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Composting Toilets & Bulking Agents

It is important to use the best available source of Carbon materials to get effective performance out of your WCT System. Here is the recommended bulking agent list.

Clivus Multrum Systems

Best bulking Materials for Clivus Multrum Systems (read this section as it has information relevant to the Ecolet and Sun-Mar systems)

 

The Clivus Multrum performs the best with a 20mm (large) wood shavings.  These large wood shavings are available from suppliers around NZ typically in 20 and 100 kg bales, ranging from 30 to 100 dollars a bale.

The effect of the size and grade will achieve the following benefits;

The large wood shavings allows for

  •          Air to move easily through the compost pipe inside the system
  •          Permeability of liquids to maintain a wet condition that should ideally be between 45 to 70% moisture content.
  •          Air gaps leaving room for growth of Bacteria, Fungi and all other appropriate life forms for decay 
  •          Compost to reduce in size (shrink) feeding down in through these gravity feed systems 

WCTNZ have the following available for Clivus Multrum system (link to consumables)

  •          100kg Bales
  •          20kg Bales
  •          WCT Microbe Mix (used as starter only)

CHOOSING A BULKING MATERIAL Composting of human waste is a natural process and environmentally benign. In keeping with this, the best choice for a bulking material is one that is readily available in your local area as a waste product from some other activity. Wood shavings have been found to be the ideal bulking material and provide consistent results. Wood shavings entrap air, are absorbent and do not become compacted as does other matter such as fine sawdust, newsprint or large quantities of grass clippings. A granular pine bark mulch is also suitable.

Wood shavings are the material recommended for Clivus Multrum, and are generally available from:

  •          Joinery workshops and some timber mills
  •          Commercial distributors that collect and package it
  •          Produce stores
  •          Pet shops
  •          Nursery and landscape suppliers

Please note: Wood shavings or sawdust must not be from treated timbers as the treatment process will hinder the growth of, or even poison, the microorganisms essential to the composting process.

However, if wood shavings are difficult to source in your area, read the following information to assist in choosing alternatives. The key characteristics of a good bulking material are:

  •          Dry, but readily absorbs moisture.
  •          Has a high carbon/nitrogen ratio.
  •          Remains friable, traps air and does not form a mat or ball when damp.
  •          Is known to compost well, and has no chemical contaminants to affect the compost bacteria.
  •          Availability and cost.

Composting with CARBON/NITROGEN (C:N) RATIO

Human waste has a carbon to nitrogen ratio less than 10 parts carbon, whereas the optimum C:N ratio for composting human de-jecta (waste) is 20-30 parts carbon. A bulking agent with a high C:N ratio is therefore preferred, as this allows a smaller quantity of the agent to be used in comparison with other materials.

Representative ratios for commonly available bulking agents are shown below to indicate the relative ability of the materials to provide additional carbon.

BULKING AGENT (DRY) CARBON/NITROGEN (C:N) RATIO;

  •          650 Softwood shavings
  •          550 Hardwood shavings
  •          500 Newsprint
  •          500 Softwood bark
  •          450 Sawdust
  •          130 Wheat straw
  •          120 Rice hulls
  •          80 Straw - general
  •          60 Leaves and shrub trimmings

Not Recommended;

  •          20 Grass clippings
  •          20 Hay
  •          20 Vegetable scraps

 

For example, to achieve the same C:N ratio in the compost pile around 10 kg of leaves would need to be added if used in place of 1kg of wood shavings. Mulched leaves and garden clippings can replace or supplement wood shavings as a bulking agent. Use material that has already started to compost, for example, leaf matter that has fallen on the ground and started to decompose. Fully decomposed matter is also ideal as this matter contains useful compost bugs and microorganisms along with a high level of good bacteria.

Please note: Fresh gum leaves do not make a good bulking agent, however, those that are partly decomposed and mixed with other composting matter can be good for the system. Material such as large woodchips, un-shredded newspaper, grass clippings, straw, long grasses, treated wood shavings or highly resinous wood should be avoided as they take a longer time to break down or are unsuitable to compost.

