Continuous Composter Tanks

Sarah Allen. Spring 2015. Luke Kwan. INTA332 B

What do they do?

• A composting (or biological) tank system contains and processes carbon additives, food waste, some types of animal waste, and natural fibers such as paper based products.

How does it work?

• Unlike a septic system, a composting system relies on unsaturated conditions where aerobic bacteria break down waste.

• Waste is contained, and most odor is limited due to enclosed vessel.

• Some units end contents can be used for gardening along with mulch. Other container systems use the gas omitted form the composting process as cooking fuel

Composting Cycle

Considering the contents of tanks, they are primarily installed outdoors. Sizes can range from small households use for gardening, to larger applications such as farmsSmaller units can be constructed at home, while large pieces can be ordered pre fabricated.

The “Other” Tank

Types of composting toiletsBatch Composting

Continuous Composting

Hybrid Composting

Waterless Composting Toilet Tanks

• Solid waste is collected in a small compost chamber directly beneath the toilet pedestal. A low powered electric fan circulates air through the chamber speeding the composting process and eliminates odors. Liquids are separated from solids and evaporated by the fan. Any excess liquid is dispersed into a small trench

Nature Loo Composting Toilet

InstallationInstallation of these composting tanks take more than the basic plumbing needs of the typical toilet. There are drain hoses (10ft or more), Vent stacks, diffusers, and roof flashings. Basically you are installing an additional “ante chamber” outside of the bathroom to collect the waste and keep it contained in needed temperature levels, and prevent odors from escaping

Types of Tanks

Commercial Use of Composting Toilets

• An increasing number of commercial buildings have successfully incorporated composting toilets into their operations. They are now found in city and state parks, schools (see Bertschi School in Seattle, WA and College of the Atlantic in Bar Harbor, ME), churches (Canterbury Diocese, England ), and offices (Bullitt Center in Seattle, WA). Many building like these have incorporated these factors in to meeting the Living Building Challenge

Living Buildings

• The Living Building Challenge is the built environment's most rigorous performance standard. It calls for the creation of building projects at all scales that operate as cleanly, beautifully and efficiently as nature's architecture. To be certified under the Challenge, projects must meet a series of ambitious performance requirements over a minimum of 12 months of continuous occupancy.

The Bertschi School Living Science Building• All the sustainable features of the building are

visible and functional for students to learn ecological concepts that can become intrinsic values for future generations. Because the building must have net zero water and energy usage, students participate in real-time monitoring of the building's energy use and production, as well as the water usage and collection. Daily operations, systems monitoring, and maintenance are carried out by the Science teacher and facilities staff, with help from students and volunteers

Composting Toilet• Water needed for the building is captured rainwater for all

non-potable uses. City water is provided at the classroom sinks due to code requirements. Net zero water is achieved through a variety of methods including cisterns for storage, an interior green wall which treats grey water, and a composting toilet to treat black water. Excess captured water is absorbed by the on-site rain garden.

• The Science Wing has one unisex restroom with a composting toilet. The system employs a vacuum flush Envirolet composting system consisting of a toilet unit, vacuum/pulverizing unit, and two composting waste storage tanks. The dual tanks add capacity and allow for an average of fifty flushes per day. Each flush uses approximately one pint of rain water.

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• This system was chosen due to space constraints and the inability to have the composting unit directly below the toilet. While the vacuum system solves the space and location problem, it uses more energy than a gravity type composting system because of the need to move waste under vacuum and the additional heat required to evaporate the water required to flush.

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Bullitt Center

• The Living Building Challenge requires all water to be harvested and treated on site. To meet the Challenge with respect to management of human waste on site, the Bullitt Center team is using Phoenix Composting Toilets from Advanced Composting Systems of Whitefish, Montana

• To date, the Phoenix Composting Toilet has been installed only in one or two-story structures.

• When a user comes into the stall there is a sensor that can tell if it is a “sitter” or a “stander”. The tank of the toilet contains a soap solution, an air compressor, and water. The soap solution is introduced into the toilet. After use, the waste travels down into one of the 10 composters located in the basement of the building. Each of these units is 84” tall x 40” wide x 61” deep. Inside the composter wood shavings and water combine with the waste, causing it to decompose through the action of aerobic bacteria. A handle on the exterior rotates tines inside the composter. The tines are manually rotated to mix the decomposing waste in order to oxygenate the mixture. Most of the waste is converted into carbon dioxide and water vapor. Leachate gets re-sprayed onto the mixture and there is also a leachate tank to receive any excess. Stabilized leachate is pumped to a vacuum port in the alley where it is picked-up on a monthly basis and taken to a facility where it is combined with other field-ready compost streams. On a regular basis, wood chips will be added to the composters and a small amount of compost will be removed. Sensors and alarms located on each of the composting units will monitor their operation.

Application

• Commercial building operators may face different legal challenges than homeowners when it comes to waste management. Projects seeking Living Building status must have a closed loop water system, meaning all water supply needs must be met on-site and all wastewater must be processed and used on-site. Even buildings that have a greywater processing/recycling system and composting toilets may need a backup sewer line to meet building codes. Simultaneously meeting building regulations and project water goals will require negotiation and possibly added cost (for example, installing a sewer connection even if it will not be used).