There is a need for tests and experiments to validate the efficacy of human excreta derived fertilisers, suggests a research by UK scientists

The potential use of human excreta as a fertiliser in agricultural fields is an incentive for people to collect and treat faecal sludge so it could be used to increase soil health. Prejudice and lack of knowledge, however, can stand in the way, according to a research.

Human excreta-derived fertiliser’s (HEDF) application in agriculture does not pose a risk of pathogens or heavy metals. Local regulations and perceptions, however, can be a problem, according to a group of scientists from School of Water, Energy and Environment, Cranfield University, UK.

Regulations in Kenya recognise sewage sludge as a valid input for organic fertilisers, but private standards have more weight in defining farmer practices. A clause in the Global Good Agricultural Practices, a set of international standards, reads, “No human sewage sludge can be used on accredited fields.”

While it doesn’t specify if it includes compost derived from human sewage sludge or not, vegetable exporters usually ban the use of HEDF on fields as a precautionary measure.

“This limited knowledge about HEDF and its effect on soil creates a major barrier to the commercialisation of HEDF and for recycling nutrients to soil in areas with large horticultural export sectors,” read the research.

Sub-Saharan Africa is working harder by the day to meet the Sustainable Development Goal for coverage of on-site sanitation facilities. This has made management of faecal sludge an issue all the low- and middle-income countries in the region want to solve.

“Human excreta have been shown to have a good fertilising potential, providing essential plant nutrients as well as organic matter contributing towards building soil structure and reducing erosion. With appropriate heat treatment, such as composting, all harmful pathogens in human excreta can be eliminated to produce fertilisers safe to use in agriculture,” read the research.

Use of bio-solids commonly faces prejudice, not by farmers but by customers and regulators. “Farmers generally do not have an issue with the origin of organic amendments if they have a positive effect on soil. However, customer and regulator perceptions of products derived from wastewater or human excreta are a common barrier to their commercialisation,” read the report.

There is a great need for additional tests and experiments to validate the efficacy of HEDF in agriculture, the study highlighted.

“The creation of a certification scheme would give more legitimacy to HEDF as a product and would help in lobbying for the inclusion of HEDF in regulations and standards. Several countries (like the UK, Sweden, Australia and the USA) created specific certification or assurance schemes to improve public perception of biosolids (HEDF),” it added.

The creation of a similar assurance or certification scheme specific to fertilisers made from source-separated human excreta would be a step into formalising them as a product, establishing production procedures, limits on contaminants content as well as testing protocols. Such certification scheme could increase the confidence of regulating bodies in HEDF and lead to its acceptance by global farming standards, highlighted the study.