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          Bulking Agents & Dosing Guide

          Types of Bulking Agents

          Composting toilets require addition of carbon-based materials to the compost pile to ensure composting takes place. Different systems require different bulking agents for optimum performance. Commonly used bulking agents are:

          • Wood shavings - wood shavings are the most commonly used type of bulking agent as they provide the best source of carbon for microbes to feed on. While some bucket systems and urine diversion systems can be used with sawdust, sawdust can clog drainage of some systems and wood shavings are preferred. Additionally, wood shavings allow for formation of air gaps which aerate the compost and leave room for bacteriological growth. They also allow for permeability by liquids, maintaining good moisture levels within the pile (this should be 45-70%). Wood shavings must be untreated, as treated timbers can hinder and even poison microorganisms essential to the composting process. Wood shavings are available from WCTNZ®, but can also be sourced locally from farm supply stores, pet shops, nursery and landscape suppliers, joinery workshops and timber mills.
          • Coco peat - coco peat does take a while to break down, but it is highly absorbent and great for moisture control. It is also very sustainable as it is a byproduct of coconut plantations that would be dumped otherwise. Coco peat can be hard to come by, especially at a cost-effective price, so WCTNZ® supplies this product at a lockdown price.
          • Peat moss - peat moss is easily compostable and highly absorbent, making it great for composting and moisture control. However, it is not as sustainable as coco peat. Peat moss is available from WCTNZ® or from your local garden supplies store.
          • Mixes - WCTNZ® supplies specially formulated mixes for optimum performance of certain systems. These mixes are often a blend of wood shavings, coco peat and/or peat moss and a number of additives for superior moisture and odour control.

           

          Dosing System Classes

          All composting toilets require a layer of bulking agent at the bottom of the composting chamber to start the system (usually 50mm). Once in use, bulking agent is added in one of the following ways, depending on the system:

          • Scoop per poop – one scoop per number 2s.
          • Dose per use – one scoop per use (number 1s and 2s).
          • Cover it up – enough to cover your deposit. Usually one scoop per number 1s, two scoop per number 2s.
          • Top it up – keep topped up to the level specified by the manufacturer. Once the composting mass has reduced in size, top up to the specified level.
          • Scheduled– add at intervals specified by the manufacturer and/or equivalent to the number of users (time or user-number based schedule).
          • Fill to batch – pre-load the system with the required amount of bulking agent for the batching process. There is no need to add more bulking agent until a new batch starts. 

           

          Bulking Agent and Dosing Class per System

          It is important to use the right bulking agent and in the right amount to get the best out of your system. Below are the recommended bulking agents and dosing guides for our systems.

          Self-contained Systems (SCS)

          All-in-one (AIO) systems with leachate drain

          Bulking Agent: CM2 Mix or make your own mix with coco peat and wood shavings
          Dosing Class: Per use

          Bulking Agent: Nature Mix or make your own mix with coco peat and wood shavings
          Dosing Class: Per use

          All-in-one bucket systems

          Bulking Agent: Bambooloo Mix or make your own mix with coco peat and wood shavings
          Dosing Class: Cover it up

          Urine diversion systems (UD-S and UD-C)

          Bulking Agent: Fine, wet cover material - ideally coco peat or peat moss, otherwise sawdust
          Dosing Class: Scoop per poop

          Zero leachate, automatic, heated CHP systems

          Bulking Agent: Eco Mix or make your own mix with 30% coco peat, 30% peat moss and 40% wood shavings
          Dosing Class: Top it up

          Mechanical heated and Mechanical non-heated CHP systems

          Bulking Agent: Sun Mix Green or make your own bio-active mix (60% wood shavings blended with a range other organics and water, composted over 3 months)
          Dosing Class: Scheduled AND Scoop per poop

          Split Systems (SS)

          Batching Processor (BP) Systems

          Bulking Agent: GAP10 wood shavings
          Dosing Class: Scoop per poop

          Continuous Processor (CP) Systems

          Bulking Agent: GAP20 wood shavings
          Dosing Class: Scoop per poop
           
          Mechanical, heated and Mechanical non-heated CHP systems

          Bulking Agent: Sun Mix Green or make your own bio-active mix (60% wood shavings blended with a range other organics and water, composted over 3 months)
          Dosing Class: Scheduled AND Scoop per poop


          Mechanical, heated and Mechanical non-heated CHP systems with micro flush

          Bulking Agent: Sun Mix Blue or make your own bio-active mix (60% coarse wood shavings blended with a range other organics, 10% bio-char and water, composted over 3 months)
          Dosing Class: Scheduled
           
          Solar Desecration Drying (SDD) Systems

          No bulking agent required.
          Additive: Kazuba Dry
          Dosing Class: Scheduled (commercial spec)


          Need help choosing a system? Call WCTNZ® on 0800 022 027 for free advice on system specification and setup. Advanced design consultancy services are also available.

           

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