DARK CITIES.. >>> DARK CITIES
Kinkajou : An unusual term: “Dark Cities”
Erasmus :The concept of dark cities is not about building cities with no light. It is about building cities which have a minimal footprint on their environment. (Hence the term “dark”).Much of the development and planning of our cities has grown from the technologies we have had available to us in the past. These traditional plans for city development are not appropriate to the demands of our population and do not take advantage of our technological expertise.
Kinkajou : Let’s look at some old ideas of city development.
Erasmus :Well, for example in Australia, initially land blocks of a quarter acre were given to people to build a home. The concept was that people could grow their own vegetables to feed themselves on their own block of land. The problem with this concept is that not all soils are suitable for farming. Also not all environments are suitable for farming. If you are depending on your own crops and the rains do not come, there will be no crops. If you have stony or rocky ground with a poor coverage of soil or clayey soils, it may not be very suitable for agriculture. There will be few or no crops.
Broadacre farming on suitable soils such as extensive plains areas of sandy loam is far more productive and able to feed far more people for far less effort. It is an efficient way to produce food.
Nowadays, the concept of the quarter acre block is rapidly disappearing from our cities. Increasing numbers of people require homes. Our town planners are constantly working out ways to increase the population density in suburbia. This is to limit urban sprawl and to limit the impact of cities on our environment. In many countries especially those with larger populations such as India, most available space is already allocated or owned.
Kinkajou : So what impact do cities have in our environment?
Erasmus :A city is a phenomenon which is visible for many kilometres outside its boundaries. The light pollution generated by a city, lights up the night sky and washes away the stars.
Cities generate heat. One source of heat is the electrical energy incident to the city environment. Another source of heat arises from the utilisation of roofing materials. The roofs of buildings reflect solar energy. This creates a high intensity of reflected sunlight energy. Prior to the building of a city, the environment would have been covered in trees which soaked up the incident sunlight energy. So there is a substantial difference in the heat signature of a city versus the natural environment in terms of reflected or retained heat.
The issue is we neglect to consider is the impact of cities on regional climates. Cities are a regional phenomenon. They alter the weather and even the climate over many kilometres around them. I grew up in a “village type” city (Brisbane) with lots of space and lots of greenery. Time and the increase in the population have generated an increased density of housing, and a reduction in vegetation in the landscape. I remember that regular rainfall occurred across the city environment in which I lived.
However, I believe the city (Brisbane) has become much more arid as result of human development.
And this is where it gets complex. Arid environments (such as perhaps cities) have less cloud cover, allowing more heat / infrared to escape, in effect cooling the hot arid city. So we have inadvertently created some compensating changes, rather than single direction energy flows. Understanding what a city does to its environment and climate gets difficult.
Humans and their propensity for creating structures does make an impact on the weather across substantial regions. Not necessarily always in good ways. Yet this is not a consideration when we consider town planning and development. Understanding how a city makes an impact on its climate is not an issue that we even really worry about, except to hope that the wind blows the pollution away.
Kinkajou : Anything else?
Erasmus :Technology has grown to the point that allows us to process and use of “micro” resources in our environment. Take the example of water supplies. Water is generally supplied from public supply (large scale regional facilities), not as a micro supply (i.e. > backyard single property based collection and storage systems).
The average person living in a city uses 300 L to 400 L of water per day. In a city of 1 million people this represents a slab of water of 1 km² to a depth of 30 cm. In 100 days this represents a slab of water of 1 km² to a depth of 30 m. What we do with this water in an arid country such as Australia? Basically we pump it into the rivers and oceans and dump it. Water Recycling- Grey and Black
Kinkajou : Is this sustainable?
Erasmus :No! In Australia, we are rapidly approaching the limits of the water resources available from virgin catchment areas. Historically, water has been sourced from virgin catchment areas to limit human contamination. Pure water generates fewer diseases and generates better health and wellness for the population, (being free from human “germ” contamination).But as the population keeps rising, this collection process is rapidly becoming inadequate for demands.
Many years ago in Australia, city councils worked hard to remove backyard water storage tanks. And at the time this was a reasonable proposition. Backyard storage tanks silted up with roof debris, and were a haven for the growth of mosquito larvae. Because mosquitoes carry disease, by reducing backyard water storage tanks, mosquito borne disease were reduced across our cities.
