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CCAT compost 2017

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Engr305 Appropriate Technology page in progress
This page is a project in progress by students in Engr305 Appropriate Technology. Please do not make edits unless you are a member of the team working on this page, but feel free to make comments on the discussion page. Check back for the finished version on May 15, 2017.


For the Spring 2017 semester, we will be rebuilding the Humboldt State University compost system at CCAT (the Campus Center for Appropriate Technology). CCAT is a model home dedicated to demonstrating renewable and carbon neutral practices you can do in your home. CCAT needs a new compost system because their current one doesn't have enough insulation and is difficult to use. As you can see below, the frame of the system is beginning to break down making it even harder to access the mature compost. A working compost system is essential to the identity of CCAT and needs to be functional as well as educational. The current compost system is a three part compost but the system we hope to implement will be a tumbler compost which will be more compatible with what CCAT needs. More details of different compost systems can be found below. This gallery shows photos of the current compost system in place.

Problem statement[edit]

The objective of this project is to redesign and rebuild the compost system at CCAT in HSU to be more insulated, accessible, and protected.

Literature Review[edit]

Composting Basics[edit]

"The word compost comes from two Latin roots, one meaning "together," the other meaning "to bring"". [1] This essentially boils down to the practice of combining a bunch of organic material together to create useful and organic fertilizer. Many cultures have re-purposed organic materials for farming, building material and fuel that it is hard to give credit to just one for the origin of composting. [2]

The basics of composting include organic material, a certain level of aeration, and insulation. The idea is that the insulated area creates its own heat which speeds up the decomposing process while the aeration helps to reduce the odor that decomposing material produces. The organic materials that can be composted are fruit/vegetable scraps from the kitchen, yard clippings, and paper materials. The things that should not be composted are meat, eggs (though the shells are compostable), dairy products and any material that has been processed such as metals or plastics. [3]

There is a balance of nitrogen and carbon to be aware of also. Carbon ("browns") is usually found in dried things like straw, dried leaves and wood chips. Nitrogen ("greens") is in most kitchen scraps and yard clippings. The ratio of carbon to nitrogen or browns to greens needs to be close to 25-30:1. [4] If there is too much carbon, the decomposition will slow down and if there is too much nitrogen the pile may begin to smell. The balance helps keep the microorganisms working with enough protein and energy to turn the organic matter into nutrient rich compost.

Methods of Composting[edit]

There are many different styles of composting. Determining which one is right for an individual is determined by a few different thing. How much waste is produced, how much maintenance is needed for the system and how quickly the compost matures are just a few elements to consider.

Barrel Compost[edit]

The barrel compost system is a relatively new system. It is a system that is easy to operate but there is some thinking to do about placement. This system doesn’t have a large storage space but it creates mature compost in as little as one month. [5] The maintenance of this system is very easy. The barrel should be turned once a week for proper aeration and once the compost is matured it must be removed and the cycle starts again. The mature compost can be used right away or it can be stored elsewhere for later use. One down side to this system is that once the barrel is full the addition of new materials but stop. This halts the constant production of compost but rather it is made in ‘batches’ which may not be compatible for high waste producing households.

3 Part Compost[edit]

A three part compost system is very useful. It takes up more room than a barrel compost but material can be continuously added and turned for the constant production of usable compost. The idea is to have a three blocks where one side is the incoming block, the middle block is the “in progress” compost and the last is the ready to use, finished compost. The maintenance is a somewhat involved, since the incoming compost must be moved to the middle compartment and then once again to the finished side. If mixed and proportioned properly, there shouldn’t be much more maintenance than that but it is possible for it to need turning if it begins to produce odor. [6]


Also called vermicompost, this uses worms to process the organic material. It has the same basic methodology as regular composting but the worms speed up the process and requite a little more attention. They are a little more sensitive to temperature which means they should be located close to a home or in the home itself. There also needs to be some specific things added to the compost in order to make it easier for the worms to breathe. Things that aerate the compost not only makes it easier for the worms to breathe and move around but it also cuts down on odor that is produced naturally by compost. There are many structures to choose from when housing the worms. The most common structure is the stackable unit. There are many square containers that have holes in the bottom of the unit. The basic idea of this unit is the new organic material is added to the top level. When there are no more levels to be added, the very bottom layer is taken out and the worms are removed from the mature compost. The worms are added back into the unit and the compost is used. The now empty level is placed on top and the process starts over. [7] The holes in the unit allow for the worms to move up toward the fresher organic material. Other structures have one level that they harvest more frequently and all at once. The maintenance of vermicultures require a little more work than the non-wormy compost. The worms need to be monitored and kept alive in extreme temperatures and when time comes to harvest the compost, they need to be sorted out of the compost in order to continue on with the cycle.

