The project components are now being maintained by gardeners at RCG. Please click here to view our Mission and our Vision (please note that these statements were written prior to the garden changing names from Neighborhood Community Garden to RCG).
Segmented Pit Composting
RCG Project Segmented Composting System
How it works:
Gardeners who have collected organic matter (i.e. banana peels, melon rinds, coffee ground etc.) at home or from the garden can add that matter to the system. Over time and with additions of water, air and heat the organic matter added will degrade. Soil is added to the top of the organic matter to ensure it does not smell up the area directly around the system too bad. Ultimately compost that has completely degraded into nutrient rich soil (or has finished “cooking”) can be taken from the bin and put where the gardeners want to give plants a boost of nutrients (around trees at the garden, on edible plants or flowers) ultimately to aid their growth and enhance their yield.
This type of composting relies more on heat input, air, and volume than the vermpicomposting system (see below). Having a greater volume allows for greater heat absorption from the sun and further increases microbial activity that creates the compost.
This composting system is a 15.6 ft x 5ft x 3.8ft (LxWxH) rectangular structure that is divided into three individual sections separated by horizontally placed planks of wood. The wood used for the frame is cedar, which is naturally resistant to bacteria and fungi. Three poles of redwood were placed into the ground to fight the erosion effects our system will encounter over time. This container is referred to as a segmented pit composting bin because it is dug about six inches into the ground (i.e. the pit part of the name) and is segmented into three separate bins (separated by the aforementioned horizontal cedar planks).
The purpose of dividing the container into three separate sections is to separate compost that is closer to being usable soil from compost that needs to “cook” (that is, biodegrade) longer.
The maximum volume that can be contained in the segmented pit composting bin is about 195 cubic feet or about 5.5 cubic meters (about 1,459 gallons, 5,522 liters). At an assumed rate of 18 gallons (68L) of matter being added to the system per week, there will be 432 gallons (1635L) of compost produced after the six month composting period is over (the time it takes will be based on season: during the summer the compost will prepare quicker, during the winter it will prepare slower due to heat input).
How it works:
This worm composting (vermicomposting is the technical term, “vermi” meaning worm) bin was another part of the RCG Project. Gardeners at RCG collect organic matter at home or from the garden add it to the worm bin not including things like citrus peels, onions, garlic, or any volatile (strong odored) things to the bin, the worms inside the container are very sensitive to the oils released by these things, they prefer watery organic materials like cucumber peels, melon rinds, celery, and coffee grounds. Egg shells pulverized into little pieces are another good thing to add, worms store these little pieces in their stomach to aid in digestion (a similar technique is used by birds as well, only with small pebbles). Once the organic matter is added, it will begin decomposing naturally with air and water being added to the bin, worms will begin to eat the matter and produce fresh compost for use in the garden.
Red wigglers are the preferred worm for worm bins such as this because they are ideal for creating compost (they apparently leave behind more nutrient rich material for composting systems), when they eat organic matter they leave behind “worm castings” (or feces) which are great for nourishing plants at the garden. This type of composting relies less on heat than the first (but still a balance in temperature as well as moisture is important, worms do not like hot temperatures and too much moisture).
The bin is a rectangular box raised off the ground and sitting on four posts, featuring 2 drop-doors on either side for easy access to compost (latches hold the drop-doors in place). The dimensions of the bin are (LxWxH): 3.1ft x 2.6ft x 1.9ft, which is held 4ft off the ground. The maximum volume that can be contained in the worm-composting bin is about 9.6 cubic feet or about .3 cubic meters (about 72 gallons, 271 liters).
From left to right: Inlet piping –> sink structure –> outlet piping + water storage barrel
How it works:
The sustainable sink is composed of three main components: inlet piping, the sink structure, and outlet piping ending at a water storage barrel. The sink is located in RCG, behind the garden shed (directly in front of the segmented pit composting system). The inlet piping is connected to a water pipe near the shed in the garden, it carries water from this pipe (which is fed by the watermane at the Che Cafe) to the sink structure. The sink structure is composed of a metal sink basin mounted on a wooden cabinet structure, here the water flows from the inlet piping onto your hands, produce or into your watering can, and any water not used will drain out of the basin via the outlet piping. The outlet piping takes the water down a hill about five feet to a water storage barrel, the water is then stored here for gardeners that need it to water their plants or perhaps add water to the compost.
From this point gardeners can use a water pump made from PVC to pump water from the water barrel and bring it to where they want it. Be sure to view the videos below for a demonstration of how the sink works!
The inlet piping is composed completely of PVC glued together. In total there is about 30 feet of PVC piping laid connecting the sink to the water pipe near the shed. The ends of the inlet piping are fitted with hose bib valves and aerator attachments (to control the pressure of the water leaving the inlet piping).
The sink structure is composed of a metal sink basin mounted onto an all-wood cabinet structure. The metal basin was already in the garden when the project started, it is believed that the basin originated from the biomedical facilities on campus, perhaps it was dropped off at the garden as a donation some time ago and it was put to use for this project. The metal basin’s dimensions are 3ft x 6ft x 6 inches (L x W x Depth). It has a precut hole for drainage, a sink drain attachment was attached to this to connect the outlet piping and the sink.
