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A network-based model of the carbon footprint of the Internet is presented and used to determine the carbon abatement provided by Internet-based telecommuting and teleconferencing services to replace car and air travel. The model includes DSL, FTTN and PON access technologies, edge and core network architectures and is based upon currently commercially available equipment. We show that carbon emissions of the Internet need to be taken into consideration in order to obtain an accurate estimate of carbon abatement provided by the Internet.
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CARBON FOOTPRINT OF THE INTERNET
Jayant Baliga, The University of Melbourne
Kerry Hinton, The University of Melbourne
Robert Ayre, The University of Melbourne
Rodney S Tucker, The University of Melbourne
A network-based model of the carbon footprint of the Internet is presented and used to determine the
carbon abatement provided by Internet-based telecommuting and teleconferencing services to replace car
and air travel. The model includes DSL, FTTN and PON access technologies, edge and core network archi-
tectures and is based upon currently commercially available equipment. We show that carbon emissions
of the Internet need to be taken into consideration in order to obtain an accurate estimate of carbon
abatement provided by the Internet.
INTRODUCTION
For a number of years, it has been suggested that broadband telecommunications may be able
to reduce the need for business travel, through the use of telecommuting and teleconferencing
(Telecom Australia 1975; Nairn 2007; Mallon et al. 2007; Webb et al. 2008). In the past, the
claimed benefits have focused on savings in travel time, cost and fuel. More recently the relation
between the energy and greenhouse emission cost of travel has renewed impetus to studies of
telecommunications as an alternative to travel. A reduction in business travel would reduce
greenhouse gas emissions (Nairn 2007). However, the capacity of the Internet would need to be
significantly increased to support good quality video conferencing. If Internet capacity is increased,
the energy consumption, and consequently the greenhouse footprint of the Internet will also in-
crease (Baliga et al. 2007). The authors are not aware of any models that provide a quantitative
measure of the increased greenhouse gas emissions from the Internet if it is to support a significant
reduction in business travel.
In this paper, we present a network-based model of the energy consumption of the Internet,
formulated with data from major equipment vendors (Baliga et al. 2007; 2008a; 2008b). We
model the network infrastructure required to service increasing per-subscriber traffic volumes,
including core, metro, and access networks, and take into account energy consumption in
switching and transmission equipment (Baliga et al. 2007). In the access network, we consider
currently used digital subscriber line (DSL) as well as two future high-speed access technologies
– shared passive optical networks (PON) and fibre to the node (FTTN) (Baliga et al. 2008a).
Using this model we estimate the current annual energy consumption of the Internet in Australia
to be about 75 kWh per subscriber, equivalent to 81 kg of CO2-e, at average access rates in the
order of 500 Kbit/s. The model is then used to estimate the increase in energy consumption re-
quired to support increased access rates that would allow standard definition (SD) and high
definition (HD) video-conferencing. The estimations of increased energy, and resultant greenhouse
gas emissions, are compared against savings from telecommuting and teleconferencing.
BROADBAND FOR THE SUSTAINABLE ENVIRONMENT
TELECOMMUNICATIONS JOURNAL OF AUSTRALIA, VOLUME 59, NUMBER 1, 2009 MONASH UNIVERSITY EPRESS 05.1
NETWORK MODEL
A basic IP network, as used by Internet Service Providers (ISPs), can be logically split into three
main layers – the access network, the metropolitan and edge network and the network core, as
shown in Figure 1. In this section, we outline the technologies commonly used in higher capacity
IP-based networks and develop a model for energy consumption of the network. We model each
of the access technologies using specifications of representative commercial equipment, together
with corresponding metropolitan and core network components to estimate the energy consumed
by the entire network.
Figure 1 Schematic of network structure showing the core, metro and access networks.
Our calculations include the energy required to maintain redundant routers and fibre links
for availability, but do not include the energy consumption of data centres or home networks.
We have deliberately modelled a minimalist network, assuming a national-scale operator deliv-
ering a service, and have not included the inter-network gateways used when multiple service
providers share network facilities. In addition, it must be noted that any future network will
need to incorporate a large amount of legacy network equipment, such as IP over ATM over
SDH over WDM. Such overlays in legacy networks often result in large inefficiencies because of
the need for electronic processing to interface between the network layers. This paper therefore
provides a conservative (i.e. under) estimate on the energy consumption of the Internet. To cal-
culate cooling requirements, we assume that for every watt of power consumed in metro and
core networks, another watt of power is required for cooling (Koomey et al. 2004).
ACCESS NETWORK
The access network connects each home to one of the edge nodes in the provider's network.
There are several different technologies in use today, and new technologies are being developed
(Chanclou et al. 2006). We consider three technologies: asynchronous digital subscriber line
(ADSL), passive shared optical networks (PON) and fibre-to-the-node (FTTN). Shown in Figure
2 are the three access technologies that connect homes, which are on the right, to the Ethernet
switch in the edge node, which is shown on the left. Access technologies differ in the means by
which each home is connected to the edge node. In the following we describe the access techno-
logies, and the equipment they use, in greater detail.
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT
05.2
Figure 2 PON, FTTN and ADSL access networks.
