Estimating the carbon footprint of the GRAND Project, a multi-decade astrophysics experiment
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Estimating the carbon footprint of the GRAND Project,
a multi-decade astrophysics experiment
Clarisse Aujouxa , Kumiko Koteraa,b , Odile Blanchardc ,
for the GRAND Collaboration
a Sorbonne Université, UPMC Univ. Paris 6 et CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France
b Vrije Universiteit Brussel, Physics Department, Pleinlaan 2, 1050 Brussels, Belgium
c Université Grenoble Alpes, GAEL Laboratory (UMR CNRS 5313, UMR INRAe 1215), CS 40700 - 38058 Grenoble CEDEX 9, France
arXiv:2101.02049v2 [astro-ph.IM] 10 May 2021
Abstract
We present a pioneering estimate of the global yearly greenhouse gas emissions of a large-scale Astrophysics experiment
over several decades: the Giant Array for Neutrino Detection (GRAND). The project aims at detecting ultra-high energy
neutrinos with a 200,000 radio antenna array over 200,000 km2 as of the 2030s. With a fully transparent methodology
based on open source data, we calculate the emissions related to three unavoidable sources: travel, digital technologies
and hardware equipment. We find that these emission sources have a different impact depending on the stages of the
experiment. Digital technologies and travel prevail for the small-scale prototyping phase (GRANDProto300), whereas
hardware equipment (material production and transportation) and data transfer/storage largely outweigh the other
emission sources in the large-scale phase (GRAND200k). In the mid-scale phase (GRAND10k), the three sources
contribute equally. This study highlights the considerable carbon footprint of a large-scale astrophysics experiment, but
also shows that there is room for improvement. We discuss various lines of actions that could be implemented. The
GRAND project being still in its prototyping stage, our results provide guidance to the future collaborative practices
and instrumental design in order to reduce its carbon footprint.
Keywords: Greenhouse gas emission, large-scale astrophysics experiment, climate change, carbon footprint,
radio-detection
1. Introduction Large-scale experimental projects are part of the build-
ing blocks of the astrophysics community. They gather a
Global warming poses critical risks to humanity and large fraction of the scientific staff and absorb a signif-
demands immediate actions in order to be mitigated. An- icant volume of the science budget. As such, it seems
thropogenic greenhouse gas emissions, largely driven by essential to assess their environmental impact. Besides,
economic and population growth, are the leading factors these experiments could turn out to be interesting for
of the observed climate change. Reflections towards a other laboratories to elaborate and test ideas, and to ap-
drastic reduction of these emissions should be central to preciate the best practices to be implemented in other
the conception of any scientific project. contexts.
In the near future, the climate crisis will certainly chal- We present here a rough estimate of the carbon foot-
lenge the way astrophysicists carry out their research. print of the Giant Radio Array for Neutrino Detection
Several working groups have been devising on solutions (GRAND) project. GRAND is a planned large-scale
and their implementation at different levels in the interna- observatory of ultra-high-energy cosmic particles — cos-
tional astrophysics community (e.g., [1, 2, 3, 4, 5]). This mic rays, gamma rays, and neutrinos with energies ex-
is however a new path, and efforts are to be carried out in ceeding 108 GeV [6]. The design of GRAND will be
terms of methodology, creativity, and experimentation. modular, consisting of several independent sub-arrays,
each of 10 000 radio antennas deployed over 10 000 km2
in radio-quiet locations. The collaboration consists today
Email addresses: clarisse.aujoux@gmail.com (Clarisse
of 67 international researchers and engineers.
