In-Vessel Systems

Earth Tub

The Earth Tub is designed specifically for on-site composting of food-waste. The Earth Tub is a fully enclosed composting vessel featuring power mixing, compost aeration, and biofiltration of all process air. This self-contained unit is ideal for composting at schools, universities, restaurants, hospitals and supermarkets.

Earth Tub: Step by Step
Earth Tub Step By Step Video

Earth Tub

With more than 200 tubs sold worldwide, the Earth Tub is the most popular in-vessel, commercial composting system of its size.
Each Earth Tub can individually compost up to 100 pounds per day (total biodegradables).  Two Earth Tubs can jointly compost up to 200 pounds per day.  Three Earth Tubs can jointly compost up to 300 pounds per day.

 

The New Earth Tub

The New Earth Tub (Version 9.0) is now available! We’ve listened to our customers and incorporated great new features and benefits into the new Earth Tub design!

  • Easier to mix! The tub and lid design has been modified for smoother turning of the lid.
  • Better protection against rain! Cover has a new sloped design to help it shed rain water and prevent rain from entering the Earth Tub.
  • No leachate requirements! Leachate can now be recycled back into compost. An optional leachate drain provides options for disposal of excess leachate.
  • Easier to unload compost! The Earth Tub now has a new larger, discharge door that provides better access to the interior of the Tub.
  • Easier to clean! No more perforated floor. The smooth floor makes it easier to remove compost and clean the Earth Tub.
  • Recycled content! The Earth Tub vessel is now made with 50% post-consumer recycled content plastic!*
  • Cool new look! Enhanced structural design imparts a sleek, rugged aesthetic. Neutral colors look great in a variety of environments.

* Tub base is made of 50% post-consumer and 50% post-industrial recycled content plastic.

The Earth Tub Process

Loading the Earth Tub

Organic materials such as food scraps, manure or yard waste are loaded through the large hatchway in the cover. These wet organic materials are then covered with dry materials such as wood chips, shavings, leaves or small weeds to prevent odors and insure that porosity and moisture levels are ideal for composting.

Mixing

Turn on the auger motor and rotate the cover to shred and mix the new organic material into the active compost. Two revolutions of the rotating cover are required to mix the outside and center of the Earth Tub. The auger will shred and mix a ton or more of compost in 10-15 minutes. During active composting, the Earth Tub should be mixed at least two times per week.

Aerobics and odor control

Maintaining aerobic conditions and controlling temperatures are essential for fast, effective composting and odor control. The aeration system draws air through the compost and forces the exhaust air through our biofiltration air purification system to remove odors. The overall cleanliness of the in-vessel design allows the Earth Tub to be placed in commercial settings close to where waste is generated.

Waste reduction

Heat generated in the Earth Tub rapidly breaks down the food scraps. The volume reduction is typically 50% or higher. After 2-3 weeks of active composting, open the discharge door and remove the compost product. The compost can be cured for 20-40 days for further stabilization if you are blending it into a soil mix.

Earth Tub Compost Harvest 1.2014

Key features

  • Easy to operate
  • Rapid process reduces compost volume quickly
  • Heavy-duty plastic construction
  • Minimal need for bulking agent
  • Short time required for mixing/loading
  • Temperature controlled system
  • Insulated for cold weather operation
  • Thorough compost mixing
  • Bio-filter odor control system

Specifications

Tub Vessel Height 48″
Overall Height 68″
Overall Diameter 90″
Foam Insulation R-12
Shipping Weight 846 lbs
Volume 3 cubic yards
Mixing Auger 12″ Diameter Stainless Steel
Auger Motor 3 Ph 2 hp 230/460V
Aeration Blower 80 CFM 100 watt
Power Usage ~1080 kWh per year
Liquid Drain Optional leachate drain (plus water condensate drains on biofilter)
Processing Capacity up to 100 pounds per day per Earth Tub*

* Pounds per day of total biodegradables for each Earth Tub.

Video: Fort Collins – We Make Dirt


Created by Alexis Hmielak, Environmental Services, City of Fort Collins for CAFR’s “You Make Recycling Work” Video Contest

Video: Composting Process at Guilford College


Courtesy of The Guilfordian

Video: Mercyhurst University


Courtesy of the Office of Sustainability at Mercyhurst University in collaboration with Parkhurst Dining Services.

