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Complementary to the methanisation and pyro-gasification sectors, hydrothermal gasification alone could provide 58 TWh and 138 TWh of renewable gas production by 2050, i.e. up to 1/3 of projected French gas consumption. It offers a relevant solution to reduce the amount of final waste and develop a circular economy.
A promising technology for waste that is currently poorly or insufficiently used.
Hydrothermal gasification is based on a thermochemical process at high pressure (250 to 300 bar) and high temperature (between 400 to 700°C), to treat and convert liquid organic waste with a low dry matter content (between 5 and 25%) into a renewable gas. Among the nearly 40 possible types of feedstock analysed in the study, GRTgaz identifies four that are particularly relevant for hydrothermal gasification in France. These are: sludge from wastewater treatment plants, digestates from methanisation units, organic effluents from industrial activities and liquid effluents from livestock activities.
Significant potential to contribute to the country’s renewable gas mix.
The study of liquid biomass feedstock generated in France (from liquid waste and residues) shows a potential of at least 340 million tonnes/year, of which about 100 million tonnes/year can be mobilised now. The renewable gas potential resulting from this technology could, depending on the assumptions for mobilising the feedstock, represent between 58 TWh and 138 TWh/year by 2050. The first installations could be operational in France as early as 2025.
A complementary solution to other innovative renewable gas production sectors.
Depending on feeedstock and the local ecosystem, hydrothermal gasification is a complementary or alternative technology to methanisation or pyro-gasification. It can monetise digestates downstream from agricultural methanisation units or treatment plants and could play an essential role in the management of large volumes generated by the development of this sector. Hydrothermal gasification can also become an alternative to methanisation if there is a constraint on digestate recovery (e.g. lack of spreading area). Like pyrogasification for solid waste, it offers a recovery route for liquid biomass waste by avoiding the use of incineration and/or landfill. Hydrothermal gasification is perfectly aligned with sustainable development targets, circular and bio-economy approaches and the objectives of reducing waste and final residues.