Aujoux), kotera@iap.fr (Kumiko Kotera),
odile.blanchard@univ-grenoble-alpes.fr (Odile Blanchard) Within the collaboration, questions about the environ-
Preprint submitted to Elsevier May 12, 2021
Figure 1: Roadmap of the GRAND project. The different stages of the project are presented, with information on the envisionned set-up, growth of
the collaboration, and major greenhouse gas emission sources with their contribution in tCO2 e/yr and their corresponding percentage, as estimated in
this work.
mental impact of the project have arisen, and this is the at the heart of the day-to-day scientific work performed
object of this article. This paper focuses on the method- by the bulk of the collaboration. The hardware equip-
ology used to assess the greenhouse gas (GHG) emis- ment will be dominated by the numerous radio detection
sions linked to the GRAND project, and discusses the units, each composed of a radio antenna, its mechanical,
results and possible lines of actions, taking into account electronics and power devices. The evaluation of their
technological and scientific possibilities, and budgetary carbon footprint will be crucial to this study, as the an-
scenarios. tennas will be deployed in great numbers and over large
This study is a pioneering attempt to assess the car- areas.
bon footprint of a large-scale physics experiment. To Note that these main factors (travel, digital, hardware)
our knowledge, no other global GHG assessment of a are not inherent to this project, but common to many
Physics experiment has been published so far, and the astrophysics and particle physics projects.
estimates given in this paper can serve as a basis for com- According to the Intergovernmental Panel on Climate
parison and reflection. The specificity of this methodol- Change, in order to limit warming to 1.5°C, global
ogy is that it is fully transparent and uses open source net anthropogenic CO2 emissions have to decline by
data. Hence, the method is replicable to any other sci- about 45% from 2010 levels by 2030, reaching net zero
entific consortium. The estimates given in this work are emissions by 2050 [8]. Interestingly, these timescales
subject to large uncertainties related to emission factors correspond to the GRAND roadmap, as the full-size
and assumptions on future developments. The scope of experiment is expected to be deployed by the 2030s. By
this study is not to calculate precise carbon emissions, that time, it is possible that unforeseen technological
but to give estimates of the relative weight of each emit- progress will have happened in various domains that
ting category, in order to orient the action plans of the could be implemented in the experiment, such as travel,
collaboration. solar panels, the carbon footprint of electronic devices
Greenhouse gas assessments may cover numerous and data centers. Also by the 2030s, it is highly likely
sources of emissions [7]. In this study, three sources of that taking into account the carbon emissions will
emissions are examined: travel, digital technologies, and be mandatory in all scientific projects. Today, the
the hardware equipment. Those three categories were GRAND project is starting its prototyping phase, hence
chosen because of their obvious importance in terms of it is an ideal time to adapt the experiment to climate
emissions, but also because of the lever for action the requirements. For all these reasons, this study appears
collaboration has on them. Travel cannot be neglected, timely and necessary.
as one obvious source of emissions of the collaboration.
The digital contribution is often underestimated, but is We first present the GRAND projet and the collab-
2oration in Section 2 . We then introduce the general collaboration meetings are organized every year to dis-
methodology of this study (Section 3). We examine cuss the results and future plans. These annual meetings
the three main sources of GHG emissions of the exper- are held in a city harboring one of the GRAND-member
iment, namely travel (Section 4), digital technologies institutes, or near potential experimental sites in China.
(Section 5) and hardware equipment (Section 6). We
work on projections for the three stages of the project 2.2. Collaboration members
(GRANDProto300, GRAND10k, GRAND200k) in a
The GHG emissions generated by the collaboration
Business as usual scenario in Section 7. We propose
depend on the number of people involved in the project
and discuss action plans which could help to reduce the
and the degree of their involvement. The level of involve-
emissions compared to this scenario in Section 8, and
ment of a member can be evaluated as the percentage of
give our conclusions and perspectives in Section 9.
the working time spent on GRAND-related work. Note
that this level can also vary in time.
2. The GRAND Project and Collaboration In our framework, the knowledge of these levels for all
members is a prerequisite to estimate the fraction of basic
In this section, we first present some elements of the
daily emission factors that should be attributed to the
GRAND project and collaboration that are relevant to
GRAND collaboration. Specifically, in Sections 4 and 5
estimate the present carbon emissions, to estimate pro-
we calculate the share of emissions due to commuting
jections and discuss action plans.
and to the daily use of electronic devices (e.g., laptop,
2.1. Project roadmap smartphone) associated to the project.
Three populations can be identified in a collaboration.