However technology has changed. We now have the capacity to process water on- site from stormwater, better and more safely. But even this is handled poorly in cities such as Brisbane with little thought to the problems that develop.
The concept of using rainwater captured from suburban house roofs is a good one. However, problems do occur. The water is often not suitable for use in sewerage systems or even for washing clothes. For a short time after the water tank is installed, the water quality is good and can be used for many purposes. However eventually, the water coming from the bottom of the tank, begins to show increasing contamination. With time as the tank gathers debris, the water that emerges from the tank is increasingly contaminated with organics such as leaves or even soil type particles arising from dust present in the atmosphere. It becomes unsuitable for anything except watering the garden.
Rainwater Tanks - Recycling -Dark Cities
Often these tanks are installed in situations where gravity feed is the only output. The solution is to install an “on demand” water pump. However a pump requires power. So a water tank has substantial energy requirement even if it operates only at irregular intervals on demand. The pumps operate in a standby mode but this still uses electricity.
Water tanks are installed as stand-alone items. It makes more sense to install them in a “series” with a pump designed to move water between tanks through filters. This would guarantee the supply of water of suitable quality to use in housing systems such as sewerage or even laundry. This creates further technological demands. The operation of such a system becomes time intensive. It becomes obvious that microprocessor sensors need to be used to assess the status of the water storage. If this information is exported to a CPU unit, decisions can be made automatically to manage water quality and water storage, without human involvement. Filters will also need to be replaced or maintained at intervals, with these filters having low pressure flow characteristics and particle removal down to 1 µm. Ideally these filters can be cleaned and recycled. Also, the catchment tank will require periodic maintenance.
All these things are achievable with basic technology we have today. Strangely, we have not done so. During a period of drought in Australia, government did not invest in creating these types of systems. The solution was to tell everyone to install a water tank and to use them. Unfortunately the plumbers through hard experience learnt that the water quality was not adequate for the sewerage systems and tended to make the flush toilet tank parts stick and cease to operate. And when your laundry comes out full organic particles, you learn that the water is unsuitable for this application as well. Yet government promoted these uses with no appreciation of the problems inherent in this type of water supply. Even worse they generated no solutions to these problems, even though such solutions are well within our technological capacity and especially within the government’s financial capacity.
In the long term, maintenance becomes a “system” issue. Note the example of the backyard water tanks being removed years ago to reduce mosquito infestations. (It was also about making people buy water from the council, thereby increasing council profits). Now the council is running out of water, so it’s back to supply your own water.
Kinkajou : what about Blackwater?
Erasmus :Blackwater is highly contaminated water (full of faeces) arising from sewerage. It requires extensive processing for purification, to reduce bacterial colonisation, to reduce potential disease spread, and to make it safe to dispose of into the environment. In many Western countries, sewerage processing systems have progressed beyond merely dumping the sewerage into the ocean. Tertiary processing now occurs. This generates good quality effluent water, (essentially pure enough to drink potentially). It also generates minimal waste for landfill. The nutrient value of the waste also makes it suitable for a number of other applications, (albeit with safety concerns to be addressed).
I think sewerage processing is best left as system level task. Greywater (clean waste water from showers or laundry) is a very different proposition. Greywater probably can be processed quite safely on site with dedicated “septic type” systems specifically designed to handle it. Greywater creates a much lower sediment output, requiring much less maintenance than Blackwater processing systems such as typical septic systems.
Kinkajou : So what you propose to do with all this water?
Erasmus :The basic problem is as our cities grow the demands for clean water also grow. Water exits the average suburban backyard at different quality levels.
Whitewater (rainwater) is suitable with minimal processing to be used even for household applications such as laundry or sewerage flushing. Processed Greywater can be suitable for applications such as garden irrigation, with minimal extra processing. Blackwater is best handled in specialised facilities.
Current septic systems in areas without sewerage routinely handle all Blackwater and Greywater. These systems use the classical “septic” tank, perhaps today enhanced with powered aeration to speed up degradation. Sewerage enters a tank on site where it is essentially composted and the final fluid effluent then drains to “trenches” in the ground. So the sewerage is processed on site, and the water enters the ground adding to the ground water table.
