composting project? Let us know your thoughts!


[The current layout and design of the Frist Gallery post-consumer compost bin contributes to contamination of the stream as shown above in which non-compostable materials such as a soda cup with a plastic lid and straw were thrown into the bin]

Weekly Data: 2/25 – 3/1

We continued to load roughly 3,000 lbs. of food scraps and off-loaded a similar amount in compost. 

[Besides these few pieces, most of the cardboard pizza boxes that we processed last week have composted successfully inside of the system.]

Food Wood shavings (BA/CS) %
Compost Off-loaded
Week Totals (lbs.) 3,098 1,013 33% 3,000
CUMULATIVE (lbs) 55,734 16,952 30% 44,500

The Weekly BioDIGESTer (2/21): Tiger Sustainability Night

In this week’s post, we highlight our effort at Friday night’s Tiger Sustainability Night double-header basketball game at which we partnered with Campus Dining and student EcoReps to recover food scraps at our first major event. Check out the below photo essay to learn more:

[EcoRep and Biodigester Operational Assistant, Wesley Wiggins ’21, staffs one of the five “Zero Waste Stations” stationed around the gym. Wesley and the other EcoReps instructed fans on how to properly sort their unwanted materials into either “Landfill,” “Recycling,” “Compost” or “Liquids”]

[About 15 gallons of compostable material was diverted from the landfill over the course of the night, consisting mostly of napkins, paper plates, popcorn, and…

[… 22 pizza boxes! Although cardboard from pizza boxes is technically a recyclable material, once it becomes saturated with pizza grease, it can no longer be recycled because the absorbed oil interferes with standard recycling processes. However, greasy cardboard pizza boxes can be shredded and composted at our facility. They will be gradually added over the course of this week and will act as a supplemental carbon source. ]

Weekly Data: 2/18 – 2/22

Unfortunately, we were unable to use our scale last week due to a temporary data transmission issue, so the data represented below are estimates. On the bright side, we were able to leverage several months of experience and data to assist in making informed estimates!

Although we received the same number of food scraps totes as the week prior in which we processed around 3,000 lbs., we estimated that we loaded a few hundred pounds over 3,000 lbs. because several of the totes were heavier than usual, most likely because of last Wednesday’s snow storm which led to an earlier closure time for our campus cafes. 

Food Wood shavings (BA/CS) %
Compost Off-loaded
Week Totals (lbs.) 3,334 1026 31% 3,000
CUMULATIVE (lbs) 52,636 15,939 30% 41,500

The Weekly BioDIGESTer: 2/4 & 2/11

Hello fellow compost aficionados!

Apologizes for the overdue blog post! We’ve been busy preparing for several  new efforts in between continuing our compost operations. Check out the exciting new partnerships and initiatives that will start later this week:

  • Compost Concierge Pilot : We’ve been working with grad students and departmental managers to begin a pilot food scraps collection program in three academic departments (Mechanical & Aerospace Engineering, Geosciences, Ecology & Evolutionary Biology). The food scraps, collected in 5-gal bins, will be picked up twice weekly by the operational team and dropped off at our composting facility.
  • Composting at Tiger Sustainability Night (2/22): We will be partnering with Campus Dining and EcoReps Greening Athletics to recover food scraps at our first major event – double-header basketball games against Cornell at 5:30pm and 7:30pm at Jadwin Gym on Friday, February 22. Watch the promo video featuring Lexi Weger ’22 and Gabrielle Rush ’19
  • Lastly, this week we will be finalizing a new name for the project to  better reflect that the biodigester is a composting system that decomposes food scraps into compost aerobically (with oxygen), not a digester,  which generally refers to systems that break down organic waste anaerobically (i.e. without oxygen) and produce digestate, which is similar to, but technically not the same as compost. We will unveil the new name next week!

Weekly Data: 2/4 – 2/15

Now that the spring semester is in full swing, our  weekly food scraps volume is starting to creep back up again, closer to the 3,000 lbs./week range. We are also experimenting with a higher percentage (by weight) of wood shavings to food scraps, increasing slightly from 30% to 33%.

 FoodWood shavings (BA/CS)% BA/CS Compost
Week of 2/4 (lbs.)2,67987533%2,500
Week of 2/11 (lbs.)2,99798533%2,750
CUMULATIVE (lbs.)49,30214,91330%38,500

The Weekly BioDIGESTer (1/28): Welcome McGraw Center + Intersession Week

This week we welcome another project partner to our growing list of composting venues: the McGraw Center for Teaching & Learning!

Like the Scully Co-op, the McGraw Center will collect any food scraps generated in its office in a 5-gal bucket for weekly pick-ups.  The effort will be spearheaded by the McGraw Center’s Manager Sandra Moskovitz, a sustainability ambassador who has been composting herself for 30 years.

