While there is growing interest in composing shelters and a lot of anecdotal evidence to suggest they can positively impact many parts of the farm system, there is very little research on them.
A team led by Rachel Durie of Perrin Ag is looking to change that. As one of 12 projects to get the green light under round two of the National Science Challenge Our Land and Water Rural Professionals Fund, the project aims to take a whole systems focus on evaluating how a composting shelter could be integrated into a farm system. It is also seeking to quantify the impact on all areas of the farm business from environment through to production.
“They’re not common in New Zealand,” Durie says.
“The first shelter locally was built in the Waikato completely by accident. It was built to provide shelter to the cows both in winter and summer but soon found that the wood chip bedding was heating up and composting.”
“And with changes farmers are facing like winter grazing rules, I think that’s (building composting shelters) going to continue.”
The project team is interviewing farmers who have composting shelters to identify the different ways farmers are incorporating composting shelters on farms.
The shelters are specifically designed for composting, which means there are a lot of design elements to get right. Typically there are no sidewalls, so are designed to ensure good ventilation. While the size of the shelter depends on how many cows and how often it will be used, the ability to mechanically till the bedding is critical.
The composting process keeps the bedding warm, dry and clean for the cows. If you get it right, depending on the level of use, the bedding can stay in the barn for one to three years before it needs to be replaced.
While wood shavings are a common bedding source, some farmers are experimenting with other plant-based materials for bedding. Canterbury farmers involved in the project are trialling miscanthus. Its high lignin content gives it good potential as a bedding material.
Through a combination of incorporating a composting shelter, decreasing cow numbers, and trialling miscanthus bedding, one farmer has been able to shift towards a more self-contained system. They now have the ability to rear all replacements and winter all stock on farm and are growing the bulk of their feed on farm as well.
“The neat thing about this research is there is so much we still don’t know, and a lot that we are learning from innovative farmers that have already adopted the system,” she says.
“We are still learning about different bedding types, the impact these have on the composting process and the different compositions that come out the other end.
“Similarly, we’re still learning in what ways the shelter can be incorporated into the farm to maximise beneficial impacts for the environment, animals, people and business – and that’s what this project is about.”
Research to date shows a number of benefits of composting shelters when the design and management of the shelter is done correctly. No liquid effluent comes out so there is no need for the effluent systems required for other types of barns.
“Several farms are looking at composting shelters as a way to meet environmental restrictions around nitrate leaching. Having the cows in the shelters in the late autumn and winter period can have a considerable impact on reducing nitrate leaching, with the potential reduction dependent on the system operated. I’ve completed Overseer modelling for a few farms around this, and so far, it’s looking promising,” she says.
On the animal welfare front, cows are warm and comfortable when in the shelters. One farmer involved in the project noted their winter feed requirements dropped by a third, as a result of less wastage and requiring less energy to keep warm.
“Anecdotally, farmers have also observed increased health and welfare of animals, lower mortality and potential for increased production. These are all points we are wanting to put some evidence against,” she says.
There are also some benefits on the human side of the business. Staff on farms with composting shelters have noted that the working environment is more pleasurable and satisfying with less time spent outside in the elements in the middle of winter and animals seeming to be far more content.
A common misconception around the composting system is the use of the term ‘composting barn’.
People hear the word barn and think of a fully enclosed shed that conjures up many animal welfare concerns. Composting shelters, in principle, have no sides, just a roof, which is an important part of their design to facilitate the composting, and the flooring is a soft plant-based material as opposed to concrete. The composting process generates a warm and dry environment which the cows seem to love, Durie says.
“There are some people out there who think they’ve got composting shelters, but they weren’t built for composting. They’ve never tilled it and the ventilation isn’t right, so they get steam coming out of the compost, which comes down as condensation when it hits the roof. Things get wet and smelly, which can put people off the system. In a true composting shelter, you can pick up the bedding, and it’s clean, dry and doesn’t smell at all,” she says.
The biggest question most farmers have around composting shelters is the cost. Because of the variety of different ways they can be incorporated into a farm business, the answer is, it depends.
Over the coming months, further interviews and modelling will be completed with the project due to wrap up in June and plans for further research to continue afterwards.
