Why Is the Surface of the Fermentation Bed Constant for Many Years?
Fermented bed pig farming offers significant economic and ecological benefits. Due to its advantages such as environmental protection, health, energy efficiency, grain conservation, and labor saving, it has gained popularity in both European and American aquaculture industries and is now widely promoted in China. The fermentation process typically occurs in the middle layer, where the temperature can reach 30–50°C or even higher. However, many reports mention that the surface remains at a constant temperature for years, often stable around 20°C. Why is this the case?
Take, for example, a pig-farming fermentation bed made using a starter culture similar to a goldfish starter. The thickness of the fermentation material is usually around 50 cm. The top layer, about 10 cm thick, acts as a protective buffer layer and is not fully fermented or only slightly so. The core fermentation area is generally within 10–30 cm below the surface. Why is this the case? Here are some key reasons:
(1) The surface has a large contact area with the outside world, leading to frequent air exchange. This results in fast convection, rapid heat dissipation, and less heat retention. Therefore, the surface temperature is more influenced by external conditions.
(2) Pigs occasionally urinate and defecate on the surface, which leads to waste accumulation. When this happens, manual stirring and the pigs’ natural movement—such as stepping and turning—prevent the surface from maintaining consistent warmth or undergoing effective fermentation.
(3) The structure of the fermentation bed is designed with ventilation in mind. Hot air rises, and cold air enters, creating a natural convection cycle that helps regulate temperature. As a result, the bed remains cool during summer. When the sun is strong, shade nets can be placed over the bed, and plastic films can be used around the edges to enhance ventilation and cooling. Additionally, the stocking density of pigs is carefully controlled. For a goldfish fermentation bed, each pig should have about 1.2 to 1.5 square meters of space, with piglets allowed to be slightly more densely packed. This ensures good airflow and prevents overheating. Thus, the surface temperature remains stable at around 20°C for a long time, effectively creating a thermostatic environment.
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