Waste sanitation to produce alkaline biofertilizer adapted to acidic land

Problem statement

High production of agriwastes that can become an environmental problem.

Executive summary

Elaboration of a liquid and solid alkaline biofertilizer that adapts the soil for a greater use of nutrients using waste to give them a second life.

Technology description

It is a chemical reaction that produce heat to sanitize organic wastes. The process consists of adding a mix of calcium oxide (quick lime) and wood chips (or other lignocellulosic waste) that reacts with the moisture of the residue, produces a significant increase in the temperature and in the pH of the mixture, so that all bacteria and pathogens present in the initial residue are eliminated. This process has to be maintained for 2 h around 50-55 degrees Celsius and the pH will remain above 12 for 72 h. The chemical reaction that occurs can be described through this equation: CaO + H2O à Ca (OH)2 + heat. The lignocellulosic part of the mixture enhances the Nitrogen concentration of the biofertilizer since it avoids partially its vaporisation. The biofertilizer increases soil organic matter and pH and its peculiarity is that, in addition to this, it also manages to provide, in small doses, Nitrogen, Phosphorous and Potassium as well as a contribution of lime that benefits the soil. This process only requires an uncovered extension of land (adapted to retain landfill leachates) and shovels to move the material and the mixture.

Market deployment considerations

The main factor lies in the simplicity of the process, it allows a low level of automation to start and a simple technical training to a certain extent, which implies a much smaller investment than for other technologies.

Environmental considerations

Obtaining huge amounts of calcium oxide (quick lime) causes negative environmental impact. Also, Quicklime, used for the stabilization of organic waste, currently has no more environmentally sustainable substitute. Nor can it currently be partially replaced by the use of biomass ash (waste) by legislative change and in our authorization. Moreover, the carbon emission to the atmosphere is a current impact due to the mobilisation and logistics of the wastes to valorise.