The Weekly ComPOSTer (6/21): More Compost Applications & Audio Journalism

Happy First Day of Summer!

This week we will feature other ways compost from the S.C.R.A.P. Lab is being applied on campus in addition to the departmental garden highlighted in last week’s post.

So what happens when compost is off-loaded from the composting system?

Twice a week after the S.C.R.A.P. lab team rakes off-loaded compost into a trailer bed, our Grounds crew hooks the trailer bed to a truck and transports it to a stockpile yard just south of main campus where the compost is dumped into its own outdoor pile covered with a tarp to prevent nutrient leaching.

Periodically, the Grounds crew will draw compost from the pile and blend it with leaves, soil and other compost generated from the campus. When lab tests indicate that this combined or “blended” product reaches a certain maturity index level, the Grounds crew will use it in one of three ways as a soil amendment on campus:

  1. Mixed into planting mediums during transplantation
  2. Top-dressed on campus lawns after aeration and before overseeding to break up soil that becomes compacted over the year due to foot and vehicular traffic. Aerating soils by perforating it with small holes and then spreading compost allows for better water, oxygen, and nutrient flow to plant roots.
  3. Used to make compost tea: a small amount of compost will be placed in a large mesh “tea” bag which is then steeped in water and aerated in a container to create a brewed, water extract of compost. The process extracts the full diversity of beneficial microorganisms from the compost (plus more if additional ingredients are added), and when applied to soils and plants, it can assist in better plant production, soil structure, nutrient cycling, and less disease incidence. It’s like kombucha but for plants! More on this later!

All of this information plus more can be heard in an audio-journalism piece that was nicely composed by graduating senior, Angela Mao ’19. For her final class project, Angela captures a sound journey from food scrap to compost. Hear it here:

Weekly Data: 5/31 – 6/20

As we enter into summer mode with our dining venues on a reduced hours schedule, the total weekly amount of uneaten food processed at the S.C.R.A.P. Lab is about 60% of that during the academic semester.

WEEK Total Food Campus Center & Cafes Academic /Residential Buildings/Events* Wood Shavings (BA/CS) % BA/CS Compost Off-Loaded GHG Emissions Saved (MTCO2-eq)
5/31 – 6/6 2,222 2,160 62 642 29% 2,000
6/7 – 6/13 2,232 2,101 131 772 35% 2,000
6/14 – 6/20 2,375 2,302 73 818 34% 2,000
Cumulative (lbs) 96,875 94,983 1,892 30,278 31%* 83,500 29

* Included in these totals is about 125 lbs. of uneaten food that was recovered from two events on campus

Thanks to all of the friends and alums who came to the S.C.R.A.P.  Lab Reunions tour on the 31st!

The Weekly ComPOSTer (6/7): Compost Applications & Clarification

Happy Friday!

We have an update on how compost from the S.C.R.A.P. Lab is being applied on campus. This week’s update comes from Luiza Wainer and Peter Green who received some of the first batch of compost from 2019 for use in a new community garden for their department. When it came time to apply the compost in their raised bed this spring, they decided to do an experiment  – they split the garden in half and applied compost to one side and not the other. Can you guess which tomato plant in the below picture received the compost application?

Answer: The tomato plant on the right! Although the two plants were planted at the same time, the soil that received compost benefited from the microorganisms and additional nutrients that have supported plant growth and health in the form of a taller and greener plant.

More application updates to come!

Lastly, this post will end with a quick clarification on last week’s mention about the relationship between compost and humus. To clarify: compost and humus are not exactly the same form of matter.

Compost generally refers to a stabilized state of the controlled aerobic decomposition of organic matter when the individual parts of the organic matter are no longer recognizable. It typically occurs outside of the soil system. This is the product that we use as a soil amendment. However compost is technically not completely decomposed as all of the microorganisms are still present and are continuing to decompose the remaining material.

Humus, which is created in the soil system, is found when the decomposition process is fully completed and all of the usable nutrients have been extracted by microorganisms, a process which takes many years.

Weekly Data: 5/24 – 5/30

The S.C.R.A.P. Lab processed less uneaten food over “Dead Week” on campus due to Memorial Day and as most undergraduates left campus for the summer. However, the volume started to increase again on the last day of the loading week with the start of Princeton University’s Reunions weekend.

