Sustainability Blog

Biogas from Sewage to Power EVs

By Simon Johns - Jul 30, 2021

Sewage engineers in Australia have developed a car that they say is powered by human waste. While this is technically true, it’s a little more complicated than that. Queensland Urban Utilities, a waste water treatment company, recently demonstrated their company Hyundai Kona Electric charged by electricity generated by the combustion of biogas from treated sewage.

On the surface, this could be an ideal convergence between electric vehicles and sustainability. But this convergence works up to a point.

There is an almost unlimited supply of human waste that can be processed into what’s known as biogenic methane. Methane can be combusted to generate steam to power a turbine. The process in the company’s own words:

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“The sewage enters the plant via our vast sewer pipe network. First, the solids are screened out, the wastewater then moves on to the bioreactors, which are like big ponds where bugs work to break down about 60% of the nutrients. The next step is the digesters, where further nutrients are broken down. This process is anaerobic, meaning no oxygen is present. This is where the biogas is produced, which is mainly made up of methane gas. That methane then goes into the cogeneration units to drive an engine which generates power.”

The calculation of biogenic methane’s carbon benefits becomes complicated. Combusting methane creates carbon dioxide, which is also a greenhouse gas that stays in the atmosphere for hundreds of years compared with decades in the case of methane itself. 

According to the Environmental Defense Fund, an American environment NGO, if processed biogas is derived from existing resources, such as landfill and animal waste, it can be climate neutral since it can offset the extraction of fossil fuels. But this net benefit is negated when refined biogas is derived from purpose-grown crops, which adds to global carbon production instead of offsetting fossil-fuel.

As with many aspects of mitigating climate change through environmental sustainability and zero-emissions mobility, there is no one-size-fits-all solution. But for the lube makers, a battery EV still doesn’t need engine oil regardless of the provenance of the electricity charging it.

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