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Where Do Your Food Scraps Go?

Where Do Your Food Scraps Go?

Going Green in the Home: How Food Waste Disposers Can Play a Role

AUCKLAND, November 10, 2017 - Each year in New Zealand, 700,000 tonnes of organic waste is trucked to landfills according to information from the NZ Ministry for the Environment. Organic waste is the single largest component of municipal solid waste sent to landfills. Once there, it quickly decomposes and produces methane, an environmentally harmful greenhouse gas at least 21 times more potent than carbon dioxide. Landfills are considered the third largest sources of methane.

Most people agree on the goal to reduce food waste at the source, but when it comes to discussing alternatives for managing the ‘unavoidable’ fraction, people often focus on one alternative, such as composting. However, if the goal is diverting organics from landfills, instead of viewing any one system as a silver bullet, it is important that the discussion includes multiple options. Unfortunately, because of myths and misconceptions, one device, common in many New Zealand homes, is left out of the conversation – the food waste disposer.

“While composting and kerbside food bin schemes have received a lot of attention as of late, it’s not for everyone,” said Michael Keleman, manager of environmental engineering for InSinkErator, the world’s leading manufacturer of food waste disposers. “Food waste disposers offer one alternative to composting, but less than 40% of New Zealand homes have an installed disposer.”

Used mainly for convenience by homeowners for plate scrapings, disposers are now present in nearly 40% of all New Zealand homes. Since results from studies in five U.S. cities found disposers have the potential to reduce food waste in the solid waste stream by 30%, and given that food waste is 70-90% water, rather than managing just plate scrapings, there is an opportunity to divert more food waste from New Zealand landfills. Outdated and spoiled food can also be processed in disposers, and instead of ending up in landfills, this material will travel through the sewer to wastewater treatment plants, otherwise known as water resource recovery facilities. There residential, commercial and industrial sewage is converted into clean water and fertilizer, and in some cases, renewable energy. Advanced facilities now harness anaerobic digesters to generate methane which can be used to make energy. Auckland’s Mangere facility and the Palmerston North Totara Road plant are two examples where anaerobic digestion is utilized to produce renewable energy. Watercare, the wastewater authority in Auckland even established a goal to become energy self-sufficient at two of its plants by 2025.

Not every wastewater treatment plant utilizes anaerobic digestion, but a life cycle assessment of twelve systems for managing food waste, including eight types of wastewater treatment plants with and without anaerobic digestion, determined that using a disposer in conjunction with a treatment plant always results in lower greenhouse gas emissions than landfilling. More importantly, where the treatment plant does utilize anaerobic digestion, the greenhouse gas emissions are lower than even composting.

Composting food waste is a great option for homeowners who are willing and able to do so, especially for those in more rural areas, or those not connected to centralized sewage treatment infrastructure. Composting meats and dairy products can be problematic though, because green bins can create odours and attract vermin.

“Considering food waste makes up as much as 40% of the solid waste stream in New Zealand, consumer and governmental officials should look at multiple options for managing food waste, and they should also be wary of the many myths and misconceptions about food waste disposers,” Keleman added.

Waste disposers do indeed use water, and because of this they are often perceived as ‘water wasters’, but they account for only about 1% of a household’s total daily use of water. They also only use about 3-4 kwh of electricity per year, so the cost to run them is negligible.

“Modern waste disposers are capable of grinding nearly all types of food waste, but proper use is the key to reducing the risk of clogs”, said Barnaby Thompson, General Manager InSinkErator New Zealand. “First turn on a moderate stream of water before turning on the disposer, then add food scraps gradually and grind to completion before letting the water run a few extra seconds”.

Homeowners should also never pour fats, oils and greases (FOG) down their sink, which can lead to issues in both plumbing and sewers. Sewage collection system around the world, including many areas nearly void of disposers, experience serious issues with blockages from hard deposits resulting from the improper disposal and management of FOG. Homeowners need to understand that processing FOG in a disposer is inappropriate, as well as pouring it down the toilet.

“Given so much focus on better managing food waste, stakeholders should take a closer look in their own homes – the answer might be right in their kitchen sink”, Keleman added. “With better education and outreach, additional use of food waste disposers can be a win for the industry, consumers and the environment.”

For more information, visit FOOD WASTE DISPOSER MYTHS or

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