Total Food Campus Center/Cafes Academic /Residential Buildings Wood Shavings (BA/CS) % BA/CS Compost Off-Loaded GHG Emissions Saved (MTCO2-eq)
5/24 – 5/30 2,164 2,126 38 685 32% 2,000
Cumulative (lbs) 90,049 87,680 1,626 28,046 31% 77,500 27

The Weekly ComPOSTer (5/29): National Learn About Composting Day

Did you know that May 29th is National Learn About Composting Day?

In its honor, this blog post will provide a brief account of composting throughout U.S. history.

In general terms, composting refers to a natural process in which organic matter is biologically reduced into a soil-building substance.

While the above definition doesn’t imply any human intervention, composting can also be more narrowly defined as a process in which we (humans) transform organic material into a soil amendment to create a beneficial growing environment for our lawns or gardens.

This second definition was “discovered” by ancient civilizations when the earliest people learned how to use organic matter, most likely in the form of manure, to enhance crop production. Ever since, the composting process has been practiced and adapted along the way by different cultures over time.

In the Americas, indigenous people used  organic matter such as buried fish and seaweed in corn planting and taught these practices to European colonists to help them grow food in the poor soils of New England.

Presidents George Washington and Thomas Jefferson were compost proponents in farm operations and benefited from the knowledge and skills of their enslaved workers.

However such a strong tradition gradually fell out of practice, starting with the westward expansion into already fertile prairie soils of the Midwest, and then the introduction of chemical agriculture. Farmers were able to achieve high yield rates without  having to invest in soil-building practices. Over time these consequences included the Dust Bowl of the 1930s and the current aquatic dead zones due to nutrient run-off.

Fortunately, the organic farming movement that includes practices such as composting to control erosion and retain and provide nutrients to plants, is making a comeback. Ever since Rachel Carson helped spark the environmental movement in the 1960s, farmers and consumers have become more aware of the environmental and health consequences of chemical farming. Today, composting is also becoming a growing solution to the municipal solid waste challenge, and a lot of research is being conducted to investigate compost’s role in mitigating climate change through carbon sequestration.

Source/Learn more: The Rodale Book of Composting: Simple Methods to Improve your Soil, Recycle Waste, Grow Healthier Plants, and Create an Earth-Friendly Garden

Weekly Data: End of Spring Semester

We saw a gradual decrease in the amount of uneaten food processed in the composting system over the last three weeks as the academic year came to a close with students finishing their papers and final exams and eventually leaving campus.

The S.C.R.AP. Lab will continue to be operational over the summer. While we will lose some of our academic/residential partners during this time, we will continue to receive a steady, but reduced, stream of uneaten food from the Frist Campus Center and Cafes.

WEEK Total Food Campus Center & Cafes Academic /Residential Buildings Wood Shavings (BA/CS) % BA/CS Compost Off-Loaded GHG Emissions Saved (MTCO2-eq)
5/3 – 5/9 3,567 3,401 166 1,099 31% 3,500
5/10 – 5/16 3,340 3,134 206 1,033 31% 3,000
5/17 – 5/23 3,149 3,022 127 1,067 34% 3,000
Cumulative (lbs) 87,885 86,792 1,591 27,361 31%* 75,500 26

*In addition to the wood shavings, we also diverted and processed 85 pizza boxes over the semester as a supplemental source of carbon

The Weekly ComPOSTer (5/10): Exciting Research Plans!

Good afternoon from the S.C.R.A.P. Lab!

The big news this week was the announcement of two research projects involving the S.C.R.A.P. Lab that were awarded Dean for Research Innovation Funds for the Campus as a Lab.

Adapted abstracts of the two projects that will start this summer are below:

Building better compost

Xinning Zhang, assistant professor of geosciences and the Princeton Environmental Institute, will lead undergraduate research that will explore conditions for creating high-quality compost that is high in nutrients and low in greenhouse gas emissions. The team will test various proportions of food waste, carbon inputs and air as well as operating conditions to identify conditions that create compost with superior levels of nutrients while reducing the natural emission of greenhouse gases due to biodegradation of compostable materials. The team will also explore the use of waste cardboard and other feedstocks from the campus to replace the current wood shavings.

