Department Sanitation, Water and Solid Waste for Development

Windrow Technique

The windrow technique is suitable for medium size to large scale composting schemes. For manual operation the capacity should not exceed 10 tons of waste per day. The fresh waste is piled up in heaps - the so called windrows. The biological process of decomposition generates heat inside the pile (up to 70 °C), which ensures the hygienisation (destruction of pathogens and weed seeds) and a fast degration of the raw material. In order to ensure a sufficient oxygen supply the windrows have to be turned frequently (every 3-4 days) during the thermophilic (hot) phase. After 3-4 weeks, the activity of the mico-organisms decreases and the windrow enters the maturation phase. After a total of 8 weeks the compost is mature and is ready for sieving and sale. The following pictures show the windrow technique used by Waste Concern in Dhaka, Bangladesh:





Piling of the sorted organic waste on the bamboo aerator
Fresh windrow on a bamboo aerator, which allows a better oxygen supply from beneath
Same windrow after 40 days and several turnings - the volume and mass reduction is obvious
After 8 weeks the decomposed material is sieved manually - either through a flat screen or a rotating drum sieve
The final product compost after sieving
The compost is bagged and sold directly to farmes and a fertiliser company

A more detailed description of the process is available in the following documents: