FA info icon.svg Angle down icon.svg Project data
Authors Luis Garcia
Makenna Waterfield
Team 6
Location Arcata, California
Status Prototyped
Instance of Compost bin
OKH Manifest Download

A rapid composting system was designed by Engr205 Introduction to Design Team 6 to find a better use for the green waste generated at the Humboldt Coastal Nature Center. Below is a detailed page on the process and cost of building the rapid compost system.

Problem Statement[edit | edit source]

The Friends of the Dunes invites volunteers every week to remove invasive plants in the Humboldt Coastal Nature Center. Each week, a volume of approximately 6'x6'x6' of green waste is generated and shipped off the site to be disposed of miles away. In an effort to manage the waste on site, rather than shipping it, this rapid composting system was designed.

Criteria[edit | edit source]

Criteria Weight Constraint
Cost 4 Less than $400
Ease of Use 7 Usable by untrained volunteers
Educational Value 6 At least volunteers learn more about rapid compost systems
Effectiveness 9 Must be able to process about 6'x6'x6' of yard waste every 14-21 days
Labor Intensity 5 Cannot require more maintenance than 1-2 times a week for 2-3 hours each day
Availability of Amendments 2 Bought locally and cheaply
Aesthetics 6 More professional than a tarp
Safety 10 Non-toxic and will not spontaneously combust
Durability 8 Stable for at least one year

Description of Final Project[edit | edit source]

The rapid compost system is a three chamber compost bin with no mechanical parts. The structure is supported by wood beams and insulated with beach grass bales. To protect the insulating bales from wet weather, a hand mixed lime plaster seals the walls. The ground under the structure has been compacted thoroughly and covered with wood pallets to prevent the compost materials from contacting the earth. A roof will be slightly larger than the structure, and pitched at an angle, to keep rain from soaking through the plaster. Doors were made from donated wood that slides into place.

Project Site

Find an open space.

Three Chamber compost System

Compress and flatten the ground where the compost bin will go.

Three Chamber compost System the 2nd

Find some pallets to build the frame of the composter. Pallets can be found almost anywhere that receives freight. One of the best places to search are hardware stores, who will often give away the pallets for free.

Some picture

Nail three pallets together to make a chamber for the compost.

Some random picture

Place another pallet at the bottom of the chamber. This pallet will prevent the compost materials from contacting the ground while also allowing air to enter the compost bin form below.

Some picture

Because of the large amount of waste being generated at Friends of the Dunes, three chambers were built. One or two chambers would be more appropriate for individual households.

Slots for door

Take six boards that are about the height of each chamber and cut slots into them. These slots will be placeholders for planks of wood which will make the door.

Some picture

Drill the boards directly onto the chamber walls.

Some random picture

Take any extra pallets you may have and remove the planks of wood. This wood is perfect for doors and will save money since pallets are free.

Some picture

Place the planks of wood into the slots.

Some picture

Once all planks are in place, the door will be complete.

Some picture

Latch on a metal roof to protect the compost materials from rain.

Beach Grass Bale

Properly insulate the chambers by placing straw bales around the system. In our design we used beach grass because it is an invasive plant that is always readily available.

Materials Cost[edit | edit source]

Materials Quantity Potential Cost Our Cost
Pallets 3 $23.75/pallet Donated
Beach Grass Bales 18 Free Donated
Straw Bales 18 $9.12/bale $9.12/bale
Lime Plaster 48ft2 $50.00 $50.00
Wood twelve 2"x4"x4' Free Free
Nails and Wire Staples 1lb $2.49/lb Donated
Chicken Wire 48ft2 $12.00 $12.00
Rebar five 4' bars $3.00/bar $3.00/bar
Corrugated Sheet Metal one 4'x15' sheet Free Free
Total with Beach Grass Bales $161.24 $86.00

Design Cost[edit | edit source]

Figure 8: Time Invested[edit | edit source]

Group Time input.jpg

Update October 2017[edit | edit source]

Unfortunately the rapid compost system fell apart and is no longer available to compost green waste. An employee said that, "They were not used as often as they would have liked." It was also mentioned that, "They fell over and it was a eye sore."

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