Hyperthermophilic Composting and Biochar-Biomass Co-Composting

Hyperthermophilic Composting (HTC)  differs from traditional composting processes in that, through specific microorganisms, it is possible to carry out a part of the composting process at a temperature between 80 and 95°C. In order to start the process, it is necessary to have compost from an HTC plant available which acts as an inoculum. Subsequently, it is possible to maintain the operation of the plant thanks to an appropriate recirculation of the produced compost.
The microbial communities involved with this type of biological process have been recently studied and include various types of bacteria from the Thermaceae, Thermoactinomycetaceae, Bacillaceae and Sulfobacillaceae families.
The main advantages of HTC composting are:
• increase in biological kinetics and consequent decrease in composting times
• destruction of potentially pathogenic organisms (viruses, bacteria, insects) by heat
• inhibition of nitrification and denitrification phenomena and consequent lower nitrogen loss (significant reduction in N20 production)
• possibility of working with C / N ratios of 10 or even lower
• degradation of microplastics
• removal of antibiotic residues and ARGS (Antibiotic Resistance Genes)

Full-scale plants have been built (in China) that treat tens or hundreds of tons of sewage sludge or livestock waste every day; at these scales, temperatures> 80°C are reached without the addition of external heat sources as the heat generated by microorganisms causes endogenous heating of the heaps. On a small scale, the heat generated by microorganisms is dispersed very easily so it is necessary to provide heat to the process. Machines have been developed for these scales which, through the combined effect of hyperthermophilic microorganisms and dehydration, are able to stabilize organic waste in 24-48 hours. The HTC system in the figure is installed in the Marina di Ravenna laboratory.


This work is partially connected to the BTF Project.