Waste to hydrogen: Plasma gasification
Imagine how convenient it would be to convert waste to hydrogen. This might sound too good to be true, but a number of projects are working to make this a reality. Here we discuss the developing technologies and projects that are enabling waste materials to produce greener than green hydrogen.
Where does all our waste go?
For the most part, the global economy operates according to the following linear economic model: take → make → waste. Common waste products include plastics, synthetic fabrics, tires, and food. While these materials have the potential for reuse, many such resources are ultimately burned up or deposited into landfills. Not only does this result in substantial energy and material losses, but it also introduces harmful pollutants into the air.
As resources are finite and environmental needs are of increasing concern, it is critical to transition toward a circular economy that constructively utilizes waste. A complete transition from a linear to circular economy will require major overhauls of production methods. Fortunately there are solutions already in the works, such as plasma gasification.
How does plasma gasification work?
Plasma torches work by flowing gas between two electrodes to create a plume of plasma (ionized gas) that can reach temperatures over 6,000 °C. At such high temperatures, the torch can be used to gasify solid waste. Plasma gasification converts the organic waste matter into syngas (primarily H2 and CO), and the inorganic and metal waste matter into slag. Syngas is then often used to produce a variety of synthetic fuels. It can also be used as a method of high purity hydrogen production.
Plasma gasification can be used on most waste products, including sewage and hazardous waste. Its primary limitation is the breakdown of nuclear waste. While this technology is an excellent way to utilize waste materials, it doesn’t negate the need to optimize systems to minimize waste in the first place.
Is plasma gasification environmentally friendly?
Plasma gasification provides a way to reuse unused waste and prevent landfill buildup. But is the process itself environmentally friendly? This depends on the specifics of the system setup and how the process outputs are utilized. There is a balance that must be struck between process cost/efficiency and environmental consideration.
For example when conducting plasma gasification, the syngas produced is separated into CO and H2. The CO can then be burned to produce energy to feed the process, which effectively increases energy efficiency and minimizes waste. It also, however, produces CO2. The efficiency and cleanliness of plasma gasification also depends on how well the syngas is separated, processed, and utilized. If the proper setup is used, gasification has the potential to turn waste into truly green hydrogen.
Energy and cost requirements of plasma gasification
First, consider electrolysis, as it is an up and coming technology aimed at producing environmentally friendly hydrogen. While electrolysis promises a fairly straightforward method of green hydrogen production, it requires substantial amounts of renewable energy. Significant technological advances are therefore still required before electrolysis is able to effectively produce efficient, affordable hydrogen at large scale.
Plasma gasification, on the other hand, has very low energy requirements. Whereas a MW-scale electrolyser requires about 53 kWh/kg of H2, a plasma torch only requires 2 kWh/kg of H2 (to create the current between the electrodes). The cost of plasma systems can vary a bit depending on the gases they use. While some basic systems can run simply using air, others use a combination of oxygen, nitrogen, argon-hydrogen, and various other gases. The gas cost depends on the system, with higher performance systems requiring more expensive gases.
Waste to hydrogen projects
Applying plasma technology to produce hydrogen from waste is still a relatively novel concept, and each of three companies are taking slightly different approaches to the process.
- SGH2 signed a deal in 2021 with two of California’s largest hydrogen refueling stations. They agreed that in 2023, they will begin to provide 3,850 tonnes of hydrogen from waste each year.
- Ways2H made a deal with Element 2 to provide hydrogen (from waste) the 2,000 hydrogen pumps they plan to add in the UK by 2030.
- Standard Hydrogen is also in the final stages of R&D to establish plastic waste to hydrogen plants in Canada.
Plasma gasification is an effective way to utilize waste materials and move toward a circular economy. With careful management of system processes, this is also a promising source of carbon neutral hydrogen to support the rising hydrogen economy. It will be exciting to keep an eye on these processes as they continue to improve, and to watch for the development of other new technologies along the way.