In Kenya, the substrate based on volcanic pumice rock is now being recycled by means of hot steam treatment and made reusable.
After the volcanic soil in Kenya had got under protection, it became necessary to recycle and to re-use the available volumes of pumice substrate in many gardening companies, especially in floriculture. Steam proved to be a suitable mean for this task. For this purpose, large special containers were equipped with a sophisticated drainage system and the product in these containers was cleaned with hot steam.
With this method, 16 cbm pumice rock are sanitised in 1 hour and thus can be used anew. The steaming completely liberates the substrate from pathogens, pests, seeds and/or sprouting weeds.
The volcanic substrate has proven to be an ideal steamed product. The heating oil consumption is only 16-18 l per hour. Due to the ideal properties of pumice, you need only 12-15 kg steam per 1 cbm to achieve temperatures higher than 80°C and, thereby, an optimal sanitising result.