Waste not, want not: Investing the use of disposable nappies and black wattle biochar for land rehabilitation in the upper uMkhomazi River Catchment (Environmental Pollution programme)
Residents in communal lands in the upper uMkhomazi River Catchment, in the KwaZulu-Natal Province, South Africa, do not have access to waste collection services. This results in the rise of improper and indiscriminate waste disposal including disposable nappies thrown away from the homestead, often in water courses, posing potential health and environmental risks. Faecal matter in nappies can contain pathogens and potential toxins. However, they are also a source of nutrients – particularly nitrogen, phosphorus, and potassium – that can be used for agricultural purposes. Burying nappies can enhance soil water holding capacity (through superabsorbent polymers (SAPs) contained in disposable nappies) and improve soil nutrient supply. Therefore, they can help rehabilitate degraded and nutrient-poor soils.
In the upper uMkhomazi Catchment there are ~7,500 ha of abandoned cultivated lands which have become degraded due to erosion and bush encroachment by black wattle (Acacia mearnsii). Clearing these trees/bushes could improve the ecosystem health and converting the wood to biochar can provide a source of carbon to improve soil biological processes and restore degraded soils.
This project aims to assess the utility of simple, low cost, and culturally acceptable options for the use of disposable nappies and biochar from black wattle, both individually and in combination, as in-field soil amendment media in degraded and abandoned agricultural lands at selected sites in the upper uMkhomazi Catchment. The initial experiments included two species of fodder plants (Napier Fodder and Vetiver Grass) and will be monitored over a period of two years (i.e., two growing seasons under rainfed conditions) with measurements of biomass yield, sediment capture, soil biological indicators, soil fertility, soil chemistry, soil water, pollution, and pathogens.
This is the first year of a 3-year programme. Although too early to fully determine and measure the impacts, preliminary measurements suggest that treatments that included fertiliser show greater crop growth.
A hot, dry spell delayed the monitoring of the vetiver grass component of the trials for the first growing season. The team planted replacement tillers and provided temporary irrigation to assist with propagation. The dry spell is likely a consequence of climate change, and more frequent and erratic dry or wet climate events could be expected in the future.
Lessons learnt and next steps
Results from the first growing season show that this type of intervention yields positive outcomes. However, longer-term monitoring from multiple growing seasons will be needed to determine the full impact on the soil and plant growth and subsequent replicability.