The GRAND project was initiated in 2014 by a hand-
The distribution of these populations and their evolution
ful of researchers. In order to discuss its feasibility and to
will be essential tools for projections. The populations
attract interest, two workshops were organized in 2015
are defined according to the level of involvement of the
in Paris and in Chicago, from which a core of active
members, i.e., their percentage of working time spent on
scientists emerged. Since then, the collaboration has
GRAND-related tasks:
steadily grown to reach its current size of 67 members
(see Section 2.2). I. Strong involvement: > 30% of working time,
The GRAND project will follow a staged construction II. Moderate involvement: 10% to 30% of working
plan, to ensure that key techniques are progressively time,
validated. The collaboration is currently working on III. Light involvement: < 10% of working time.
GRANDProto300, a 300-antenna prototype, which will
be a test bench for the further steps of the experiment. Members with a strong involvement are likely to mas-
The array is to be deployed in 2021 over 200 km2 , in sively travel for the GRAND project. The population
a desertic area in Western China. The following stage consists of experimentalists traveling on-site for mea-
corresponds to GRAND10k, with 10 000 antennas to be surements and deployment, core-team members of the
deployed around 2025. GRAND10k is designed to reach project who travel for administrative reasons and pro-
an ultra-high-energy neutrino sensitivity comparable to mote the project, active members, including fully in-
that of other potential contemporary detectors. The final volved students and postdoctoral scholars, who visit one-
stage, GRAND200k, will replicate GRAND10k arrays another to discuss and obtain results that they present at
in different locations worldwide, in order to reach the conferences. These members are also likely to physically
ultimate target sensitivity of GRAND in the 2030s. join most annual collaboration meetings.
The various stages of the project are depicted in Members with a moderate involvement will join some
Fig. 1. The collaboration will likely grow to reach annual collaboration meetings, and occasionally partici-
about 100 members for the GRAND10k stage. Be- pate in conferences to present GRAND-related results.
yond this stage, the collaboration is foreseen to reach Finally, members with a light involvement will
400 − 1000 members. This number is based on a sheer rarely join the annual collaboration meetings physically,
budget necessity (each member contributes to funding and will rarely travel for the primary purpose of
the running costs of the experiment), as it is the case in communicating for GRAND.
most astroparticle physics experiments (e.g., the Pierre
Auger Observatory, the IceCube experiment). Besides a The left panel of figure 2 presents the evolution of the
large number of contributors help achieving a diverse sci- collaboration size over the years and the 3 populations
ence case and obtaining quality physics results. GRAND listed above. These numbers were derived from the
3Collaboration Survey sample
2020 32% 30% 38% 2020 35% 30% 35%
2019 31% 32% 37% 2019 28% 28% 44%
2018 29% 31% 40% 2018 40% 27% 33%
2017 32% 32% 36% 2017 31% 31% 38%
2016 38% 38% 24% 2016 25% 25% 50%
2015 35% 35% 30% 2015 25% 25% 50%
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0
Collaboration size Collaboration size
Strong involvement Moderate involvement Small involvement Strong involvement Moderate involvement Small involvement
Figure 2: Trends of the collaboration size over the years and of the fraction of members with strong (> 30% of the working time), moderate
(10% − 30%) and light (< 10%) involvement in the project. The size of the collaboration is normalized to the initial number of members in 2015.
