The effects of climate change are being felt, first, on the fringes. The world’s hottest cities are most vulnerable to rising temperatures. The world’s driest cities are most vulnerable to decreasing rainfall. The world’s coastal cities are most vulnerable to rising sea levels. So when, in June this year, the mayors of 19 major cities around the world signed a commitment to cut greenhouse gases in their cities, it was partly through concern for the environment, but mostly through fear of a hotter, drier, sinking future.
The leaders of Tshwane and Johannesburg were joined by New York City, London, Copenhagen, Los Angeles, Montreal, Newburyport, Paris, Portland, San Francisco, San Jose, Santa Monica, Stockholm, Sydney, Tokyo, Toronto, Vancouver and Washington DC in committing to ensure that all new buildings in their cities operate at Net Zero Carbon by 2030.
By the World Green Building Council’s definition, a Net Zero Carbon building is one that is highly energy efficient and fully powered from on-site and/or off-site renewable energy sources. Similarly, achieving Net Zero Water means limiting the consumption of water and returning it back to the same watershed, so as not to deplete the resources of that region in quantity or quality over the course of the year.
Johannesburg and Tshwane would be particularly interested in both Net Zero Carbon and Water. Over the past decade, SA has faced electricity shortages and rolling blackouts, followed by a devastating drought. No region of the country has been spared, as terms like ‘load shedding’, ‘water harvesting’ and ‘day zero’ have dominated conversations around shebeen tables and braais, from eThekwini to Cape Town.
In 2017, the Green Building Council of South Africa (GBCSA) launched its push towards Net Zero by introducing a labelling system that recognises buildings that achieve Net Zero, either by completely neutralising (Net Zero) or by positively redressing (Net Positive) their environmental impacts under four categories: carbon, water, waste and ecology. Net Zero certification is awarded by the GBCSA over and above any Green Star certification a project may already have.
The first four projects to be certified under the GBCSA’s pilot programme were the Vodafone Site Solution Innovation Centre in Midrand, Gauteng (Net Zero Carbon and Ecology); Greenfields Industrial Park in Cape Town and Two Dam Sustainable in Montagu in the Western Cape (both Net Zero Carbon); and Estuaries Plaza in Century City, Cape Town (Net Zero Water).
As chief technical officer, Manfred Braune has headed up all technical-, education- and certification-related matters at the GBCSA since 2010. Commenting on Estuaries Plaza’s Net Zero Water rating, he says: ‘One of the big driving factors for that project was that they were targeting a Green Star rating, but they only started that consideration when the building was already designed and under construction. The professional team then had to look for opportunities to achieve that Green Star rating, and one of those was water.’
Braune explains that Estuaries Plaza was able to capture some water from the Century City canal system. ‘It’s treated sewage water from the City of Cape Town’s Potsdam [Wastewater Treatment Works]. So it’s not to a drinkable or potable standard, but it is at a level where it’s safe for irrigation,’ he says. ‘Estuaries captured some of that water, and treated their own grey- and blackwater on-site to achieve the required levels. So it worked out, because they had that extra supply. If they relied only on blackwater, greywater and rainwater, they might potentially not have achieved Net Zero because there just isn’t enough recyclable water generated within the building.’
Every building and every situation is unique though, so the solutions will differ from project to project. ‘A hospital is very different to an office building or a residential building, for example,’ says Braune. ‘Your ability to achieve Net Zero Water will depend on your building’s use, and on the opportunities for recycling and capturing water. Then, what space is available for storing that water? You can’t keep capturing water and not use it; otherwise you need massive storage facilities. And what capex does the organisation that owns the property have to spend? All of those factors will determine how easy or difficult it is to get to Net Zero. One has to model the water consumption, demand and production potential for a full year, then analyse that to see where the water can be used.’
The GBCSA’s standard has been structured to account for both Net Zero and Net Positive. ‘It’s definitely possible to achieve that with water,’ says Braune. ‘The challenge just becomes more technical on a project where you have got excess water. What do you do with it?
‘For the project to be Net Positive, that excess water would have to be used, rather than just being dumped into a stormwater system, where it’s lost. So then it’s a case of asking if that water could go to a neighbouring site, like perhaps a park, where it could serve the public.’
Braune cites a case of a gym that hoped to source excess water from a neighbouring site, only to encounter legal issues around metering and the sharing of water across site boundaries. ‘Similar issues that have come up in the energy industry over the past few years will now also be faced regarding water,’ he says. Here, Braune suggests, a case may be made for a general ‘water grid’.
It’s the same as with energy, he says. ‘There’s a real benefit in being connected to a grid, where you can share the responsibility. There will always be a time where you’re short or where someone else is short, so – speaking now from a water perspective – if you can share your surplus water onto a grid, others could benefit from that. You could also benefit from that grid when you need to draw from it.’
As with all environmental issues, the focus will, eventually, turn from individual buildings to entire cities. Going into the GBCSA’s 11th Green Building Convention in October 2018, the words delivered by Mark Swilling, distinguished professor of sustainable development in the School of Public Leadership at Stellenbosch University, spoken at the 2017 convention, echoed louder than ever.
In his view, he told delegates, ‘cities in Africa have an extraordinary opportunity to do things differently. We are still going through the big decisions on the types of urban systems required, and we can learn from cities in more developed countries. Are we going to emulate older outdated nodes, or are we going to anticipate and act? Are we going to say we don’t need private cars, we don’t need sprawl, we can do zero waste, we can do Net Zero multi-storey buildings?’.
It was a bold challenge, but a challenge that the GBCSA took up right away, with its Net Zero rating system – and a challenge that SA’s two biggest cities have since accepted in emphatic style. ‘There are cities around the world that are completely recycling their sewage water at a city level, and taking it to a drinkable level,’ says Braune. ‘There is huge potential for South Africa to do more of that – recycling water to a drinkable level – at a city and municipal level.’
Braune believes there is a strong argument for demand-side management, reducing, recycling and reusing water at each point of use. But he warns about the potential impact of reducing demand by too much.
‘The pipes, and the falls within the pipes, of a city’s water infrastructure will have been designed based on a certain flow rate and on certain consumption patterns,’ he says. ‘That’s why, with the recent water restrictions in Cape Town, some of the pipes were getting blocked. There just wasn’t enough water flowing through them.
‘So as a city, one really has to think about it very carefully. Whatever strategy is taken, one has to take the infrastructure into account. One might have to upgrade or change the slope of the piping, or maybe over time install vacuum systems so that you’re not getting blocked pipes.
‘Cities and municipalities will really have to understand the problem and develop a strategy on how they’re going to solve it.’