Hydrothermal carbonization
It can be used to make a wide variety of nanostructured carbons, simple production of brown coal substitute, synthesis gas, liquid petroleum precursors and humus from biomass with release of energy.
Technically the process imitates, within a few hours, the brown coal formation process (German "Inkohlung" literally "coalification") which takes place in nature over enormously longer geological periods of 50,000 to 50 million years.
[2] It involves moderate temperatures and pressures over an aqueous solution of biomass in a dilute acid for several hours.
The resulting matter reportedly captures 100% of the carbon in a "charcoal" powder that could provide a feed source for soil amendment (similar to biochar) and further studies in economic nanomaterial production.
[3] Biomass is heated together with water to 180 °C (356 °F) in a pressure vessel, in particular vegetable material (in the following reaction equation, simplified as sugar with the formula C6H12O6).
The reaction can be stopped in several stages with incomplete elimination of water, giving different intermediate products.
After a few minutes, liquid intermediate lipophilic substances are formed, but their handling is very difficult because of their high reactivity.
Subsequently, these substances polymerize and peat-like structures are formed, which are present as intermediates after about 8 hours.
As a result of the exothermic reaction of hydrothermal carbonization, about 3/8 of the calorific value of the biomass based on the dry mass is released (with a high lignin, resin and/or oil content of at least 1/4).
In a large-scale technical implementation of hydrothermal carbonization of sewage sludge, it has been shown that about 20% of the fuel energy content contained in 90% end-dried HTC coal is required to heat the process.
Alternatively, the liquid intermediates that are formed during the incomplete conversion of the biomass could be used for fuel and plastic production.
Mexico City started the construction of the first HTC module for the conversion of 23.000 tons of organic waste per year in 2022.
[12] In Phoenixville, Pennsylvania in the US, HTC will be used in the first municipally owned wastewater treatment in North America built by SoMax BioEnergy[13] In Mezzocorona (TN), Italy, the first HTC in the country was built in late 2019 by CarboREM and it is in service treating the digestate from an existent anaerobic digestion plant (AD).
In Relzow, Germany near Anklam (Mecklenburg-Western Pomerania) an HTC plant was officially inaugurated in the middle of November 2017 in "Innovation Park Vorpommern".
