By Gatonye Gathura
Food crops being grown with manure from biogas digesters and human urine have been found to contain unhealthy levels of the metal cadmium.
Researchers from the Nairobi based World Agroforestry Centre (ICRAF) and the Swedish University of Agricultural Sciences investigated how human urine and biogas digestate affect cadmium concentration in wheat grain.
The team in a report published last Friday in The Science of the Total Environment found that levels of cadmium in wheat grain grown with these additives to be higher than limits recommended by the World Health Organization and dangerous for human consumption.
The researchers found the digestate and urine-grown wheat to contain much more cadmium compared with crops grown with traditional farm manures and mineral fertilizers.
The authors warn that as the world moves towards what is being called Circular Economy, experts first ensure that the effects of applying complex materials to different types of agricultural land are fully understood and do not jeopardize food safety.
This development if confirmed could have serious implications in recent development agenda especially in poor countries where green technologies are a big buzz.
Human overdose of cadmium, a metal mainly used in batteries, can lead to kidney or lung damage, infertility or mental problems.
Kenya for example has been implementing a UN sponsored programme on popularizing biogas digesters whose waste is used as farm manure. Several schools in the country are also using human urine in agricultural projects.