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Our Difference - Waste to Energy
Waste to Energy – A Layman’s Guide by JRH
Clinical Related Waste is a high value waste stream with an average calorific value of 28 MJ/Kg. By way of comparison Coal is around 33 MJ/Kg with Natural Gas at 46 MJ/Kg.
This means that in the case of the Ace Waste high temperature Incineration Systems (Thermal Capacity of 32 GJ/Hr) the Medical waste provides around 95 % of the energy required to maintain combustion conditions.
Auxiliary Fuel in the form of Natural Gas is required to ramp up to the required temperature, however once EPA conditions are met the only inputs required are the Medical waste blend together with combustion air. Providing waste feed is maintained combustion conditions are maintained at up wards of 1,000 degrees Celsius – purely on waste and air. The marvel of Chemistry of Combustion at work.
This is where the benefit of shredding comes in to provide the homogeneous blend of calorific values. By mixing and blending the various waste feeds – medical, quarantine etc the fuel inputs are averaged out.
Incinerators don’t operate on kilograms they function on energy input (calorific value). Not a function of weight but more a function of the energy in the weight - if that makes sense.
At the activation energy of 1,000 Celsius the major component of Medical waste namely the Hydrocarbons in human tissue, body fluids, plastics etc breakdown to the constituent components of Carbon and Hydrogen. Carbon oxidizes to initially Carbon Monoxide (good source of auxiliary heat energy as taking Carbon Monoxide to Carbon Dioxide releases more energy – again important for maintaining combustion conditions within the Secondary Combustion Chamber).
An important part of the Medical waste fuel is the relatively high levels of Hydrogen present. When Hydrogen is oxidized it converts to Water H2O and there is nothing purer than water formed during high temperature incineration. The Ace Waste facility is capable of producing up to 6 tonnes of water per hour – generated purely from the oxidation of Hydrogen with Oxygen.
In some respects Medical Waste is a better potential fuel (pound for pound) than Coal when it comes to fueling Waste to Energy Plants due in large part to the higher levels of Hydrogen in the input. Coal is mainly Carbon. Carbon oxidizes to Carbon Dioxide whereas Hydrogen oxidizes to Water. Also Hydrogen releases 3 times more energy in oxidizing to Water than Carbon does in oxidizing to Carbon Dioxide.
Comparison of Landfills to Incineration
Incineration is rapid oxidation of Hydrocarbons whereas Landfilling is by contrast very slow oxidation – two phases aerobic decomposition (several years) whereas the Methane producing phase (anaerobic decomposition) can take considerably longer (decomposition without oxygen).
Landfills produce Methane CH4 whereas Incineration converts the CH4 to CO2 and H2O – no chance for Methane to form.
One tonne of Methane = 24 tonnes of Carbon Dioxide
This is why Incinerators are a much Cleaner Option over Landfilling quite apart from the safer, no residual/contamination risk issues.
This is why Europe has developed a No Landfill Policy and opted for Incineration as the best solution for firstly its growing Energy needs as well as conserving its available landfilling capacity. Landfills are used for the non combustible fractions – minimizes soil and water contamination.
But then Europe is enlightened when it comes to pro actively solving its waste problems. Australia has some catching up to do and this is where Ace Waste can help as it is the only Australian Company that has based its Business Model around Waste disposal by incineration.
Backing Landfills over Incineration is a short sighted commercial decision that will ultimately leave them behind. Forever the Optimist!
Whilst Dioxin is often cited as a problem with Incineration in fact the opposite is true when it comes to what Landfilling of chlorinated compounds are capable of producing. All combustion processes produce dioxin. Dioxin is produced during the cooling phase (range 200 to 400 C) wherein Hydrocarbon reforms with Chlorine to form a complex chain molecule.
Rapid quench water cooling and sulfur naturally occurring in the flue gas assist in inhibiting this process. In fact Ace Waste has the lowest levels (well within License limits) on the East Coast.
Dioxin is evident in motor and truck exhausts (15 diesel trucks equivalent to the Ace Waste Brisbane incinerator) at measurable levels with bush fires and Crematoriums (5,000 ngs per body cremated) as being acknowledged major sources for Dioxin. Ace Waste produces around 70 ng per hour – quite a difference to Crematoriums.
By contrast Landfills produce Vinyl Chloride Monomer – a far deadlier carcinogen than Dioxin. Again Chlorinated compounds produced by the Sterihealth Shredder/Grinder would be a source as it produces a chlorinated medical waste residue. How this can be classed as equivalent to Domestic waste will remain a continuing mystery to the Writer.
The other major Point of Difference is that Incineration Systems are able to be monitored whereas Landfills are not subjected to the same level of monitoring due to vast area and uncontrolled nature of emissions.
It is for these reasons Landfilling is Old Hat Thinking and Incinerators are the New Hat Thinking.
There is little point in continually landfilling our high energy waste streams when they could be better utilised for not only improving the Environment but more importantly directed toward solving our growing energy needs.
I am firmly of the view that 100 years from now Society will be mining Landfills to recover the high energy wastes (such as medical wastes amongst others) which earlier short sighted generations buried.
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Waste Minimisation
Incineration is also a great waste minimiser in that only 10% of the volume remains as inert ash – mainly glass and metal – non-combustible fraction.
By landfilling only the non-combustible fraction landfilling space is conserved.
The high calorific value waste is converted into heat energy to either fuel the Plant in the Ace Waste case or for WTE Options.
Alternate Treatment/Landfilling Options – means cubic metre in cubic metre out.
Think of it this way Incinerators convert mass solid/liquid to mass gas inert solid – Mass Converters
Treatment Options do not convert Mass – Mass In Mass Out