Vermicomposting of sludge from a malt house

• Published in: Waste management (Elmsford) 2020-12, Vol.118, p.232-240
• Main Authors: Hanc, Ales, Hrebeckova, Tereza, Pliva, Petr, Cajthaml, Tomas
• Format: Article
• Language: English
• Subjects: Earthworm; Malting sludge; Microorganism; Vermicompost
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/j.wasman.2020.08.027

•Earthworms were able to convert sludge from a malt house into a value-added product.•The addition of moistened straw pellets at a minimum of 50% (vol.) was necessary.•Vermicomposts were characterized by optimal agrochemical properties and maturity. Malting sludge is waste that could be used as a good soil conditioner after proper treatment. In the current study, the feasibility of vermicomposting malting sludge and its mixtures with straw pellets on the basis of physico-chemical and biological properties was verified. A vermicomposting system with continuous feeding of earthworms Eisenia andrei was used. The greatest number and biomass of earthworms was found in the variant with 25% malt house sludge + 75% straw pellets (on average of all layers: 320 earthworms/kg and 35 g/kg, respectively), followed by a variant with 50% malt house sludge + 50% straw pellets (on average of all layers: 47 earthworms/kg and 13 g/kg, respectively), indicating that a minimum of 50% (vol.) straw pellets is necessary for successful vermicomposting of malting sludge. Most earthworms lived in the youngest upper layer (42% and 52% of total number and earthworm biomass, respectively). On the contrary, the oldest bottom layers (final vermicomposts) after 180 days of vermicomposting were characterized by maturity, indicating lesser contents of microorganisms and enzyme activity. These vermicomposts had favorable agrochemical properties (pH = 7.8, EC = 1.2 mS cm−1, C/N = 11, Ptot = 1.23%, Ktot = 2.55%, Mgtot = 0.42%). The proportion of the available contents in the total contents were 10%, 59%, and 19% for P, K, and Mg, respectively.