Are waste disposers bad for the environment?
Are kitchen sink waste disposal units bad for the environment?
Gurgling, grinding kitchen waste disposal units are a fairly common kitchen convenience these days, but how convenient are they really? And more to the point, are they supporting or degrading the health of our natural world?
We’ve taken a good look at this, and like a soggy old onion there are many layers to consider.
How do waste disposal units work?
First we need to look at how waste disposal units function.
The basic concept is that they’re mounted to the underside of a kitchen sink so that food waste can be added directly into the unit. A grinding chamber then breaks up the food waste and mixes it with water, disposing it via the household waste water system.
Imagine putting your food scraps in the blender with a bit of water, then flushing that down the toilet, it’s pretty much the same idea.
What impact do waste disposers have on the regional waste management system and the environment?
What actually happens to a person's waste once it leaves the house depends on the waste management system in their region. Once the waste reaches a treatment plant, water is evaporated off, solid particles are screened out and turned into fertiliser, sent to landfill, or pumped out to sea.
Some water treatment plants in Aotearoa (such as in Palmerston North) use methane from waste solids to produce electricity which then powers nearby buildings. This might seem like a great idea, but turning waste into gas is a whole other topic for another time. Where Leo went to school in Te Puke, some of the town's bio-solids are being mixed with industry waste and fed to worms.
However, in Wellington that’s not currently the case. The city’s ageing wastewater system is not designed to handle food waste and therefore waste disposal units create significant environmental and structural challenges as pipes are pushed beyond breaking point and contamination leaks into the harbour.
More than a million litres of sludge per day is piped 9 km from the wastewater treatment plant at Moa Point to Carey’s Gully sludge dewatering plant at the Southern Landfill. Recently, the pipes broke and the waste needed to be transported via truck and trailers. At the landfill most of the water is removed, resulting in about 45 tonnes of solids per day being buried in the landfill and the water returned to Moa Point via the wastewater network. Ironically, the sludge must be mixed with solid general waste for disposal in the landfill, which creates the need for more general waste.
Talk about broken systems.
Leo’s observation after learning about local challenges is that people in the capital are thinking 10 steps ahead, but are faced with a reality that’s 10 steps behind. This doesn’t just apply to waste, but transport, food systems and also housing.
In the case of Wellington (and most solid waste situations around NZ aren’t much better), using a waste disposal means that water and electricity is used to pump waste through frail sewerage infrastructure only to end up in a landfill. This creates the same greenhouse gas outcome we so urgently need to avoid. Want some good news? The solution is to build soil, locally.
How do waste disposers impact on household sewerage?
Another important consideration regarding waste disposer units is that when fats head down the drain they may accumulate in pipes either at home or in the public system.
When this occurs on a large scale and mixes with synthetic contaminants (such as wet wipes) they cause infrastructure to burst or overflow. When this occurs, contamination of natural water systems is highly likely, and the price to local government is huge. The heavy toll that the gurgler takes on our sewer systems is certainly a mark against using waste disposal units. Some parts of the world have used legislation to prevent this, such as in Scotland where disposing of food waste into public drains or sewers is illegal.
Tom, a registered Drainlayer and Plumber from Tauranga comments about the impact of Waste Disposal Units in the building industry.
“I work mostly on new builds and Waste Disposal Units are installed as standard practice even though they place additional strain on the whole system which ultimately rate payers foot the bill for.
In Tauranga the council provides an alternative for food waste disposal system, so there is truly no need for these to be going in new builds.
It would be good to see the big companies like GJ Gardner homes encouraged to not suggest waste disposal units and more education happening about the impact waste disposal units have on the wastewater system and the environment”.
What’s the better alternative to a kitchen waste dispoSAL UNIT?
The lost opportunity for making soil by throwing organic waste into the sewerage system is even greater than the huge problems Waste Disposal Unit’s present.
In New Zealand and around the world, we are experiencing the ongoing degradation of soils and nutrient deficiency. Composting and vermiculture are, in our opinion, far superior options than waste disposal units based on this alone.
Some people have concerns that these solutions are messy, smelly, time consuming or require a large space. But this is largely due to a lack of awareness or experience with good systems and services. In reality, a properly maintained worm farm, such as the Hungry Bin that Why Waste supplies and services, keeps smell and vermin away while producing incredibly rich, easy to use fertiliser.
Other composting services include Sharewaste (NZ wide), Kaicycle (parts of WGTN only) and MakeSoil (International). We cannot find any other worm farm hire services - so feel free to help us get the word out by sharing our Website, or join us on Facebook or Instagram
Why Waste worm farms can consume up to 2 kilos of waste a day without impacting the public sewer system. They make rich soil and can fit in a carport, small balcony or tucked round the side of a building. Considering the challenges facing our world right now, it’s our conclusion that waste disposal units are a lazy, irresponsible choice for home users, and given the recent science on our changing climate it’s fair to say it’s not really that convenient after all.
Get in touch with us or purchase a worm farm subscription if you want to speak about choosing a new organic waste disposal system for your household. A worm farm is a very simple alternative and we can get you set up in no time.
Organic Waste Hierarchy Diagram from the Organic Waste in Landfill discussion doc 2021, Zero Waste Network.
What to do if you have a kitchen waste disposer and want to change it?
You can fairly easily have a plumber replace your kitchen waste disposal with a strainer plug for catching scraps. Tom, the plumber quoted above said this task should take around an hour of labour plus materials costing an average of $200 to achieve.
Or, you can simply plug up the disposer and choose a new organic waste disposal strategy for your household. Check out our blog on choosing the right system for you.