What Links Urban Metabolic Energy Flows and Urban Ecosystems – a literature review.

Eight energy and material flow characteristics of urban ecosystems (12 page pdf, Xuemei Bai, Ambio, Apr. 22, 2016)

Today we examine a review of current literature about two apparently conflicting urban concepts: one that is concerned with the material energy flows, the other with the ecology of wildlife and plants in a city environment. As cities become more complex and larger these concepts become more important in themselves, as well as between each other with intercity distributions and the regulation of processes across large urban areas and estimating the capacity of a city when to comes to the flow of materials, such as waste Approaching cities in this way also allows for a better defined environmental footprint, as demonstrated in one example in Barcelona, where a park designed for carbon sequestration was found after analysis to be one twelve the size needed to produce the desired absorption of carbon emissions from the city. The concluding words are worth noting: “A better understanding of the interactions between anthropogenic material and energy flows and ecosystem processes can help reduce unintended consequences of narrowly focused policy and management decisions.”

   

Key Quotes :

 « The concept of urban metabolism has been widely used to study energy and material flows into and out of cities… recent urban energy and material flow studies have extended far beyond the original metaphor of cities as organism, and started to reveal important characteristics of urban system features and interactions.. Urban energy and material flow efficiency can be defined as how much social/economic services per unit of resource consumption or waste generation can support. It shows how efficient the urban system is in supporting its function, and is an important system performance indicator.”

“The input part of the urban metabolism includes various tangible materials such as food, water, construction and other materials, products, energy, as well as inflow of energy, capital, information, and people. Such input supports societal activities and drives urban functions within a city; forms urban stocks such as housing, building, infrastructure, and green parks; and produces products and services, as well as managed and unmanaged waste and emissions.”

“The output part consists of industrial products, services, knowledge, and various wastes and emissions. The magnitude, distribution, and internal interactions and feedbacks are regulated by policy, governance, culture, and individual and collective behaviour of the urban system.”

 “Understanding biogeochemical budgets of ecosystems, in particular nutrients such as carbon, nitrogen, and phosphorus, has been one of the crucial elements of urban ecology” “The metabolic budget can be used to assess the total ecological footprints of cities”

 “The total budget and pathways of material and energy flows reveal the magnitude of impacts and other important characteristics of urban system, such as the functional role of the city, development stages (i.e., mature or growing city), level of infrastructure and development, income, and other socioeconomic characteristics of the city”

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How Does Global Climate Warming Look Locally?

Regional estimates of the transient climate response to cumulative CO2 emissions (Abstract, Martin Leduc, H. Damon Matthews & Ramón de Elía, Nature Climate Change, Jan.4, 016)

Also discussed here: Impact of human activity on local climate mapped (Science Daily, Jan. 20, 2016)

Today we review research that examines the projected climate warming using 12 model runs from cumulative carbon emissions from pre-industrial levels to four times those emissions on different regions of the world. Not unexpectedly, temperatures increase the most in polar regions (more than 5 deg C per trillion tons of emissions) than in low latitude areas and more over land (1.3 deg C) than over oceans (less than 1 deg C). The influence of ice albedo and ocean circulation caused warming that was linear than in land areas far from ice. This approach offers much in the assessment of future climate impacts on a regional or locals scale.



 

Key Quotes:

"a map that shows how the climate changes in response to cumulative carbon emissions around the world. They found that temperature increases in most parts of the world respond linearly to cumulative emissions…the results of simulations in which CO2 emissions caused the concentration of CO2 in the atmosphere to increase by 1 per cent each year until it reached four times the levels recorded prior to the Industrial Revolution. “

"Globally, the researchers saw an average temperature increase of 1.7 ±0.4°C per trillion tonnes of carbon in CO2 emissions”

"As these numbers show, equatorial regions warm the slowest, while the Arctic warms the fastest. Of course, this is what we've already seen happen -- rapid changes in the Arctic are outpacing the rest of the planet,"

"This provides a simple and powerful link between total global emissions of carbon dioxide and local climate warming. This approach can be used to show how much human emissions are to blame for local changes."

"To date, humans have emitted almost 600 billion tonnes of carbon. This means that land areas on average have already warmed by 1.3°C because of these emissions. At current emission rates, we will have emitted enough CO¬2 to warm land areas by 2°C within 3 decades."

 “high-latitude ocean regions deviate more strongly from linearity as compared to land and lower-latitude oceans. This suggests that ice-albedo and ocean circulation feedbacks are important contributors to the overall negative deviation from linearity of the global temperature response to high levels of cumulative emissions.”

