Sam Judd
Comment on the environment from columnist Sam Judd

Sam Judd: Valuable poop

Photo / Thinkstock
Photo / Thinkstock

New Zealand wastewater treatment plants (which account for 85%) of our wastewater) produce 234,112 tonnes of sewage sludge each year. This figure is rising annually as treatment plants are upgraded - more of this filth is captured rather than poured into the ocean - which is good.

But what to do with this increasing tide of stinky sludge?

79,440 tonnes of this solid human waste is very expensively disposed of in our ever-growing landfills each year and the rest is "diverted".

The vast majority is used in land reclamation - which the Ministry for the Environment calls a "beneficial use" of the material. I am far from an expert on this, but would be interested to know the major differences between filling up a hole in the ground with sludge and rubbish and reclaiming land with sludge.

Studies show that reclaiming land with sewage sludge can release heavy metals, ammonium and nitrates into the ground, which carries serious environmental risks.

I remember playing rugby as a youngster on an old landfill with grass on top (Ian Galloway Park) - every time I was rucked and suffered a scrape - it ballooned infectiously red immediately and whenever it rained, the place stank. I wondered why.

The sweet smell of success

Next year Micromidas - a Californian company, plans to launch plastic made out of sewage sludge. This incredible process uses bacteria that eat sewage sludge and poop resin, just like how we eat sugar and produce fat.

The major difference is that our bodies produce something stinky, pathogenic and expensive to deal with.

This "poo plastic" creates a high-value, low¬-cost plastic resin which does not stink, using raw materials that every wastewater operator wants to get rid of.

Micromidas actually gets paid to collect the sludge - an excellent example of closing the loop that many industries should take heed from.

Oh, and as if all of this wasn't enough to show the superiority of this new process - unlike the tonnes of detritus that we pick up from the beach, poo plastic actually biodegrades in under 18 months.

Check out the video here to see their story.

Feeding our plastic addiction with poo

Micromidas has turned a major corner with this process. They aim to sell their hungry little poo-eating bacteria around the world, which would allow people to continue to consume huge amounts of plastic without having to feel bad about all the oil and landfill space they are using up.

Now, I don't agree that this innovation is the answer to our plastic addiction. It will take too long for the process to become mainstream worldwide.

Considering that over 600 million tonnes of plastic enters our oceans each year, I still believe that we have to consume less.

But in the meantime, this new product could become an excellent sustainable alternative for our favourite type of plastic - LDPE (Low Density Polyethylene) of which we imported over 60,000 tonnes of raw materials in 2010.

There is an obvious challenge in perception when it comes to food packaging here - people may not want their loaf of bread served to them wrapped in something that used to be sewage. But, according to Plastics New Zealand, over half of the LDPE we use in not for food contact, so there is a lot of packaging that we could make out of all of the sludge that goes to landfill.

If anyone out there has examples of "closing the loop" that they would like to share, please leave a comment or email me with details.

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