Finely chopped vegetable scraps and peelings may be added to the process as long as they are not too wet and have been kept in an airtight container to prevent insect infestations. However, because of their high nitrogen content the addition of these scraps will require even more bulking agent, not less, unless earth worms are also used. Addition of these materials will reduce the working capacity of the tank available for processing human wastes.

 

CM2

If you have a CM2 system, there is a large range of bulking materials that can be used. Please refer to the respective manuals and read the section above to get a better idea of the nature of Carbon to Nitrate ratios to choose your bulking materials for effective composting.

Please note: that these systems are a batching type and complete composting is done in two stages.

 

Ecolets Systems

Best bulking agent for Ecolet Systems

 

The Ecolet performs the best with a 10mm (medium) wood shavings.  These medium sized wood shavings are available from suppliers around NZ typically in 20 and 100 kg bales, ranging from 30 to 100 dollars a bale.

The Ecolet (heated) systems must have a mixture to performance there best both in the friability for the mixing of the compost and for moisture retention to prevent the system from drying out. 

 

There are two types of Bulking materials that benefit the moisture control the Ecolet systems.

  •          Peat Moss - this material is easily compostable and has a high ability to absorb moisture. It is readily available from suppliers but here at WCTNZ we do not consider it a sustainable material as its harvesting affects the ecological system it is taken from.
  •          Coco Peat - this material is a little harder to break down but have a very high ability to absorb moisture. It is not readily available from suppliers at a cost-effective price so we at WCTNZ do supply this product at a lockdown price. This product is very sustainable as it is a by-product from Coconut plantations that would have to be dumped otherwise.

 

Make your own bulking agent mixtures.

Bulking material Mixture Recipe:

  •          Fine Grade Peat Moss 50% + Untreated Wood shavings 50%

Or

  •          Fine Grade Coco Peat 20% + Untreated Wood shavings 80%

 

WCTNZ have the following available for Ecolet systems (link to consumables)

  •          100kg Bales
  •          20kg Bales
  •          WCT Eco Mix - 20 Litres (Fine Grade Coco Peat 20% + Untreated Wood shavings 80%)
  •          WCT Microbe Mix (used as starter only)

 

If you have any of the Ecolet NE systems, there is a large range of bulking materials that can be used. Please refer to the respective manuals and read the section on Clivus Multrum systems above to get a better idea of the nature of Carbon to Nitrate ratios to choose your bulking materials for effective composting.

Please note: that these systems are a batching type and complete composting is done in two stages.

 

Sun-Mar Systems

Best bulking agent for Sun-Mar Systems

 

The Sun-Mar performs the best with a 5-10mm (fine) wood shavings (special grade).  These medium sized wood shavings are available from WCTNZ or Pure Pine and are around NZ$30 per bale.

This special grade wood shaving has been selected because of it course property that works best in the Sun-Mar Bio-Drum™ to mix and reduce any blockages of the moisture management system.

There are two types of Bulking additive materials that benefit the moisture control the Sun-Mar systems.

  •          Peat Moss - this material is easily compostable and has a high ability to absorb moisture. It is readily available from suppliers but here at WCTNZ we do not consider it a sustainable material as its harvesting affects the ecological system it is taken from.
  •          Coco Peat - this material is a little harder to break down but have a very high ability to absorb moisture. It is not readily available from suppliers at a cost-effective price so we at WCTNZ do supply this product at a lockdown price. This product is very sustainable as it is a by-product from Coconut plantations that would have to be dumped otherwise.

 

Make your own bulking agent mixtures

Bulking material Mixture Recipe:

  •          Fine Grade Peat Moss 20% + Untreated Wood shavings 80%

Or

  •          Fine Grade Coco Peat 10% + Untreated Wood shavings 90%

 

WCTNZ have the following available for Sun-Mar systems (link to consumables)

  •          20kg Bales (special grade wood shavings)
  •          WCT Sun Mix - 20 Litres (Fine Grade Coco Peat 10% + Untreated Wood shavings 90%)
  •          WCT Microbe Mix (used as starter only)