urban metabolism slu lecture 13 -...

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Jakob Magid, Dept. Agriculture and Ecology

Urban Metabolism

Recycling, Risk Management and Ressource Allocation


Historical background

Future inclusion of food production in cities?

Waste recycling potentials and risks

Risk related to recycling and to growing urban food

Land and water associated with food production and waste disposal

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..Fifty years ago nearly all London had every house cleaned into a large cesspool …. Now sewers having been very much improved, scarcely any person thinks of making a cesspool, but it is carried of at once into the river. The Thames is now made a great cesspool instead of each person having one of his own..’.

Thomas Cubitt, 1840


'Death in the Cup'

A small girl in Hamburg drinkinginfected water during the 1892 epidemic; a few hours later the child was dead, This picture,fromthe Illustrated London News, reminds us of the fear the diseasestill caused.

(Illustrated London News, 1892)

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Justus von Liebig


In a letter to Sir Robert Peel, Prime Minister of the UK in 1840, Justus Liebig wrote: The cause of the exhaustion of the soil is sought in the customs and habits of the towns people, i.e., in the construction of water closets, which do not admit of a collection and preservation of the liquid and solid excrement. They do not return in Britain to the fields, but are carried by the rivers into the sea. The equilibrium in the fertility of the soil is destroyed by this incessant removal of phosphates and can only be restored by an equivalent supply. ...If it was possible to bring back to the fields of Scotland and England all those phosphates which have been carried to the sea in the last 50 years, the crops would increase to double the quantity of former years.

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When London's authorities decided to construct a sewage disposal rather than a recycling system, Liebig decided that it was necessary to find ways to replace the fertility removed by cities from farmland by artificial means.

He set about developing artificial fertilisers to keep the land feeding cities productive. Today, the use of artificial fertilisers is the norm all over the world.


The introduction of water-closets into most parts of England results in the loss annually of the materials capable of producing food for three and a half million people; the greater part of the enormous quantity of manure imported into England being regularly conveyed to the sea by the rivers. ..like a vampire it hangs upon the breast of Europe, and even the world; sucking its life-blood…..

Originally quoted from:Liebig von, J. (1855) Die Grundsatze der Agriculturchemie mit Rucksicht auf die in England angestellten Untersuchungen. Braunschweig.

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Copenhagen’s night soil solution


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Emerging solutionsBlue skies technologies

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Cities are metabolising and growing organisms in the global landscape.

A fundamental and simple prerequisite for sustainable development is that cities of the future must control their metabolisms to an extent where recycling of waste products is near complete.

In the industrialised world, waste management systems have originally been designed to ensure a high local hygienic standard and has been developed to maturity without primary concern for recycling.


Current Household Waste Production pr. person / yr

Total volume(including water for bathing and washing): 57 m3

of which is

Urine: 0.45 m3

Faeces: 0.06 m3

Organic household waste: 0.16 m3

Thus: 90-95 % of the nutrients, much of the organic matter and >99% of pathogens, is contained ca. 1% of the waste volume…..

The disposal of this waste is estimated at an annual cost of ca. 350 Euros pr. Danish citizen

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Present day distributionof Nitrogen

14 g mostly from urine and faeces delivered via wastewater to sewage treatment

1,7 g in solid waste (organic waste fromhousehold and garden)

N distribution afterincreased utilizationof urine and faeces

12 g utilised as fertiliserfor agricultural land

1,5 g delivered via waste water to sewage treatment

2,2 g in solid waste(organic waste fromhousehold and garden)to be recycled upon treatment (composting or bio-gas production)

3 gSludge

1 gSludge

0,5 g to the sea

0 g to air

8 gto air


Future waste management systems could be based on a separate handling of these fractions

avoiding the need to purify sewage effluent with regard to nutrient content

and returning the nutrients to land based production systems

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Future inclusion of food production in cities?

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Urban Agriculture Narratives

Crisis type:

Currently, we import food from all over the world and in some cases, the food generates its own weight in CO2 during its journey around the world - such as New Zealand gala apples

As industrial agriculture fails due to a scarcity of oil- and gas-based inputs, we will certainly have to grow more of our food closer to where we live, and do it on a smaller scale.

The reason why we need vertical farming is that horizontal farming is failing,

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Urban Agriculture Narratives: Canada/US/EU

Urban agriculture is an environmental and social movement acting on the critique of the industrialized food system, with the desire to reconnect to food and develop and implement sustainable and local alternatives.