The most common technology in use today is ADSL, shown at the bottom of Figure 2. In
ADSL, copper pairs, originally installed to deliver a fixed-line telephone service, are used to also
deliver a broadband service (Chanclou et al. 2006). The telephone service, which uses the band-
width below 3.4 kHz, is left in place and the higher frequency bandwidth is used for high-speed
broadband services. A modem in each home connects to a digital subscriber line access multiplexer
(DSLAM) at the local exchange.
Copper pair-based access technologies, such as ADSL, are limited by usable bandwidth and
reach, so many ISPs have begun installing fibre-based technologies. Fibre to the premises install-
ation most commonly takes the form of a passive shared optical network (PON), which is shown
at the top of Figure 2. In a PON, a single fibre from the network node feeds one or more clusters
of subscribers through a passive splitter (Chanclou et al. 2006). An access concentrator or Optical
Line Terminal (OLT) is located at the local exchange, and serves a number of access modems or
Optical Network Units (ONUs) located at each of the subscribers' premises. Each subscriber
ONU in a cluster connects via a fibre to the splitter, and from there shares the same fibre connec-
tion to the OLT. ONUs communicate with the OLT in a time multiplexed order, with the OLT
assigning time units to each ONU based on its relative demand.
In areas where subscribers are already served by good-quality copper pairs, a hybrid fibre-
to-the-node (FTTN) technology may be used (Chanclou et al. 2006), shown in Figure 2. Dedicated
fibre is provided from a network switch to a street cabinet close to a cluster of subscribers, and
high-speed copper pair cable technologies used for the final feed to the subscriber premises
(Chanclou et al. 2006). A common copper-based access technology used with FTTN is very high
speed digital subscriber line (VDSL). The street cabinet houses a VDSL DSLAM, which connects
to the VDSL modem at each subscriber premises. The street cabinet also houses one or more
ONUs which connect via fibre to the OLT at the local exchange.
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT 05.3
On the network side, each of the access technologies connects to the metro network through
an Ethernet switch. Table 1 lists equipment used in our model for each of the access technologies
as well as the power consumption and capacity of the equipment.
Table 1 Equipment used in access network models (Baliga et al. 2008a).
OVERSUBSCRIPTION
In general, the transmission and routing capacity provided upstream of the access network is
significantly smaller than the product of the number of subscribers and their maximum access
rates. Much Internet and data traffic is of a bursty nature, with subscribers loading a web page
or block of data via the network, and then generating no further traffic for a period of time whilst
reading or processing this data. Network operators take advantage of this high peak-to-average
traffic ratio and share capacity among subscribers through oversubscription. However, as IP
networks are increasingly used for large file transfers and for streaming services such as IP video,
conferencing, and IP telephony, the traffic demand is both much greater and relatively more
constant. This means there is significantly less scope to employ oversubscription.
In our model we use an oversubscription level of 10. For an access rate of 512 Kbit/s per
subscriber, an oversubscription level of 10 corresponds to 51.2 Kbit/s of capacity per subscriber
in the metro, edge and core networks. We define the access rate as the access rate advertised/sold
to the subscriber. Although we set the oversubscription level to 10, we note that this does not
predetermine the results, as the important parameter is the per-subscriber capacity in the network.
The oversubscription level simply translates the capacity an ISP installs to the access rate it sells
to subscribers.
METRO AND EDGE NETWORKS
The metro network aggregates/concentrates the highly fluctuating traffic from the end subscribers
and serves as the interface between the access network and the core network. Typically within
this part of the network, specialised routers control access to different services within the network,
control access rates, provide authentication and security services, and compile statistics for billing.
Edge routers or switches concentrate traffic from a large number of access nodes, and may home
to more than one core router to improve network availability. Figure 3 illustrates key elements
of the metro, edge and core networks used in our model. On the left side of Figure 3 are the
routers and switches used in the metro and edge networks. Table 2 lists equipment used in the
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT
05.4
metro and edge networks as well as the power consumption and capacity of the equipment. In
the following we describe the equipment used in greater detail.
Figure 3 Metro, Edge and Core networks.
In our model, the aggregation is performed by a Cisco Catalyst 6513 switch, which is a large
Ethernet switch. A Cisco Catalyst 6513 switch has 384 Gigabit Ethernet ports, a switching capacity
of 720 Gbit/s and consumes 3.21 kW. The Ethernet switches uplink to Border Network Gateway
(BNG) routers. The BNG routers perform authentication and access control and we use the Cisco
10008 router as our BNG router. The Cisco 10008 gateway router consumes 1.1 kW and has a
full-duplex capacity to support 8 Gbit/s. Finally, a provider edge router connects to the network
core. Provider edge routers groom and encapsulate the IP packets into a SONET/SDH format
for transmission to the network core. As we are modelling a high growth and high capacity
scenario, we use the large Cisco 12816 as a provider edge router. This device is typical of large
routers available from other manufacturers. A Cisco 12816 router consumes 4.21 kW and in
the configuration used in our model has a full-duplex capacity of 160 Gbit/s. In our model the
provider edge routers connect to the core routers by 10 Gbit/s PoS or SDH links. It is possible
that in some situations the provider edge routers interconnect directly. However, in our model
we assume that all routing is handled by the core routers.
