Process Turns Liquid Sludge Into Energy and Fertilizer



We recently covered a startup, Ostara, that turns sludge liquid into high-quality commercial fertilizer. Now Victoria University of Wellington in New Zealand wants to do Ostara one better with Wetox, a project that breaks down sludge and turns it into a number of byproducts, including fertilizer, water, steam, and acetic acid.

According to Water and Wastewater, Wetox uses a process called wet oxidation (get it?) to clean up sludge. In the past, the process has only been affordable enough for industrial waste streams, but Wetox aims to make the process cheap enough for use on sludge from smaller waste streams–i.e. dairy farms and wineries. Water and Wastewater explains the process:

Wetox uses a vat
or autoclave that is fed organic liquid waste made up of 4% to 15%
solids. Through a patented process, the formerly problematic waste in
the vat is turned into water, steam, acetic acid, nitrates and
phosphates that can either be used by the business or sold on. The
high-pressure steam that is generated in the process can be used to
drive a turbine for power generation or the heat generated can be used for industrial process heating.

So like Ostara’s process, Wetox recovers phosphates–nonrenewable elements of fertilizer that are in danger of decline. But the Wetox process also offers up acetic acid, which is used in manufacturing and often comes from petroleum feedstocks.


Next up for Wetox: more testing and scoping out different international markets. Judging by Ostara’s success (two massive plants in the year since launch), Wetox won’t likely have any problems finding customers.


About the author

Ariel Schwartz is a Senior Editor at Co.Exist. She has contributed to SF Weekly, Popular Science, Inhabitat, Greenbiz, NBC Bay Area, GOOD Magazine and more


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