The urban farming initiatives often build on a culture of community values by re-integrating the production / consumption cycle within the local community were the production is carried out in a social context by active members of the community.

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Roles of urban agriculture in Japan (MAFF):

Source of fresh and safe products, including organic and low-chemical crops, that are increasingly demanded by urban consumers, based on relationships of trust between farmers and city dwellers.

Opportunity for urban residents’ engagement in agricultural activities, both directly (e.g., allotment gardens) and through exchange between producers and consumers with the sales of agricultural products at local farm stands.

Open space for disaster management, including fire spread prevention, evacuation space for earthquakes and open space in case of other disasters.

Resource for recreation and well-being, including green space for personal leisure and spiritual comfort.

Education and awareness-raising for improving urban residents’ understanding of agriculture and food issues.

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Urban Agriculture

Food disconnect

Children with no understanding of where food comes from

Obesity - lifestyle

Food ‘deserts’

Human / Nature interrelationship

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Short break

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A pointer for estimation of nutrient

production on campus


A ballpark figure for prescence

on campus…

3500 students might spend 25 hours per week, 40 weeks per year (max) � appr. 400 person years

1500 employees would spend 40 hours per week 46 weeks per year � appr. 315 person years

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In current practise we could recycle solid waste

Magid,J., Eilersen,A.M., Wrisberg,S., Henze,M., 2006. Possibilities and barriers for recirculation of nutrients and organic matter from urban to rural areas: A technical theoretical framework applied to the medium-sized town Hillerod, Denmark. Ecological Engineering 28, 44-54.

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How ?

1kgN

Low – techLocal

Composting

High – techCentralised

Results in a loss of N

Degassing

Produces energy

0.6 kg N

Equivalent to0.2 kg NPK N

1.0 kg N


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How far does that take us?

10 g N per m2 equals100 kg N ha-1

Intensive vegetable production requires 200 kg N ha-1

High yield fruit and berry 100 kg N ha-1

One single person could fertilize 10 – 20 m2

with compost from household waste

0.6 kg N



System approaches

Storage-tank

Sludge truckSludge truck

Storage tank

Agricultural use

Recipient

Kitchen

Feces

Urine

Grey

Sewage plant

Sewage pipe

Biogas

Truck

Collection tank Sludge truck Storage tank

Storage tank

Agricultural use

Recipient

Kitchen

Urine

GreyFeces

Sewage plantSewage pipe

Organic wastebin

TruckTruck

Truck

Biogas

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What would be the potential problems in

applying a recycling strategy ?


Heavy metals and Xenobiotics in human urine (from grassroot– projects) compared to standard values for Danish sewage sludge and Municipal Solid Waste compost (1998).

Source Human urine

MSW Compost Sludge

Relative purity of HU

Substance --------- mg kg-1 N ------------- Cd 0.028 35 32.9 0.001 Cr 0.666 1118 929 0.001 Cu 19.2 5588 17857 0.001

DEHP 2.2 1176 857 0.002 Hg 0.214 12 31.4 0.018 Ni 1.98 1000 571 0.003

NPE 5.05 59 357 0.086 PAH 0.096 59 143 0.002 Zn 65.6 16471 7000 0.009

Risk factors

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Risk factorsFecal contamination and microbial die-off was studied for a 6-months period in tanks containing urine collected from urine separating toilet systems, including family-based and public separating toilets (urban ecology demonstration projects).

E. coliwas found only in a few samples in low numbers in the first month of study, whereas Salmonellaand Campylobacterspp. were not found in any sample. The initial concentrations of fecal enterococci varied, but were usually around 105-106/ml with a rapid reduction to below the detection limit (<10/ml) following 3 to 4 months of storage.

The protozoan parasites, Cryptosporidiaand Giardia, were found in a few samples.


Comparison analyses of pig and cattle slurry used for fertilization in agriculture showed in general much higher concentrations of bacterial indicators and parasites than found in urine.

Relative risk assessment – a level playing field

These initial results indicate that urine may be used as fertilizers in agriculture with little if any additional risks compared with animal slurry.

