Influence of Storage Conditions on a Quality of Pelletized Waste-Derived Fertilizer

Abstract

A mixture of digestates from biogas plant and bottom ashes from biomass combustion can be a valuable source of nutrients and organic substances as well as an improver of the adsorption capacity and water-air properties of the soil. Pelletization of such a mixture makes its composition more stable and the handling easier. However, the properties of pelletized fertilizer are affected by the external factors. The paper presents the results of the research on the impact of air accessibility during the storage of fertilizer pellets produced on the basis of digestate from biogas plants, bottom ashes derived from the biomass combustion and mineral additives (quicklime, zeolite and bentonite) on their fertilizing properties, enzymatic activity and technical parameters, such as resistance to mechanical loads. The research showed that the fertilizers stored under the roof, exposed to the atmospheric air for 1 year, contained by 5.5% more water compared to the samples shielded from the air. These more humid fertilizers were also characterized by slightly higher nitrogen content and 1.7-fold lower enzymatic activity of dehydrogenases and 1.6-fold higher activity of phosphatases, but their resistance to mechanical loads, both static and dynamic was lower. On the other hand, the effects of storage conditions on the urease activity and the content of potassium, phosphorus and heavy metals were not observed. Generally, the storage of fertilizers in airtight containers is more advantageous, because under such conditions the changes in the fertilizing properties are insignificant, while their resistance to mechanical loads is much higher.

Analysis of the physical-mechanical properties of a pelleted chicken litter organic fertiliser

“…However, it should be noted that mentioned standards are focused on pellet biofuels intended for combustion within energy generation, while the investigated pellet samples represent an organic fertiliser. The DU represents the main quality indicator for both a pellet solid biofuel intended for burning and a pelleted organic fertiliser (Pawłowska et al 2019). In both cases, this indicator describes the pellets strength and resistance towards mechanical impacts causing the abrasion of the pellets, thus, their damage and related material and financial loss.…”

Energy Potential of Urban Green Waste and the Possibility of Its Pelletization

“…During storage, transportation, and handling, pellets are mechanically damaged when they rub against each other, the container, or the conveyor walls. Grinding of the edges and surfaces of the pellets creates fine particles that are undesirable: it wastes material and creates dust, and there is a risk of ignition [64,65].…”