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Researchers at Washington State University announce on their website that they have tried a new method for dealing with sludge in wastewater. By adding a step in the handling of sewage sludge, it breaks down more easily, while simultaneously converting it more efficiently into biogas; which can then be used to generate electricity, or convert it into renewable natural gas and connect it to the natural gas grid.
With the method, the sludge is broken down with high-pressure steam containing oxygen. This means that over 85 percent of the organic material can then be transformed into biogas, unlike the current method, which succeeds in converting less than 50 percent. They also managed to produce almost twice as much methane – 98 percent more – through the new method.
"It turned out to be extremely effective, and it's very exciting," says Birgitte Ahring, lead researcher behind the study. “This is applicable and is something that we can begin to explore in Washington state. Not discarding waste, but instead making use of its potential, has great advantages," she continues.
Wastewater management is often very energy-intensive, and in many cases is the most energy-consuming activity found in smaller communities. Through this process, the plants can be responsible for their own electricity production, and larger plants can convert it into renewable natural gas, which becomes part of the public natural gas grid.
"Here we start to move into the idea of a circular economy," says Ahring.
The researchers are now scaling up their work to further demonstrate the process. They are also studying how to efficiently convert the biogas into natural gas, through a new bioprocess. Although biogas can already be used for electricity production, natural gas is considered more valuable as it can also be used to power vehicles.