Video: Cook County Sheriff’s Boot Camp Videos

Video accompanying WLS-TV article “Inmates learn how to grow food, garden

Video: Cook County Sheriff’s Boot Camp

Director of the Cook County Sheriff’s Vocational Rehabilitation Impact Center

Frequently Asked Questions

  1. What is the Earth Tub?
  2. What is unique about the Earth Tub?
  3. What are the key features of the Earth Tub?
  4. How much organic waste must an institution generate to use the Earth Tub?
  5. How long will it take to fill the Earth Tub?
  6. What if your organic waste stream increases?
  7. What are acceptable Materials for Composting?
  8. Do I need two Earth Tubs to compost?
  9. What are the operational needs of the Earth Tub?
  10. What is the power usage for operating the Earth Tub?
  11. How cold can it be and still maintain compost temperatures in the Earth Tub?

What is the Earth Tub?

The Earth Tub is a small scale, in-vessel composting system for recycling organic waste materials at the site where they are generated. Complete with a bio-filter for odor processing and control, this system provides a neighborhood friendly efficient composting technology. The Earth Tub has been developed specifically to meet the composting needs of universities/schools, restaurants/cafeterias, commercial food processors, hospitals, multi-unit residential dwellings, camps and other institutional organic waste generators.

What is unique about the Earth Tub?

The Earth Tub offers the sophistication of large in-vessel composting systems to the small institutional generator at an affordable price.

What are the key features of the Earth Tub?

Modular and expandable design allows flexibility in application

Bio-filter processes odors and accelerates the compost process

High rate composting reduces volume and stabilizes material quickly

Powered auger is thoroughly effective for mixing and shredding most foods

Insulated design allows for operation under winter conditions

Durable, heavy duty plastic construction (double walled rotomolded polyethylene)

Finished potting soil mixes can be blended within the Earth Tub by adding peat moss etc to compost

How much organic waste must an institution generate to use the Earth Tub?

For on-site composting, the Earth Tub is capable of processing as little as 25 lbs (13 kg) per day or as much as 150 lbs (75 kg) per day. The modular design of the system allows it to be adapted to a wide variety of applications and configurations.

How long will it take to fill the Earth Tub?

Assuming a 5-6 day per week operation, it will take 13 weeks to fill an Earth Tub at 40 pounds per day, 10.5 weeks to fill at 50 pounds per day, and 3.5 weeks to fill at 150 pounds per day. The Earth Tub has a total volumetric capacity of 3 cubic yards. Each unit has a total of about 3200 lbs (1500 kg) biomass capacity when full. This data was collected at University of North Carolina, Charlotte installation.

What if your organic waste stream increases?

Expansion capability is one of the key features of the Earth Tub System. By virtue of its modular design, the system is ideally suited to incremental capacity increases. This system is a perfect application for gradually introducing composting to the institutional organic waste generators.

What are acceptable Materials for Composting?

The system is designed to process Kitchen prep waste and plate scrapings. Green garden waste and manures will easily compost in the system. Meats, cheese, and other fatty foods should be kept below 25% of total waste input. Avoid adding large pieces of meat, fats or oils to the system.

Do I need two Earth Tubs to compost?

If you are composting less than 50 pounds of food per day, a single Earth Tub will provide continuous composting by adding food on one side and removing compost from the opposite side when the unit is full.

What are the operational needs of the Earth Tub?

The estimated daily operational time is about 20 minutes. This does not include material collection time, which varies from site to site.

What is the power usage for operating the Earth Tub?

The power usage for operating the Earth Tub comes from operating the blower (to aerate the compost and filter the air) and the auger (to mix the compost). For these two power sources, we estimate a typical daily power usage day for the Earth Tub to be 2-3 kWh per day.

How cold can it be and still maintain compost temperatures in the Earth Tub?

The Earth Tub has been installed in some very cold locations. It may need supplemental heat if the temperature remains below 10F for more than 7 days. The aeration system should be shut down during cold weather.

Ranch at Little Hills: Case Study with Lori Caldwell

Since 1975 California Parks Company, TCPC, has been a provider of recreational, retail, hospitality and event management services for local, state and national parks throughout California. The Picnic People is a division of TCPC that provides concessionaire services for parks within California. The Ranch at Little Hills is an East Bay Regional Park serviced by The Picnic People that hosts company picnics, weddings, day camps and team-building activities.
(see more)

IslandWood Earth Tub

When IslandWood opened in 2001, Green Mountain Technologies donated an Earth Tub to support the vision of exposing children to the wonders of the natural world. The Earth Tubs have now been composting the food scraps from their kitchen for over 11 years. The Earth Tub manages all the food scraps from over 150 residents and staff on the campus. In 2009, IslandWood purchased a second Earth Tub when the campus expanded to include over 100 additional students.
(see more)

Mercyhurst University – Composting Initiative

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(Earth Tub Success Story Contest Winner!)