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A Check List for Managing Urban Air Quality

Growing Public Health Concerns from Poor Urban Air Quality: Strategies for Sustainable Urban Living (9 page pdf, Bhaskar Kura, Suruchi Verma, Elena Ajdari, Amrita Iyer, Computational Water, Energy, and Environmental Engineering, Apr. 2013)

Today we review a paper that zeroes in on the issue of urban air pollution and its health impacts, identifying which pollutants cause the greatest harm and what to do about that in terms of identifying and controlling pollution sources. Given that a million premature deaths and another million pre-native deaths are linked to urban air pollution, along with 2-5% GDP costs for developed and developing countries respectively, much more attention is needed at the municipal level now.

   

Key Quotes:

 “more than 1 billion people are exposed to outdoor air pollution annually. Urban air pollution is linked to about 1 million premature deaths and 1 million pre-native deaths each year…is estimated to cost approximately 2% of GDP in developed countries and 5% in developing countries”

“ contribution of these transportation sources to the overall ambient concentration of that particular air pollutant:
• Carbon monoxide (CO) [70% to 90%]
• Hydrocarbons likemethane (CH4), gasoline (C8H18) and diesel vapors, benzene (C6H6), formaldehyde (CH2O), butadiene (C4H6) and acetaldehyde (CH3CHO). [50%]
• Oxides of nitrogen (NOx) - [45% to 50%]
• Greenhouse gases like carbon dioxide [30%] in developed countries and [15%] worldwide.
• Particulate matter ((PM10/PM2.5) - [25%]. In Europe, the average levels for PM10is approximately 40 μg/m3, and in Beijing the average level is 141 μg/m3.
 • Sulfur dioxide (SO2) - [5%]
• Lead– Lead is a toxic metal mainly used as an anti- knocking agent in gasoline (Lead tetraethyl - Pb(C2H5)4) and is also used in batteries (lead dioxide as an anode and lead as a cathode).
 • Odors- Diesel and gasoline engines are the major sources of odors”

“Conceptual urban air quality management approach:
 • Identify sources of air pollution in the immediate urban area..
• identify the specific pollutants that may be released in the air environment
• Conduct preliminary air quality monitoring to identify the concentration ranges for air pollutants.
. • Identify the best monitoring techniques, equipment, and resources needed to understand the short term and long term trends of these pollutants
 • Establish a permanent network of air quality monitoring stations to measure criteria pollutants…
• Develop a database of air pollutant emission quantities from various sources…
 • Evaluate the relationships between the emission quantities and the ambient concentrations under various meteorological conditions
 • Prioritize the sources of air pollution for regulating.
 • developing policies to control emissions and also to make changes in public behavior which may be responsible for poor air quality (traffic; open burning; fuel combustion; others)
 • Develop a decision support system to integrate the ambient air quality data to compute exposures and health risk probabilities..
• Use the data from the decision support system to assist the policy makers, scientists, and the public to achieve the required air quality management goals”

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Modelling Emissions from Stop-and-Start Traffic Congestion

A congestion sensitive approach to modelling road networks for air quality management (Abstract, James O'Brien; Anil Namdeo; Margaret Bell; Paul Goodman, Int. J. of Environment and Pollution, Dec. 2014)

Also discussed here: Stop-start driving in city centres creates higher pollution levels (Phys Org, Dec. 12, 2014)

And here: New regional traffic model to combat urban road congestion (Phys Org, Jan. 9, 2014)

And here: Verkeersvoorspellingen met modellen: een voorspelling over modellen (in Dutch language) (3 page pdf, Victor L. Knoop and Serge P. Hoogendoorn, Nationaal verkeerskundecongres, 6 Nov. 2013)

 Today we review research into improved modelling of emissions from congested traffic which takes into account instantaneous starts and stops instead of assuming a constant speed of vehicles. The results indicate that previous mobile transportation pollution models may underestimate emissions by as much as 60%.and this has large potential consequences for environmental impact assessments of large transportation projects, as well as for regulating or reducing emissions from currently congested cities.

 

 Key Quotes:

 “Traditional methods of modelling traffic pollution could be under-estimating emissions by as much as 60%”

“Previously, traffic emissions models have only looked at the average speed of traffic as a whole and assumed traffic was travelling at the same speed at the same time, ignoring the stop-start related vehicle emissions often associated with congestion.”

“The new technique, called PITHEM (Platform for Integrated Traffic, Health and Environmental Modelling), looks at congestion emissions based on individual vehicle type, its speed and acceleration and, crucially, takes into account meteorology and local terrain”

“Findings from microscale modelling have revealed that the use of an IEM [instantaneous emissions model ]to calculate emissions as an input for air quality dispersion modelling significantly improved the performance of the dispersion modelling when measured against monitored data. Findings from microscale modelling have revealed that the use of an IEM to calculate emissions as an input for air quality dispersion modelling significantly improved the performance of the dispersion modelling when measured against monitored data.”

"Whereas previous models looked at 'steady state' traffic conditions, in reality, during peak hours congestion vehicles often decelerate and accelerate and move at different speeds, especially when the road goes up or down hills.”

