This invitation provided me with the opportunity to research the composition of so-called residual waste -- you know, the roughly 35 to 40 per cent (depending who you talk to) of residential waste that's left over after blue box recycling and source-separated 'green bin' composting.
Luckily, the Regions of York and Durham (just outside Toronto) have, as part of their recent EA process, modeled what would remain in (what they label) the 40 per cent of waste after maximized diversion. The results -- what's in that final 40 per cent -- are as follows.
Almost a fifth (17.2 per cent) is material that wouldn't even burn, including metals (13.3 per cent) and glass (3.9 per cent).
Another almost fifth (18.1 per cent) is food that on average (we're told) contains between 70 and 80 per cent water. You don't get much energy from burning water, last time I tried. (See for yourself; tonight, build a small fire and then throw dinner on it to see what happens.)
To continue, there is 4.3 per cent in leaf-and-yard material (easily composted). Rounding out this group are HHW (0.3 per cent, and stuff you most certainly don't want to burn) and textiles (2.4 per cent -- also something that'd be nice to not burn).
Taken together, all of the above totals 42.3 per cent of the 'residual waste' -- stuff that either won't burn or that we should not burn.
This helps explain why waste-to-energy plants are so inefficient and why the small amount of power they produce is so expensive.
So, what remains?
First, there's the paper/fibre category, more than a quarter of the total (26.6 per cent). This has two sub-categories; recyclable (15 per cent) and non-recyclable (11.6 per cent). Obviously we could recycle the 'recyclable' paper/fibre. What about the non-recyclable sub-category. It's described as compostable paper and sanitary products. As with food scraps, I wonder just how much energy can be generated by burning a soaking wet diaper and why we wouldn't compost the 'compostable' paper.
What am I missing here?
Within the all-important plastics category are: recyclable plastic (3 per cent), film (2.5 per cent) and mixed plastics (6.8 per cent) for a total of 12.3 per cent.
Note that combined the paper fibre and plastic categories total 40 per cent. Now, imagine if by reduction, packaging legislation, reuse, stimulat- ed via taxation, simple separation for recycling (and, of course, market development for this recycled material) we could divert two-thirds of the '40 per cent residual waste.' What would we be left with?
Just 13.6 per cent of the original 40 per cent of the paper/fibre and plastic categories!
Is it really worth building a mass-burn incinerator or a new-fangled (and expensive!) gasification plant to address that tiny fraction of the waste stream? I think not.
To say we have 'maximized diversion' (at 60 per cent) is, to me, false. Like any other product or service we have non-users, light users, medium users and heavy users of diversion, and there is much more we can do to move residents onward and up this continuum. As I like to say, if can get people to eat at McDonalds, we should be able to get them to do anything!
And remember, we now know have a great reason when recycling a tonne of paper and plastic recyclables; recycling them eliminates two to three tonnes of CO2.
Okay, so now what's left?
The last, rather large category (18.6 per cent) is called 'combustible material' which is described as building renovation material, miscellaneous goods and other material.
Imagine, again, if by Internet exchanges, depots, a fourth stream of collection and return-to-retail we could reduce this category by two-thirds, leaving us 6.3 per cent of the original 18.6 per cent. Add to this the 13.6 per cent in paper fibres and plastics, and I'd argue we have 20 per cent of the so-called 'residual waste', or just eight per cent of the total waste stream to deal with as residual, not the 40 per cent that many wish which to burn.
Just eight per cent. (Remember that number.)
MBT and stabilized landfill
Some people say that rather than incinerate 'residual waste' it should be treated in a different process.
Another interesting way to cut the numbers is to examine the amount of methane-producing carbon in residual waste. By adding food (again, 18.1 per cent), leaf-and-yard (4.3 per cent) and paper (26.7 per cent) and let's -- for exactness -- say one per cent for cotton and other natural textiles, you arrive at 50 per cent.
Add to this a good portion of the 18.6 per cent identified as combustible (as, after all, if it's combustible it has carbon in it) and it's very easy to imagine that 60 per cent or more of 'residual waste' has the capacity to generate methane.
It seems to me that only the food portion (18.1 per cent) would really be suitable for mechanical biological treatment (MBT) and stabilization (for a stabilized landfill). There's not much stabilization of the leaf-and-yard, textiles or paper, which can occur in just 14 days, and of the other materials. There's no stabilization of the oil-based materials (12.3 per cent) nor metal or glass (17.3 per cent).
This would appear to be the case in Halifax where applying MBT to the 50 per cent of the city's waste not diverted plucks out just three percentage points of metals and gains another five percentage points via moisture reduction of the food -- at a cost once calculated by Toronto Councilor Bas Balkissoon at $2,000 per diverted tonne!