A promising new way to make the most of wet organic waste by producing as much renewable gas as possible
Hydrothermal gasification is an innovative process for high-pressure (210 to 300 bar) and high-temperature (360 to 700°C) thermochemical conversion of wet organic waste, alone or in a mixture, into a renewable gas that can be injected into the system after treatment. Water, used as the main reagent under very specific conditions, is essential for the operation of the process.
The technology makes it possible to recover mainly biological waste such as:
- sludge from sewage treatment plants,
- digestates from methanisation plants,
- agricultural effluents including livestock effluents,
- industrial organic effluents (food, chemicals, paper, etc.)
- urban wet organic waste.
but also other waste such as many plastics, mixed or soiled, being non-recyclable in the state, thus avoiding their incineration or burial.
A process with multiple positive externalities
The technology converts more than 90% of organic matter into gas. It recovers large quantities of water, metals, mineral salts including phosphorus, potassium but also nitrogen that can be used for the production of fertilizers for agriculture.
The quantity of the ultimate waste, limited to the presence of heavy metals and some inorganic, is reduced to a minimum by a factor of 15! The technology also eliminates all traces of pathogenic elements.
Running 24/7, a hydrothermal gasification plant converts the input in a few minutes with a high energy efficiency (75 to 85%).
Technology particularly well suited to the treatment of all organic effluents
Hydrothermal gasification provides an alternative response to spreading (digestates polluted or limited by spreading) and incineration, which is not very efficient for waste containing a lot of water.
Faced with 400 million tonnes per year of wet organic waste generated in France, this new technology saves both time and cost of treatment while optimizing their recovery and ecological footprint.
This great wet waste recovery tool complements the very positive results with other benefits:
- A significant decrease or even a total elimination of the costs (including taxes) of the treatment of the final waste (incineration, landfill, etc.) and their transport,
- A reduction in energy requirements for drying or dehydration as well as the use of chemicals (coagulant, flocculant, etc.) significantly improving the balance of associated greenhouse gas emissions,
- A multiplication of revenues through the sale of renewable gas produces and the recovery of liquid residues (water of industrial quality at least) and solids (metals, mineral salts and nitrogen).
A technology in the process of final optimisation, with the start of industrialization by 2025
The main developers estimate that their technology will reach industrial scale by 2025 with facilities equipped with modules that can each process up to 4 to 6 t/h of inputs. In France, the industry estimates that renewable gas production capacity from HG facilities of at least 2 TWh/year in 2030 and 50 TWh/year in 2050 is achievable.
The first industrial GH facility in Europe will also be by far the largest in the world
The Dutch company SCW Systems plans to put its first industrial HG project into commercial mode by the end of 2022. Totaling 20 MWth with 4 modules, an extension of the project to 100 MWth is planned by 2025.