From waste to water: how biorefineries combine water treatment with value recovery

The year 1980 represented an important tipping point for humankind. That has been estimated to be the last year in which our per capita consumption of Earth’s natural resources was in balance with nature’s ability to replenish them.

In other words, we are now using or degrading Earth’s natural capital at a rate far in excess of the rate at which it can be replenished. Chief amongst these resources is water. It is estimated that by 2030 global demand for water will outstrip supply by 40%.

Little wonder then that the possibility of applying bioprocess technology – the commercial application of biological processes, such as fermentation – to wastewater has gained so much attention in recent years.

“Considering water as part of the new bioeconomy is something that has emerged as an area of interest around the world over the past 15 years,” explains Professor Sue Harrison.

Harrison holds the South African Research Chair in Bioprocess Engineering and is also director of the Centre for Bioprocess Engineering Research (CeBER) at UCT’s Department of Chemical Engineering. According to her, South Africa is a good candidate market for such technology: “It is both a water-scarce region and home to some very water-intensive industries which produce large amounts of wastewater,” she says.

“While there are serious hurdles to be overcome, this technology is part of a wider move towards systems that can help us to recover and reuse the wastewater produced by many different kinds of industries while also creating valuable by-products.”

Between 2010 and 2016, a group of scientists housed in CeBER and drawn from a range of disciplines across the university investigated the viability of wastewater refineries in South Africa. Now, follow-up research, also conducted under the aegis of the Future Water Institute and the Water Research Commission (WRC), has corroborated the initial findings: wastewater biorefineries are a viable option for South Africa.

A third-generation process: wastewater biorefineries defined

Dr Bernelle Verster recently completed her PhD research in Bioprocessing Engineering at UCT. She defines a wastewater biorefinery as a process that takes raw materials and uses them to generate – sustainably – a spectrum of products, while minimising the production of waste.

“It combines the ideas of wastewater treatment with biorefinery,” she says, “Basically this means we take wastewater and send it through a number of bioprocesses, which allow us not only to recover water fit for use but also to recover products that are of sufficient value to make the process economically viable.”

A wastewater biorefinery these days uses many kinds of bioreactors to treat water. These might include algae, bacteria, larger water-based plants or even solids-based bioprocesses. The complexity of this third-generation process differs from earlier biorefinery approaches. First-generation biorefineries focused on converting a single raw material to a single product, such as biodiesel. Second-generation processes also used a single raw material but produced many different products. Wastewater biorefineries are third-generation processes that are not reliant on agricultural or biomass crops as feedstock. 

“This means that not only do wastewater biorefineries produce a number of different by-products but they are also capable of using diverse raw materials,” says Verster.

“Wastewater biorefinery technology can be applied equally to organic wastewaster, such as sewerage, and inorganic wastewater, such as that produced by mining.”

As project coordinator for CeBER, Shilpa Rumjeet coordinates the WRC pulp and paper wastewater biorefinery project. “This is a very water-intensive industry,” says Rumjeet. “Together with the petroleum industry, it accounts for almost 70% of wastewater in South Africa.”

“As an example, this kind of wastewater would undergo bacterial biotransformation, thermal processes and anaerobic digestion in order to recover water that can be recycled back into the process or used in another industry close by while generating products, such as lactic acid, polyhydroxyalkanoates (a biopolymer that can be used as a plastic) and energy in the form of biogas.”

Where things get murky: investment and infrastructure

According to Harrison there are several hurdles that need to be overcome if wastewater biorefineries are to gain traction in South Africa. “One of the most troubling aspects that has emerged in the follow-up project with the Water Research Commission is the lack of information available about wastewater in South Africa.”

Another issue is the legal framework governing wastewater in South Africa. Dr Cheri Young is a natural resources law specialist based in the UCT Law Faculty. She has collaborated with the Future Water Institute to investigate the legal parameters that govern wastewater in South Africa. According to Young, the management of waste, generally, and wastewater, specifically, is subject to detailed restrictions in South Africa. A waste management licence is required to undertake waste management and, in the context of extractive operations, for example, the Minister of Mineral Resources grants this licence.

“This is part of the government’s One Environmental System approach, where the Department of Mineral Resources allocates all licences for activities related to mineral and petroleum extraction, including the environmental authorisation and waste authorisation, save for the water licence,” she says.

According to Young, this approach has been criticised in that it places too much authority and discretion in the hands of the Department of Mineral Resources, as opposed to the Department of Environmental Affairs.

“The approach of the legal framework governing waste is largely consistent with the laws regulating the management of other natural resources. As such, similar issues are likely to plague the proper implementation of the legal framework in this context, such as failing to ensure compliance with legal obligations, as well as failing to ensure enforcement of penalties when there is non-compliance.

“This is a common criticism with regards to the shortcomings of the governance of the natural resources sector.”

Lastly, the capital investment required to create biorefineries at a useful scale must be considered carefully, especially in the context of South Africa where ageing water infrastructure is already under pressure. Harrison also points out that to make wastewater biorefineries economically viable, it is essential to focus on either high-volume, low-value products or high-value, low-volume products.

“But we must not forget that we would need to pay the cost of remediation anyway, in the absence of the wastewater biorefinery, so this must be offset in considering financial viability,” says Harrison.

Remediate, recover, reuse: water in the bioeconomy

Dr Jo Burgess is a research manager at the WRC who focuses on industrial water management and mine-water treatment and management. She believes that despite the difficulties, wastewater biorefineries remain a viable option in South Africa.

“South Africa is not unique in facing a demand – for all types of resources – that outstrips supply, and in facing rapid population growth,” she says. “The world is going to have to learn to do more with less.”

In Burgess’s view, South Africa has the advantage of being able to go straight to the 4th Industrial Revolution, in which new technologies fuse the physical and digital worlds, without repeating the negative aspects of other countries’ industrial journeys. “The biggest benefits will include a shorter path to renewable energy, an appetite for transforming waste into energy or useful products, an overall much smaller resource footprint, and a drive to minimise waste.”

Dr John Zvimba, a fellow research manager at the WRC agrees: “The biorefinery of wastewater has significant opportunities in South Africa, provided there is traction from the research community. There is a need to focus on either high-value products or low-cost technologies to improve chances of commercial uptake.”

In 10 years, will South Africa be using wastewater biorefineries across a variety of industries?

Harrison believes so. “We are already seeing industries processing and re-using their wastewater because it is more effective economically than sourcing additional water externally, and it often carries less risk. Wastewater disposal is also becoming increasingly costly and carries more legal ramifications.

“The mining sector is piloting ways to recover sulphur and trace metals through biological processes, as well as using treated wastewater from other sources as feedstock water. The pulp and paper industry body approached us to apply the initial wastewater biorefinery work to a more detailed case study using their wastewaters.

“Given this country's availability of biomass combined with the more labour-intensive nature of biological processes – as well as their ability both to produce value and to contribute to economic growth while contributing to environmental bioremediation – this approach carries much potential for South Africa and abroad.”