An analysis of the costs of the collection and debagging systems for residential yard (garden) waste used in Canada

Abstract

There has been a dramatic increase in the number of residen tial yard waste collection and composting programs in Can ada. A survey of the large-scale systems found that 68% of the programs use non-biodegradable plastic bags as their primary collection contamer, while 20% use paper bags. Simple math ematical models were developed to compare debagging sys tems and to compare plastic and paper bags. These models can be used to: select a debagging unit cost target, select labor force productivity targets, select the appropriate level of debagging automation, and compare the cost of using paper or plastic bags in their program. The models were applied to the City of Winnipeg's program, which currently debags 2 280 tonnes per year and is predicting a future throughput of up to 10 000 tonnes per year. Tremendous economies of scale were shown as the debagging unit cost decreased from $30 to $9 per tonne as the annual debagging throughput was increased from 500 to 10 000 tonnes per year. A comparison of the costs of using paper or plastic bags found the retail price of the bags to be the most significant cost component of the collection and pre-processing costs. It represented 94% of the cost of a pro gram using paper bags, and 72% of the cost of a program using plastic. When the retail price of the bags was included, the use of paper bags was found to be 24% more expensive than the use of plastic bags. If the retail price was excluded, the use of plastic bags was found to be 75% more expensive than paper bags.