Design criteria for the efficient co-collection of solid wastes

Abstract

When a municipality is looking to add collection services as a means to lessen the amount of waste that is reaching landfills, collecting two streams of waste in one truck is a feasible option to consider. Co-collection remains a feasible option even with the inherent problem of possibly having to travel to two separate disposal facilities to unload. The purpose of this report is to study the effects different parameters have on the feasibility of co-collection in terms of efficiency (i.e. how many households are served). With the addition of a new waste stream to be collected (i.e. organics), municipalities are placing an increased* number of vehicles on the road. The efficiency of a single stream collection system is threatened with increased vehicle costs and labour requirements. Co-collection offers a viable alternative by collecting two streams of waste in one truck potentially lowering the total collection costs. In completing this study, a derived probability modeling program for recycling collection designed by Wilson & Baetz (2001) was altered in order to make it applicable to co-collection system design. This model may become a valuable tool for solid waste managers in their planning efforts. Preliminary investigations of co-collection systems suggest that the number and location of unloading facilities and the capacity of the collection vehicle have major impacts on the efficiency of collection programs. For instance, once two streams of waste are collected in a single vehicle, the problem arises of having to travel to and unload at two different disposal facilities, and then potentially return to the collection route and collect additional waste. This increased travel time affects the efficiency of co-collection, along with the capacity of the vehicle. The results from the modeling program utilized in this report indicate that the preliminary investigations are correct in the fact that co-collection serves a smaller number of households as compared to single collection. However, this must be weighed against the potentially lower vehicle and labour requirements and the benefit of additional waste streams being collected that may not have been previously. The results from the study indicate that the most efficient design for a split co-collection vehicle is a 60/40 split. This was compared to a 50/50 split for a vehicle with a capacity of 12mA3. The results from the study indicate that a collection system with garbage & organics collected one week and recyclable containers and paper collected the second as the most efficient. For co-collection, a greater number of households can be served when the garage is situated with both of the disposal facilities and when it is separate for longer haul times. For shorter haul times, a greater number of households are served when the garage is situated with one of the disposal facilities with the other at a separate location. This is dependent on the specific design of a municipality and if they are in the position to be able to chose the optimal location for new disposal facilities. The main objective of this project was not to prove that one collection system is better than another, but to develop a mechanism to assist in determining what is more appropriate for a particular municipality. The secondary objective was to utilize the derived probability model for co-collection to determine the conditions under which co-collection is feasible, as summarized above. If a municipality is in the position to locate the disposal facilities required in close proximity, then co-collection may be beneficial to lower collection costs and increase waste diversion. However, if the sites are fixed in their location, then a separate collection system may be more efficient (i.e. if the landfill is situated across town from the compost facility). The specific of a particular municipality makes it necessary to have available a modeling tool for solid waste managers in their planning efforts.