10 Homebuilt Tech Tools for the Developing World


Compost Bin

This wire and metal compost bin is a variation on the wire-mesh design we describe. Go for whichever one works for you.
This wire and metal compost bin is a variation on the wire-mesh design we describe. Go for whichever one works for you.

Like rainwater harvesting, composting has been popular on small farms for centuries. The process involves converting organic debris -- vegetation, food scraps and manure -- into a rich, all-natural fertilizer. Farmers use high-quality compost because it enables soil to hold more water and provides nutrients to crops, eliminating the need for synthetic fertilizers. This in turn increases the productivity of their land and leads to higher profits. It also reduces the amount of solid waste entering processing facilities and landfills.

Biological decay occurs whether you want it to or not, but the idea behind composting is to make the process happen more rapidly. One technique, known as heap composting, doesn't require a structure. You simply throw organic material into a pile, about 3 feet (1 meter) high and 3 feet wide, and then turn the material regularly using a pitchfork. You can increase the efficiency of composting, however, if you use a compost bin -- a structure to hold and concentrate organic debris and to provide a suitable home for the organisms that make the decay possible. The easiest structure to make is a wire-mesh holding unit, which requires a 10-foot (3-meter) length of 36-inch (91-centimeter) wide galvanized chicken wire, heavy wire for ties and three or four wooden posts. You simply form the length of chicken wire into a cylinder, connect the ends together with wire and then attach the whole thing to posts driven in the ground.

Bins that can rotate work even better because they mix the organic material more thoroughly and speed up the decaying process. It's possible to build a horizontally mounted rotating barrel, but it requires a significant input of time and energy. Another solution is to buy a food-grade plastic barrel, with a removable lid, and then drill a series of holes across the entire surface. After filling the barrel with organic material, you simply lay it on its side and roll it regularly over a level surface. Using this method, a large volume of yard waste can be composted in three weeks to six months.