The Trash Dilemma

THE TRASH DILEMMA – SOME OPTIONS

Humankind has been generating garbage for its entire existence. And, for most of our existence, and still in Canada, we buried our waste, or just left it to rot. This was acceptable when we were few in number and the “wilderness” seemed endless. Today, with over six billion of us on this finite planet, we are in desperate need of better strategies and better compliance with those strategies if we are to avoid drowning in our own waste.

Let’s look at a promising strategy for dealing with wastes. We will consider solid municipal waste for the moment. As everyone knows, we are running out of places to dump waste. Toronto trucks its waste to Michigan, which obviously cannot continue, and several plans to use old mine pits have run into strong opposition from neighbours of those pits. It would be almost impossible to obtain regulatory approval for a new dump site in today’s climate.

Ottawa’s Plasco Energy has developed a very promising technology. The principle is that municipal waste, the kind we put out in our green bags, is incinerated using a plasma. A plasma is a jet of gas, nitrogen or air, from which most of the electrons have been stripped, leaving an extremely hot (over 25,000 deg. F.) stream. A lightning bolt is an example of a high energy plasma, and those globe-style lamps that glow pinkish with filaments that move and pulse when you place your hand near the globe is an example of a low energy plasma.

The heat and energy of the plasma is used to break down the garbage to its basic atomic components, that is, carbon, hydrogen, oxygen, iron, etc. This is done in an atmosphere low in oxygen, as we don’t want to generate carbon dioxide. These elements recombine to form carbon monoxide and hydrogen, plus some chlorine-containing compounds, water, and slag. Slag is the non-gaseous insoluble solid residue.

So what is this residue, and what can you do with it? First, we need to take a quick look at household garbage – it is mostly paper and cardboard (cellulose), plastic wrap (hydrocarbon), and food waste (protein, fibre, water, cellulose). Some metal and other components such as calcium (eggshells and bones) and silica (dirt) may be present. When this mixture is subject to the high energy and temperature of the plasma, it breaks down into the materials noted above. The gases, carbon monoxide, hydrogen, and chlorine-containing gases are cleaned and the chlorine compounds are removed. The result is called syngas, and forms the fuel for an electrical generator. The inorganic materials, such as dirt, metal, form a liquid slag, which is dumped from the reactor into water. This solidifies the slag into a sand-like material that can easily and safely be incorporated into concrete or road-building products.

This plasma process differs dramatically from the older incinerators that used to burn garbage, stink up the neighbourhood and generate carbon dioxide and numerous pollutants. The plant in Ottawa has completed a successful test run, and tests on larger quantities of garbage are pending. The gaseous effluent (the stuff going up the smokestack) has been analysed for all major pollutants at well below Provincial standards. The costs are competitive with landfill, currently about $40 per tonne, when the revenue from the electricity is factored in. This process generates electricity at about 1.4 megawatts per tonne of waste. At 200 tonnes per day, the design capacity, this could supply about 4000 homes.

Some other issues related to this are that household garbage makes up about 35% of the total garbage requiring disposal. Even the most dedicated reduce-reuse-recycle program, where we all could do better, must have a parallel effort, with appropriate incentives, in the commercial, industrial and construction areas. These efforts will lower the overall amount of waste requiring disposal. The issue of PCBs and dioxins, which led to the phasing out of the old type of incinerators, is not expected to be a problem with plasma technology, due to the high temperatures involved, but detailed analyses have yet to be carried out. Explaining the process to a public that recoils at the word “incineration” is not easy, as the Swedish Ambassador in Ottawa pointed out recently. He described an operational state-of-the-art plasma system in Sweden, with its extensive experience treating a variety of wastes, and its exemplary emissions record.

The article in the Recorder and Times on Feb. 20th points out that the Ontario Government is looking at various options aimed at extracting energy from waste; the plasma technology is one approach.
Another technology to extract usable energy involves trapping the methane that buried waste gives off as it decomposes, and using it to generate electricity. An existing landfill is “capped”, or covered in such a way as to capture the methane, then the methane is cleaned and dried before it can be used or piped into the natural gas distribution network. There are numerous landfills where this technology could be applied. An abandoned cement quarry on Montreal Island was used as a landfill for many years, and the waste methane is currently being flared, or burned off, but it could be cleaned and piped to Montreal-area homes. As fuel prices rise, this option becomes more economically attractive.

Governments have limited practical options, but it does appear that plasma waste disposal offers several clear advantages, and deserves a realistic trial. We all contribute to the problem and we must collectively take responsibility for the solution.