Biochar-Urine Nutrient Cycling for Health

In Bangladesh, around 35% of children under five suffer from chronic undernutrition which leads to compromised physical and cognitive development. The Bengali diet is dominated by rice with few fruit and vegetables. The limited dietary diversity leads to micronutrient deficiencies, particularly affecting pregnant women and young children. Mobility of women in Bangladesh is severely restricted and gardening close to the home can provide an opportunity for women to produce fresh and varied food for the family and to gain a small income. However, land for homestead gardening is limited given the high population density in Bangladesh and it is often not very fertile due to erosion and non-adapted garden management leading to the depletion of soil organic matter.

Commercial mineral fertilisers are not very suitable for eroded tropical soils as most soluble nutrients leach to the ground water resulting in low fertilising efficiency and ecological damage. Moreover, commercial mineral fertilizers constitute a substantial expense for poor farmers and their production is energy-intensive and contributes to climate change. If correctly prepared and applied, organic fertilizers are not only more environmentally friendly, they can be dosed much easier and they can be prepared almost for free on a household level.

Urine is known to be an excellent fertilizer with at least the same efficiency as commercial mineral nitrogen and potassium (NK) fertiliser but is underused because of the odour nuisance and associated socio-cultural barriers. The recycling of human urine of a 7-person household can yield around 10 kg of nitrogen and 10 kg of potassium per year, corresponding to 2 sacks of mineral NK fertilizer. 

The Ithaka Institute developed an innovative sustainable low-tech method to improve soil fertility by combining liquid organic nutrients (human or animal urine) and biomass (transformed into biochar) on a farm or household scale. Biochar is a very light and porous material that can soak up urine more than three times its own weight, and allows hygienic and odourless recovery of urine, transforming it into a solid fertilizer rich in N, K and micronutrients. This granular urine-biochar fertilizer can be applied directly to garden plants, without the toxicity of concentrated urine. It reduces leaching of nutrients while increasing soil organic matter content, biological activity and water-holding capacity through the micro-porous and highly adsorptive properties of the biochar. The biochar can be produced from crop and wood wastes, invasive shrubs and other biomass leftovers. 

The project aims to explore the feasibility of recycling organic household nutrients to improve the fertility and productivity of tropical garden soils using the novel urine-biochar technology within a Homestead Food Production project in rural Bangladesh. In nine villages, kilns will be built together with the farmers and urine recovery systems installed, while training local NGO field workers and assessing technical and social obstacles. Farmers will set up field trials in their own gardens to compare crop yields between the new urine-biochar fertilizer and usual practice.

When the new technology is adapted and accepted by the farmers, it can be scaled up to further villages in the area through the local NGO and to other areas of the country and beyond through other NGOs and government agencies, using the knowledge generated.