Studies on the Possibilities of Processing Buckwheat Husks and Ash in the Production of Environmentally Friendly Fertilizers

Abstract

The sustainable utilization of different food waste and other products is one of the challenges of the European Green Course. Buckwheat has major potential as a food ingredient; however, processing buckwheat into food products generates a large amount of solid waste that needs to be sustainably disposed of. The by-products that come from the processing of the buckwheat contain high contents of carbon and hydrogen and can be used as raw materials for the production of granular biofuels. This work proposes and explores the potential of a different route of buckwheat husk ash utilization. Chemical analysis of the buckwheat husk ash (BHA) and uncleaned buckwheat husks (UBH) showed significant amounts of primary and secondary nutrients (0.28 ± 0.06%–5.84 ± 0.43% P2O5; 4.56 ± 0.46%–38.63 ± 1.82% K2O; 0.09 ± 0.01%–12.18 ± 0.38% CaO and 0.47 ± 0.08%–3.56 ± 0.18% MgO) as well as micronutrients (Zn, Mn, Cu, and Fe) and carbon (29.53 ± 0.50%–54.35 ± 0.58% C). It has been determined that granular biofertilizers can be produced by using drum granulators from the mixture of raw materials in an 80–20% BHA, 20–80% UBH, and 10% polyvinyl acetate (PVA) solution. However, when more than 20% of the UBH is present in the raw material mixture, the humidity of granules is high (more than 6%), and bulk density is low (less than 450 kg/m3). The pH values of 10% solution of the produced granules range from 12.0 to 9.7; thus, the fertilizers can act as a liming agent, which can be recommended for acid soils. This suggests a potential for a cradle-to-cradle type of regenerative engineering process design, where the end product of buckwheat processing—buckwheat husk ash and untreated buckwheat husks—can be returned back to the soil to replenish the nutrients, resulting in an overall sustainable process.