The left panel analyzes the whole collaboration (67 members), and the right panel is based on a 33% sub-sample, collected via a survey sent to the
collaboration.
history of the collaboration memberships and by sorting Due to various types of uncertainties, emission factors
the different members by involvement category. They are only orders-of-magnitude estimates. Therefore, the
enable us to evaluate any bias that a sub-sample of the results presented in this report are given within orders
collaboration might have compared to the full population, of magnitude. All hypotheses and emission factors are
as discussed in Section 4.1. mentioned, in order to allow for comparisons with other
One can see in Figure 2 that the collaboration size greenhouse gas assessments.
has grown regularly since 2015, and has almost quadru- As in any greenhouse gas assessment, uncertainties
pled in size by 2020. The proportion of the different can be high depending on the origins of the data. We
populations has remained almost constant over time. adopt the uncertainties of the Methodological Guide of
As an international collaboration, GRAND members the French Association Bilan Carbone [11]. The uncer-
originate from institutes located in several countries. The tainties are as follows:
main countries presently involved are (in alphabetical
order): Brazil, China, France, Germany, the Netherlands, • 0% to 5% for an emission factor from a direct mea-
and the United States. This geographical spread, not surement,
specific to GRAND but to any international collabora- • 15% for a reliable non-measured data,
tion, raises obvious concerns about communication (e.g., • 30% for a calculated data (extrapolation),
physically gathering collaborators regularly, and hence • 50% for an approximate data (statistical data),
about travel, but also about the digital infrastructure). • 80% for an order-of-magnitude estimate.
The emissions will be computed in units of CO2 e.
3. General methodology
GHG emissions are determined by multiplying GHG-
generating activity data (e.g., kilometers traveled, elec- 4. Travel
tricity consumption, Central Processing Unit -CPU-
time...) with emission factors (e.g., CO2 e1 emissions The travel sector produced 8.2 Gt CO2 e of direct green-
per kilometer traveled by plane, CO2 e emissions per house gas emissions in the world in 2018 (including
kWh of electricity consumed, CO2 e emissions per CPU non-CO2 gases) and hence was responsible for approxi-
hour...). This enables to aggregate all GHG emissions in mately 24% of total energy-related CO2 emissions [12].
one single indicator, called the "carbon footprint". With daily commutes and regular academic travels, re-
searchers contribute to this source of emission. The
impact of the daily commutes of the GRAND members
1 Short for "Carbon Dioxide equivalent". There are several green-
has been computed along with the impact of academic
house gases other than CO2 in the atmosphere: water vapour, methane
(CH4 ), nitrous oxide (N2 O). Each greenhouse gas has a different global travel. Although it is likely that the GHG emissions re-
warming potential (GWP), which indicates the amount of warming lated to travel will be dominated by academic travel, it
this gas causes over a given period of time. The GWPs used here are is interesting to be aware of their distribution between
relate to a period of 100 years and refer to the IPCC 5th report values
[9]. For any quantity and type of greenhouse gas, CO2 e corresponds to
the two sources. This can help us to choose the actions
the amount of CO2 which would have the equivalent global warming that will have the greatest impact on the greenhouse gas
impact [10]. emissions.
4350 MyClimate.org panel of Figure 2 presents the evolution of the collabora-
300
Emission factor of plane
tion size and the three populations over 2015 − 2020, as
250 KLM
[gCO2e per pkm]
200 estimated from the survey respondents.
150 ADEME Given the small sample of answers received, it is dif-
100
50 French Ministry
ficult to use inferential statistics to extend the results to
0 of Ecology the whole studied population. As a first approximation,
0-1000
1000-2000
2000-3000
3000-4000
4000-5000
5000-6000
6000-7000
7000-8000
8000-9000
9000-10000
10000-11000
More than 11000
Average one can assume that the respondents have similar charac-
teristics on average as the global population. An overall
correction factor of ∼ 3 can then be applied to global es-
Distance flown in one continuous leg (km) timates obtained using the survey, in order to correct for
the limited sample size, given that the proportions of the
Figure 3: Different greenhouse gas emission factors for flights, de- involvement populations are roughly well-represented.
pending on the database chosen. The flight distance is flown in one In detail, we note that the growth of the collaboration
continuous leg. The black solid line corresponds to the average of the size is underestimated in the survey by a factor of 3/4. In
4 datasets.
particular, the growth between the years 2015 and 2016
are not represented in the survey. However, this correc-
GRAND scientists travel regularly for purposes that tion is sufficient for our purposes, as we are interested in
can be split into three main categories: orders-of-magnitude estimates.