CORE NETWORK
The core network usually comprises a small number of large interconnected routers located in
each major city. An example is the Cisco CRS-1 core router. The Cisco CRS-1 is shown on the
right side of Figure 3. These core routers perform all the necessary routing (packet switching)
and also serve as the gateway to neighbouring core nodes. High capacity Wavelength Division
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT 05.5
Multiplexed (WDM) fibre links interconnect these routers and connect to networks of other
operators. Typically these WDM links comprise 10 Gbit/s Packet over SONET (PoS), SDH, or
10 Gbit/s Ethernet. For long-haul links many use 40 Gbit/s PoS or SDH. In our model we assume
core routers are interconnected by 40 Gbit/s PoS or SDH links. A single-rack Cisco CRS-1 core
router consumes approximately 10.9 kW and has a full-duplex switching capacity of 640 Gbit/s.
In today's Internet, packets traverse an average of 12 to 14 routers between source and des-
tination (Mieghem 2006). Most Internet traffic is from the subscriber premises to a web server,
which is often within a few hops of the network core. In our model, subscriber traffic must traverse
three routers to reach the network core so we assume an average of 10 core routers, giving us
an average of 13 routers in total.
WAVELENGTH DIVISION MULTIPLEXED SYSTEMS
The optical data output from the edge and core routers can only be transmitted relatively short
distances and are generally not suitable for wavelength-division multiplexing into a single fibre.
For this reason wavelength division multiplexed (WDM) transport systems are required for the
long-range communications between the edge and core routers as well as between core routers.
In our model we assume the edge routers are within 200 km of the core node. The WDM
terminal systems connecting the edge nodes to the core node consume 811 W for every 176
channels. If the distance between the two terminal systems is greater than 100 km an intermediate
line amplifier (ILA) is required and consumes 622 W for every 176 channels. In this model the
core nodes are assumed to be an average of 1,500 km apart and so 14 ILAs and 2 terminal systems
are required for every 176 channels.
Table 2 Equipment used in models of metro, edge and core networks (Baliga et al. 2008b).
CARBON EMISSIONS FROM ELECTRICITY AND TRAVEL
In this section we summarise the carbon emissions resulting from electricity consumption, car
travel and air travel. In this paper, the term “carbon emissions” refers to carbon equivalent
(CO2-e) emissions. Carbon equivalent emissions include CO2emissions as well as the global
warming effect of other gases released, such as CH4and N2O (Department of Climate Change
2008).
ELECTRICITY
In recent years there has been a major push toward the production of electricity from renewable
energy sources. However, in the medium term future, the majority of electricity in Australia will
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT
05.6
continue to be generated using brown and black coal, which produces a high level of carbon
emissions (Energy Supply Association of Australia 2008; Department of Climate Change 2008).
The rate of carbon emission per kWh varies across the Australian states because of the different
fuels used, and ranges from 1.31 kg CO2-e/kWh in Victoria to 0.98 kg CO2-e/kWh in Western
Australia and Queensland (Department of Climate Change 2008). In this paper, we assume an
emission rate of 1.08 kg CO2-e/kWh, which is very close to the figure for New South Wales.
CAR TRAVEL
The efficiency of the combustion engines in cars has improved significantly over the past decade.
In addition, low emission hybrid, and all-electric cars are becoming popular, with hydrogen-
powered vehicles projected for the future. However, in the medium term future the overwhelming
majority of passenger vehicles used in Australia will be petrol-based cars (Australian Bureau of
Statistics 2007)
The average rate of fuel consumption of a petrol-based passenger vehicle is 0.112 L/km (11.2
litres per 100 km) (Australian Bureau of Statistics 2007). A petrol-based car produces 2.5 kg
CO2-e per litre of fuel consumed (Department of Climate Change 2008). Combining the average
rate of fuel consumption and the carbon emission rate per litre of petrol consumed, the rate of
emission per kilometre is 0.28 kg CO2-e/km.
AIR TRAVEL
Air travel is believed to be a major source of carbon emissions (Penner et al. 1999). In Australia,
the emission rate of domestic air travel is 0.183 kg CO2-e/km (Wilkenfeld et al. 2002). In addition,
the emissions from aircraft occur in the upper atmosphere and so the effect on global warming
is believed to be 2.2 to 3.4 times greater than carbon emissions from other human activity (Penner
et al. 1999). To account for the increased greenhouse effect of carbon emissions at high altitude
we include a factor of 2.8 (half way between 2.2 and 3.4) and assume the emission rate is 0.512
kg CO2-e/km.
CARBON EMISSIONS OF THE INTERNET
In this section we estimate the carbon emissions of the Internet with ADSL in the access network
and then with FTTN or PON in the access network.
ENERGY CONSUMPTION OF THE INTERNET
Figure 4 is a plot of the electricity consumed per year by an Internet subscriber against the access
rate provided to the subscriber. Included in the plot are the energy consumption of the access,
metro, edge and core networks and the total energy consumption of the network. On the right
vertical axis are the CO2emissions (CO2-e) per year. We have assumed an oversubscription rate
of 10, which corresponds to 10% of subscribers simultaneously using the Internet at full capacity.