All household waste water enters this system. (I.e. Blackwater AND Greywater). The problem comes if the ground is unable to hold huge quantities of water. The water then rises to the surface and saturates the ground. If each person in a family uses 200-300 litres of water daily, the average family could generate a cubic metre of waste water daily. That is a lot of water, day after day to feed into the landscape.
The inherent problem here is that our current planning systems do not allow for differential processing of wastewater. Greywater and Blackwater exits through the sewerage system. Whitewater exits through storm drains. None of this is used or recycled in most cities. Do we need a greywater collection and reprocessing system in our cities?
There needs to be a substantial cultural shift in how we plan our living environments to allow for more efficient utilisation of our water supplies. As population increases, their demand for resources especially water, increases as well.
Kinkajou : The average backyard does not use a cubic metre of water on the grounds / property daily. This quantity is substantially in excess to the amount of water required on site. Four people living in a single suburban residence would use 1.0 m³ of water per day (Perhaps up to 1.5 m³). This is far in excess of the requirements for on-site usage.
Suburban Backyard- Home
Kinkajou : So what you do with it?
Erasmus :An excellent point! Currently in most cities all this water is dumped, generally in rivers or into the ocean. There are a number of possibilities for using this huge supply of water generated from a city. Some options require in site processing, while others can have processing done at a “city” level.
- Reuse on site for laundry / sewerage system flushing
- One suggestion would be using reasonable quality water to recharge underground aquifers, though likely distant to the city locale. Very little attention is paid in Australia to the recharging of the great Artesian basin which supplies groundwater for many agricultural uses in inland Australia.
- Pump to drier areas inland
- Feedback into water storage, allow biological reprocessing and reuse for town water supplies.
This “dam” proposal is to rethink our usage of dams. Currently dams are built on specific locations on catchment areas were substantial amounts of water can be impounded and stored. In much of the world many of the sites suitable for dams have already been utilised. To develop more water storage we will often now be forced to use secondary catchments at increasing cost and a lower yield. Another proposal is to recycle this water by pumping it into storage dams. There are probably many locations suitable for siting as storage dams because they do not require a catchment area to feed them. Water is pumped to them utilising wastewater from the city.
Terminal processing of the water is done by biological systems introduced into the storage dam environment. While human processing of water can guarantee high quality water, I believe that biological processing can achieve very high quality results, at perhaps substantially lower costs. This type of system would of course require planning and the change in our culture with regards to usage of water. For example, primary secondary and tertiary dam systems would probably be a much more ideal system than single dams. By utilising multiple stages in biological water processing, water purity can probably be much more guaranteed.
The population keeps rising. We will need to stretch limited virgin resources to provide for more and more people while reducing the impact on the environment.
Kinkajou : How has the availability of the modern car affected our construction cities?
Cars On Road - Brisbane
Erasmus :Vehicles have changed the way we live our lives. Once upon a time people clustered close to facilities to reduce travel time and to reduce the difficulties inherent in carrying foods or goods to their homes. People would be unwilling to walk up large hills. Therefore people clustered closer to flat areas next to habitation facilities such as schools, hospitals, workplaces and shops. Today, the availability of modern car makes travel easy. People may be willing to travel for a further time and of course for much greater distances to perform tasks such as waste disposal, shopping and attending facilities such as schools and hospitals.
Vehicles generate pollution, have requirements for their maintenance and require supplies such as fuel. If we are to make our cities work as a population increases we need to make “public” travel more realistically acceptable as a viable alternative to the private car.
In many inner-city areas, the difficulty of parking and the availability of public transport along multiple corridors easily accessible as roads converge in the city centre, encourages public transport choices. However, as we reach into outer city suburbia, the density and availability of public transport decreases, the availability of space for usage such as parking increases, and travel time increases substantially, often due to traffic constraints impacting on travel speed.
I remember once making a bus trip to catch a ferry. In a private car, this trip is about 35 minutes. In a bus it took close to1 ½ hours, as the bus stopped to pick up and let off passengers and proceeded more slowly to its destination than the traffic around it. The service only ran every two hours, so if you missed the service alternatives are simply not available unless you have private transport. This type of service is not a viable option for transport. I think research has shown that there are considerable adverse consequences at a personal and at a social level of commutes over half an hour twice daily.
