Q: Is there sewage sludge in soil you buy at garden centres?
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A: You know that kids’ book Everyone Poops? Well, that premise has yet to be refuted, but where it all ends up really does vary town by town. Poop raises suspicions wherever it’s dumped.
Victoria, for example, is considered one of the most ecologically genteel places in the country, yet it’s been piping its raw sewage straight into the sea for decades.
And here in T.O.? Nearly 200,000 tons of biosolids a year gets flushed to the digesters at four wastewater treatment plants. From there, well, according to the city’s 2009 biosolids report, 42 per cent of the sludge is trucked to landfill, and a disturbing 21 per cent is incinerated at the antiquated Highland Creek Treatment Plant (though a motion passed by the city’s Works Committee on May 16 recommends that the incinerator finally be closed it goes to council in June).
Some sludge helps remediate old mines. And the rest? About 30 per cent ends up on farmland, upsold as a natural phosphorus-rich soil amender. Of this, two-thirds is dried and pelletized by a city contractor, and the rest is dried into cakes. Sewage-based fertilizers are much cheaper and arguably more climate-friendly than fossil-fuel-based fertilizers, but they’re also more controversial.
Okay, yes, many traditional farming cultures around the globe have used humanure for eons, but that was before the modern sewer system, in which illegally dumped chemicals can mix with trace pharmaceuticals and excreted endocrine disruptors to scare the pants off people.
Even Toronto’s own Biosolids Master Plan report notes that the normal wastewater treatment process can only remove up to 90 per cent of endocrine-disrupting compounds and that trace amounts in biosolids have understudied impacts.
Biosolids advocates (including the same city report) say sewer pollution has greatly declined and that sludge has to meet tough provincial limits for heavy metals and pathogens.
And Ontario Ministry of Environment rep Kate Jordan says, “We have been approving the spreading of sewage biosolids for over 30 years without any evidence of health or environmental impact incidents.” She adds that there are virtually no biosolids on crops grown for direct human consumption in this province.
And at this point you won’t find sludge remnants retailing at your local garden centre either, the way you would in many other provinces – but that’s soon to change.
Under revised rules, if municipalities compost their sludge (with food, wood and/or leaf waste) instead of just drying it into cakes or pellets, you can pretty much put it on any crop or backyard tomato plant you like. This has caused a major stink among sludge activists, who say the province is lowering the bar on toxin limits in compost to get sludge out of landfills.
But advocates say the finished compost will have to meet the same toxin standards it always did. The Compost Council of Canada maintains that we’ll only be bringing Ontario in line with the rest of the country and that composting may actually be sludge’s great green redeemer.
More natural and less energy-intensive than pelletizing, composted sludge, says the head of the Greater Moncton Sewerage Commission, Conrad Allain, blends bathroom waste with food, yard and forestry waste to create not just dried-out dung but a soil-building hummus that won’t combust the way pellets can and is lower in trace contaminants than any other sludge.
In fact, Rajeshwar Tyagi, research chair in enviro engineering at the U of Quebec, has tested Moncton’s biosolid compost and found that micro-organisms in it actually degrade 80 to 90 per cent of the nonylphenols and bisphenol A present.
Do they get rid of all of it?
No. Would Tyagi use some on his own veg garden? “It depends on the crop. Probably not on leafy vegetables like salad consumed directly without any cooking, but certainly for agriculture crops, yes.”
So where does that leave us?
Kelowna, Edmonton, Medicine Hat and Moncton are already selling their bags of blended biosolid compost to the public, and not everyone in those communities is happy about it.
One MP in Nova Scotia has just tried and failed to get biosolids banned from the province’s fields. Peeved San Franners just got “organic biosolid compost” giveaways cancelled, arguing that nothing organic should have sewage in it. (Sludge is strictly illegal in certified-organic foods.)
Do I think there’s a place for very well-composted biosolids? As long as the biosolids in it are labelled, I’m coming around to the idea. It’s certainly better than non-composted biosolids.
Would I buy a bag for my own yard? Honestly, I don’t even buy bags of composted cow manure, because of the drugs regularly given to factory-farmed animals, so no.
If I’m buying compost, it’s from yard waste (which in this province can no longer be sprayed with chems) or free-range animals like sheep.
Of course, your own backyard compost will win seven days a week.
Got a question?
Send your green queries to ecoholic@nowtoronto.com