 "By gaining a better understanding of how road networks are influencing emissions, councils can make more effective decisions about how to deal with congestion in our city centres and help reduce the 50,000 premature deaths in the UK each year that are associated with traffic emissions."

 “The model currently only works with cars, but Knoop and his colleagues hope to be able to integrate pedestrians and cyclists into it in the future. He is also hoping to expand the tool in order to calculate emissions.”          

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Modelling Cities According to Isobenefits

Simulating future societies in Isobenefit Cities: Social isobenefit scenarios(16 page pdf, Luca D’Acci, Futures Journal, Sep. 25, 2013)

Today we review a paper about a model of various urban forms that are evaluated according to the benefits that each confers to its citizens. The forms include a traditional Central Business District form where the population and economy is highest in the centre and radiates outward to a second form where there are several sub centres or sub cities of activity to a third form where there is a ring city surrounding .The isolines of benefits (isobenefits) are based on formulae which estimate such things as benefits to pedestrians and cyclists (pedestrian and bike paths for example) and specific examples from cities around the world are tested. Results indicate the types of cities that could be designed as well as what might be done to existing cities to improve benefits. The optimum one seems to be a multi-centre city.  

Key Quotes :

“visionary examples of virtual future societies habitats:

• the Ring City (a city without the ‘city centre’, where the ‘city centre’ is all around the peripherical ring, or in a series of rings),
• the Homogeneous City (a city where the ‘city centre’ is everywhere), the Annulus City (a city without any geometrical centre in the city) and
• the Punctiform City (an interconnected net of urban hyperdense ‘points’ throughout nature, parks and lands)”

“When these influences are objectively negative (pollutions, stress, daily wasting of time for commuting, crime, low quality of life, segregations, urban sprawl or over density, obesity, etc.) and predictable, why not try to avoid them at their origin rather than wait decades and change them just after having continuously suffered their negative effects rather than before?”

“re-transition in some cases is in a forced way, by planning and laws even with strong opposition from the populations which still want to park and pass through the city centre by car; in some opposite cases it is the population who force planning and laws because they want pedestrian areas; in some other cases there is a mutual influence”

“In an isobenefit city there will be a uniform distribution of public transport, streets, and attractiveness, and the typology (parks, pedestrian areas, libraries, shops, etc.) and amount of the attractiveness (both Urban Centralities and Urban Fuzzy Quality) will (ideally) meet the preferences of citizens.”

“Models in modern economics are structured on decision-making-agents; in urban terms this means models which should value individuals who balance decisions.” “the isotropic approach shapes our urbs, which shape our civitas, which shape our urbs.”

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How Does Waste Heat from MegaCities Affect the Global Atmospheric Circulation?

Energy consumption and the unexplained winter warming over northern Asia and North America(5 Page pdf, Guang J. Zhang, Ming Cai and Aixue Hu, Nature Climate Change, Jan 27, 2013)

Also discussed here: Cities change temperatures for thousands of miles(UCAR ATMOS News, Jan. 27, 2013) And here: City heat affects temperatures 1,000 miles away(The Times of India, Jan. 28, 2013) Today we review global climate modeling research that examined the contribution of the waste heat produced by buildings and vehicle emissions in very large cities. Although this heat is small compared to the warming from greenhouse gasses in the atmosphere for the entire world, the model simulations reveal large changes in the regional circulation near these cities which may intensify local weather events such as droughts or extreme storms.  

Key Quotes:

 "The burning of fossil fuel not only emits greenhouse gases but also directly affects temperatures because of heat that escapes from sources like buildings and cars..The extra "waste heat" generated from buildings, cars, and other sources in major Northern Hemisphere urban areas causes winter warming across large areas of northern North American and northern Asia”

 “At the same time, the changes to atmospheric circulation caused by the waste heat cool areas of Europe by as much as 1 degree C (1.8 degrees F), with much of the temperature decrease occurring in the fall..Although much of this waste heat is concentrated in large cities, it can change atmospheric patterns in a way that raises or lowers temperatures across considerable distances,"

 "The world's most populated and energy-intensive metropolitan areas are along the east and west coasts of the North American and Eurasian continents, underneath the most prominent atmospheric circulation troughs and ridges,"

 “The world’s total energy consumption in 2006 was equivalent to a constant-use rate of 16 terawatts (1 terawatt, or TW, equals 1 trillion watts). Of that, an average rate of 6.7 TW was consumed in 86 metropolitan areas in the Northern Hemisphere.”

“ a doubling of CO2 can cause regional surface temperature changes of as much as 6 K, whereas land-cover changes due to deforestation .. can cause up to 2 K regional surface temperature change. In response to anthropogenic heating resulting from energy consumption, high-latitude regions of Eurasia can be warmed by as much as 1 K, and the northeastern US and the Canadian Prairies and Northwestern Territories can be warmed by up to 0.6 K"

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