The current capacity of the Internet corresponds to an access rate of 0.5 Mbit/s. If used for video
conferencing this would only provide low quality video. For video conferencing with standard
definition (SD) quality, the access rate would need to be increased to 2 Mbit/s. At an access rate
of 0.5 Mbit/s the network consumes 75 kWh of electricity per year per subscriber and results in
81 kg of CO2-e. If the access rate were to be increased to 2 Mbit/s, the network would consume
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT 05.7
80 kWh of electricity per year per subscriber and result in 86.4 kg CO2-e. This increase from 75
kWh to 80 kWh is quite modest because the per-subscriber energy consumption of the network
at low access rates is dominated by the energy consumed in the access network, in particular the
subscriber’s access modem. The energy consumption of this modem is almost independent of
access rate. The small increase in energy consumption arises from the increased transmission and
switching capacity required in the metro, edge and core networks. Thus as a consequence of
upgrading network capacities to deliver SD quality video conferencing to each subscriber, the
carbon emissions of the Internet, assuming ADSL in the access network, would increase by 5.4 kg
CO2-e per-subscriber or 6.7%.
Figure 4 Per household/subscriber electricity consumption and CO2-e emissions of the network with
ADSL in the access network.
ENERGY CONSUMPTION OF ACCESS NETWORKS
As shown in Figure 4, energy consumption in the network is dominated by the consumption in
the ADSL access portion of the network. Thus it is appropriate to consider alternative broadband
access technologies on the basis of capacity and energy consumption. The theoretical maximum
attainable access rate with ADSL2+ is 24 Mbit/s. However, the theoretical maximum degrades
with distance and so the full access rate is attainable by only a small percentage of the population.
FTTN and PON access networks are capable of delivering an access rate in excess of 10 Mbit/s
to all subscribers they serve. Figure 5 is a plot of the electricity consumed per year against access
rate with ADSL2+, FTTN/VDSL and PON in the access network. On the right vertical axis are
the CO2emissions (CO2-e) per year. We have again assumed an oversubscription rate of 10. At
an access rate of 2 Mbit/s, a network with a PON consumes 73.5 kWh of electricity and results
in 79.4 kg CO2-e per year. For the same access rate, a network with FTTN consumes 149 kWh
of electricity and results in 161 kg CO2-e per year.
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT
05.8
Figure 5 Per household/subscriber electricity consumption and CO2-e emissions of the network with
ADSL, FTTN or PON in the access network.
For high definition (HD) video conferencing, an access rate of 10 Mbit/s is required. To
provide an access rate of 10 Mbit/s, a network with FTTN would consume 176 kWh of electricity
and result in 190 kg CO2-e per year. In comparison, a network with PON providing an access
rate of 10 Mbit/s only consumes 101 kWh of electricity and results in 109 kg CO2-e per year.
Table 3 summarises the carbon emissions of the Internet when ADSL, FTTN and PON are used
in the access network at current access rates (0.5 Mbit/s) as well as access rates suitable for video
conferencing – 2 Mbit/s (SD) and 10 Mbit/s (HD).
Figure 5 indicates that to provide HD video conferencing using FTTN in the access network
the electricity consumption and carbon emissions would need to increase by 135%. If PON was
used in the access network the electricity consumption and carbon emissions would only need
to increase by 35%.
Table 3
Carbon emissions per subscriber attributed to the Internet with ADSL, FTTN and PON when the access rate is 0.5 Mbit/s (current),
2 Mbit/s (SD) and 10 Mbit/s (HD).
CARBON EMISSION SAVINGS FROM THE INTERNET
In this section we analyse the carbon emissions savings that would arise from use of broadband
leading to reduced car and air travel. We analyse SD (2 Mbit/s) as well as HD (10 Mbit/s) quality
video conferencing. In both cases we assume an oversubscription rate of 10. If we consider SD
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT 05.9
quality video conferencing, an oversubscription rate of 10 means that during the busiest period
of the week, at most 10% of subscribers are using video-conferencing with SD quality. The re-
maining 90% of subscribers are not using the network in any way, including web surfing. Net-
works are dimensioned to support the busiest period of the week/month. Consequently, the ac-
tual number of hours video-conferencing is performed is irrelevant. In addition, with current
technology, although at most times the network is well below its capacity, the network equipment
remains fully operational and consumes the same amount of power it would during the busiest
periods.
It may seem disproportionate, for example, to compare a 2% reduction in car travel and a
network capacity with support for 10% of homes using video-conferencing. However, it should
be noted that 2% is an average value while 10% is a peak value. For example, if 10% of people
were to telecommute on Fridays, this would only result in a 2% reduction in travel. If this 10%
of people used video-conferencing at the same time on any given Friday the network would be
at full capacity and any additional traffic during this period would result in degraded service for
all users. Additional traffic includes viewing web pages, downloading email, music or video.
The emissions from broadband with each access technology for SD and HD quality video
conferencing is given in Table 3. When calculating savings, we sum the required increase in
broadband carbon emissions from the current level of 81 kg CO2-e with the savings from reduced
car and/or air travel. We note that our results showed that FTTN consumes more energy than
ADSL while PON is more efficient than ADSL. In particular, a network with PON with a 2 Mbit/s
access rate would consume less power than is currently consumed by the network with ADSL at
an access rate of 500 Kbit/s. In the following we analyse the savings that arise from reduced car
and air travel and compare them to carbon emissions from broadband.