The private car has a substantial impact on the design and operation of cities. Often the road system does not operate sufficiently well to allow for efficient travel. To make our cities more sustainable, the private vehicle needs to operate as an accessory to the public transport system (which is capable of moving large volumes of people per unit of road space). Public transport is limited in its access to many areas due to the need to maintain volumes of traffic. Perhaps one answer is to supplement public transport such as trains and buses with accessory transportation systems such as minibuses to operate within a single suburban area. The bus or train gets you roughly to your location. The minibus drops you off next to your home.
Kinkajou : But how do you pay or it? Who will work there?
Erasmus :The average Western country has unemployment around 5%. There are plenty of people around with not much to do. People will pay for a service if it is cheaper than using their own cars and at least to close to as convenient as suing their own cars.
Kinkajou : Do you have any other issues with the construction of our cities?
Erasmus :Yes! I have already mentioned that cities create a heat signature which alters the weather and the climate around them the substantial distances. I think we need to rethink our construction of roads and our utilisation of roofs with a view to controlling what their effect is on our environment. I believe we have currently not considered computer modelling of microclimate regions such as around cities. It is only by understanding how the heat signature of city affects the weather or Regional climate that we can implement changes to improve our environment.
Another issue is our design of cities to be dependent upon heavy transport. We routinely truck food supplies into cities, often from remote locations. I believe in the long-term a city needs to have some inherent self-sustainability built into its structure.
- "Vertical farms" are a concept which improves the self-sustainability of our cities. Food production within our city areas is not an impossible concept. The development of hydroponics can substantially increase yields. Commercially however, city land is expensive. So the economic model under which we operate would preclude the development of the sorts of systems unless special planning considerations are made. Urban sprawl increasingly squeezes out farmland surrounding city areas. Perhaps such a concept can become a realistic possibility if our population rises to the point where we need to reduce the strain on our transportation systems, by developing local agricultural production facilities.
Vertical Farming trays
Imagine supplying / feeding a planet sized city like that seen Isaac Asimov’s Trantor (Foundation Series). There is no farmland. Transportation infrastructure is too precious to use simply to move things around. You now need to plan to reduce the impact / demand for transportation systems. There will never be enough roads, unless you plan to “not need” them.
Hober Mallow : Trader: expert in moving goods across the star systems.
- Photovoltaic and wind powered energy systems are another method of improving the self-sustainability of our cities. The trouble with photovoltaic energy systems is that they generate power while the sun is shining. However, much energy utilisation occurs in the evenings when people come home from work and it is dark. People cook in the evenings when there is often not much light. People utilise entertainment such as televisions in the evenings. People may do their washing in the evening.
I think in the long term improvement in battery design will allow the generation of electrical energy during the daytime, and allow it to be used at night. This will result in a substantial redistribution of the energy requirements of the city environment. However there are a number of problems with this initiative. Batteries are relatively expensive. Batteries have a limited life expectancy, (a limited number of charge recharge cycles), before they need to be replaced. The creation of batteries creates a need for a range of potentially toxic raw materials and creates a pollution problem when they need to be disposed.
The other important issue is that batteries need to be maintained. Different batteries have different maintenance requirements. For example, the optimization of a lead battery storage system is different from the lithium ion battery storage system and is different again from the protocol required for managing a nickel metal hydride battery storage system.
The solution here will probably require microprocessor controlled intelligence to optimize battery life. It is simply not achievable that every day when people come home they are required to take readings, pull switches and make decisions based on the rate of discharge of their batteries. Only microprocessors with sensors can make these decisions on a minute to minute basis to achieve optimal life for battery systems.
Again this is something well within our technological capabilities but currently something that we do not do very well, if at all.
SolarVoltaic Roof Power
I suppose one difficulty lies in that commercial companies require substantial research and development to create solutions to these problems. To make this sustainable, they require a return on investment. Only governments working on behalf of large groups of people are probably capable of initiating and sustaining the effort and subsidising the cost involved the development of the systems.
Unfortunately, governments have problems with making decisions. In the Western world, they do what they have to do to get by to the next election. This means they only make decisions that are critical to their survival, and are very short sighted.