Farming on campus lands

A project led by Daniel Rubenstein, the Class of 1877 Professor of Zoology, a professor in the Department of Ecology and Evolutionary Biology, and director of the Princeton Environmental Institute’s certificate Program in Environmental Studies, and Gina Talt, food systems project specialist with the Office of Sustainability — will explore how to improve Princeton’s farmland stewardship practices in ways that encourage sustainability while improving agricultural yield. Princeton University enables local farmers to raise crops on large portions of its land, but in recent years farmers have reported finding it hard to make a profit due to crop consumption by deer. Additionally, years of growing monoculture crops with herbicides and fertilizers have led to nutrient-deficient soils and a system reliant on fossil-fuel-based inputs to suppress weeds.

The project will involve undergraduates in examining the cost-effectiveness of fencing the lands to keep out deer while also exploring a variety of soil enriching and anti-weed control methods. The team will grow field corn in one-acre test plots, including fenced and non-fenced areas, to compare how farming practices affect crop growth, soil health and farmland profitability. The sustainable practices to be tested include applying compost and compost teas made from campus food scraps, planting cover crops during the off-season, and weeding with equipment rather than applying herbicides.

Read the original article on the Princeton homepage here:

Weekly Data: 4/26 – 5/2


Total Food Campus Center/Cafes Academic /Residential Buildings


Wood shavings (BA/CS)  %
Compost Off-loaded GHG Emissions  Saved (MTCO2eq)
Week Totals (lbs.) 3,214 2,972 242 1,035 32% 3,000
CUMULATIVE (lbs) 77,829 76,736 1,092 24,162 31% 66,000 23


The Weekly ComPOSTer (5/3): EQuad Cafe Pilot

Happy Friday!

Although this week might have been the last week of classes, there is still a lot happening around the S.C.R.A.P. Lab as we started a 2-week pilot food scraps and compostable service-ware effort at the EQuad Cafe.

This week, staff and volunteers from Campus Dining, Building Services, and the School of Engineering and Applied Sciences monitored the bucket dedicated to compostables and educated diners at the cafe about the effort. Key findings so far include:

  1. Most people were very receptive to the idea of composting and took time to stop and and look at the signage and information on the LCDs.
  2. The team received insights into consumer disposal behavior and how to better position the compostable bin in the cafe in order to attract people and divert material.
  3. Similar to other events, napkins and the food service-ware (World Centric plant fiber clamshells and Chinet plates) made up the majority of the contents of the compostables bucket

In Week 2 of the EQuad Cafe Pilot, there will be no bin monitoring and education. We will evaluate how well prior messaging/education as well as the continued signage impact usage and contamination rates (unfortunately other items offered at the cafe such as utensils, soup containers, and coffee cups are not compostable in our composting system due to the greater thickness of their respectable materials and the need for higher decomposition temperatures).

Check back for our findings!

Weekly Data: 4/19 – 4/25

Last week we processed 3,454 lbs. of uneaten food, 188 lbs. of which came from our satellite locations in the academic/residential buildings which is an all time high as diversion awareness continues.

Total Food Campus Center/Cafes Academic/Residential Buildings


Wood shavings (BA/CS)


Compost Off-loaded GHG Emissions Saved (MTCO2eq)
Week Totals (lbs.) 3,454 3,266 188 1,054 31% 3,500
CUMULATIVE (lbs) 74,615 73,764 850 23,127 31% 63,000 22

The Weekly ComPOSTer (4/24): Sustainability Action Plan; More Materials Testing

Happy belated Earth Day from the S.C.R.A.P. Lab!

The S.C.R.A.P. Lab represents one way in which students and staff from across campus can partner on a daily basis to reduce waste and promote a circular economy on campus through a “table to soil” approach. Pictured above is just a handful of those involved in the project.

In bigger news, Princeton University’s Office of Sustainability released its new Sustainability Action Plan on Earth Day which sets bold targets and outlines innovative strategies to engage all faculty, staff and students in creating a sustainable campus and future toward 2026 and beyond.

In addition to a target for net zero greenhouse gas emissions by 2046 — the University’s 300th anniversary — the Plan calls for six other action areas including an aim to cultivate healthy and resilient habitats and achieve zero waste by reducing waste and expanding sustainable purchasing.

