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In the previous modules you have seen that urbanization is a pervasive phenomenon in today’s world.

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This makes it all the more relevant to investigate
if urbanization as such is good or bad news

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for the environment,
and to investigate what role infrastructures

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can play in building eco-cities,
and in eco-transformation of existing cities.

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Let me briefly go back to the essence of a
city.

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Its physical expression is in the built environment:
homes,

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offices,
industrial facilities,

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and infrastructures.

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But a city is not only defined by its physical
dimension.

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It is also defined by its socio-economic dimension,
including for example labor market,

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jurisdictions,
commuting patterns,

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and by its cultural dimension,
which gives it a distinct identity.

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The city is a socio-technical system,
and given the many non-linearities in the

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interactions between citizens,
authorities,

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industries and other actors,
within and with the built environment,

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it is also a complex adaptive system.

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Previously I showed you how the Pearl River
Delta changed over the past decades.

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The NASA satellite images do not leave room
for any doubt that the natural environment

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was drastically changed as a result.

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Nature made way for buildings and pavements.

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Habitats have shrunk and been lost.

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Rural agriculture has been replaced by manufacturing
industries.

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Surface waters have been polluted,
and air quality has been affected by particulate

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and gaseous emissions from industry,
power plants and car traffic.

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Cities worldwide account for nearly 70% of
global CO2 emissions,

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they demand huge amounts of resources and
produce huge amounts of waste.

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Does all this imply that urbanization is bad
news for the environment by definition?

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The short answer is:
it is often so,

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but it is not inevitably so.

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Urbanization can be good news for the environment,
as cities can achieve higher levels of resource

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efficiency than can be accomplished in a sparsely
populated rural area.

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I already explained that cities do more with
less,

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in comparison with rural areas.

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And the bigger cities get,
the more productive and efficient they tend

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to become,
as found by Luis Bettencourt and Geoffrey West.

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When the size of a city doubles,
its material infrastructure—think of the

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total length of roads,
pipelines,

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or cables—does not.

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Instead these quantities rise more slowly
than population size:

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a city of eight million typically needs 15
percent less of the same infrastructure than

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do two cities of four million each.

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In terms of physical infrastructure needs,
cities show a sublinear scaling pattern:

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the bigger the city,
the more efficient its use of infrastructure,

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leading to important savings in materials,
energy and emissions.

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Besides Luis Bettencourt and Geoffrey West
at the Santa Fe institute,

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many other research groups in the world are
working on a better understanding of cities

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as complex systems,
and on visualizing the emerging structures

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and dynamics of cities.

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Let me briefly refer you to Michael Batty
and his co-workers at the Bartlett Centre

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for Advanced Spatial Analysis,
at University College London,

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or to the work of Juval Portugali,
at Tel Aviv University.

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Density is of course a factor that influences
how efficient a city can be.

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This can be illustrated from a comparison
between cities worldwide of per capita energy

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consumption for transport.

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As shown in this graph,
the densely populated megacities in Asia are

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far more efficient than the relatively thinly
populated American cities.

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In the list of 26 megacities that I showed
you previously,

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New York City is the one with the lowest population
density,

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whereas it is relatively densely populated
in comparison with other cities in the US.

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In a denser,
more compact city,

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people consume less energy resources for transportation,
as walking,

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cycling and public transport are viable alternatives
to commute for many of them.

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But in a less densely populated city,
however,

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where there is no viable business case for
public transport,

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people keep commuting in private cars,
thus using more energy,

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emitting car exhaust fumes and clogging the
city’s road system.

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According to Mark Roseland and Fiona Harvey,
eco-cities should be built according to the

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following principles:
• Has a well-planned city layout and public

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transportation system that makes the priority
methods of transportation as follows possible:

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walking first,
then cycling,

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and then public transportation.

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• Operates on a self-contained economy,
resources needed are found locally

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• Has completely carbon-neutral and renewable energy
production

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• Resource conservation—maximizing

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efficiency of water and energy resources,
constructing a waste management system that

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can recycle waste and reuse it,
creating a zero-waste system

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• Restores environmentally damaged urban areas

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• Ensures
decent and affordable housing for all socio-economic

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and ethnic groups and improve jobs opportunities
for disadvantaged groups,

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such as women,
minorities, and the disabled.

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• Supports local agriculture
and produce

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• Promotes voluntary simplicity in lifestyle choices,
decreasing material consumption,

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and increasing awareness of environmental
and sustainability issues

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But as we can see at a glance,
many of these criteria are not easily applicable

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to megacities.

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It is hard to imagine a megacity which is
completely self-sufficient in food,

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water and energy.

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In rural areas,
where people live in a relatively isolated

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fashion,
it may be possible to be self-sufficient.

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However,
the rural model of living off-grid,

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with solar panels on your roof,
cutting your own trees for firewood,

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pumping water from your own well,
disposing of your waste water in your own

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septic tank,
and burning your own waste,

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or leaving it in your backyard,
is not feasible in cities.

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It does not take much imagination to see what
would happen if city dwellers would to the

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same thing - the city would be unliveable.