Building Materials[edit]

Building materials for a compost system can range from anything from wooden pallets to recycled plastic bins you might find lying around. Depending on the size, location, and type of composting system you wish to build the materials may vary. Wire mesh and pallet planks can be used to build simple outdoor square or rectangular compost systems along with cinder blocks, bricks, or even cardboard for a simpler but less sturdy option.[8] If your building a tumbler composter, which is essentially a drum or any cylindrical contain that can be rotated to help move and aerate the compost inside materials such as trash cans, recycled food drums, or old wine barrels can be used. [9] Essentially all that needs to be accomplished is a contained, protected environment that successfully allows for the natural process of breaking down organic materials to occur.

Client Criteria[edit]

When speaking to CCAT about their needs and what improvements they are looking for, there were a few elements that stood out as more urgent needs. One of those needs was more insulation to speed up the decomposition time which makes the system more efficient. The current compost bin has little insulation on the bottom of the lid but all the inner walls are bare which allow a lot of heat to be lost. Another was accessibility to the mature compost which currently is only accessible by either lifting the compost over the side through the top or by removing a panel in the wall, both of which can be physically strenuous. There was a mention of pests but this isn't a very urgent problem, just something to keep in mind while designing. [10]


Criteria Constraints Weight
Accessibility Mature compost must be easily accessible and unit must be easy to open
Aesthetics Compost bin should look professional and pleasing to look at
Cost Must not exceed budget (max $200)
Dimensions Should have dimensions close to 12ft long X 3ft tall X 4ft deep
Insulation Must have enough insulation for proper composting to occur
Materials Used Materials should coincide with appropriate technology techniques

Proposed timeline[edit]

Activity Due Date
Visit local examples of composting systems February 17-19
Finalize budget February 25
Prototype/design new system March 1
Acquire building materials March 3-5
Build new compost March 9-11
Test new compost March 12- April 12
Redesign/ make changes if needed April 12-16
Create signage April 21-23
Present final project May 1

Proposed Budget[edit]

Our funding will be coming from CCAT and will simply be used on buying the building materials to upgrade the compost system

Quantity Material Source Cost ($) Total ($)
4 4x4x8 Pressure Treated Wood The Mill Yard $10.99 $43.96
2 2x4x18 Douglas Fir Wood The Mill Yard $7.19 $14.38
2 Sturdy Door Hinges The Mill Yard $9.99 $19.98
3 Rust Proof Handles (for rotating) Ace Hardware $6.00 $18.00
Total Cost $96.32


  1. Campbell, Stu. "Let it rot!". Storey Publishing. 1993. Pg. 3
  2. Smith, Martha, and Duane Friend. "History of Composting." History of Composting - Composting for the Homeowner - University of Illinois Extension. Accessed January 26, 2017.
  3. Elmore, Dave. "Composting Basics & Getting Started." Green Action Centre. September 9, 2010. Accessed January 26, 2017.
  4. Adekalu, K.O., Ogunjimi, L.A.O., Ogunwande, G.A., Osunade, J.A. (2008, November). Nitrogen loss in chicken litter compost as affected by carbon to nitrogen ratio and turning frequency. Bioresource Technology. Volume 99 (Issue 16), pp. Pages 7495–7503.
  5. "How to Compost in a Rotating Barrel." Home Guides | SF Gate. Accessed January 26, 2017.
  6. Martin, Deborah L., Grace Gershuny and Jerry Minnich. The Rodale Book of Composting. Emmaus, PA: Rodale Press, 1992.
  7. Appelhof, Mary. Worms Eat My Garbage. Kalamazoo, MI, USA: Flower Press, 1997.
  8. Admin. 18 Cool DIY Compost Bin Designs. Compost Guide: tips for home composting. 2013 Online article.
  9. G6957. How to build a compost bin. Uinversity of Missouri Extension. Online article. 1993
  10. Anderson, Austin. "CCAT Compost." Interview by author. January 27, 2017.