Supercritical (hydrothermal) gasification is a new technology that can convert wet biomass into gas. The conversion takes place in water at high pressure and temperature resulting in fast and near complete conversion of organics to gas.
Wet biomass waste streams are composed of water, organic matter and minerals (salts). If wet biomass is pressurized and heated to conditions above the thermodynamic critical point, water reaches a state that is between that of a liquid and a gas. Its properties change drastically. It becomes a solvent for the organic components, a reactant and catalyst, which results in fast and near complete conversion of the organics to gas. The mineral salts no longer dissolve in supercritical water and they form inorganic particles. This allows solid minerals such as phosphorus to be separated from the process, producing a small mineral concentrate. Since the waste is nearly completely converted, the production quantity of (biomethane) gas and the savings on waste management costs are considerably higher than any other alternative wet waste processing method.
Simplified process flow diagram of the supercritical gasification system developed by Gensos.
Viable large-scale commercial application requires a reliable and efficient gasification process. Few key technological challenges remained until recently. Gensos has developed and patented key technological improvements required to solve these challenges, resulting in a viable and reliable system. The principles have been proven experimentally in a small-scale prototype and the process has been scaled up to a pilot plant at commercial scale (0.5 metric ton per hour), the largest and most advanced of its kind. Gensos is thoroughly testing this pilot plant in preparation of a demonstration project followed by commercial applications, while still continuing its research and development for product improvement.
Supercritical gasification can economically convert a variety of wet feedstocks into a gaseous fuel. It has many other benefits over conventional methods such as dewatering and incineration or anaerobic digestion:
Convert wet waste into gas and minerals – With supercritical gasification nearly all of the organics are converted to gas, thus producing up to 50 percent more gas as compared to digestion. The minerals are separated as a small mineral concentrate that is rich in phosphorous, which could be used as a natural fertilizer.
Product flexibility – The gas that is produced is already compressed. In our system the gas is upgraded to biomethane quality so that it can be fed into the natural gas grid. It can also be converted to green electricity.
High thermal efficiency – Patented heat integration minimizes external energy needed to operate the process, which is essential for producing high gas yields from very wet waste.
Reliability – Patented reactor technology guarantees stable and reliable operation.
Reduces ecological footprint – The gas produced from waste is a renewable fuel that can replace fossil fuels. This closes the carbon cycle (making it carbon dioxide neutral) and reduces the carbon footprint of waste. The water that is produced can be cleaned to irrigation or proces water standards, reducing the water footprint of the waste. Pathogens and pharmaceuticals present in waste are inherently eliminated at supercritical temperatures.
Cost competitive – Depending on the waste composition, the total cost of ownership can be considerably reduced.