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Revision as of 16:29, 17 July 2020

FA info icon.svg Angle down icon.svg Device data
Hardware license CERN-OHL-S
Certifications Start OSHWA certification

Abstract

Finished composting bins

The objective of this project was to develop a cost-effective composting system that is durable, educational, and safe for children gardeners to use at Catherine L. Zane Middle School in Eureka, CA. As of spring 2017, teachers at Zane had tried to adopt a couple of different composting systems for the garden, but they had to be removed for a variety of reasons. The school requested a compost system that would be educational, safe, and able to accommodate garden waste, woody debris, and organic waste from the cafeteria. The new composter at Zane Middle School is a 2-bin system. The left-side bin is used for depositing fresh organic matter, while the right-side bin houses maturing compost. The structure is painted with weather-resistant paint, which prevents the wood from warping and postpones its decomposition. It is equipped with educational posters, and is lined with hardware cloth to detour rats. Each bin has a front door to encourage ease of access, although the corrugated steel roof is too heavy. In the future, a plastic or wood roof should be used.


Background

Catherine L. Zane Middle School in Eureka, CA focuses their curriculum around science, technology, engineering, art, and math (STEAM), and caters to a diverse group of children. Zane and the Environmental Resources Engineering department at Humboldt State University have a rich history of partnership around the STEM programs. As of spring 2017, the school had tried a couple of composting systems in the past, but were faced with a variety of problems including rats, the need for excessive maintenance, and destructive children, so they removed the compost altogether.

Problem statement and criteria

The objective of this project is to develop a cost-effective composting system that will be strong and safe for the children gardeners to use. This composter will be low-maintenance, simple to use, and will accommodate a variety of garden waste, woody debris, and the occasional organic waste from the cafeteria. The design will ensure the compost is free of pests such as rats and raccoons, and will be sturdy enough to stand up to the test of rowdy middle-schoolers.

Criteria Constraints Weight (0-10 high)
Pet Resistance Must be rat-proof 8
Maintenance Maximum of five hours of maintenance each week 5
Durability Must not be easily altered by middle-schoolers 6
Safety Must not be sharp or splintery 10
Educational Value Includes an appropriate display for middle-schoolers 9
Simplicity The compost must be accessible to the middle-schoolers 7
Cost Maximum cost is not to exceed $425 4
Aesthetics The aesthetics must agree with those of the garden and the school 3

Description of final project

The new composter at Zane Middle School is a 2-bin system. The left-side bin is a receptacle for fresh organic matter, while the right-side bin houses maturing compost. Each bin has an attached poster that contains information for users about how to maintain the compost, and also a little bit about decomposition.

The structure is 8 feet long, 3 feet deep, and 4 feet high at its highest point. The compost is easy to access through the fold-down doors, and the slanted roof directs rain away from the compost. Together, the bins can reasonably accommodate about 18 cubic feet of compost at any given time. This leaves plenty of room for garden waste, as the only school produces about 12 cubic feet of food waste each year. The bottom is open, which will encourage exchange of decomposer organisms with the environment (like worms). The bottom is lined with 1/4" hardware cloth to keep rats from entering the compost.


The composter in the garden at Zane Middle School
Finished composting bins

Include a how to use and maintain section. See the how to template below.


Costs

The capital costs for the project stayed within the budget of $425. In total, the number of labor hours spent on the design process, from conceptualization to implementation, was 204.

Quantity Material Source Cost ($) Total ($)
1 Corrugated metal, 73 sq. ft. Arcata Scrap and Salvage 17 17
2 Weather-Resistant Paint (quart) Ace Hardware 14.37 28.74
1 Wood Glue Ace Hardware 3.99 3.99
2 Hinge (small) Ace Hardware 4.59 9.18
1 Hinge (large) Ace Hardware 5.99 5.99
1 Corner Brace Ace Hardware 5.99 5.99
1 Mending Brace Ace Hardware 7.99 7.99
2 Hook & Eye Closures (2-pack) Ace Hardware 2.59 5.18
4 2 x 6 (Doug Fir) Pierson's 6.00 24.00
2 4 x 8 (Cedar) Pierson's 38.89 77.78
7 2 x 2 (Cedar) Pierson's 2.00 14.00
6 2 x 4 (cedar) Pierson's 3.84 23.04
1 2 x 2 (pine) Pierson's 6.98 6.98
20 Wood Screws Pierson's 0.33 7.16
1 Compost Thermometer Amazon.com 22.84 22.84
1 Galvanized Mesh, 2'x50' 1/4" Ron's Home and Hardware 42.37 42.37
1 Staples for staple gun Ace Hardware 4.49 4.49
1 5/32" Drill bit Ace Hardware 2.59 2.59
1 1/4" Nut driver Ace Hardware 4.59 4.59
1 Gasketed screws Ace Hardware 9.29 9.29
1 Mending brace Ace Hardware 8.59 8.59
1 Hinges Ace Hardware 13.98 13.98
1 Plasti Dip Ace Hardware 10.08 10.08
1 Poster lamination Ace Hardware 19.98 19.98
1 1/2" Hardware cloth Ace Hardware 18.98 18.98
Total Cost $394.80

Testing Results

This table describes the prototyping of different components of the composing system.

