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.
• Hemp hurd - hemp hurd is a highly effective and sustainable bulking material for composting toilets. Derived from the woody core of the hemp plant, it is both absorbent and biodegradable, making it ideal for promoting decomposition. Its fibrous structure enhances aeration, crucial for maintaining airflow in the composting process, while also balancing moisture levels. Being hygroscopic, hemp hurd efficiently absorbs moisture without compromising the compost's ability to breathe. As an eco-friendly byproduct of hemp farming, it minimizes waste and supports sustainability. Hemp hurd can be sourced from WCTNZ®, as well as from suppliers of hemp-based products.
• 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 organics 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

• Nature Loo™ | NL3

Bulking Agent: Nature Mix or make your own mix with coco peat, hemp hurd, and wood shavings
Dosing Class: Dose per use

All-in-one bucket systems

• Bambooloo™ | Carbon
• Bambooloo™ | Classic

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

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

• CompoCloset™ | Cuddy Lite
• EcoLet™ | Separera Mini - Urine Extraction (UD-S)
• EcoLet™ | Separera Mini - Urine Container (UD-C)
• Sun-Mar™ | GTG
• Trelino® | Evo S
• Trelino® | Evo M
• Trelino® | Evo L

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

Urine diversion systems (UD-S and UD-C) with agitator mechanism

• CompoCloset™ | Cuddy

Bulking Agent: Fine, wet cover material - ideally coco peat
Dosing Class: Fill to batch

Zero leachate, automatic, heated CHP systems

• EcoLet™ | 240 25a
• EcoLet™ | 240 65a

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

• Sun-Mar™ | Compact 240
• Sun-Mar™ | Excel 240
• Sun-Mar™ | Excel NE (non-electric)
• Sun-Mar™ | Spacesaver 240

Bulking Agent: Sun Mix Green or make your own mix (50% hemp hurd, 50% wood shavings, OR 50% hemp hurd, 25% wood shavings, 25% coco peat)
Dosing Class: Scheduled AND Scoop per poop

Split Systems (SS)

Batching Processor (BP) Systems

• Nature Loo™ | Alectura Comfort
• Nature Loo™ | Alectura Premium

Bulking Agent: hemp hurd
Dosing Class: Scoop per poop

• Clivus Multrum™ | CM HP

Bulking Agent: 50% hemp hurd, 50% GAP10 wood shavings
Dosing Class: Scoop per poop

Continuous Processor (CP) Systems

• Clivus Multrum™ | CM8
• Clivus Multrum™ | CM14
• Clivus Multrum™ | CM40

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

• Sun-Mar™ | Centrex 2000 A/F
• Sun-Mar™ | Centrex 3000 A/F
• Sun-Mar™ | Centrex 2000 NE (non-electric) - A/F (air flow)
• Sun-Mar™ | Centrex 3000 NE (non-electric) - A/F (air flow)

Bulking Agent: Sun Mix Green or make your own mix (50% hemp hurd, 50% wood shavings, OR 50% hemp hurd, 25% wood shavings, 25% coco peat)
Dosing Class: Scheduled AND Scoop per poop

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

• Sun-Mar™ | Centrex 2000 M/F (micro flush)
• Sun-Mar™ | Centrex 3000 M/F (micro flush)
• Sun-Mar™ | Centrex 2000 NE (non-electric) - M/F (micro flush)
• Sun-Mar™ | Centrex 3000 NE (non-electric) - M/F (micro flush)

Bulking Agent: Sun Mix Blue or make your own mix (45% hemp hurd, 45% coarse wood shavings, 10% compost black)
Dosing Class: Scheduled
 
Solar Desecration Drying (SDD) Systems

• Kazuba™ | STK System

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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