Almost five years ago, the Office of Sustainability interviewed Moskovitz for a staff profile. When asked, “How could the University become even more sustainable? she replied:

“My number one wish is for a campus wide composting program, it saddens me to see the waste around campus that could so easily be composted—miles of pizza boxes, tons of used paper towels and paper plates, not to mention the pounds of food scraps that are thrown away in offices and classrooms each day. I know that this is something that is being discussed, so I hope that a program will be in place soon. It will make a huge difference in reducing the amount of waste that the University’s population makes every day.”

Thanks to outspoken people like Moskovitz, the University now has an on-site composting system that will continue to support expanded food scraps diversion efforts while contributing to an ethos of sustainability where organics recycling will ultimately become the norm on campus.

To realize this goal, we plan to partner further with Moskovitz and the McGraw Center around green office strategies so that all of their events are zero-waste, and to share these best practices across campus.

Weekly Data: 1/28 – 2/1

The lower volume of weekly food scraps continued into the last week of January as finals wrapped up and led into Intersession (a 1-week break before the start of the spring semester).

Food Wood shavings (BA/CS) %
Compost Off-loaded
Week Totals (lbs.) 2,504 776 31% 2,000
CUMULATIVE (lbs) 43,626 13,053 30% 33,250

The Weekly BioDIGESTer: 1/21

With campus cafes closed on Monday (1/21) in observance of Martin Luther King Jr. Day,  we only loaded  2,238 lbs. of food scraps into the composting system last week, or about 40% less than the average weekly amount.

We did not detect any visible pieces of recently tested bioware in the 2,000 lbs. of off-loaded compost. These results are promising, but we will wait for this week’s batch of compost to know for sure just in case the material didn’t fully migrate to the end of the vessel.

Weekly Data: 1/21 – 1/25

Food Wood shavings (BA/CS) %
Compost Off-loaded
Week Totals (lbs.) 2,238 706 32% 2,000
CUMULATIVE (lbs) 41,122 12,277 30% 31,250

The Weekly BioDIGESTer (1/14)

First Off-Loading of 2019 & Bioware Testing!

We had an exciting first full week operating the biodigester in 2019. Highlights included our first off-loading session as the vessel neared its capacity, and materials testing to help inform our Campus Dining team about types of food service ware that may be composted in our system versus sent to the landfill.

[Composted off-loaded on January 18th]

Henry Wietfeldt ’22 drops one of 50 palm plates into the loading hopper to be shredded before it enters into the rotation vessel. We also tested World Centric plant fiber clamshells, and the Huhtamaki ‘Chinet’ plate. In about a week or so we will be able to tell how well each of the items broke down in the system based on their presence (or lack thereof) in the finished compost.

Click here to watch as shredded pieces of Chinet plates fall from the auger into the input port.

Weekly Data: 1/14 – 1/18

We processed just under 3,000 lbs. of food scraps last week, which is lower than the average of about 3,500 lbs. for a full week. Composting is a great way to return nutrients to the environment to enrich soils and grow healthy plants, but ultimately we want to reduce the amount of food (especially leftover food) from compost whenever we can, so the reduced weight from our campus center and cafes is a win and a metric we will continuously track!

Food Wood shavings (BA/CS) %
Compost Off-loaded
Week Totals (lbs.) 2,986 950 32% 1,250
CUMULATIVE (lbs) 38,884 11,571 30% 29,250

The Weekly BioDIGESTer: 1/7

Welcome to the first weekly bioDIGESTEer of 2019!

In our first (partial) week back in operation since Winter Break, we loaded 2,346 lbs. of food scraps and 727 lbs. of wood shavings into the biodigester, thus maintaining the approximate 3:1 ratio of food to wood given the moisture content of the food scraps.

We didn’t off-load any compost because the vessel was nearly empty after having off-loaded the majority of the compost from the system before Winter Break. It will take about 2 weeks from the first loading session of the New Year on January 7th until we off-load the first batch of compost in 2019 (i.e. when the vessel drum is about 75% full).

Weekly Data: 1/7 – 1/11

Food Wood shavings (BA/CS) %
Compost Off-loaded
Week Totals (lbs.) 2,346 727 31% 0
CUMULATIVE (lbs) 35,898 10,621 30% 28,000



Biodigester Ribbon-Cutting Media Coverage!

Thank you to all who came out yesterday to celebrate the official unveiling of the Princeton University Biodigester Project with us.

If you were unable to attend, see below for several links to media coverage around the event:

Princeton University shows off their ‘Biodigester,’ which turns food scraps into compost in 5 days (

TV clip (6ABC Philadelphia)

Princeton University’s new biodigester makes food scraps sustainable (Princeton University)

KyuJung Whang cutting ribbon in front of biodigester

Ribbon-Cutting Ceremony!

Happy New Year!

To begin 2019, please join us next Tuesday, January 8th, for a celebratory ribbon-cutting ceremony to formally introduce the Princeton University biodigester initiative to the greater community.

See below for additional event details. Hope to see you there!