The S.C.R.A.P. Lab is one strategy that can simultaneously move the campus toward zero waste and healthier and more resilient habitats by…

  1. Advancing evidence-based sustainable landscape management solutions. The S.C.R.A.P. Lab will strengthen and further support studies by faculty, staff, and students on how to use compost and compost tea to reduce the University’s reliance on fossil-fuel based landscape inputs to control disease and pests.
  2. Providing an outlet for increased food scraps collection across campus to locations other than major dining venues. If done strategically, expanded food scraps collection would not only reduce landfill waste, but the number of loads of recyclable material that are rejected at the MRF (materials recycling facility) due to items coated with food residue.
  3. Advancing evidence-based sustainable purchasing solutions by studying the compostability of different food service ware so that the items that the campus buys can be tied to compostable products whenever possible. We’ve had some successes so far on a smaller scale with World Centric plant fiber clamshells, and the Huhtamaki ‘Chinet’ plate, so we have initiated efforts to test larger loads of these products, starting with last week’s effort to collect the Chinet plates (made from molded recycled paper) after Frist Late Meal (see below).

[Pictured at left: Members of the sustainability group, Greening Dining, helped students correctly sort their unused items during Late Meal. All food scraps and Chinet plates were captured and sent to the S.C.R.A.P. Lab for processing  the next day (Pictured at right)]

Stay tuned for results!

Weekly Data: 4/12 – 4/18

Total Food Campus Center/Cafes  

Academic/Residential Buildings



Wood shavings (BA/CS)


Compost Off-loaded GHG Emissions Saved (MTCO2eq)
Week Totals (lbs.) 3,089 2,954 135 1,011 33% 2,000
CUMULATIVE (lbs) 71,161 70,498 662 22,073 31% 59,500 21

The Weekly ComPOSTer (4/17): Coffee Club Partnership!

Good evening,

This week’s ComPOSTer welcomes Princeton’s newest coffee shop, the Coffee Club, to our growing list of partnering venues!

Located in the taproom of Campus Club, the Coffee Club held its grand opening on April 14th and is run and staffed entirely by students.

With sustainability being one of its core values, collecting coffee grounds for composting at the S.C.R.A.P. lab  is now one of the Coffee Club’s initiatives to promote more environmental and socio-economic  practices. Additionally, the club also sources pastries and roasted coffee beans from local vendors, and is committed to maintaining affordable — if not the lowest — coffee prices both in and off campus to foster an inclusive environment.

In just under 2 days, the Coffee Club has produced 25 lbs. of coffee grounds, which will provide nitrogen-rich material to our feedstock, and a good source of energy for the microbes that convert the organic matter to compost.

Fun fact: Contrary to belief, coffee grounds will NOT lower pH and make compost more acidic.  While fresh coffee grounds may be acidic, once brewed, they are closer to pH neutral. Since acid is water-soluble, any acid in the beans would have already leached into your cup of Joe.


Weekly Data: 4/5 – 4/11

Total Food Campus Center/Cafes  

Academic/Residential Buildings



Wood shavings (BA/CS)


Compost Off-loaded GHG Emissions Saved (MTCO2eq)
Week Totals (lbs.) 2,697 2,589 108 928 34% 2,000
CUMULATIVE (lbs) 68,072 67,545 527 21,062 31% 57,500 20

The Weekly ComPOSTer (4/10): Tiger Chef Challenge Composting

Hi all,

Last week we teamed up with Campus Dining to collect compostable material at our largest event to date – the Tiger Chef Challenge, which featured a Food Expo with complimentary food samples while student teams competed in an Iron Chef-like culinary challenge to see who could create the best plant-based entrée with the day’s secret ingredient (jackfruit).

Check out the photo essay below to learn about the process from collection to compost!

[At the event each compost bin had a sign picturing the acceptable items -food scraps, napkins, bamboo sampling plates]

[To prevent contamination, each resource recovery area was staffed by a student or staff member directing attendees on how to properly sort their items into either compost, landfill, recycling, or liquids]

[At the end of the event, Sanitation staff transported the 12 full totes to our facility. All together we recovered 154 lbs. of compostable material. Since the majority of the contents comprised of bamboo plates, we included this material as part of our weight total in the bulking agent/carbon source category because bamboo plates are essentially plant fibers just steam pressed together]

[Next we dumped the contents of the totes into the hopper via the lifter and the material was processed smoothly, needing only a few swings from the agitation arm to move material so that it could reach the cutting blades of the shredder. The shredded pieces then traveled up the auger via a screw conveyor and were emptied into the vessel]

[A few of the larger pieces that were not completely shredded by the cutting blades passed through after 4 days and ended in the compost that was off-loaded. We will continue to run these pieces back through the shredder so that they eventually break into smaller, more unidentifiable pieces. They will then finish biodegrading when applied to campus soils.]

