Portland Community College | Portland, Oregon Portland Community College


What is Compost?

Compost is simply decomposed organic matter. Composting is a natural process of recycling organic matter such as food waste, coffee grounds, leaves and other material that has lived or grown recently into a rich soil amendment.

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  • smiling woman raises compost bin and compost instructions poster

Why Compost?

Benefits of composting include

  • Reducing the amount of waste destined for landfills
  • Reducing carbon emissions from transportation to landfills and methane emissions from the landfills
  • Converting waste product into material that is useful for gardening, landscaping, agriculture and houseplants
  • Instilling a sense of environmental stewardship
  • Encouraging production of beneficial bacteria and fungi that break down organic matter to create humus, a rich nutrient-filled material
  • Helping sequester carbon dioxide in soil
  • Demonstrating scientific principles, inquiry and discovery
  • Creating a fertilizer product that is less toxic than chemicals alternatives
  • Loosening clay soils and helps sandy soils retain water
  • Helping soil fertility and stimulating healthy root development in plants
  • Providing food for microorganisms
  • Suppressing plant diseases and pests
  • Replacing trace minerals in soils
  • Reducing storm runoff and soil erosion

Composting on Campus

Compost is a critical operation on the Rock Creek campus. We have a multi-component composting system that generates rich soil amendment that is returned to the Learning Garden ensuring our soil health.

Worm Bin

Worm Bin

The showcase feature of our composting system is our thriving vermicomposting system, housed in a worm composter bin, a Worm Wigwam crafted by Sustainable Agriculture Technologies, Inc. in Cottage Grove, Oregon. Comprised of a large specially designed box capable of holding two tons of material, the bin is filled with compostable material and red wiggler worms. The worms, aloing with other beneficial insects process the material into worm castings, a dark, nutrient rich, healthy compost which we use as a soil amendment in our Learning Garden.

Finished compost is harvested from the worm bin using a winch that scrapes a grate across the bottom of the bin, releasing the fully processed compost.

The Learning Garden worms have received international attention and serve as a highlight in our Closed Loop System tours to campus classes and community groups.

Worm nursery

Worm nurseryThe worm nursery serves to replenish our vermicomposting system. A large Juniper wood raised bed filled with post-consumer food waste and tea and coffee grounds, our nursery is specifically designed to propagate and cultivate red wigglers. We then harvest the wigglers and transplant them in our vermicomposting bins where they kick into high gear and make high quality, great compost for our garden.

Aged animal manure

Aged animal manureThe RC Campus has a working farm with livestock, large and small. Campus animal manure is aged and used as a composted soil amendment around our campus. Aged manure compost helps build the organic matter content, adds nutrients, increases microbial activity and improves drainage and moisture retention capacities in soil and enhances the health and beauty of our campus landscaped areas..

Note: Thank you for your interest – we only use manure generated by the campus farm

Geobin with a compost aerator tool

Geobin with a compost aerator toolThe Geobin is a flexible, expandable compost bin that allows for ventilation, drainage and rapid decomposition for compost production. The Rock Creek Learning Garden uses the Geobin in combination with the Compost Crank & Twist aerator.

Black compost bin by EnviroWorld

Our FreeGarden EARTH compost bin provides us 11 cubic feet of capacity and generates high quality compost. A slower processor than the Sun Mar rotating bin and the GeoBin used with the Crank & Twist, this system allows us to compare results with a more traditional system. And one that is frequently available to backyard composters in our Portland Metro area.

All compost generated by our compost system is produced from campus based materials and is reintroduced into the Learning Garden to enrich the soil and growing environment, supporting high quality herbicide, pesticide and chemical free crops.

While we keep most of our food and green waste on campus to use on our campus grounds, not all of the food waste can remain on site.  A large part of the post-consumer waste comes from food left over at catering and food service lines and buffets.  Much of this food cannot be composted in our learning garden or worm bin.  Therefore, we have one collection bin for post-consumer green waste (meat, fried food, fats, processed food, etc.) that is collected weekly by our waste hauler.  This food waste ends up at JC-Biomethane Biogas Plant in Junction City, Oregon.

The facility is designed to take in not only food but grease trap waste along with grass straw to render heat, biomethane, and a liquid/fiber fertilizer. The biogas is used onsite to produce enough electricity to power at least 1500 homes (1.55 MW).


While we use 100% of the compost generated by our loop system, our compost needs are much greater than we can supply ourselves. We partner with Recology to provide the balance of the compost needed in the Garden.

Recology conducts curbside compost collection throughout the city of Portland and transforms this waste into a high quality, nutrient rich soil amendment that we use to fill our raised beds and amend our field crops. Recology operates Nature’s Needs in North Plains and describes their operation thusly

recology delivery“This site currently processes approximately 50,000 tons of yard trimmings, municipal organics, and land clearing materials each year.

Nature’s Needs uses a bio-covered aerated static pile with negative air and biofilters to optimize the composting process. This system produces the best and highest quality compost from the incoming feedstock.

Nature’s Needs’ quality assurance program includes routine nutrient, metal and pathogen analysis to ensure a high quality, consistent product that meets the needs and high expectations of our customers.

All compost produced by Recology meets federal standards and is certified organic by OMRI, Nature’s Needs epitomizes the loop concept on a large scale – community-wide food waste to compost to soil amendment used to produce more food. We are delighted to have such a stellar example and resource as our neighbor!


Using different compost systems allows us to increase the educational benefit to our students and community. Organic waste is collected daily by students and staff from central deposit locations across campus. This waste is then weighed, documented and placed in the various compost systems.

This hands-on learning provides us many opportunities for further exploration
    • We collect input data – specifically weight of the various locations and types of waste input. Ex., pre-consumer food waste from cafeteria food prep, coffee and tea from office area collections, post-consumer food waste from students

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    • We collect output data – comparing results from various sources and processing systems. Ex., weight of compost produced from our InSinkerator system that grinds pre- and post- consumer waste, tea and coffee grounds.
    • We compare the volume and rate of compost production

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  • We compare the quality of the compost produced
  • We have various compost systems for demonstration
  • We offer experiences and inspiration to meet different instructional objectives (ex., writing, biology, art, health, etc.)

In addition to the operations listed above, all organic landscaping waste (from grounds maintenance, tree pruning, forest management, etc) from our 260 acre campus is retained for composting on campus. Much of the larger material is ground to mulch and then used as part of the landscape maintenance on the Rock Creek and other PCC Campuses.

The Rock Creek Loop

Closed loop systems are a model of sustainability, transforming waste into nourishment within a community. Here at Rock Creek, we continuously strive to reduce and repurpose waste, and to feed more people from our on-site food production. Here’s how our loop works: we compost 99% of the pre-consumer waste produced on campus, and much of the post-consumer waste. This food waste, in turn, becomes food for our worms, who transform it into healthy compost to fuel the Learning Garden. The vegetables, fruit and flowers from the garden go to our farm stand, our volunteers, and local donation centers, where they become nourishment for the people of our community. Watch the video below for even more information, and to see the Rock Creek Loop in action.