Windrow composting

Windrow composting is the most common composting method. Basically, the method consists in accumulating the biodegradable material in large narrow piles above the ground, moisten and turn it every two weeks or three weeks. In the next lines I'm going to show you the experience at the Agrarian University (Peru):

The Waste Treatment Centre of the Agrarian University collects all the garden waste (carbon source) generated at the university and compost it mixing it with the manure generated at the University farms. The mixing is done in similar weight proportions: 50 % carbon source and 50 % manure. This is the common proportion applied to compost manure because under this proportion is possible to reach the 20:1 - 30:1 carbon:nitrogen proportion. So, if we want to treat 250 kg of manure, we mix it with 250 kg of carbon source. To do windrow composting I suggest to use at least 250 kg of both materials combined  because with less volume there will be heat loss and composting will take an eternity.

Garden waste (carbon source)

Manure (nitrogen source)

A 500 kg composting pile

Temperature monitoring is suggested to see if composting is going all right. A soil thermometer is very cheap. 

As you may see in the figure above, the composting pile is placed in a concrete base. This is not necessary in small-scale. Large scale composting does require a concrete floor because of the leachate percolation which can contaminate the groundwater.

Water needs to be added frequently, perhaps once every two days during the first weeks. This varies depending on the moisture content of the organic material and weather conditions. There is not a specific water amount, but the important thing is to keep it humid. Many people complain that their composting pile does not reach enough temperature, this can be easily solved by adding more water or adding nitrogen-rich material like manure.

The first turning should be done at the day 15. The reason is very simple, if water has been added constantly and the composting pile has enough nitrogen-rich material, one can be sure that by this day the temperature has reached enough temperature to kill animal and vegetable pathogens (70 degrees for three days or 55 degrees for ten days). When you turn the composting pile you are aerating the organic material which is good because this is an aerobic process (requires oxygen). Because turning cools the composting pile, this should not be done constantly during the first two weeks (I even doubt you will even try it because 500 kg is very heavy to turn) or the pile will not reach the 70 degrees Celsius desired temperature. In the image below you can see the first turning, the material is well degraded by the second week.

The first turning is done at the day 15

The next turnings can be done every two or three weeks, and water does not need to be added so constantly because the compost is acquiring the capacity to retain water.  A mature compost can be obtained at the fourth month.

Just a final screening (optional) and the compost is ready to be added to the soil! Mature compost does not have smell, has a cool temperature, has a coffee colour and seeds are capable to germinate on it.