The all-wood cabinet structure was made out of wood glued together and secured by L brackets around edges. The cabinet structure is supported by four wooden posts standing ontop of flat bricks. For extra support, diagonal pieces of wood were added at the sides of the cabinet structure (see pictures below of structure). The cabinet props the sink basin up about three feet, keeping in mind the varied heights of gardeners it was important to ensure the height was not too tall or too short. The walls of the structure are composed completely of reused wood. The structure itself is partially composed of reused wood, about 50% of the wood used for the structure was already at the garden.
The outlet piping consists of PVC connected to the sink via the aforementioned sink drain attachment. The piping makes a 90 degree turn after coming out of the right wall (while facing the sink head on) of the structure. It then travels about five feet downhill to a water storage barrel where it fits into the barrel via a hole cut to the diameter of the piping. The water storage barrel, which holds about 70 gallons of water, is a reused food waste storage barrel donated to the garden some time ago and put to use in this project. Aside from the inlet piping hole made on the barrel, an emergency drain was added just below the inlet piping hole to ensure the barrel will not overflow. There is a hose bib valve attached about two feet down from the top of the barrel which connects the sink pump to the water in the barrel, an L shaped piece of PVC was added to the inside of the barrel to ensure that the pump could reach the water at the lowest 10 inches of the barrel.
The water pump is composed of 3/4 inch PVC piping, two check valves, two hose-to-PVC attachments and a piston with handle (made out of a wooden dowel). The inlet side of the pump attaches to the hose bib valve on the water storage barrel via a short piece of hose, while the outlet side of the pump is attached to a hose that may be taken at most a height of four ft uphill or easily down hill for watering. The piston is made of a wooden dowel that has a smaller diameter than the 3/4 inch PVC piping and is fitted with a handle for easy pumping at the top end and five or so round pieces of foam screwed into the bottom end. The piston fits tightly (thanks to the circlular pieces of foam) into the cylinder created with the 3/4 inch piping.
The pump is put together in the following way (going from left to right in the picture seen below, or from the inlet side of the pump to the outlet side of the pump): the inlet side with the hose attachment –> checkvalve –> T fitting (a PVC attachment which splits flow from one inlet, in this case, into two outlets) ==> 1) cylinder where piston is inserted and 2) outlet pvc checkvalve –> outlet side with hose attachment (–> = 3/4 inch PVC, ==> = two seperate pieces of 3/4 inch PVC, separated due to the T fitting).
By pushing the piston up and down, in and out of the cylinder, you create a pressure difference inside of the pump causing the inlet check valves to fluctuate in such a way that water is sucked out of the water storage pump and pushed into and finally out of the pump into the garden. When using the pump, raising it quickly will open the inlet check valve and close the outlet check valve, then when the piston is pushed down rapidly the inlet check valve closes while the outlet check valve opens. Eventually air is pushed out of the pump to the point where a vacume is created that pulls water out of the barrel, the vacume is then propelled out of the pump by force caused by pushing down the piston.
Special Considerations for Building:
1. The ground where the sink was to go needed to be made as flat as possible. Luckily the ground was saturated in pebbles, so during the process of moving dirt, that was creating a hill behind the shed where the sink was to go, volunteers along with the RCG project group sifted out pebbles and set them aside for use in the foundation of the sink.
2. After the ground was flattened we dug six inches into the ground in the shape of the sink cabinet structure (following the length and width dimensions as a guide for the digging pattern). All of the pebbles collected, mentioned in consideration 1, were put into the rectangular ditch and flattened. Ontop of this some scrap concrete bricks were placed to create a ground for storage within the cabinet structure. Four pieces of flat bricks were laid where the posts of the sink structure would go later.
3. Water moves out of the sink completely by gravity, so after the ground was flattened and the sink structure had been built the outlet piping had to be put in at a descending angle down the hill (going around the corner of the garden shed). This caused some changes in plans with the water storage barrel we were working with, we had to drop the barrel at least 1.5 feet on the side of the shed, this was accomplished by digging the ditch, placing concrete bricks on the uphill facing side of the ditch, securing those with rebar, placing other bricks around the perimeter of the ditch and fixing them into place with more long pieces of rebar (about three foot long pieces). To ensure the ditch would not fill in, water drainage moats were dug going around the outside of the ditch. A flat ground was made for the barrel inside of the ditch via three bricks placed into the bottom. Putting the barrel down this far into the ground had implications for how low the water outlet valve could be placed as well as how the barrel can be removed from the ditch for cleaning. Unfortunately the ditch makes it very difficult to pull the water storage barrel out for cleaning when it has not been drained low.
Video Demonstrations of the Sustainable Sink:
(Man with hat – Erik Hauenstein, Director – Pule Wang)
About Roger’s Community Garden
Roger’s Community Garden is an on-campus student run garden where students, faculty and staff alike may come and grow what they would like to.
The Garden is located behind (South in relation to) The Che Cafe, in the Revelle district of UCSD. Please stop by to see the garden as well as the RCG Project.
Pule Wang, Mario Zúñiga, Sebastian Hanna,Zhouyi (Katie) Liao, Ji Yoo, Jackie Ho, Zack Osborn (RCG), Earl Kang (RCG), and the many RCG volunteers that came out and lended their hands!