Sotkon’s system promotes crane-based collection
We don’t need to debate this issue in too much detail but a combination of hot sun, enough tourists to increase the population of a resort town by a factor of three and heaps of waste do not go well together!
Tourists visit coastal holiday resorts to enjoy themselves. On that ‘to do’ list might be ‘play golf’, ‘visit a night club or casino’ or just simply ‘sit on the beach all day with a cool beer’. What is unlikely to be on that list is ‘get woken up at 4am by refuse truck crew dropping metal containers in the alley beside hotel’, or ‘choke on the smell of rotting food waste containers while visiting the local market in the old quarter of the city’.
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| Luis Barbosa Fernandes, director of EMARP, the municipally owned company that looks after waste collection and disposal in the Portimao area (right) with Joao Martins, marketing director of Sotkon |
On the face of it, issues such as having to send refuse truck crews out very early in the morning to get the work done before the sun gets too hot, or finding ways to prevent paying guests being woken (when most of them have only just gone to bed) could be seen as a odd starting point for the design of a new waste container storage and handling system. But that’s very much what we have in the Sotkon underground waste container storage system.
The original design brief was to enable busy (but not especially financially well-off) municipalities with large numbers of tourists to remove refuse containers from view, while at the same time reducing infestation from rodents and flies – and of course the odour associated with conventional waste containers in public places. It would be nice to suggest that all municipalities throughout the world would want to do this for the benefit of its residents, but the fact remains, it’s often tourist dollars that drive inner city infrastructure developments.
A few years ago, the Portimao municipality on the Algarve in Portugal had considered a move over to wheeled containers – either individual 240-litre units or larger 1100-litre communal containers. However, there are a number of problems associated with their widespread adoption in busy, congested old parts of towns of which easy access by collection crews was just one issue. There was also another factor to consider – the need to continually improve recycling ratios; for if there were already problems accommodating one waste container for each shop or cafe, it was likely to prove impossible to accommodate three, five or more individual recycling ‘fraction’ containers in the same space.
No more nasty smells
The solution? More regular collection of smaller containers was an option, but any added costs would have to be paid for out of taxes levied on the all-year-round residents.
The alternative? All the waste containers could be made bigger if they were buried underground, increasing waste capacity which, in turn, helps promote greater flexibility in collection frequency. Going underground also had the advantage of putting the waste containers out of sight.
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| Typical Sotkon underground container ‘nest’ site with a separate container for each waste/recyclable material |
The Algarve attracts traditional sun-seeking tourists in the summer months as well as large numbers of golfers at either end of the season when temperatures are a bit more in tune with some physical effort! From an economic viewpoint that’s a good thing for Portimao. From a waste handling perspective, however, the influx of visitors increases the population of the town from its normal 44,000 to three times that figure. ‘This placed a serious strain on resources,’ explains Luis Barbosa Fernandes who is head of the municipally owned waste, recycling, street cleansing and grounds maintenance organization, EMARP (Empresa Municipal de Água e Resíduos de Portimão). The tonnages of waste collected also increase dramatically at the very time of year when the summer heat makes the task more stressful for the crews.
But which underground system to go for? Narrow congested streets ruled out larger collection trucks and the headroom needed for systems requiring a side-loader, while crane handling systems (those that lift containers up directly into the loading hoppers of compaction-type refuse collection vehicles) were ruled out by the large numbers of overhead cables, signs and overhanging balconies in the town. ‘Ideally we required a system that enabled us to use conventional rear loading collection vehicles with container lifters, while storing suitable containers out of sight underground,’ Luis explained. And essentially, that is the beauty of the Sotkon system – it allows existing designs of refuse collection vehicle (RCV) to be used.
How is this possible? Essentially, the Sotkon 3 m3 capacity underground storage containers have the same length and width as a current 1100-litre wheeled container. This enables existing twin-arm binlifters (as used on 1100-litre type containers) to also pick up Sotkon units. The Sotkon container doesn’t, however, have wheels so it can’t run away down a steep slope. And in line with the original design brief to reduce noise, Sotkon containers are not made of metal or injection-moulded hard plastic, but of rubberized plastic. So they are safer in use and make very little noise when being handled – it is claimed.
