Challenge

Anaerobic digestion transforms organic wastes into methane and fertilizer, which saves money while improving energy security, air quality, public sanitation, and crop yields. Unfortunately, in Uganda, 50% of digesters are abandoned within a year because farmers find the process unsustainable. Current designs require every kilogram of waste to be mixed with a kilogram of water for the system to function. Women and children must fetch more than 80 liters of freshwater a day to feed their digesters, wasting precious natural and labor resources.

Solution

Green Heat Uganda Ltd.’s innovative slurry-separation system greatly reduces water demand. The system creates an easily managed fertilizer product while increasing gas production. Utilizing a solar-powered sewage pump and innovative heating process, slurry is dewatered and converted into solid fertilizer that can be packaged, stored, or applied directly to the fields. Water by-products are separated during the process and re-used to mix with organic wastes later in the system. Green Heat Uganda increases the potential of success by enabling all farmers to enjoy the benefits of digesters, regardless of their water access.

A solar-powered submersible chop pump transfers slurry into a black bag that absorbs UV radiation. Heat is applied to kill pathogens and stimulate microbial activity to increase gas production. Solids are removed from the slurry using dewatering fabric, and can then be used or sold as fertilizer. The remaining liquid is mixed with wastes entering the digester, replacing freshwater. The system is eco- and gender-friendly, efficient, and a true cost-saver.

Photos

Slurry-Separation System – Green Heat Uganda