Alternative solutions to deal with landfill issues discussed

How to deal with the George Town Landfill is an ongoing issue. The current proposal, not yet finalised, is that the Dart Group caps the existing landfill and swaps land with the Cayman Islands government to create an alternative waste management site outside Bodden Town in Grand Cayman. 

At the STEM Carib 2012 conference at the University College of the Cayman Islands, engineer Walling Whittaker presented waste management models that could be possible solutions to Cayman’s waste management problem.  

Mount Trashmore, as the landfill is colloquially known, stands around 85 feet high, takes up an area of 68 acres and has been in its current location in George Town for 40 years. It is an environmental hazard, as when it rains it causes leachate to make its way into the ground water, while decomposing rubbish also produces gases that contribute to global warming. 

Mr. Whittaker explained that an original plan to mine the dump was technically possible, but has lots of risks. According to a report by consultants DBB, it would take about 19 years to mine, the Island would be exposed to noxious gasses and odours, there was a risk of explosion and fires and workers would be exposed to hazards. 

He then went on to explore new alternative and renewable solutions to coping with landfills, the engineering challenges and the advantages and disadvantages of each system. 

In a typical land fill cap, a cover of thick geo membrane liner is laid to contain the waste. The membrane is then covered with a deep layer of soil and vegetation. A gas vent through the middle of the heap enables flow. One of the drawbacks to this that it requires a lot of soil as the layer has to be at least 24 inches thick, which is an expense in Grand Cayman where soil is limited. 

Solar energy landfill caps, using rigid or flexible solar panels, are being used in places such as Italy and North America. A solar energy landfill cap does away with the need for top soil and vegetation while also providing energy. The advantages are that it transforms a liability into a revenue; has the potential to reduce post-closure care costs; protects the environment and provides clean, renewable energy. 

Because water runs off the panels rather than into the ground it promotes positive drainage, minimises infiltration and there is reduced need for maintenance.  

Mr. Whittaker estimated that a small section, about 10 acres, of the George Town land fill could accommodate 9,300 rigid panels of 235 watts each, giving a potential capacity of 2.18 MWp, on just 40,950 square metres of the site and would provide enough electricity to power about 300 homes. 

The cost of this would be about US$6.1 million with a project life of 25 years, but with energy sold could pay for itself in eight years. 

The final example was a sustainable landfill, basically a huge compost heap, designed to break down quickly, built on a new site. The site is divided into four cells that are designed to operate as “bioreactors” so that they can be reused again and again. The engineering part is to create conditions for waste degrading organisms to thrive, which is done by increasing moisture content and introducing air and leachate recirculation.  

While one heap is decomposing you start on another, removing the need to build a new landfill. This model also converts gas to energy.  

When Mr. Whittaker took questions from the audience, the main questions were about recycling. Mr. Whittaker did stress that more recycling than ever was being done in Grand Cayman and a new landfill site would hopefully have recycling. However, as one member of the audience pointed out, if rubbish is not separated at source, in other words at household bins, a sustainable landfill would soon get filled with non-biodegradable rubbish and so the whole cycle starts again.  

Mr. Whittaker ended his talk by reminding students that green engineering solutions were something that those engineers among them would have to think about in the future. 

Solar energy landfill caps, using rigid or flexible solar panels, are being used in places such as Italy and North America. 

1 COMMENT

  1. Alternative solutions – let us build a new land fill in the middle of no where – well only Caymanians live their and we can just ignore them. But even better we can get the same management time which screwed up the last site to run the new one but this nobody will see it until it is really big. Now we then cover the existing site with a great big tarpaulin and cover it in solar panels. Slight problem the pile faces west and not south so the solar panel will not work very well between that and the cruise ships and CUC they will get covered in soot making work even less but who cares it will look go to the cruise passengers.

    What about the smell? – oh yes by the time we are finished the political stink which cover up the smell from GT landfill and the one in BT – who cares it is in BT!

    I think most people went to the talk to hear about recycling methods that could be set up locally and alternative idea to using landfill instead of hearing about a new type of landfill which is the same as the old type but has a liner and some pipes to allow it drain but we did not learn how this liquid is treated- probably dumped in the sea!

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