Our current global resource model is linear: it involves take-use-dispose. This can lead to waste and places little emphasis on making the most of our resources. With the consumption of global resources expected to rise because of a growing population, new ways of optimising our resources are needed to ensure we do not consume beyond what we have.
An economic model based on circular economy principles has been gaining traction. This approach promotes the continual and efficient use of resources through reduction, reuse and recycling. Circular economy models attempt to create a closed-loop system, minimising the use of resources and the creation of waste.
An example of this is the research at South African universities that has developed processes for turning human waste into fertiliser and biobricks. In Kenya and Uganda, faecal waste has been converted into charcoal briquettes.
In sanitation, the current take-use-dispose models are wasteful. We routinely use two modes of sanitation. In urban centres, we use flush toilets. This technology uses six litres to nine litres of drinkable water — of which there is a limited supply — to move our urine and faeces in sewers until it reaches a wastewater facility.
When the sewage arrives at a treatment facility, selected constituents in the wastewater are consumed by microorganisms. Eventually, these microorganisms grow to a point at which the tanks must be emptied. In South Africa, the majority of this “waste” ends up at land disposal sites.
Areas without sewage infrastructure use dry sanitation technology. Although this method saves water, the human waste becomes a thick, sticky paste called faecal sludge. This faecal sludge needs to be emptied and transported to a landfill.
Landfills can handle only a certain amount of sludge disposal and many can fill up fast if the balance is skewed towards disposal rather than degradation. In this context, circular economy principles are a sustainable option to manage human faecal waste.
The Water Research Commission in Pretoria is conducting research to examine if the resources contained in human faecal waste can be repurposed into products of economic value.
To understand the types of products that could be manufactured, we need to understand what is contained in our urine and faeces. Water makes up the largest fraction of both. Urine contains about 90% water. It also contains essential plant macronutrients (nitrogen, phosphorus and potassium) that are used in fertilisers. If urine can be separated from faeces, we can harvest and recycle these nutrients.
In comparison, about two-thirds of faeces is water. The remainder comprises solid material. Organic material makes up the highest fraction, followed by bacterial biomass, protein or nitrogenous matter, carbohydrate or any other non-nitrogenous undigested plant matter, and undigested lipids. These can be extracted and their properties changed through engineering processes to manufacture products of economic value. Below are of some of the innovations that have this capability.
Large volumes of urine can cause eutrophication of water bodies, which leads to oxygen depletion and subsequent adverse aquatic life effects. Several urine innovations have been demonstrated in South Africa that seek to repurpose urine. If urine can be separated from human waste streams, we can repurpose it and prevent downstream pollution challenges.
At the University of KwaZulu-Natal, Professor Ademola Olaniran has shown that it is possible to convert urine into struvite, a phosphate mineral that can used as a fertiliser. Olaniran’s research also looked at the health and safety implications of reusing urine-derived struvite for horticultural purposes.
At the University of Cape Town, Dr Dyllon Randall has been exploring the production of biobricks from urine. Randall’s research involved collecting urine from men’s urinals and feeding this to selected bacteria. The result was a gel-like substance, which can bind masonry sand together to form a biobrick. The research first aimed at illustrating this possibility; new research is aimed at optimising the processing of products and developing the business models to scale up production.
The capability to repurpose faeces has also been demonstrated. By turning faeces into products of economic value, there is an opportunity to generate additional revenue streams from products that would otherwise become waste.
Worldwide, many wastewater works are converting their plants into resource recovery facilities. The process used involves anaerobic digestion, which coverts the fermenting waste into biogas. This biogas can be scrubbed, cleaned and reused for heating or generating electricity.
More recent advancements involve producing renewable fuel options for vehicles that can cut diesel usage and greenhouse gas emissions. Several car manufacturers have noted the possibility: Toyota has developed a concept car that runs on fuel derived from faecal waste. The concept car has hydrogen fuel cells, which are fed with fuel derived from faecal waste.
In South Africa, BMW has been using a similar process at its factory in Bronkhorstspruit to supplement its electricity demand using cow faeces and other organic waste. This indicates that South Africa has the capability to undertake such engineering projects and there is potential to convert our wastewater treatment works into fuel-generation centres.
When there is potential for revenue, businesses will follow. In sub-Saharan Africa, large populations have no access to toilets. New social-driven business models havesprouted in Kenya and Uganda to provide toilets and collect the human faecal waste and convert it into economic products.
In Kenya, a social enterprise called Sanivation provides mobile toilets to households. The waste is collected twice a week and taken to a resource recovery facility, where the high temperatures in solar concentrators sterilise the waste. It is then processed further and turned into charcoal briquettes that are used as fuel.
In Uganda, Water for People has been using a similar approach to convert human sanitation waste into charcoal briquettes. As part of its business model, Water for People investigated the quality and market potential of the briquettes. They were compared to charcoal that is used to heat houses. The investigations found that sanitation-derived briquettes can deliver the same fuel value as charcoal.
Other processes involve the conversion of human faecal waste into protein feeds or commercial oils. Several of these concepts have demonstrated in South Africa by the Water Research Commission, but it has yet to sprout resource-recovery business models linked to service delivery as occurred in Kenya and Uganda.
Many of these concepts have been successfully demonstrated: the next stage is translating research into practice and developing the appropriate business tools for municipalities to use them as part of their operations. This will include canvassing users on their views of alternate fuels, determining their price-competitiveness, and ensuring the reliability of the products’ quantity and quality.
Dr Sudhir Pillay is a research manager at the Water Research Commission. He writes in his personal capacity