New advances in different technological fields occur every day. In the area of bioenergy, scientists have already developed treatment processes that transform wastewater and sludge in our sewage into fertilizer, green building materials, and methane gas that can be burned to generate electricity. Recently, researchers at RMIT University in Australia have also successfully produced a type of charcoal from sewage for the production of both fertilizer and hydrogen gas. This solution not only supports the development of sustainable agriculture but also has the potential become a viable approach to the mass production of green hydrogen.
The sludge from wastewater treatment plants contain biosolids that can be converted into fertilizer and soil conditioner. However, as researchers from RMIT University point out in their study, around 30% of the sewage-related biosolids produced worldwide is either stored or goes directly to landfills. This “waste” is actually a “resource” that has not been utilized efficiently. As for the methane gas that emits from sewage, many treatment plants have equipment that can capture the gas so that it can be used as a biofuel. On the other hand, methane gas is also a major contributor to global warming.
The study from the RMIT University proposes a new solution in which the biosolids from treatment plants are turned into “biochar”. This material can include heavy metal particles that allow it to act a catalyst for splitting methane gas into carbon and hydrogen.
To produce biochar, the RMIT team has built a special pyrolysis reactor that extracts hydrogen gas and creates biochar from sewage. Coated with carbon nanomaterials, the pieces of biochar that are manufactured via pyrolysis are touted to have many high-value applications apart from hydrogen production. These uses include soil improvement, carbon sequestration, and energy storage. Kalpit Shah, the associate professor who is leading this research, has stated that there is basically an unlimited supply of biosolids for making biochar. Therefore, the solution designed by his team has the potential to enable the mass production of green hydrogen while substantially reducing the level of carbon emissions. It could be a win-win for the environment and the economy.
The RMIT team has secured the patent for the design of its pyrolysis reactor. The results from laboratory tests also show that the reactor is able to convert 65-71% of the methane gas that accompanies sewage into hydrogen gas within the first half hour of running at 900°C. The production of hydrogen gas also correlates to the rate of the conversion of biosolids into biochar or activated charcoal. On account of the fruitful results from this research project, South East Water, a public utility operating in the Australian state of Victoria, is building a trial platform for assessing the adoption of this solution in the wastewater treatment system.
(Photo credit: RMIT University.)