CARBON EMISSIONS SAVINGS THROUGH THE INTERNET: CAR TRAVEL
In Australia there are 7.9 million homes with 11.3 million cars (Pink 2008). This equates to 1.4
cars per home. In addition, the average passenger vehicle travels 8100 km to and from work per
year (Australian Bureau of Statistics 2007). When comparing the carbon emissions of broadband
and car travel (to and from work) we assume one broadband connection per home and 11,340
km to and from work per home per year. The carbon emission savings calculated as a function
of percentage reduction in car travel to and from work. Figure 6 is a plot of CO2-e savings for
percentage reductions in car travel from 0% to 10% with each of the access networks for SD
and HD video conferencing. We see that with ADSL and PON with SD quality video conferencing
even a reduction of 0.2% in car travel results in CO2-e savings. However, with FTTN and SD
quality video, a 2.5% reduction in car travel is required to start realising CO2-e savings. The
CO2-e savings are reduced when HD quality video is used with both PON and FTTN.
Nairn analysed the environmental benefits of a 5% reduction in daily commuting travel
(Nairn 2007). If 5% of people were to work from home using broadband, this would result in
an average of 567 km less travel per vehicle and a carbon emissions reduction of 159 kg CO2-e.
Table 4 is a summary of the net saving from reduced car travel for each of the access technologies.
In all cases, using the Internet to work from home does indeed result in significant carbon emission
reductions. If the currently used ADSL network is augmented to support SD video conferencing,
the carbon emission reduction would still be 153 kg. With a FTTN access network, carbon
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT
05.10
emission savings are well below 159 kg CO2-e. This indicates that increased carbon emissions
from the Internet must be accounted for when estimating carbon abatement. We note that using
a PON in the access network results in more than 159 kg CO2-e saving and this arises because
a PON consumes less energy than ADSL.
Figure 6
CO2-e emission savings per household/subscriber for a given percentage reduction in car travel with ADSL, PON or
FTTN in the access network, and SD or HD quality video-conferencing.
Table 4 Summary of carbon emission savings for car travel per home.
CARBON EMISSIONS SAVINGS THROUGH THE INTERNET: DOMESTIC AIR TRAVEL
In this section we analyse the carbon emissions savings that would be realised if broadband res-
ulted in reduced domestic air travel alone. We do not include the carbon emission savings from
reduced car travel calculated in the previous section.
In 2006, approximately 38.4 million domestic air trips were taken annually, resulting in a
total of 46.9 billion kilometres travelled domestically via air (Pink 2008). In Australia there are
7.9 million homes (Pink 2008) so the number of air kilometres travelled per household is approx-
imately 5900 km. The carbon emission savings arising from reduced air travel are calculated as
a function of percentage reduction in domestic air travel per household. Figure 7 is a plot of
CO2-e savings for percentage reductions in air travel from 0% to 10% with each of the access
networks for SD and HD video conferencing. ADSL and PON, with SD quality video conferencing,
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT 05.11
require only a small reduction of 0.2% in air travel to begin realising CO2-e savings. If the access
network is a FTTN network a 2.6% reduction in air travel is required before CO2-e savings are
realised. The CO2-e savings are lower when HD quality video is used with both PON and FTTN.
Figure 7 CO2-e emission savings per household/subscriber for a given percentage reduction in domestic
air travel with ADSL, PON or FTTN in the access network and SD or HD quality video-conferencing.
CARBON EMISSIONS SAVINGS: CAR AND AIR TRAVEL COMBINED
A modest reduction in car and/or air travel will result in net CO2-e savings. Given costs of con-
struction for new cable installations, FTTN is likely to be the most economically viable option
for upgrading Internet in existing urban areas, especially when underground cabling is mandated
(Chanclou et al. 2006). On a per-year operational basis, a FTTN network is capable of producing
net carbon abatement if increased levels of telecommuting and teleconferencing lead to a 1.3%
or larger reduction in car and air travel. Our results counter-intuitively suggest that reducing car
and air travel are equally important. On a per kilometre basis carbon emissions from air travel
are double the emissions from car travel, but the distance travelled to and from work by car per
household is double the distance travelled using domestic aviation. Businesses should put equal
effort into encouraging telecommuting and teleconferencing.
CONCLUSION
We have presented a model to quantitatively estimate carbon emissions of the Internet. Our
model includes the metro, edge and core networks and in the access network we have considered
ADSL, PON and FTTN with VDSL. We estimate that the Internet in Australia currently emits
81 kg CO2-e per-year per-subscriber. Our results confirm the widely held belief that significant
carbon emission savings can be achieved if broadband-enabled services result in reduced travel,
in particular through increased telecommuting and teleconferencing. However, we also show
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT
05.12
that the energy consumption of the Internet will need to increase to support the higher access
rates required by video conferencing. Our results indicate that some access technologies provide
greater abatements than others. We believe that in future, more effort needs to be given to im-
proving the energy efficiency of network infrastructure in the Internet. This will enable optimum
carbon abatement as access rates increase.