We talk of government as a huge animal, but there are often very few decision-makers who have the capacity to undertake the types of decisions required. In the government, by definition, many people are followers and so do what they are told. The culture does not encourage innovation. The budgeting and financial process does not encourage the development of new solutions. The lack of experience in the commercial sector means that very few developments are licensed commercially.
So things that are well within our technological capabilities, often just don’t get done.
Windmill Power generator - Dark Cities
Kinkajou : I think our building designs fail to recognise that roof space is potentially usable and valuable space.
Erasmus :Yes. Roof spaces are capable of being used for power generation by either solar photovoltaic systems or even perhaps wind systems. Currently we just build them for shelter. In many larger city buildings, the roof space is an empty space perhaps populated by few air-conditioning systems. Planning systems need to consider what usage can be made of space to improve the efficiency of our cities and to reduce the footprint of human habitation on the environment.
Simply planning to put a few vegetables are rooftop is perhaps not a good idea. Water is a pervasive and damaging element the structures. When structures are built they need to be planned so that they can cope with water being used on rooftops or water being captured from rooftops.
Kinkajou : So what about recycling of household waste? We have general waste bins and recycling paper, cardboard, some plastics and glass.
Erasmus : Yes, but we need to process many other types of waste and to do a lot more primary processing.
Schoolchildren need to be taught about recycling. Systems need to be set up to recycle and to do so more efficiently. Systems need to be promoted or advertised and people need to be persuaded to use them.
- Currently we generate a lot of toxic waste from batteries.
- Many lubricants and oils are harmful to the environment. Most people are encouraged to dump them within the bounds of their properties. (Therefore not a problem to the local government until they face the problem of swathes of contaminated soil in the city scape). ("How could we have known that would happen?", I’m sure they’ll say.
- Metals can be recycled.
- Timber and general wood waste can be recycled. Treated timber is such as those containing CCA (copper, chrome and arsenic) need to be handled differently.
- Dangers material such as asbestos also require specialist handling.
The infrastructure to recycle these materials on the scale required essentially does not exist to the level of complexity needed to improve the commercial viability of the recycling process.
There are also social problems inherent in recycling. When does one put the recycling bins? Would you want to be the person outside the property where all the recycling bins are located? Do you want random people arriving next to your property to dump things in the bins outside your property?
House Rubbish Recycling Required
I would suggest we need to decide as a society how to undertake this task. One obvious solution is to use petrol or gasoline stations as depots for recycling. This may become a requirement for their zoning permission. As usual it is the social aspects of change which are the most difficult.
Kinkajou : So summarise the main issues in the “dark cities” concept.
Erasmus :City planning needs to consider processing of black water (sewage), processing of greywater (shower and laundry water),utilisation of Whitewater (rainwater), heat output generated by buildings and roads, generation of electrical energy to support human habitation, agricultural food production issues and recycling waste material.
Vehicles have changed the dynamic of human life. People are willing to travel further (distance) and across a variety of topographies to perform tasks such as waste disposal, shopping and attending facilities such as schools and hospitals.
City climate modelling should be an adjunct to the planning of every city.
Kinkajou : Do you think there are any consequences of a failure to plan for “dark cities”?
Erasmus : indeed! I believe humans are capable of solving many problems. However, implementing solutions takes time. If humans wait until a crisis emerges there may well be insufficient time to develop solutions and implement them.
One example in Australia was the drought which restricted water supplies to all the major cities on the eastern seaboard of the country. The Government proposed that people get water tanks to solve the crisis. Unfortunately, since there is a drought this does actually restrict one’s ability to cope with lack of water. How do you fill your new water tank? Land was resumed for the development of dams and further water storage. However, when the rains came, all this planning was abandoned. No further dams or water storage was developed. The land resumed at great expense to develop these facilities was sold off.
Kinkajou : Where do these fools come from?
Erasmus : I don’t know where they come from, but a lot of them end up in government.
Unfortunately, the population still continues to grow at an alarming rate of 25% (in Brisbane). If the crisis is not now it will be in our future. (A growth rate of 25% equates to the growth over 10 years. This means that roughly there is 2.5% annual increase in the population in a region. While this does not seem much, the demands this places in the provision of services is cumulative.
Fail to plan, plan to fail.