PROJECT
INCORPORATING COLD CHAIN
The compost( with the mushroom spawn) is placed into aluminium shelves and topped with a 5cm layer of peat.
steam, they should produce 25 tonnes of mushrooms a week!
Although the electricity bill was lower at the old site, there were the added costs of boiler fuel for growing tray sterilisation. The old site used about 17 000 litres of fuel a month for sterilisation. Not to mention that in winter, they used to have heating elements in the ducts, which almost doubled the electricity bill. Now that the new system has heat recovery built in, this is a great saving as the water is mostly heated by the chiller.
The rooms all have hot water and chilled water feeding through. Fresh water is fractured through a nozzle and compressed air to get the humidity. Negating the fuel expense of a boiler to create humidification was also a bonus here.
ALL ABOUT CONTROL
During the peak summer months, it is quite hot in the area and with often high humidity levels, the air takes longer to cool. That is why it is essential to take into account the environment you work in, explains Baring Richardson.“ You need a climate control system that can cope with the environment.”
Each one of the rooms is equipped with climate control to ensure the best possible yield.
When trying to understand the role that HVAC & R plays in a mushroom farm, it is crucial to first understand the various stages of mushroom growing and the requirements for this fine science. Temperature and humidity play a crucial role in the production of mushrooms.
MUSHROOM GROWING
Mushroom growing is a highly complicated production process involving both nature’ s processes and technology. Luckily, Highveld Mushrooms( the majority stakeholder in Medallion Mushrooms) has all the info broken down into the following main steps:
• Step 1 Compost making
• Step 2 Pasteurisation
• Step 3 Spawn running
• Step 4 Case running
• Step 5 Airing
• Step 6 Cropping
• Step 7 Packing and delivering
• Step 8 End of crop and compost disposal
1. COMPOST MAKING Compost is the substrate that the mushroom feeds off and is made from wheat straw, chicken manure, gypsum, and water. Compost is made following a recipe that is constantly altered based on the structure and quality of the raw materials.
Medallion uses large bunkers that are at the forefront of composting technology. One main advantage is that air is supplied through holes in the floor. This ensures that the composting process occurs aerobically( meaning with oxygen) and so odour is limited. The converse is anaerobic compost making, which is without oxygen and that is when bad odour is generated.
This process takes approximately two to three weeks depending on the time of year. Interestingly, the internal compost temperatures during this process can go as high as 84 ° C as a result of the chemical and microbiological reactions that are taking place.
After a few days, the mushroom mycelium grows from the compost through the wet peat to the top of the mushroom beds.
The mushrooms are picked by hand once fully grown.
14 www. coldlinkafrica. co. za COLD LINK AFRICA • May 2018