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CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT 05.13
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Cite this article as: Baliga, Jayant; Hinton, Kerry; Ayre, Robert; Tucker, Rodney S. 2008. ‘Carbon footprint
of the Internet’. Telecommunications Journal of Australia. 59 (1): pp. 5.1 to 5.14. DOI: 10.2104/tja09005.
CARBON FOOTPRINT OF THE INTERNET BROADBAND FOR THE SUSTAINABLE ENVIRONMENT
05.14
... Models based on this have proven that reduced travel through telecommuting and teleconferencing results in overall emission savings (Baliga, Hinton, Ayre, & Tucker, 2009). ...
Chapter
Full-text available
The high occupancy that typically occurs in South African clinics, and the accompanying risk of airborne infection, make ventilation and thermal comfort particularly important considerations in the design. Passive (natural) ventilation offers a low-cost, energy efficient alternative to mechanical ventilation to dilute air, decreasing the concentration of contaminated particles (Nice et al., 2015). However, the performance of natural ventilation is variable and its success is reliant on constant monitoring. Passive design takes advantage of local environmental and climatic conditions to provide lighting, thermal comfort and ventilation, with the principal aim of minimizing the energy consumption and subsequent carbon footprint of a building (New Zealand Ministry of Education, 2017).The following case study considers the efficacy of a hybrid (passive and mechanical) design strategy to achieve suitable indoor conditions for a healthcare facility. The Hillside Clinic, Beaufort West, was completed in 2017 by the Western Cape Government (WCG) Department of Transport and Public Works, for the WCG Department of Health (the end user). The design brief set out to achieve a suitable indoor environment for a healthcare facility, while challenging designers to consider green building principles, a zero-emission design, and affordability of construction and operation within the specific context. The appointed consultants responded with a number of passive design strategies, including, amongst others, the installation of rock-bed thermal stores and attention to the building envelope materials. These passive techniques were supplemented with mechanical ventilation systems to form a hybrid design. The authors conducted an independent study of the performance of the facility, a year after completion. Beaufort West is situated in a relatively extreme climate, currently classified as cold arid desert, with high diurnal and seasonal temperature differences. Assuming a 2 °C global warming, it is predicted that this area will become a hot arid climate. Furthermore, the area of South Africa resembling the current Beaufort West climatic conditions could increase by up to 16% (Engelbrecht and Engelbrecht, 2016). The Hillside Clinic thus provides a useful study precedent for the application of hybrid design principles applied in healthcare buildings in these arid climates in South Africa. While stating a preference for natural ventilation, the client’s brief recognised that conditioned, mechanically driven air is necessary to achieve the required ventilation rate in certain areas where 100% ducted fresh air supply is recommended.
... Models based on this have proven that reduced travel through telecommuting and teleconferencing results in overall emission savings (Baliga, Hinton, Ayre, & Tucker, 2009). ...
Chapter
Full-text available
Vehicle emissions contribute significantly to the greenhouse gas (GHG) content in the earth’s atmosphere, with transportation emissions constituting 24% of the global carbon dioxide (CO2) emissions (IEA, 2020), contributing to climate change. With the possibility to conduct most business activities by remote, thanks to developments in information communication technology (ICT), this paper considers the environmental impact of telecommuting. As a party to the United Nations Framework Convention on Climate Change (UNFCC) Paris Agreement, South Africa has committed to climate change mitigation through its Intended Nationally Determined Contribution (INDC). In 2015 South Africa’s GHG emissions was reported as 460 Mt CO2e (McSweeney & Timperley, 2018). The current INDC target is to see GHG emissions peak and plateau at between 398 and 614 Mt CO2e over the period 2025 to 2030, following a trajectory of a 42% decrease in GHG emissions. Currently, South Africa is set to fall short of this target (WWF, 2018). Cities in South Africa are significant consumers of energy and conversely provide a key opportunity to reduce GHG emissions, especially in the transport sector (Wolpe & Reddy, 2015). The potential effect of vehicle emission reduction on achieving the INDC target is considered through a hypothetical case study of a large organisation with 2 600 employees commuting to work in the South African commuter context, specifically in the City of Tshwane, a major metropolitan area in Gauteng Province.
... However, the necessary hardware for this work can also have tremendous economic footprints due to the rare earths included in electronic devices and evershorter product lifetime cycles (Resende and Morais 2010). Additionally, the transfer of online data consumes significant amounts of energy today, thereby increasing the carbon footprint of digital nomadic work (Baliga et al. 2009). ...
Chapter
During the last two decades, the labour market of the advanced economies has changed, with the increased use of short-term contracts and higher flexibility in terms of working spaces and work organization. Due to ongoing processes of the globalization and the Industry 4.0 Revolution, distance, location, and time are often no longer considered necessary conditions to make business. In this context, we have witnessed the development and diffusion of coworking spaces (hereinafter CSs). This chapter aims to investigate and compare development, typology, and dynamics of spatial distribution of CSs in two alpha global cities, Prague and Milan, between 2015 and 2019. Using two original geo-referenced databases, the chapter firstly proposes two metrics for quantitative mapping of CSs within basic settlement units in Prague and local identity units in Milan. Local spatial autocorrelation is used to identify spatial clusters in given years, and local spatio-temporal analysis investigated by differential spatial autocorrelation is applied to identify whether changes in spatial patterns over time are spatially clustered. Based on these findings, the chapter highlights similarities and differences in spatial patterns, spatial diffusion, and evolution of CSs in the two cities. Secondly, the chapter provides a discussion on micro-location of CSs in relation to the internal urban spatial structure and its transformation (urban core commercialization, inner city urban regeneration, and gentrification) and thereby the transition to the polycentric city model.
