Composting winery marc while protecting your soil, groundwater and waterways

Grape marc can have a negative impact on the environment if not disposed of quickly and correctly.

Repurposing your grape marc to replenish your vineyard’s soil is a resourceful use of this biproduct. There are just a few things you need to know to do this safely for your vineyard and surrounding environment.

How to compost marc safely

Composting of marc produces leachate which may pollute your soil, groundwater and waterways, so it is important to consider carefully where and how the marc will be stored.

Marc composting and storage must be undertaken on a sealed surface which can contain all leachate produced by the compost. A concrete or clay-lined pad with nibbed walls is ideal to prevent run-off of leachate and ingress of stormwater. Another option is sealed polyethylene bags.

We suggest you seek advice from industry groups or an environmental or agricultural professional to design a system that works for you, your vineyard and your surrounding environment. A Resource Advisor at Greater Wellington can help answer any of your further questions about winery marc composting rules.

Potential impacts on the environment when marc is not composted safely

• Leachate can alter the soil structure through the accumulation of potassium
• Leachate can contaminate surface water and ground water with nutrients (nitrogen and phosphorus)
• Leachate can reduce oxygen levels in the soil from anaerobic decomposition
• Storage can create odours and dust and may encourage the breeding of insects and pests

Rules for composting marc to protect your environment

The manufacture and storage of marc compost is a permitted activity under Greater Wellington Regional Council’s proposed Natural Resources Plan (PNRP) Rule R77, subject to several conditions.

The key conditions of Rule R77 are:

• The composting and storage area(s) must not be located within 20 metres of a surface water body or bore used for abstraction of domestic or stock water supply
• The marc must not contain other hazardous substances such as chemicals, human waste or winery sludges
• Composting and storage must be undertaken on an impermeable surface
• Leachate must be contained within a specifically designed composting or storage area
• Stormwater must be prevented from entering the composting or storage area
• Odours must not be offensive or objectionable beyond the boundary of the property where the composting or storage is occurring.

These conditions aim to create an environment where winery marc can be used to replenish the soil while containing harmful substances from reaching our soil, groundwater and waterways.

More information

If you have further questions or concerns about winery marc composting rules, please contact a Resource Advisor at Greater Wellington who will be happy to help you.