urban metabolism? wow! it sounds interesting... what is it about? (I mean, what is "metabolism" referring to in the respective expression?)

It is an ecological term to describe the energy flows of an urban system based on the same concepts which are used to describe the metabolism of living organisms. I have read a lot of things on this subject, I saw a lot of different approaches but I feel that the theoretical concept of urban metabolism is quite subjective with a lot of speculations. Check the following paper

aha, so it is something like ”the rivers are the blood-vessels of the Earth”...

It's a concept originally from Karl Marx: "Marx used the concept of metabolism in Capital to describe the material exchanges and interdependent relationship between human society and nature" (see http://www.ucl.ac.uk/environment-institute/forthcoming-events/urbanlitreview)

Did you considered the Emergy Accounting? I know a paper about Emergy in Urban Farming, but it can be used in all the ecosystem.

I had a closer look to emergy and exergy concepts but there a lot of limitations to use them in cities. For agricultural and natural systems they look functional... but no for cities.

Check out the following article. It treats the city as if it is a super-organism and then characterises it by the relationship between its metabolism (i.e. city wide energy consumption patterns) in relation to temperature and concludes that the city behaves pretty much like an endothermic animals does: increasing energy metabolism below some lower critical temperature at which 'basal' energy metabolism is observed. They draw some interesting conclusions about strategies for energy use in a warming world.

Hill RW, Muhich TE, Humphries MM (2013) City-Scale Expansion of Human Thermoregulatory Costs. PLoS ONE 8(10): e76238.

here is the abstract from the article I just mentioned if you are interested

John

The physiological maintenance of a stable internal temperature by mammals and birds – the phenomenon termed homeothermy – is well known to be energetically expensive. The annual energy requirements of free-living mammals and birds are estimated to be 15–30 times higher than those of similar-size ectothermic vertebrates like lizards. Contemporary humans also use energy to accomplish thermoregulation. They are unique, however, in having shifted thermoregulatory control from the body to the occupied environment, with most people living in cities in dwellings that are temperature-regulated by furnaces and air conditioners powered by exogenous energy sources. The energetic implications of this strategy remain poorly defined. Here we comparatively quantify energy costs in cities, dwellings, and individual human bodies. Thermoregulation persists as a major driver of energy expenditure across these three scales, resulting in energy-versus-ambient-temperature relationships remarkably similar in shape. Incredibly, despite the many and diversified uses of network-delivered energy in modern societies, the energy requirements of six North American cities are as temperature-dependent as the energy requirements of isolated, individual homeotherms. However, the annual per-person energy cost of exogenously powered thermoregulation in cities and dwellings is 9–28 times higher than the cost of endogenous, metabolic thermoregulation of the human body. Shifting the locus of thermoregulatory control from the body to the dwelling achieves climate-independent thermal comfort. However, in an era of amplifying climate change driven by the carbon footprint of humanity, we must acknowledge the energetic extravagance of contemporary, city-scale thermoregulation, which prioritizes heat production over heat conservation.

Both West et al. (metabolic theory in ecology) and Bejan et al. (constructal law of nature and design) have done some amazing work in this field. If metabolic theory holds for cities, you should be able to measure any RATE in that city and that value will related directly to the SIZE of that city. Because these two variables are proportionally linked, you can derive rates from size or size from rates.

The mechanism for this relationship is deeply mechanistic and relates to the basic shapes that flow systems must take if they want to keep flowing (traffic, water, food, waste, contact with other people, etc). The scaling relationship between size and rate (usually in intervals of 1/4; most often 3/4) is at maximum efficiency. The variance around that relationship should be viewed as areas of inefficiency.

Experimentalists have historically tested these hypotheses using very large datasets at very large scales. As you move to smaller scales, it is harder to measure all the rates directly influencing an individual and, therefore, it's more difficult to properly relate size and rate. Much of the modern work in this field focuses on closing this gap between macro and micro.

Take-home message: With the current state of theory in this field, you are better off comparing multiple cities with each other rather than drawing trends from a single city. Accrue as many important rates as you can and see if they scale consistently with size. Have fun!

Myrna Hall and Steven Balogh have just undertaken this for the City of Syracuse NY in what I think is an excellent study. I suggest contacting Steven at [email protected]

here is the link,

http://www.sume.at/webfm_send/58

I will guess that most papers will discuss 'urban metabolism' in terms of growth, development and economics. If you want to get some ideas of that that have a different point of views that I mentioned before, I suggest that you look for authors who are not engineers or economists but toxicologists, sociologists and biologists. They will define and measure 'urban metabolism' performance according to their expertise. I also recommend to follow up on ancient history on growth and collapse of towns and cities to give yourself a good background on definition of 'urban metabolism'. For example, ask yourself why cities like ancient Rome or ancient Athens collapse.

If you are interested in Adam's last point I highly recommend Joseph Tainter's "The collapse of complex systems"

This is an intersting paper with a general view: http://iopscience.iop.org/1748-9326/8/3/035024/article

And an important contribution dealing with emergy was wrtitten by Ascione et al., 2011 http://onlinelibrary.wiley.com/doi/10.1002/cssc.201000214/full. Emergy approach in my opinion is an important contribution for a system approach to urban methabolism, taking into account the need of multicriterial model for all the complex systems (e.g. Giampietro, M., Mayumi , K. and Munda, G. 2006. Integrated assessment and energy analysis: Quality assurance in multi-criteria analysis of sustainability. Energy 31(1): 59-86)

So Vassilis, it looks like you have checked a bunch of literature already... could you be more specific in what exactly are you looking for? To avoid useless discussion and to find out to what extent can I provide you with some support, as I am working on similar subject. In the meantime, have you read this?:

Zhang, Y. (2013). Urban metabolism: a review of research methodologies. Environmental pollution (Barking, Essex : 1987), 178, 463–73. doi:10.1016/j.envpol.2013.03.052

You might also consider the political processes of urban metabolism. See, for example,

Heynen, N 2006, ‘Green urban political ecologies: toward a better understanding of inner-city environmental change’, Environment and Planning A, vol. 38, pp. 499-516.

My suggestions are define the boudary first, and then consider the role of technology and policy in regulating urban methbolisms. You can find the papers, 1.Gu Baojing, Jie Chang*, Ying Ge, Hanliang Ge, Chi Yuan, Changhui Peng, Hong Jiang. 2009, The Anthropogenic Modification of the Nitrogen Cycles within the Greater Hangzhou Area, China. Ecological Applications. 19: 974–988; 2. 24. Baojing Gu, Yimei Zhu, Jie Chang*, Changhui Peng, Dong Liu, Yong Min, Weidong Luo, Robert W Howarth, Ying Ge. 2011. The role of technology and policy in mitigating regional nitrogen pollution. Environ. Res. Lett. 6: 014011. You can download them and find the relevant papers in http://www.cls.zju.edu.cn/eae/English/

Hi, I worked on a literature review last year, about "territorial metabolism". here you can find it, hope you'll find something interesting in it: https://docs.google.com/file/d/0B_dtPx0S278hTUpkYmYzdzVvYmM/edit

It's written in French, I'm sorry, but you may find some interesting references in the reference list at the end...

Thank you, Martina, for sharing your study.

Many thanks to all of you for your interesting answers and links