Composting technologies

Composting in a community or municipality can be carried out using a variety of systems, ranging significantly in cost, space required, odour generated, time to create finished product and skill required.

The type of system used also depends on the size of the community or institution, the amount of available feedstock to be composted and the operating authority's capability to finance the system at rates comparable to other methods of organic waste treatment.

Climate and special circumstances (e.g. keeping out wildlife and rodents) may require more specialized systems and collection methods.

In terms of program performance, cost and compatibility, the average rural Alberta town and its surrounding region with a population of 4,500 can generate up to 33,000 tonnes of organic waste through municipal and agricultural sources (approximately 1,000 tonnes from the municipal stream and 32,000 tonnes from the agricultural stream).

Agricultural materials are generally managed on-farm or may be collected and treated by an agricultural composting facility.

In larger centres where feedstock is more than 250,000 tonnes per year, large systems that control odour are required. Processing costs can exceed $65 per tonne and capital costs can be more than $30 million.

General comparison of various composting technologies.

*Land area required: This depends on the type of machines used and how the compost is cured. Can depend on size of windrows or piles, which in turn is related to size of equipment available.

An in-vessel system, while compact, may require blowers, biofilters, machine rooms, curing pads, broiler rooms, etc.

For example: A small village accepts 2000 tonnes per year of source separated organics. The village has access only to a bobcat, so the piles are limited to about 1.5 metres (5 feet) in height. If the piles are no more than 1.5 metres high and 30 to 45 m long, they require less than 0.8 ha of land for windrow composting and curing. If the municipality has access to track hoes or other large front-end loaders, the same amount of input material can be stacked higher, requiring less land area.