The use of biological waste as a source of low-temperature heat for hotbeds in spring in north-eastern Poland

This article proposes a method for using biological waste, including kitchen waste and garden waste, as a substrate for hotbeds. Hotbeds have been long used in home gardens, but most of them are supplied with animal manure, usually horse manure. In this study, the temperature of ambient air, soil temperature and temperature distribution in a hotbed and a cold frame were measured with a thermographic camera. The measurements were performed in three experimental treatments - one hotbed, one cold frame and in the garden. Each treatment was sown with radishes (Raphanus sativus). The experiment began on 7 April, and temperature was measured until the temperature of garden soil reached the temperature inside the hotbed and the cold frame. After the experiment, the hotbed was left in place until the end of August to complete the composting process and grow other plants. The amount of heat generated inside the hotbed during the experiment was calculated, and the thermal efficiency of the hotbed was compared with the maximum heat capacity of composting. During the experiment, the hotbed generated 98.7 MJ of heat, and its thermal efficiency reached 12% of maximum capacity. Radishes grown in the hotbed were harvested 5 days earlier than those grown in the cold frame and 12 days earlier than those grown in the garden treatment. The compost produced in the hotbed fully meets Polish Standards for organic fertilizers. The proposed solution minimizes the quantity of biological waste collected from households.