Mercyhurst Earth Tub

Mercyhurst University’s Erie Campus installed two Earth Tubs in the fall of 2012, funded in part by the students, through their green fee, and through the university operations. The composters are a partnership between the Sustainability Office and Parkhurst Dining Services, the university’s dining services provider; kitchen prep waste is collected from the Egan Dining Hall Monday through Friday during the fall and spring term. (see more)

Crestwood Elementary School Earth Tub

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(Earth Tub Success Story Contest Winner!)

Crestwood11Crestwood12

Student volunteers work with staff to turn food scraps into compost with the help of an Earth Tub, a composting system that students call “bEARTHa.” In 2011, students increased the food waste going to bEARTHa instead of the landfill because they began eating in a central lunchroom where they could be better instructed. Also, during a long power outage in 2012, perishable school food that had to be disposed of was brought to bEARTHa instead of being placed in the trash.
(see more)

The Dirt Factory, Philadelphia, PA

University City 4University City 3

A New Community Composting Facility for University City(see more)

Edwards Elementary School, Newberg, Oregon

We got off to a slow start in getting everyone trained and ready for the adventure of recycling/reducing/reusing. The journey is an ongoing one that has opened several paths of academic inquiry. Students have helped to cut our garbage bill in half, taken home what they learned, and some have begun a life practice to compost wherever they are.
(see more)

Cook County Sherriff’s Boot Camp

Cook County

Partnership between Cook County Sheriff’s Boot Camp and Chicago’s Botanic Garden teaches Inmates Composting
(see more)

Mary Hooker Environmental Science School

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(Earth Tub Success Story Contest Winner!)

See how students use GMT’s Earth Tub to help compost at their school.


Lafayette College, Easton, PA

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Lafayette College Composts (from the Lafayette College website here)

  • Nearly 100 percent of food waste through the composted end-product is utilized by the Grounds Department for campus landscaping
  • As of the 2009 Spring Semester, all of the College’s food services locations utilize fully compostable packaging and cutlery
  • Composting has been added to the Environmental Science curriculum, which is supported by College real estate assets, Dining Services, and maintenance staff and equipment support
  • Earth Tubs, which are small-scale, self-contained composting systems, are installed at Bushkill Commons
  • By request, composting facility tours are conducted with peer institution group discussions. To request a tour, please contact sustainability@lafayette.edu
  • At the 2010 Graduation, students were wearing compostable graduation gowns and caps which were collected, shredded and composted in the Earth Tubs located at Bushkill Commons. The fabric used was developed using 100 percent acetate material; the fiber is made from wood sourced exclusively from renewable, managed forests. The fabric is proven to decompose in the soil in one year.

Holmes Elementary

Holmes Elementary is in their second year of using an Earth Tub to successfully create compost for their school garden with the invaluable help from their local Master Composters.

The Earth Tub has garnered a lot of attention from the local community. They have had other schools come out and look, high school students volunteer to help, and they have been a highlight on a “green bike tour” and earned a Green Award from their Village. They also participate in their local Earth Fest, showing off their compost and have been asked to participate in the Green Festival at Navy Pier in Chicago twice!

Teachers have their students come out and help with turning and recording and every Spring they plant in the garden and help take the compost out, spread it on the beds and get a quick lesson on compost and how the Earth Tub works.

Holmes Elementary 4 IMG_0007
IMG_0010 Holmes Elementary 3

NedCompost, Nederland, Colorado

The NedCompost composting facility comprises two 1,000 gallon Earthtubs, two bicycle trailers, ~30 5 gallon buckets, and 2 bicycles. Each earthtubs can process up to 150 lbs of biomass per day. They are basically large cyclindrical composters with a motorized auger mixer. The auger runs on a track on the lid of the earthtub and the lid must be rotated by a human walking around it to thoroughly mix the compost. A full batch of compost can be processed every 20-40 days.
NedCompost-site

Department of Ecology, Washington State

Department of Ecology

Department of Ecology

Department of Ecology

Department of Ecology

Department of Ecology

Department of Ecology

Department of Ecology

Department of Ecology