So how are these containers ‘lifted’ out of their underground silos and moved to the rear of the collection vehicle hopper if they can’t be wheeled? The answer, as the picture illustrates, is by a small crane. Unlike other crane-based underground systems, however, the crane used by the Sotkon system differs in that it isn’t used to both lift and empty the container into the hopper of the truck. Its only function is to lift the Sotkon container out of the precast concrete silo up to ground level, slewing it from the side of the collection vehicle to the rear of the hopper (Sotkon silos are normally arranged in ‘nests’ of several units located by the kerbside). The crane hook is then unhitched before the binlifter empties the container. When this has been done, the crane hook is hitched on again and the container swung back into its silo. The only ‘special’ modification is the fitting of the loader crane onto existing collection vehicles or new units. Significantly during a time of global recession, ‘retrofitting’ cuts out the need to pay for a whole new collection fleet and the installation of the silos in one budget year.
A key advantage
Is splitting the process into two distinct operations an unnecessary waste of time and effort? That was my initial reaction when I first saw the Sotkon system at the 2009 Entsorga event in Cologne, Germany. But having observed both a day and night shift with EMARP crews in Portimao, I have to say that at just over three minutes for each container lift, the Sotkon system compares well with any other alternative while having the added advantage of enabling otherwise standard designs of RCV to be used. EMARP uses an all Volvo/Haller fleet of two-axle 19-tonne gross units; the 1.8-tonne lift capacity telescopic crane is mounted directly onto the roof of each compaction body via a steel plate containing the slew ring.
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| With lid raised, the crane mounted on the RCV is used to raise the waste container out of the silo, placing it in front of the binlifter |
According to Joao Martins, marketing director at Sotkon, part of the reason why the crane can be smaller and lighter is because it only has to lift from below ground up to ground level, and not the entire container to a height where it can discharge directly into the RCV hopper. ‘This means we can use a lighter construction, smaller cylinders and less oil. But it’s also safer in operation, I would suggest,’ he explains. ‘Also important in urban situations is that unlike other competitive systems, our customers don’t need to increase the wheelbase of the collection truck chassis in order for the crane to be mounted on the chassis behind the cab, or alternatively reduce body capacity by having to shorten the body to make space for the crane,’ he adds. He’s right – that’s a key advantage. Also, a conventional open-topped tipping body with chassis-mounted lorry loader crane can also be used for recyclable materials such as paper and cardboard if required – which helps reduce costs further.
So how well does the Sotkon system perform in real life? Thanks to the co-operation of Luis Barbosa Fernandes and the municipality of Portimao, I can confirm it performs really well. The ‘nests’ of underground storage containers are normally located by the kerbside and are used by residents of apartment blocks, small business premises and in more modern ‘retail parks’. The hinged 1850 x 1850 mm Sotkon silo covers can be located on verges or under pedestrian areas; being secure, they do not have to be tucked away out of sight as conventional containers do.
This saves collection time. EMARP statistics gathered over a two-year period suggest each vehicle working on Sotkon containers will ‘pack’ in 10 extra hours per week (that is actually working rather than waiting) with one less crew member (from three down to two). On a city-wide fleet that adds up to a much greater collection rate per vehicle, taking into account the fact that each Sotkon container is located by the kerbside and takes a 3 m3 load per tip.
One of the other key advantages of using underground containers is that existing courtyards currently used to store wheeled containers can be freed up. The space available enables commercial waste companies to offer their clients a solution to the restricted car parking in downtown areas. With the value of each individual car parking slot worth hundreds of dollars a year in potential rent in some cities that could help make the installation of an underground system far more cost-effective than you might otherwise expect.
Certainly, the Portimao authorities are convinced of the savings that come from installing an underground system and Luis Barbosa Fernandes is keen to welcome ISWA members to see the Sotkon system in action. Although there is a certain amount of disruption while each silo pit is excavated (Joao Martins suggests this only takes two days from start to finish per container ‘nest’), it is reported that residents currently not on underground containers are keen to be part of the ‘underground movement’. The installation costs will obviously vary in different parts of the world, but EMARP’s figures suggest that installing an underground system as part of an inner city refurbishment could help bring in enough extra tourist dollars to pay back the costs.
Malcolm Bates is collection and transport correspondent for Waste Management World.
e-mail: wmw@pennwell.com
