New Uses of Treated Urban Waste Digestates on Stimulation of Hydroponically Grown Tomato (Solanum lycopersicon L.)

Abstract

One strategy to re-use solid urban wastes is the production of energy by anaerobic digestion. This process also generates high volume of digestates, which are frequently disposal in landfills. The aim of this work is to assess anaerobic digestates as agricultural inputs. Three different biomethanation wastes from different plants were collected. Firstly, a complete physico-chemical characterization of the wastes was done according to the Spanish regulation, showing that the materials had the 90% of the particles below 25 mm, high values of pH, electric conductivity, organic matter, humic acids and soluble nutrients such as NO3 -, SO4 2-, Ca 2+ , Mg 2+ , PO4 3and K + . Total concentrations of heavy metals and microbiological parameters were below the threshold levels allowed for agricultural use. The wastes were then treated with a strong acid and a strong base having two different solutions (ATr and BTr respectively) which were evaluated as biostimulants for tomato plants in hydroponic culture. Those liquid extracts, ATr and BTr, demonstrated their biostimulant ability towards root system of tomato enhancing the hair root density and plant biometric parameters including plants weight and chlorophyll content. This work demonstrates the re-use feasibility of treated digestates in agriculture as fertilizers and more over as feedstock for biostimulants production.

A Tool Derived from the Vicia faba Micronucleus Assay, to Assess Genotoxicity, Cytotoxicity or Biostimulation of Novel Compounds Used in Agriculture

“…Alternatives to conventional biostimulants have made use of wastes from agriculture [24] and from cities [25], nanoparticles and nanomaterials [26], composts [27], sewage sludge [28] and waste-water from processing industries [4]. These novel alternatives may present potential risks to living organisms.…”