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Only the solar panels would be applicable
in the city,

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but you will understand that the roof surface
area available in a dense city with many high

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rise buildings would probably not be enough
to provide electricity to all the people living

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under those roofs.

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Renewable energy needs space,
and space is a scarce,

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and therefore expensive commodity in cities.

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Densely populated megacities need to harvest
their renewable energy resources outside the

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city,
implying that wind parks,

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PV parks,
concentrated solar power plants and hydropower

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plants located at favourable locations,
often far from the city,

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must supply the city through the transmission
grid.

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Considering the current state of the art in
renewable energy technologies,

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it is hard to imagine a megacity that would
be self-sufficient in renewable energy.

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The good news is that the provision of water
and energy to urban residents and the removal

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of waste and waste water can be accomplished
with higher efficiency and with better quality

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of service than in rural areas,
as infrastructures can do the trick,

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building on economies of scale and scope.

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Let me give you an example:
AEB,

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the Amsterdam Waste and Energy company,
owned by the Amsterdam municipal authorities,

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annually processes 1.4 million tonnes of municipal
and commercial waste.

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In its waste to energy plant,
the waste is incinerated,

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producing 900 kWh of electricity and 91 kWh
of heat for district heating per tonne of

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waste processed.

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By separation processes before and after combustion,
ferrous and non-ferrous metals are separated

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and recycled.

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Per tonne of waste,
AEB produces 16 kg of iron,

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3 kg of other metals

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(e.g. copper and aluminium),
4.5 kg of gypsum (separated from the flue gas)

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and 209 kg of construction material (as
an alternative for gravel and sand).

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The company supplies steam to industries in
its vicinity (within a 5 km radius) and supplies

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lower temperature heat to 20,000 homes connected
to its district heating network.

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The ambition is to expand the district heating
network to 230,000 homes in 2040.

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The Amsterdam water utility,
Waternet,

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which produces drinking water for the city
of Amsterdam and treats its waste water,

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supplies the biogas produced from its wastewater
treatment plant to AEB for conversion into

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electricity and heat.

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At present,
due to improved efficiency in waste water

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processing and in the collection of organic
waste,

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the amount of biogas produced has increased
to the extent that Amsterdam is becoming a

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green gas producer.

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The biogas is upgraded to the Dutch natural
gas quality standard and sold as green gas

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in the market.

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The distribution of heat,
as steam or as hot water,

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is not economical over large distances.

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Therefore,
the denser the city,

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the more economically waste heat can be put
to use for residential heating.

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Whereas the Netherlands is just starting on
the path of using waste heat from cogeneration

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units,
thermal power plants,

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waste incineration plants and other industrial
sources for district heating,

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Denmark is a country with a long standing
tradition of district heating.

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Denmark is now using its district heating
systems to store energy during days of surplus

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wind power.

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For this purpose,
they use large immersion heaters to convert

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electricity to heat,
which allows the cogeneration plants to be

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shut down temporarily,
thus reducing fossil fuel use and reducing

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the overall carbon intensity of the Danish
energy system.

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In the surroundings of the city of Leeuwarden
in The Netherlands,

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which is situated in an area dominated by
dairy farms,

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biogas is harvested abundantly.

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The biogas is used to fuel co-generation plants
that supply electricity to the local distribution

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grid and heat to residential districts.

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The province is the first in the Netherlands
where a biogas infrastructure is being developed,

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enabling a multitude of farms which produce
biogas from manure fermentation to feed their

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biogas into the pipeline system and transport
it to a central plant,

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where the biogas is upgraded to green gas.

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The green gas is either fed into the natural
gas distribution grid,

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but it is also used as a car fuel.

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The Danish city of Sonderborg,
with approx.

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76,000 inhabitants,
is one of the cities in Europe that) made

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an explicit decision to shift to a zero carbon
green economy.

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Sonderborg’s objective is to become carbon
neutral by 2029.

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To this end,
the municipality and district heating suppliers

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established a partnership,
with citizen participation.

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Among the actions already under way are:
• replacement of natural gas in district

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heating with geothermal,
solar,

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biomass etc.;
• a new pipeline connecting all existing

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district heating networks;
• generating biogas from pig manure,

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organic waste and energy crops;
• generating power from biogas,

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wind and photovoltaic;
• installing photovoltaic cells and heat

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pumps in rural areas.

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However,
in the words of Andris Piebalgs,

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former European Commissioner for Energy:
“The cheapest,

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most competitive,
cleanest,

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and most secure form of energy for the European
Union thus remains saved energy.” Especially

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in the built environment,
there is tremendous potential for energy saving,

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by designing homes for better use of natural
light,

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natural ventilation rather than air conditioning
systems,

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and for better heat (or cold) retention.

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The latter is a matter of building quality,
and standards such as LEED and BREEAM are

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in place to ensure energy saving,
both at the level of individual buildings

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and at the level of neighborhoods,
districts and cities.

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In the existing building stock,
much can be improved with thermal insulation,

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more efficient heating/cooling systems,
and low-energy glazing.