The most cost effective way to recover food and green waste, which account for more than 60% of an average household’s garbage bin, is via a three bin system with food and green waste (FOGO) in the same bin… but should nappy waste be included the mix?
About 15 councils across Australia currently run FOGO services with another 60 or so trialling or planning to introduce them. To manage costs and odour from the food waste portion, FOGO bins are collected weekly and residual garbage bins pushed back to a fortnightly collection.
The only real issue that has been raised with this bin arrangement is what to do with nappy waste that
remains in the fortnightly residual garbage collection.
According to Sustainability Victoria, nappies accounted for 4% of household waste in the state in 2008. However, the perception of odour problems has caused reform to stall for some councils.
Since the main retailer of nappies in Australia, Kimberly-Clarke sees collection and recycling of absorbent
hygiene waste as a key priority and to provide options for councils that were considering a move to a FOGO bin service and help them maximise their recycling rates, MRA investigated the most cost effective and environmentally responsible means of collecting nappy waste for recycling or disposal.
The study was done as part of the 2012-13 FOGO strategy preparation for a regional council, which also wanted to maximise diversion from landfill and their support was matched by generous funding from the NSW EPA.
The collection problem for nappy collection (ergo the political problem) is related to how long the bin sits at a home.
The study examined the costs/benefits of six scenarios:
- Nappies disposed in the garbage bin with a weekly collection;
- Nappies disposed in the garbage bin, fortnightly collection;
- Nappies disposed in the garbage bin, with optional weekly collection for those nappy households that have odour problems (additional costs borne by council);
- Nappies disposed in the FOGO bin for composting, weekly collection;
- Nappies disposed in the organics bin in a “red bag” for separation before composting weekly collection; and
- Dedicated nappy collection service, weekly collection.
The option of providing cloth nappies or 100% compostable nappies to every retailer in the region was regarded as impractical and cost prohibitive.
To keep costs low and still introduce a weekly FOGO collection, garbage has to be collected fortnightly. As the difference between weekly and fortnightly bin collections can be millions of dollars annually (see figure 1), this is not a simple decision for any council.
Costs will vary according to the additional collection and processing costs and while the system costs
highlighted in figure 1 were for our client council, they are relative costs that are indicative for most councils.
Nappy composting field trial
As part of our study, we also trialled the composting of nappies with FOGO (option 4) to test both the costs of and acceptability issues to the compost industry.
At the time, the proposed nappy processing plant to be established by Relivit at Nowra, was not an option, but this does not materially affect the collection/processing costs set out in figure 1.
SoilCo undertook a full scale, windrow composting trial of nappies (4%) mixed with FOGO with support
from Shoalhaven Council and GRL. The material was composted successfully with the residual elastic and tab plastics (see figure 2) removed at the final screening stage.
While it was clear that the material could be successfully composted – 71% of product achieved the AS4454 standard – a parallel survey of the composting sector found almost consistent opposition to the inclusion of nappies in FOGO composting due to contamination, possible pathogens and associated WHS concerns.
These concerns were reflected in the premium gate fees proposed by compost operators to receive nappies mixed with FOGO at a$54/t premium on top of a base gate fee of $60/t.
Not surprisingly, option two – to leave nappies in the garbage bin and collect it fortnightly – was the cheapest.
Remembering that only 4% of households have nappies, it did not make sense to collect all garbage bins
weekly (option 1) along with all FOGO bins. This was the most expensive option and would unnecessarily overservice 96% of households.
Putting the nappies in a “red bag” (option 5) into the FOGO bin was cost effective but involved new education and operational arrangements and raised concerns for composters.
Mixing nappies into the FOGO bin (option 4) was firmly rejected by the composting sector and their disdain was reflected in the gate fee they would charge, inevitably making this a relatively expensive option.
The sixth option, a dedicated nappy collection via a nappy bin was also relatively expensive.
On balance, the study found that the “best” and recommended option was option 3: nappies disposed of in the garbage bin (collected fortnightly) with an optional weekly service for nappy households (maximum 4%).
Recent anecdotal evidence from two councils with FOGO services and fortnightly residual collection
also support this finding, with few households complaining about odour from nappies. These councils
recommend deodorisers or bagging of the nappies.
Councils can choose to pass on some or all of the additional costs of the weekly collection to the nappy
household. If all of the costs of the additional weekly service are passed through, then the costs would reduce to option 2, the cheapest option.
Thus, councils should not avoid introducing FOGO services for fear of odour problems caused by nappies. The key gain is to remove the food from landfill. Leave the nappies in the garbage bin for now until realistic, cost competitive options for nappy recycling emerge. There is at least one on the horizon.