Articles English
21st Century State-Of-The-Art Technology for Treating Residual Waste
By Raye Thomas, Ph.D., P.Eng., 2005-03-13

A. Large Engineered Landfill Sites Use 25 Year Old Technology 

In its 10 page insert in the Low Down newspaper, LDC refers to the landfill technology proposed as a 21st century state-of-the-art residual waste treatment facility.  This is absolute hogwash, and to refer to it as state-of-the-art more than 25 years after its introduction is ridiculous.  The technology planned to be used is old, dating back to the 1970s – hardly a 21st century way to treat residual waste.  Only for those interested in making money from landfill, where the more the garbage generated the richer they become, may this be construed as state-of-the-art.  

LDC includes a graphic representation of the proposed engineered landfill technology in the insert which is deliberately misleading. The diagram makes you think that there is lots of protection between the residual waste and the underlying soil (which for the site proposed is sand, the most unsuitable base for this type of facility).   

The best Engineered Landfill site will have approximately half a meter of clay as a base, over which is laid a 1.5 mm thick high density polyethylene (HDPE) liner followed by alayer of earth about half a meter thick, incorporated into which are leachate collection pipes.  Then a second HDPE liner is added for extra safety. For the proposed Alleyn and Cawood site there is no underlying clay layer anywhere near the recommended thickness.  To compensate for this lack, what LDE proposes instead is a geosynthetic clay liner only ¼ inch (6 mm) thick – the pictorial representation doesn’t show the clay layer to be this thin does it? This thin clay layer will help a bit, but it is really only effective on the side slopes of the cells, and not adequate for the bottom of the site which has to support tonnes of garbage and the weight of tractors spreading earth and garbage during the landfilling operation.   

As to the 1.5 mm thick HDPE liner system, this is far from fail safe.  Since the material can not be folded it has to be laid in sheets which are welded together on-site.  Poor welding can lead to holes where the sheets are welded together.  Additional holes will occur when using bulldozers to spread a soil cover over the liner (the soil cover should be another half meter thick to ensure that the inevitable creases in the liner up to 250 mm high are covered). These faults guarantee that the liner system will leak polluted water into the sand below the liner. LDC states that the US EPA web site states that HDPE liners can last 100 years – so too can garbage bags covered with soil – this doesn’t mean that the liners will not leak.  In fact, in the same web site referred to by LDC in the insert, the EPA states unequivocally that “All liners leak”, and that even with a pristine liner system, there is leachate leakage of the order of 200 liters per day per hectare. The leakage occurs because even if there are no holes in the welds, there are inevitably pinholes in the HDPE liner which occur during the extrusion process.  Further the manufacturer of the liner proposed for Alleyn and Cawood states “Tests performed on HDPE have shown that a sharp stone as small as 1.5 cm (0.6”) can cause puncture”. An imperfect base means punctures and leakage. Then over time, once garbage has been added, chemicals will attack the HDPE liners and leakage will increase with time, so the 100 year life quoted by LDC is extremely misleading.  

Once the garbage is in place (to heights equivalent to a 13 storey building, it becomes far too expensive to remove the garbage and fix the liners once a leak is detected.  Moreover, leaks may not even be detected since experience shows that narrow plumes develop that pass between adjacent detectors.  Alleyn and Cawood must be desperate for revenue to risk our water on such a frail and outmoded system operated by a new company with no previous successful track record in this residual waste treatment field.     
 

B.  Plasma Gasification: State-of-the Art Technology 

What is the current state-of-the-art technology for residual waste treatment in the 21st century?  Incineration tends to be discarded by many people as polluting our atmosphere, however “high temperature incineration” has advanced dramatically since the introduction of the liner technology– as discussed in a recent newspaper article in the Ottawa Citizen– so should not be disregarded outright.  However, the real state-of-the-art residual waste treatment technology is Plasma Gasification.  High temperature gas plasma technology is being increasingly used in many applications (for example it is used in the manufacture of solar cells and is used to treat waste from semiconductor factories).  It is now being used in the treatment of residual waste.  The National Geographic issue of February 2006 calls it “The Fourth State of Matter”.  We believe that plasma gasification technology promises to be to garbage treatment what the laser is now to eye surgery. Cities in Europe, where space is a problem, use the technology.  Ottawa is installing a plasma gasification facility after having experimented with it on a small scale and plan to ultimately treat all their residual waste in this manner.   

In plasma gasification technology a high temperature electric arc is formed in a reactor which is starved of oxygen – lack of oxygen means that burning or incineration is not present and fumes from burning do not occur. Reactors exist which can handle various amounts of garbage of all types – for example, one we have studied can handle 20 tons per hour. Garbage introduced into the reaction chamber can reach temperatures of up to 8000 °F.  Metals melt and flow out and are solidified and taken away for re-use in re-bars for example.  The other solid materials are vitrified, that is, they form a glassy material.  This material can be used in concrete and asphalt.  The key point is that there is therefore minimal landfill resulting from this treatment and what there is, is stable, so that there is no possibility of water picking up harmful materials and carrying leachate into our water table.  Huge landfill sites are rendered unnecessary.  As an added benefit, the gases given off are non-harmful and the energy contained in them can be used to generate electricity.  This is state-of-the-art, and makes obsolete the old landfill technology proposed by LDC for Alleyn and Cawood.   

C.  Stop the Landfill and Move to State-of-the-Art

With a much better technology avaialable, we believe that the proposed landfill project should be stopped now, and all the municipalities in the Outaouais should work together to come up with a state-of-the-art solution which will protect our future. The first step in planning should definitely not be to prepare an outmoded landfill site.   

Rather, as a first step all municipalities in the Outaouais should introduce recycling programs to reduce the amount of residual waste that needs to be treated.  In parallel, the municipalities should consider a plasma gasification for the region that would accept the reduced amount of residual waste in a plasma treatment facility. The facility would recover the metals, recycle as much as possible of the vitreous materials, generate electricity with the gases, and only then landfill the remaining (stable) material in a site which is probably less than 10-20% of the size proposed by LDC.   

Our water table would not be at risk, the truck traffic carrying garbage along highways 105 and 301 would be reduced, and future generations would not have to suffer from our excesses.   
 

<< Retour
  Droit d'auteur © 2006 Coalition contre le mégadépotoir de Danford. Tous droits réservés.