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Slide 33

Slide 34

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Slide 35

Microbial divertity, antibiotic resistance and horizontal gene transfer

Soil sampled right after fertilizer amendment:

Isolation of Pseudomonas from soil using selective media (NAA 1:100)

- NAA, NAA+Gentamycin, NAA+Tetracycline

Week

0 3 9

Slide 36

Antibiotic resistance in Pseudomonas

Abundance of Gentamicin-resistant Pseudomonas

Unfertilized Sludge Manure Compost

%

0

2

4

6

8

10

12

14

16Sept Oct Nov

Abundance of Tetracycline-resistant Pseudomonas

Unfertilized Sludge Manure Compost

%

0,0

0,2

0,4

0,6

0,8

1,0

1,2Sept Oct Nov

Average CFU g-1 soil (all treatments, all sampling times):

NAA 2.5*105

Gen 1.9*104

Tet 5.3*102

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Slide 37

Multiresistance in Pseudomonas

Multiresistance of Pseudomonas in general

Unfertilized Sludge Compost Manure

%

0

20

40

60

80

100

Sept Oct Nov

Multiresistance of Gentamycin-resistant Pseudomonas


%

0

20

40

60

80

100

Sept Oct Nov

Multiresistance of Teteracycline-resistant Pseudomonas


%

0

20

40

60

80

100

120Sept Oct Nov

Slide 38

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Slide 39

The chemical quality of sludge in Western countries has constantly improved and concentrations of potentially harmful and persistent organic compounds have decreased to near background levels.

There is an overwhelming body of evidence indicating that recycling of sewage sludge on farmland is not constrained by concentrations of organic contaminants found in contemporary sewage sludges.


Risks and controvercies – reductionist vs holistic assessment of urban agriculture

issues

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Jakob Magid – Institut for Jordbrug og Økologi

Faculty of Science

Report from the EPA

Denmark is a highly regulated society

Occasionally one would think that fear for environmental risks is disproportionately affecting the environmental legislation

Faculty of Science

Conclusions

The studied compounds were only to a very limited extent taken up by roots and transported to other parts of the plants, but could be transferred via direct contact with soil

The substances were found in the highest (very low) concentrations in root vegetables (potatoes and carrots) but could be almost completely removed by peeling

Since contact with soil and soil dust is not practically avoidable there might be a possibility for an unacceptably high exposure towards children for vegetables….

Growing fruit and berries may happen without contact with soil and soil dust – so this is not a problem…..

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Faculty of Science

Presently Urban Farmers in DK are constrained by the environmental regulations that are tied to soil polution – but is this the real problem?


Faculty of Science

The soil eater ……

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Faculty of Science

Soil polution

What about air polution?

Faculty of Science

0.6 - 2,57

A tentative relative risk assessment based on the EPA report

Additional cancer cases over 70 years (per 1,000,000 inhabitants) as a result of high intake of vegetables grown in

BaP-contaminated soil

Additional early deaths pr. ýårdue to. urban background airpollution i PM2,5

780

Additional annual hospitalizations due to cardiac and respiratory diseases caused by PM2,5 in urban air

ca. 1560

Annual: 0.009 - 0,036

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Faculty of Science

Is it dangerous to eat urban grown food?

What about food from the supermarkets?

Might active ingredients be transferred from the packing ?


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Slide 50

Conclusions on risk assessment

It is unlikely that urban grown food constitutes a threat to human health – rather the opposite

Occasionally reductionist environmental risks assessments are disproportionately affecting the environmental legislation

We need to work on a holistic assessment of the urban agriculture food system

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Potentials and Needs – how do we close the loop?

• How much land should we use for recycling?

• How much land do we need for food?

• How much water do we need for food?

Using the Person Equivalent (PE) –a simple robust bottom up approach


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How much water do we need for food?

Blue: surface and ground water

Green: rainwater

Grey: water to assimilate pollutants


PE water footprint

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Some facts and figuresThe production of one kilogram of beef requires 15000 litres of water (15 m3)

The water footprint of a 150-gram soy burger produced in the Netherlands is about 160 litres. A beef burger from the same country costs about 2000 litres.

The water footprint of Chinese consumption is about 1070 cubic meter per year per capita. About 10% of the Chinese water footprint falls outside China.

The water footprint of US citizens is 2840 cubic meter per year per capita. About 20% of this water footprint is external.


Heavy meat eater 4000 m2; Demitarian 2000 m2

Vegetarian: 1000 m2

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Putting it all together – a standard European PE

• Food derived land allocation 3000 m2

• Food derived water allocation 1500 m3

(equivalent to the rain falling on 1900 m2 in DK)

• Waste derived land allocation 250-350 m2


Going back to the earlier part of todays lecture …

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Is vertical farming the grand solution?

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Thank you for your attention ….

urban metabolism slu lecture 13 -...

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