The day-to-day operation of the drum requires taking temperatures in the morning and the afternoon, collecting compost in the morning and afternoon, and regularly unloading compost from the drum (once preliminary pasteurization requirements have been met).
Food to be composted comes from one all-you-can-eat dining area, and one vegan single-plate-serving café. Students scrape their plates into a 20-gallon compost bucket located at the dish room. Buckets of food to be composted are picked up by the Recycling crew and transported in a pick-up truck, to the composting area. The cafeteria is approximately 1 or 2 tenths of a mile from the composting area.
The drum holds about 6 cubic yards. Food loaded into the drum takes approximately 2 weeks for the preliminary decomposition to be completed. The compost then spends about 4-6 months in curing piles, a.k.a. the Vector Attraction Reduction stage. There are seven piles at all times, varying from newest to oldest. We weekly fluff the curing piles, bi-weekly turn the piles, and bi-weekly screen a finished pile.
Compost is loaded once on Sunday, during the afternoon, and no compost is loaded on Saturday.
We chose a carbon source of woodchips and sawdust for the GreenDrum. Through extensive testing we have found that a 1:1:1 combination of Food : Woodchips : Sawdust, by volume, creates the best compost. More importantly, this ratio creates a better environment for the thermophilic, aerobic bacteria to thrive.
For the Fiscal Year starting in August 2008, we have been getting anywhere from 300-500 lbs of food waste EACH DAY from the two cafeterias on campus, combined. We have found that this is the maximum amount that our drum can handle. In fact, we occasionally have to throw away some of this food waste for various reasons.
The GreenDrum, and all of its constituents, are run off of a single phase panel. The drum turns for about 5 hours during loading, taking temperatures, unloading, and the scheduled evening hours (see Torque Panel). The auger and mixer run for about 90 minutes, total, during loading in the morning and afternoon. The fan is on at all times, except when unloading, or during maintenance.
We also test the moisture content of the piles and the drum using a moisture meter. We monitor the smell and look of the compost whenever taking temperatures or unloading. This testing is not required by DENR but it is necessary for the proper assessment of the compost.
We have found that compostable dishware creates issues when introduced into our system: the stiff plates and cups and corn based flatware get caught up in the auger. We are also already at or exceding our maximum capacity for food which can fit in the drum. For these reasons we have decided not to process compostable dishware. However, we hope that the compostable dishware will degrade in the landfill.
Smells and Flies
If the compost is actually composting correctly, the smell should be pleasant, a rich chocolatey decomposition smell... it's an acquired taste. However, an increase of anaerobic activity is indicated by a bad smell, this means an adjustment needs to be made for proper aerobic bacteria growth. Flies are a constant annoyance, but they disappear with the coming of colder weather, and there are more in our office most of the time anyway.