Compost barns and the potential of hemp straw

Dairy cow housing systems come in a variety of options and configurations but the aim of each should be to positively influence cow health and longevity and consequently production. One such option is a compost dairy barn.


  • In these the floor of the barn is made of a loose bedding material that offers very good cow comfort.
  • They allow the cows more freedom of movement when compared to a freestall dairy barn.
  • Potential reduction in manure storage costs and needed space, and savings in labour and manure handling costs.


Featured on Rural Delivery in April 2017, The Fletts, a third generation dairy farming family, talked about milking summer and winter with the help of the barn composting system they run. Winter milking began in 2000 as a way to utilise farm capital year round. In fact, Robert Flett reckons you can winter a cow cheaper when she’s in milk. Read about their barn and how they make it work. 

Agribusiness consultant Keith Woodford sees the potential of composting barns as huge in New Zealand, addressing both economic, environmental and social concerns. Read more about his presentation at the Centre for Dairy Excellence Dairy Barns conference in Timaru in late 2017.



Example of a compost barn in Oregon.


For optimal performance compost barns do require efficient management of both the bedding and the ventilation of the barn. Using a suitable form of bedding and in sufficient quantities is critical to a compost barns success.

The bedding needs to be aerated twice daily and this can be done very simply with a tine grubber or power harrow and tractor. This should be done to at least a depth of 250mm or deeper to keep it aerobic and fluffy. This will also allow the surface to dry and the manure to be incorporated into the pack so it can also compost.

Additional bedding material should be added when you notice manure starting to stick to the cows. The bedding material should be laid to a depth of at least 500mm.

Aerobic activity will generate heat and drive off moisture and then the barn design incorporating excellent ventilation will remove the moisture.


The stocking rate in compost barns is critical to their success with overcrowding to be avoided at all costs. If the barn is being used for extended periods e.g. over winter, a minimum of 9m2/cow is necessary.


With the increased interest in compost barns throughout the country one of the main questions is “what makes sufficient suitable bedding?” One option is hemp straw. There are a number of advantages in using hemp straw as cow bedding, such as:

  • It can can absorb FOUR times its weight
  • It’s twice as absorbent as other cereal straw or wood chips
  • It creates less dust than other bedding materials
  • It is excellent at trapping unwanted smells of ammonia
  • It decomposes faster than sawdust or wood shavings
  • It’s more renewable than wood products taking considerably less time to grow
  • It has a higher thermal rating than most other bedding options

Although the hemp industry in New Zealand is in its infancy it should be able to offer another option to farmers looking for material with which to use in their compost barns that offers some advantages over more traditional bedding options.



Hemp crop straw.