Every Monday, Wednesday and Friday, RCG collects 8-20 gallon buckets from each participating business or group. We try to avoid picking buckets up during peak lunch hour traffic and use only service alleyways to avoid spilling these wastes in public areas of price center. Furthermore, RCG has asked vendors to store these buckets in the back of their kitchens or in just outside in the service corridors so we don't interfere with their business.
UCEN has generously allowed us to borrow a pickup truck and furniture dollies to transport over 100 pounds of waste at a time from PC and SSC to RCG.
This quarter we are regularly picking up 2,000 pounds of food waste a week, up from just above 1,000 pounds at the start of this project, and above the 1,500 pounds during Summer Session.
After collection, we carefully weigh and chart the type of collected waste (vegetables, protein, etc.). At this point, a waste audit is performed to find materials suited for the Anaerobic Digester, which prefers softer foods like bread or vegetables.
Once the waste has been sorted, the non-digester waste is added to our two outer most compost piles. Waste is then covered with wood chip mulch (a combination of pine needles and wood chips from tree maintenance) produced by UCSD Facilities Management. We've noticed that adding mulch helps to reduce the often unpleasant-smelling odor associated with composting.
After the pile was first erected, it very slowly increased in temperature to around 120 F (48.9 C) after a few days. During this step, the pile produced a characteristic odor of volatile fatty acids (VFAs) which was likely caused by fermenting bacteria. Because of this we found it best to turn the pile after 1-2 days to minimize emissions of VFAs. At this stage, compost is moved from the outer two most bins into the two inner bins.
Following the first turn, the odor of VFAs disappeared and the temperature rose to above 140F (60C) in a couple of days. At these temperatures weed seeds and potential pathogens are killed. The compost is considered ready when the temperature no longer rises after turning, at which time it is moved into the central bin. This enables the most efficient production of compost, as once we've reached a few weeks old the usable organic matter left is only a fraction of what we started out with.
After all these steps have been completed, the compost is then added to the various planter bins, pots, and even RCG's orchard. This compost allows our garden to continually produce without having to worry about using potentially damaging artificial fertilizer. Additional benefits of the compost include its ability to trap water, minimizing loss to evaporation, and providing a safe habitat for beneficial insects.
We offer three sizes of buckets - 8, 12, and 20 pounds. Businesses can also elect to take multiple buckets depending on how much waste they produce.
We first weigh and chart our collected waste before adding it to our 5-bin system.
The above diagram depicts what Scientists believe happens inside a pile of compost.
New Composting Methods
In addition to traditional “hot composting”, RCG practices vermicomposting which uses red worms (Eisenia Foetida) to consume food waste. The end product is a rich, organic soil amendment called worm castings or vermicompost. They are easily reared all year round in dedicated worm bins.
RCG has begun rearing Black Soldier Fly larvae (BSFl). BSFl are vigorous consumers of any kind of organic matter and feed on anything from vegetable scraps to meats and feces. The grubs are housed in a special bin known by the brand name BioPod. The Biopod was placed in a small tent to keep adult flies in and therefore create a self-sustaining colony. These flies are then fed some food waste to help break down material that would otherwise take weeks or months in our traditional composting bins.
In addition to helping process high-protein food waste, BSFl can also be fed to our bluegill fish, as they are rich in fat and protein. Thus, they are incredibly valuable in helping RCG reach our goals of local food sustainability.