Pyro-gasification, a technology with great potential for producing green gas
Pyro-gasification involves the thermo-chemical processing of many different sources, such as wood waste, residues from waste management, and most organic waste. In a study from 2018, ADEME (the French Environment and Energy Management Agency) forecasts that the process will produce large quantities of zero-carbon renewable gas to replace natural gas, both in uses such as mobility and in the grids. Pyro-gasification has great potential to back up anaerobic digestion, a process already proving its worth.
Gas is a highly flexible source of energy, and it can be stored safely and conveniently for long periods. As a result, it has a key role to play in the energy transition. When it is possible to replace extracted fossil gas with gas in a renewable form produced from biomass, there is the additional advantage of an energy that is close to carbon neutrality.
Significant strides taken in several renewable gas technologies in recent years are increasing the attractiveness of gas, in the form of biomethane, as an essential component in the energy mix. Power-to-Gas (or P2G) uses electrolysis to convert excess renewable electricity into hydrogen, while anaerobic digestion is a process in which bacteria break down organic matter to produce biomethane. The third major renewable gas technology that stands alongside these two is pyro-gasification, a second-generation technology for producing biogas.
How pyro-gasification works
Like anaerobic digestion, pyro-gasification is based on a natural process of waste fermentation. In the pyro-gasification process, dry organic matter – such as wood – is heated to temperatures in the order of 1000° C. A very small amount of oxygen is added (this can be in the form of air, a pure oxygen stream, carbon dioxide or steam) in order to allow the thermo-chemical reaction to occur, but in a low enough quantity to prevent any combustion from occurring.
The gas that is produced is known as synthetic gas, or syngas. It consists mostly of carbon monoxide and hydrogen with a small amount of methane, but depending on the raw material used as feedstock and the form in which the oxygen is delivered, it can also incorporate variable quantities of carbon dioxide and nitrogen.
The pyro-gasification process
Mature technologies exist for each subprocess, and a few industrial operations exist throughout the world. Numerous experimental and pilot operations are under way in France and a number of other countries, in order to confirm various associations of technologies for the whole process. Two demonstrators are currently under way: Gaya, in southeastern France, and Salamander, in Normandy. When the process is mature enough for full-scale industrial implementation, it will take its place alongside anaerobic digestion to greatly boost France’s capability to produce biomethane.
GRDF and pyro-gasification
To comply with the terms of French environmental legislation – the Energy Transition for Green Growth Act passed in 2015 – our goal is to achieve a rate of 10% green gas in the networks by 2030.
According to current projections, by 2028 pyro-gasification should have the benefit of recovering roughly half a million tonnes of waste per year. In addition, it will allow the injection of 1 TWh of syngas per year into the networks in France, reducing annual CO2 emissions by around 165,000 tonnes.
It is therefore essential that we carefully monitor advances made in developing pyro-gasification. Our company’s role is to ensure the fastest possible integration of this promising process in the French energy mix.
Renewable Gas, French Panorama 2019
The French Panorama 2019 on renewable gas, published by SER, the French federation for the renewable energy sector, presents a detailed analysis of facts and figures relating to biomethane production and injection, including the emergence of new technologies.