... However, the necessary hardware for this work can also have tremendous economic footprints due to the rare earths included in electronic devices and evershorter product lifetime cycles (Resende and Morais 2010). Additionally, the transfer of online data consumes significant amounts of energy today, thereby increasing the carbon footprint of digital nomadic work (Baliga et al. 2009). ...
Chapter
By earning a living through skillful use of location-independent digital technologies while on the move, the concept of digital nomadism has become increasingly popular. Under the influence of digitalization and globalization, people – including entrepreneurs, freelancers, and employees – have started to leave the regular “9-to-5” work structures behind and change their expectations of work, particularly in terms of their balance between work and private life, thereby extending the concept of work-life balance to work-leisure balance. Due to this changing perspective, work is increasingly seen as a part of a lifestyle that encourages workers to choose their environment based on leisure preferences rather than professional circumstances. Within this chapter, we review the existing but still fragmented literature on the phenomenon of digital nomadism, which constitutes an “extreme” form of flexible work. In doing so, we aim to contribute in two ways. First, we provide a comprehensive overview and definition comprising four recurring elements of digital nomadism (i.e., digital work, flexibility, mobility, and identity and community). Second, we analyze the opportunities and risks associated with each of these four elements of digital nomadism in order to spur future research in these directions. Implications for theory and practice are discussed.
... Another example is technology-driven optimisation which highlights two different facets: (1) increasing energy efficiency of existing enabling technologies; (2) implementing new technologies (or integrating existing technologies) to be accustomed to energy efficiency. The first is having tremendous repercussions on sustainable information and communications technology industry, which strives for decreasing its impact on the global environment (Baliga et al. 2009b). In this respect, optimisation schemas for enabling technologies involving optical IP networks (Tucker et al. 2009;Baliga et al. 2009a), data centre architecture and design (Fan et al. 2007), and digital signature schemes for cryptography (Seys and Preneel 2005) have been put forward. ...
Article
Full-text available
In smart environments, there is an increasing demand for scalable and autonomous management systems. In this regard, energy efficiency hands out challenging aspects, for both home and business usages. Scalability in energy management systems is particularly difficult in those industry sector where power consumption of branches located in remote areas need to be monitored. Being autonomous requires that behavioural rules are automatically extracted from consumption data and applied to the system. Best practices for the specific energy configuration should be devised to achieve optimal energy efficiency. Best practices should also be revised and applied without human intervention against topology changes. In this paper, the Internet of Things paradigm and machine learning techniques are exploited to (1) define a novel system architecture for centralised energy efficiency in distributed sub-networks of electric appliances, (2) extract behavioural rules, identify best practices and detect device types. A system architecture tailored for autonomous energy efficiency has interesting applications in smart industry—where energy managers may effortlessly monitor and optimally setup a large number of sparse divisions—and smart home—where impaired people may avoid energy waste through an autonomous system that can be employed by the users as a delegate for decision making.
... II. RELATED WORK Different efforts have been spent for decreasing energy consumption [1,2,3]. Information and communication technology industry is one of the industries that is putting several distinct efforts for decreasing its impact on the global environment [5]. There is a need to reduce the substantial electricity consumption of networks themselves [7]. ...
Conference Paper
This work deals with the problem of energy efficiency and saving: we present a method to automatically extract behavioural rules from consumption data, so that these rules can be applied or fed to an automatic control system. To extract behavioural rules we shall be able to both define power plants similarity techniques and to analyse and gather rules from data, making the correct assumptions.
... The problem of energy saving is a widely investigated topic [10,19,24,23]. The communication technology industry has made relevant effort on this problem [8,30], by proposing new energy saving technologies, e.g., optical IP networks [7,31], efficient digital signature schemes in cryptography [25], and data centre architecture and design [17]. ...
Article
Conflicting rules and rules with exceptions are very common in natural language specification employed to describe the behaviour of devices operating in a real-world context. This is common exactly because those specifications are processed by humans, and humans apply common sense and strategic reasoning about those rules to resolve the conflicts. In this paper, we deal with the challenge of providing, step by step, a model of energy saving rule specification and processing methods that are used to reduce the consumptions of a system of devices, by preventing energy waste. We argue that a very promising non-monotonic approach to such a problem can lie upon Defeasible Logic, following therefore an approach that has shown success in the current literature about usage of this logic for conflict rule resolution and for human-computer interaction in complex systems. Starting with rules specified at an abstract level, but compatibly with the natural aspects of such a specification (including temporal and power absorption constraints), we provide a formalism that generates the extension of a basic Defeasible Logic, which corresponds to turned on or off devices.