Image:Zane Middle School Compost Pretotype1.jpg

How to build

File:SketchZaneCompost.JPG
How to Do Something

Video

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Maintenance

The following maintenance tasks should be completed as often as specified to ensure the ongoing success of the composting system [1]. Neglect of any of these tasks could result in the failure of the system to produce desirable soil.

Schedule

Complete the following tasks, as often as specified.

Daily
  • Add fresh compost to the bin on the left
  • Add water to the compost if moisture levels are low.
  • Make sure the lid and doors remain closed except when working with the compost
  • Keep an eye on the temperature of both piles, relate to information found on the informational posters attached to the bins
Weekly
  • Turn the compost thoroughly on a weekly or bi-weekly basis, depending on temperature and moisture levels
Monthly
  • When the soil in the right side bin appears relatively homogeneous in texture, it can be added to the garden
  • Move compost from the left-side bin to the right-side bin after the thermoplastic phase
Yearly
  • Make sure the hardware cloth remains securely attached to the wood


Every few years, as necessary
  • Replace hinges and hooks
  • Repaint/touch up with weather-resistant paint
  • Replace metal wire mesh and staple as needed.
  • Re-apply plastic dip to the edges of the lid
  • Replace the compost thermometer
Task Frequency Participants
Add compost to left-side bin Daily Students and teachers
Move left-side compost to right-side bin Every few months Students and teachers
Turn compost in each bin Every two weeks Students and teachers
Monitor for structural degradation, upkeep as necessary Ongoing Teachers
Add soil from right-side bin to the garden As available and necessary Students and teachers

Instructions

File:ZaneCompostMaterial.jpeg
Adding Material to the Compost

Troubleshooting

This is a list of possible problems one may encounter during regular use, and steps to resolve those problems [2].

Problem Suggestion
The compost is dripping wet Add dry browns (like sawdust) and mix thoroughly
The compost smells like methane Mix thoroughly, and increase the normal frequency the pile is turned
The compost is too hot Turn the pile and moisten if it's dry
The compost is too cold Add greens, make sure it's moist but not dripping wet, and increase the size if the pile is small.
The gopher wire came undone from the wood Staple the two back together with an industrial stapler (~14 mm staples)
The Plastic Dip is peeling off Peel all of the loose ends off, and apply more with a sponge brush.

Discussion and next steps

The client was very happy with the professional aesthetics and educational value of the final product. Although the roof is functional, it is a little on the heavy side. Hooks were installed on both sides of the roof and is designed secure it to the fence when opened. If the roof is not secured, it can act as a sail and the wind will easily blow the roof closed.

Suggestions for future changes

Although functional and sized well, the large corrugated metal roof was not ideal for this project. The roof requires too much effort to lift, both because it is so long and because it is heavy. In the future, the lid should be made from two shorter sections (one over each bin), and should be made of a relatively light material. Instead of using corrugated metal, a corrugated plastic roof would make it a lot lighter although may be more expensive to buy brand new. The wire mesh edges proved to be really sharp so if replaced, it is recommended to fold the sharp edges toward the inner walling of the compost. This is to ensure that the sharp edges are pointed inwards to prevent potential harm.

September 2019 Update

Overall the compost was well put together and stable.. The compost bin is filled with soil on one side and carbon material plus some plastic on the other side. It seems that the compost bin and the garden are not being used heavily, though this could be because of the summer break. The top lid was found to be rather heavy, stated by a teacher, this makes it difficult to use around kids. But the hooks in the fence work well. One of the posters is falling off the inside lid and the two fold-down doors were open when we found it, making it easy for pests to get in. However, no food scraps were seen inside. The school does not use too much compost, explained by a teacher who keeps it and teachers children. They also have in fava beans, kale, and squash in some beds where they use the compost. The garden is coming together as the school year starts. It seems the compost is in good use with some minor improvements necessary.

September 2019 Update
September 2019 Update

References

Template:Reflist

  1. Trautman, Nancy (1996). "Compost Physics - Cornell Composting." Compost Physics - Cornell Composting. N.p., Web. 01 Apr. 2017.
  2. University of .Illinois Extenstion (n.d.). "The Composting Process." Composting in the Home Garden - Common Questions. N.p., n.d. Web. 05 Apr. 2017.
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