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The Poo Problem

What to Do With 10 million tons of Dog Waste?

Dog Waste Image

America’s 83 million pet dogs in the USA produce some 10.6 million tons of poo every year – that’s enough to fill a line of tractor-trailers from Seattle to Boston.  Add in litter from our more than 90 million cats, and you’ve got enough pet waste to fill more than 5,000 football fields ten feet deep. Prof Christopher Lowe at the University of Central Lancashire has estimated that in the UK, 1000 tonnes of dog poo is created each day by about 8 million dogs.

Pet waste is not exactly an environmental threat on the order of carbon pollution or nuclear waste.  Still, the risk from poo is more than just a mess on your shoes. Dogs can harbour lots of viruses, bacteria and parasites — including harmful pathogens like e coli, giardia and salmonella. (A single gram contains an estimated 23 million bacteria.) Studies have traced 20 to 30 percent of the bacteria in water samples from urban watersheds to dog waste. Just two to three days of waste from 100 dogs can contribute enough bacteria, nitrogen and phosphorous to close up to 20 miles of coastline to swimming and shell fishing, according to the U.S. Environmental Protection Agency. It also can get into the air we breathe: a recent study of air samples in Cleveland, Ohio, and Detroit, Mich., found that 10 to 50 percent of airborne bacteria came from dog poo.

There is a booming market in biodegradable dog waste bags. US market leader BioBags sells more than 19 million a year. Unfortunately, this seemingly green solution can backfire. The bags are designed to be composted, not landfilled. But in the absence of composting programs many end up in landfills, where they are more likely to degrade than a conventional plastic bag producing methane, a potent greenhouse gas. 

San Francisco has an ambitious goal of achieving zero waste by 2020 — the city already diverts 80 percent of its waste from the landfill. Dog poo, at 4% of the waste stream, is one of those vexing fractions standing in the way of getting to zero.

According to a recent study, £22 million is spent per year on dog poo collection by local agencies in England and Wales.  Maybe the problem is that people are looking at poo as waste, rather than what it really is: a resource that could — and should — be recycled for compost.  Dog poo, like many other kinds of manure and animal waste, can be composted.

Poo can be anaerobically or aerobically digested.

  • Arizona State University students teamed up with the town of Gilbert to place an underground anaerobic digester in a dog park that draws about 200 animals a day. (They call the project e-TURD.)
  • Toronto has a project to process pet waste as well as dirty nappies in an anaerobic digester.
  • San Francisco plans to build an aerobic digester to handle the city’s organic waste — including the droppings of its 120,000 dogs.
  • Some UK Local Government Authorities have successfully tested the aerobic digestion of dog poo.

In our view, the best way to process poo is to load it with other wastes, such as horticultural trimmings, into an environmentally controlled vessel such as the BioDigester for aerobic digestion. Processing is rapid and the high-temperature within the vessel kills the pathogens. Cat poo can contain a hardy toxoplasmosis parasite.  Digesters that are processing both dog and cat poo can apply ozone to the output to make it temporarily sterile.  

Aerobic digesters are a cost effective and safe way to process poo.

If you would like more information on aerobic digestion, then please call us 01823 665541.



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