Compost Facility

The compost facility on the Evergreen Organic Farm is the product of a student's vision and cooperative effort of Facilities, Housing and Student Activities to capture a portion of the College's organic waste stream for use on the farm. While not scaled to accept all potential compostable waste products from the college, the facility serves as an educational tool for students to learn various compost techniques and how to manage nutrients and soil biology on an organic farm.

Composting is a naturally occurring process that converts organic material (like foodscraps, manure, or weeds) into a nutrient and microbe-rich soil amendment. When moisture, air, and the raw material mix are regulated properly, microscopic soil biology break down complex organic compounds into stable, mature forms suitable for use on the farm. These compost comrades are primarily bacteria, fungi, actinomycetes and nematodes. If well managed, cured compost applications will slowly build up biological flora in the soil, which perform many functions including nutrient release for stimulated plant growth resulting in sturdier, healthier crops.

Composting organic refuse keeps the most readily biodegradable portion of the waste stream from entering the landfill, where anaerobic decomposition of organic materials will create methane, an odor-causing greenhouse gas. Composting also prevents the point-source contamination of groundwater from mineral nitrates and phosphates contained in food scraps and yard waste.

Compost and Materials

We have a variety of composting materials available at the Evergreen State College. The Organic Farm uses woodchips from local arborists, sawdust from the campus woodshop, food scraps from campus, weeds, straw, and manure from the farm. Each week our student composters pick up pre- and post- consumer foodwaste in twenty gallon buckets from campus dorms and apartment complexes. The food is transported by truck to the Organic Farm Compost Facility where it waits to be mixed into a compost pile. The frequency of building compost piles depends on the fluctuation of accumulated resources, or "feedstocks". During winter months food waste is our primary nitrogen source; in summer, farm weeds are more prevalent.

We make Certified Organic Compost. This means we take additional care and maintenance to adhere to the Organic Standards set by the WSDA for the Process to Further Reduce Pathogens and carbon to nitrogen ratio:

"Compost must be produced through a process that combines plant and animal materials with an initial C:N ratio of between 25:1 and 40:1. Producers using an in-vessel or static aerated pile system must maintain the composting materials at a temperature between 131 °F and 170 °F for 3 days. Producers using a windrow system must maintain the composting materials at a temperature between 131 °F and 170 °F for 15 days, during which time, the materials must be turned a minimum of five times." While we successfully compost fats, oils, meats, and fish, we do not compost manure or carcasses from predatory carnivores (animals which eat other animals). When PFRP is achieved most soil pathogens and weed seeds are eliminated. However, certain soil diseases like Club Root have shown to persist despite the extreme conditions. Accordingly, we avoid composting diseased plants.

Our mechanical resources consist of a 3/4 ton truck, two 16hp Kubota tractors with loaders, a manure spreader, and a few pitch forks. Our human resource is one part time 20 hour/ week student composter who directs the facility and educates students.

Composting Systems

Aerated Static Windrow

This system is fairly simple but incredibly effective on a medium to large scale. Set up a section of perforated pvc drain pipe and a powered blower on a slightly graded impervious surface. Then take two or any number of different feedstocks, mix them together (usually with a manure spreader or pitchforks), and form into a long windrow at least four feet tall over the extended pipe. Cover the compost pile with a fabric such as a tarp or Gore material, or even a six inch cap of wood chips will do. By running the blower fan on a timer to aerate the pile, we are able to reach PFRP in a minimum of three days without turning. We are currently experimenting with this system in hopes that it will be more efficient than others mentioned below.

Aerated Vessel Reactor

Constructed from a concrete and lumber frame, the insulated vessels are roughly 8 feet wide x 10 feet deep x 8 feet high, tapering at the rear. With a closing door, this design minimizes heat loss. There is an extensive forced air plumbing system which can blow "positive" air up through the pile and out, and also suck air down through the pile (negative). Behind the reactors are electronic devices which can record data like temperature, oxygen content, and air speed, making this facility capable of doing compost research.

In the recent past, our three reactors have been used to make compost piles much like the static aerated pile. Despite the capability of reaching PFRP in three days, we choose to prolong the thermophilic (high heat) process by turning the pile into a neighboring reactor to maintain temperature for maximum decomposition. Thermophilic literally refers to "heat loving" bacteria, thriving at temperatures between about 115- 175 degrees F.

Two Stage Compost

In the less recent past the compost reactors were part of a two-step process. First, foodscraps and other feedstocks were brought up to PFRP in the reactors as part of a sterilization and predigesting before it was then dumped into the vermiculture finishing bins. The worm castings were collected in large, removable trays that are placed under the vermiculture bins. While logical on paper, this system actually proved challenging for many reasons. Firstly, it was high energy- intensive requiring many hours of labor and tractor work. Secondly, there were complications with timing rapidly ripening food waste from campus with the steady diet of the worms. Although the red wiggler worms are good at digesting food, they are particular about what form/ particle size it comes in and generally do not like citrus fruits. The worms became virtually inactive during winter with abmient temperatures between 30- 50 F.

In conjunction with understaffing, this composting system proved too difficult to manage for long term production of large food scrap volumes.

Vermicomposting

Vermicomposting is a method of decomposing organic material using surface feeding worms. Redworms (Eisenia foetida) are usually used for this purpose. They are surface feeding earthworms that consume 90% surface organic matter and 10% soil.

To achieve successful decomposition worms must be given the proper habitat and adequate food and moisture. The habitat requirement is achieved by placing a layer of bedding material at least 3 inches thick in the bottom of the vermicomposting bin. The bedding material could be straw, shredded newspaper sawdust or horse manure with bedding material in it. This bedding material is then inoculated with a population of worms. Assuming the bedding material is kept slightly moist, above 50-60 degrees and adequate food is available the populations will expand.

For optimum food waste decomposition consistent monitoring is required. If too much waste is added the worms may suffocate. If not enough is added population growth will stall and perhaps the worms will die-off. As populations grow food demand increases. As temperatures decrease in winter the demand for food decreases. This bin has gone through up to five 25 gallon drums of kitchen waste per week.

Worms do not "eat" the food waste put into the bin. They primarily feed on the microbes (bacteria, fungi and actinomycetes) that are actively breaking down the food waste. Hence all waste that is put into this bin must be allowed to partially decompose prior to introduction into the bin. The food waste is often shredded to create more surface area for microbes to feed on thus facilitating the decomposition of the material and the growth of worm populations in the bin.

Worm castings are a humus-like material rich in enzymes, plant nutrients and microbial populations. Castings contain approximately 2% nitrogen, 2% phosphorous and 1.5% potassium. They are always at a neutral pH due to earthworms capacity to neutralize even the most acidic of materials. The nutrients are also made available slowly over a period of years. These properties make castings an excellent garden soil amendment.