Weekly Data: 3/29 – 4/4

We started to off-load compost again for the first time since before Spring Break. We are also starting to experience greater usage across the academic/residential building collection bins as campus awareness increases.

Total Food Campus Center/Cafes  

Academic/Residential Buildings



Wood shavings (BA/CS)


Compost Off-loaded GHG Emissions Saved (MTCO2eq)
Week Totals (lbs.) 3,327 3,207 120 1,126 34% 2,000
CUMULATIVE (lbs) 65,375 64,956 419 20,134 31% 55,500 19

The Weekly ComPOSTer (4/2): More partnerships, testing & data!

HI folks,

We have quite a few updates as we came back from Spring Break in full force. Check out the new partnerships, bioware testing, data metrics and Earth Month activities in the photo essay below:

  1. We welcome the Geosciences and Ecology and Evolutionary Biology departments in Guyot Hall to our growing list of partnering venues thanks to the efforts of graduate students, Chris Crawford and Katja Luxem. Each of their department kitchens now has a 5-gal collection bin (shown above) similar to the ones in the McGraw Center (pictured below), the Mechanical & Aerospace Engineering department, and the Scully Co-op.

2. We continued testing more compostable food service ware after a departmental request to evaluate a caterer for future zero waste events. Items included a serving tray, bamboo tongs & serving picks, and birch utensils. The serving tray is likely to be too thick to break down inside of the composting system after 5 days, and it is likely that the picks may elude the cutting blades and pass through the shredder still intact, but the proof will be in the compost! Stay tuned for the results!

3. As part of this year’s Earth Month schedule of activities and events, the SCRAP Lab will be hosting drop-in hours every Tuesday in April (9:30 to 10:30am), as well as a guided tour on Friday, April 26th (11am – Noon).

Weekly Data: 3/22 – 3/28

We’ve updated our data chart slightly to include the break-down of the sources of the uneaten food (Campus Center/Cafes vs Academic/Residential Buildings) as well as a metric totaling the greenhouse gas emission savings from diverting the uneaten food from the landfill using the EPA’s Waste Reduction Model (WARM).


Total Food Campus Center/Cafes  

Academic/Residential Buildings



Wood shavings (BA/CS)


Compost Off-loaded GHG Emissions Saved (MTCO2eq)
Week Totals (lbs.) 3,236 3,216 20 1,046 32% 6,000*
CUMULATIVE (lbs) 62,048 61,749 299 19,008 31% 53,500 18

*Compost off-loaded before Spring Break

The Weekly ComPOSTer (3/27)

Happy Spring!

After a short hiatus for Spring Break, the SCRAP Lab is back in operation! We thank Organic Diversion for assisting us and picking up the uneaten food from the University’s retail dinning venues while we were not in operation.

Since our composting system is demonstration-scale and has a limited capacity of 5,000 lbs. of uneaten food per week, we are unable to accept all that is generated and recovered across the University dining venues. As such, the University partners with Organic Diversion to pick-up both pre and post consumer uneaten food from all campus dining halls for transport to NJ farms where the feedstock is composted in windrows or used as animal feed.

See below for a visualization of the University’s food scraps diversion program:

[Data represents monthly totals. At full operational capacity, the SCRAP Lab would process about 1/5th of the total food scraps recovered from Campus Dining venues. However the SCRAP lab is only currently operating at 60% capacity. To reach full capacity we are gradually expanding into both academic and residential buildings, starting with the Scully Co-op and McGraw Center.]

Based in Marlton, NJ, Organic Diversion is in the process of building a regional organics recycling facility that combines anaerobic digestion with composting, but until that facility is operational, the company is only accepting food-based feedstocks versus other types of compostable material such as soiled paper products (e.g. napkins, paper towels, greasy pizza boxes) and plant-based food service ware. However these are all items that are readily acceptable in the FOR Solutions composting system and we have plans during the coming weeks to recover and test more of these items.

Stay tuned for more exciting initiatives as we approach Earth Month!