... Also, the right emission factors to model emissions related to the network should be computed for each region that the ICT network crosses (assuming it is possible to map the network path taken by the data and attribute an electricity consumption property to each infrastructure of the ICT network). Research by Baliga et al. (2009) suggests that most of the electricity consumed by online data transmission via the Internet is attributed to the equipment used to access the network. Thus, a good approximation for data centres that rely on the Internet to transmit data would be to consider only the electrical mix of the region in which the data centre is located instead of considering all of the regions crossed by the ICT network. ...
Article
Among the innovative approaches to reduce the greenhouse gas (GHG) emissions of data centres during their use phase, cloud computing systems relying on data centres located in different regions appear promising. Cloud computing technology enables real-time load migration to a data centre in the region where the GHG emissions per kWh are the lowest. In this paper, we propose a novel approach to minimize GHG emissions cloud computing relying on distributed data centres. Unlike previous optimization approaches, our method considers the marginal GHG emissions caused by load migrations inside the electric grid instead of only considering the average emissions of the electric grid's prior load migrations. Results show that load migrations make it possible to minimize marginal GHG emissions of the cloud computing service. Comparison with the usual approach using average emission factors reveals its inability to truly minimize GHG emissions of distributed data centres. There is also a potential conflict between current GHG emissions accounting methods and marginal GHG emissions minimization. This conflict may prevent the minimization of GHG emissions in multi-regional systems such as cloud computing systems and other smart systems such as smart buildings and smart-grids. While techniques to model marginal electricity mixes need to be improved, it has become critical to reconcile the use of marginal and average emissions factors in minimization of and accounting for GHG emissions.
Chapter
All business projects must be certified for quality and environmental standards by some agencies. Generally, the lean projects are evaluated through Lean Six Sigma organizations or equivalent certifying bodies. There are many agencies offer services for quality certifications and compliance adherence. However, most of the companies get certified through international agencies like international standards of the organization (ISO), American Society for Quality (ASQ), quality councils (QC), or bureaus of standards of respective nations.
Chapter
This work deals with the problem of automatic detection of device types given only the power consumption curve, which can be obtained by means of a cheap measurer applied to the device itself. We defined a novel method to detect these types and we describe it in details, providing ground truth evidence coming from the application of the method to real world data. We tested the method against two different set of data coming from two separate and different environments, the first located in Italy and the second in Germany, and we provide experimental results to support the method.
Article
Full-text available
This article examines the widely cited claim that the network electricity use associated with a wireless personal digital assistant PDA is equal to the electricity consumed by a refrigerator. It compiles estimates of the data flows of wireless PDAs and related networks and allocates network and phone system electricity use based on these estimates. It also conducts sensitivity analyses to verify the robustness of these calculations. This analysis demonstrates that the network electricity use associated with a wireless PDA cannot equal that of a typical refrigerator, even under the most extreme assumptions. Our best-estimate case shows network electricity use for wireless PDAs of 0.5 kW • h/year, and therefore claims that wireless PDAs use as much electricity as a refrigerator are too high by more than a factor of 1,000. Even in our upper-limit assessment, the electricity used by a new U.S. refrigerator is about 100 times greater than the network electricity use associated with a wireless PDA.
Conference Paper
Full-text available
As concerns about global energy consumption increase, the power consumption of the Internet is a matter of increasing importance. We present a network-based model that estimates Internet power consumption including the core, metro, and access networks.
Article
Full-text available
This article presents an operators' view of the evolution towards broadband optical access networks. First, we describe a possible evolution of the optical access solution for point-to-point and point-to-multipoint architectures. Subsequently, currently available optical access solutions are evaluated and compared. Finally, we consider regulatory issues inside and outside Europe, and conclude by offering a recommendation with respect to regulation
Article
Energy consumption associated with transport is one of the major contributors to greenhouse gas emissions. As the information economy expands, the potential to use broadband to eliminate a percentage of daily trips grows. In particular, broadband can make it possible for a percentage of the workforce to work effectively and efficiently from home on at least one or two days a week. This paper explores key economic and environmental benefits of a hypothetical 5% reduction in daily trips. Using a simulation model to assess the impact on traffic flows indicates that such a reduction would result in a 5.6% reduction in greenhouse emissions in Canberra, a low-congestion city, and 17% in Sydney. It would also result in savings of 5.54% in road maintenance, accidents, motorists' time and fuel costs or about $145 million annually or $1,000 per household by 2011. In Sydney these would be 10.5% or $5 billion annually or $3,300 per household.
Conference Paper
We present a comparison of energy consumption of access networks. We consider passive optical networks, fiber to the node, point-to-point optical systems and WiMAX. Optical access technologies provide the most energy-efficient solutions.
Book
This rigourous and self-contained book describes mathematical and, in particular, stochastic methods to assess the performance of networked systems. It consists of three parts. The first part is a review on probability theory. Part two covers the classical theory of stochastic processes (Poisson, renewal, Markov and queuing theory), which are considered to be the basic building blocks for performance evaluation studies. Part three focuses on the relatively new field of the physics of networks. This part deals with the recently obtained insights that many very different large complex networks - such as the Internet, World Wide Web, proteins, utility infrastructures, social networks - evolve and behave according to more general common scaling laws. This understanding is useful when assessing the end-to-end quality of communications services, for example, in Internet telephony, real-time video and interacting games. Containing problems and solutions, this book is ideal for graduate students taking courses in performance analysis.
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