There is a cost to everything we do whether it's good for you or not. The cost of doing things when its good for you is better health and hopefully a longer, happier life. When it's not good for you, you can suffer from poor health, added costs and a lower quality of life.
There are a lot of people who claim environmental benefits to creating urban compost, myself included. But what is the cost to doing this? Is it worth it?
I want to run through the process quickly so that we're all familiar with how industrial urban compost works. There are 5 major steps to collecting and processing urban compost into a usable product.
1) Curbside collection involves designated trucks to pick up your waste at curbside. They drive around the city for hundreds of miles collectively and pick up tonnes of waste for processing. Each of the hundreds of trucks deposit hundreds of bags onto the floor of the sorting facility on any given day of the week.
2) The waste is visually inspected and unwanted items removed. As you're no doubt aware, all the plastic bags we collect our household waste in must be opened up and divested of its contents. The plastics have to separated and put elsewhere. The contents from the bags are put into an industrial blender called a hydro-pulper and made into a thick soup ready for processing. The pulp is run through a large industrial strainer to sort out any missed foreign debris which is sent off to landfill. As a side note: it helps increase the efficiency of the process when we put only what is allowed in our green bins. All remaining unwanted items such as plastics and glass are removed.
3) The pulp is piped into a special facility known as an Anaerobic Digester. This stage partially breaks everything down in the absence of oxygen. The Anaerobic Digester is a sealed tank which creates the necessary environment for the natural anaerobic process's to occur. The bacteria convert the pulp into an organic solid in about 20 days. One of the byproducts to this process is a methane/carbon-dioxide mixture which is captured and used in a co-generation facility for heat and energy. The City of Toronto website states that "about 110 cubic metres of this biogas is produced from one tonne of organic waste which is equivalent to 670 kwh of energy."
This stage does produce an odour that has to be dealt with through the construction of a bio-filter. Toronto uses woodchips and compost to their advantage. Bacteria living in the filter feed off the compounds which cause the smell, thus eliminating the smell. Here again we've got nature working for us.
4) This step in the process is to allow Aerobic decomposition for the complete conversion over to a useable organic humus. The solid material is trucked over to the secondary processing facility located outside the City where it's piled in windrows and turned from time to time to ensure a unified product. This again is a naturally occurring process whereby oxygen using bacteria break down the material further. Heat is produced from the process which helps kill off pathogens and seeds. This process occurs all year long and takes about six months to complete.
5) At this point, the compost has to be tested to ensure its safe for use and once it's given approval it's off to get used in the city again. So in just under 7 months, the waste from your dinner could be back in the park, at your local school or dumped in your own neighbourhood for use on your own lawn.
Each of these steps has significant costs associated with it.
Toronto claims it is spending $69,000,000 in capital costs and another $10,000,000.00 annually in operating costs. (You can go to Toronto's website under GreenBin/organics for further clarification if interested.) This does NOT include what savings there are from the stoppage of the existing contracts to rid our garbage problem to Michigan.
Costs included are emissions associated with vehicle haul, CO2(tonnes/yr), land displacement, land use conflicts, redundancy costs, expansion capacity, development time and annual system costs. The capital costs were estimated at $69,000,000.00 or $54 per tonne and the operating costs estimated at $10,000,000.00 per year or $91 per tonne. Simple math tells me the cost is around the $145.00 per tonne mark for composting in Toronto. Actual costs to Toronto in 2006 under their existing contracts were $135.00 per tonne so the estimates are close to reality.
So lets look at the big picture.
Toronto was sending several thousands of trucks to Michigan each year to dispose of its waste. Disposal costs increased over 300% after Toronto shut down the Keele Valley landfill site at the beginning of 2003. About 30% of waste going to landfill had organic waste in it so by diverting this to a facility which turned waste into useable compost made sense. Not to mention the many carbon footprints left behind from the trucks going to Michigan and back. The green bin process is estimated to divert 2,300 trucks from Michigan.
While the darker side to an industrial urban compost site includes a carbon footprint, CO2 emissions, some liquid effluent, and some odour, these are off-set or negated by improved systems, lower emissions than would have otherwise existed, cogeneration recovery and application of filters to reduce odours. While the capital costs aren't to be sneezed at either, I believe the alternative just didn't work. As a tax-payer I want my hard-earned tax dollars working for me as efficiently as possible. Composting is good for the environment. Landfills could well be full of hidden costs down the road which we have yet to learn about in terms of just what's been put down in them over the last 75 years (think about that for a few minutes and you'll get a sense of what I mean.) If we have too much humus laying about...well, my guess is it's much easier to deal with it than it is to deal with the issues of landfill. I believe it's worth it.
Mark Overbury is passionate about urban compost. His blog is http://www.urbancompost.info/blog
I Have A Squeaky Floor