• Annual collaboration meetings, 4.2. Travel emission factors
• On-site missions,
The data used for the emission factors is divided into
• Other (conferences, visits, seminars, etc.).
two categories : air travel and other travel modes. For the
Indeed, as an international collaboration, GRAND other travel modes (car, public transportation, etc.), we
members gather at yearly meetings across the world, in use the ADEME carbon database [13]. This database has
order to assess the progress and discuss the next steps several advantages: it covers a wide range of emission
of the project. It is also necessary for experimentalists factors and it is easily accessible. However, this is a
to travel to China in order to make field measurements database centered on French specificities. For example,
and to deploy the antennas. Scientists also travel to visit for public transportation such as the subway, the fuel
each other and hold specific face-to-face discussions, to mix for electricity generation is specific to France which,
promote the project and its results at conferences or at unlike other countries, has a low carbon intensity due to
seminars. the use of nuclear power (see Appendix A). Still, the
difference between the carbon intensity of electricity in
4.1. Survey and representativeness commuting in different countries does not affect the final
A survey was sent to the whole collaboration with the result for two main reasons: commuting represents only
primary purpose of assessing the carbon emissions of a small fraction of overall travel emissions, which are
travel within GRAND. The results are fully studied in dominated by air travel; the main type of travel used for
this section and also used in Section 5. commuting by GRAND members is car (gasoline and
The survey aims at evaluating the commuting and diesel) which represent 45% of the kilometers traveled.
travel frequency and distances of the members. Each Concerning aviation, its effects on climate change are
member was asked to provide a list of all the trips under- more than just emissions of CO2 from burning fuels. It
taken for the project, mentioning their purpose (annual is the result of three types of processes: direct emissions
meeting, on-site mission or else), and the means of travel. of radiatively active substances, emissions of chemical
As for commuting, the number of kilometers travelled products that produce or destroy radiatively active sub-
for commuting and the means of travel were asked to the stances, and emissions of substances that trigger the
collaborators. generation of aerosol particles or lead to changes in nat-
In what follows, we discuss the representativeness of ural clouds [14]. Those effects are not always taken into
the results. The survey was sent to all 67 members of the account in carbon databases that include emission factors
GRAND collaboration, and 33% responded. The mem- for planes, as they are not yet very well understood.
bers were asked to evaluate their level of involvement in Choosing one single database can lead to highly differ-
the collaboration since 2015. This information enabled ent results, up to a factor of 5 [4]. To compute our travel
us to categorize the respondents within the three involve- carbon footprint, four databases were chosen from differ-
ment populations described in Section 2.2. The right ent organizations: the database from ADEME [13], the
5database from the French Ministry of Ecology [15], data Commuting
from KLM airline [16] and a computation methodology 1%
from MyClimate.org [17]. Those four databases have di-
verse sources: one non-governmental organization, one Conferences etc...
airline company, and two state organizations. 26%
In order to have more accurate results, the emission
factors are split in categories depending on the number
of kilometers travelled by increments of 1,000 km up On-site
to over 11,000 km. The data used is already divided in missions
54%
such categories for the French Ministry of Ecology and
ADEME. MyClimate.org divides the emission factors be- Collaboration
tween short-haul flight and long-haul flights. The KLM meetings
data is a list of all the flights they offer, their distance in 19%
kilometers and the greenhouse gas emission associated
to the flight. Figure 4: Distribution of emissions related to travel: on-site missions,
Figure 3 presents the range of flight emission factors collaboration meetings, conferences, commuting, from 2015 to 2020.
spanned by the various datasets. The greenhouse gas
emissions as a function of the distance flown in one con-
tinuous leg are presented for the 4 databases described 4.4. Results
above (ADEME2 , MyClimate.org, French Ministry of In this section we present the results stemming from
Ecology, KLM). The uncertainty of these emission fac- our survey. We recall that 33% of the collaborators
tors is estimated at around 60 % in the ADEME database answered the survey and the representativeness of the
and mainly stems from the uncertainty pertaining to the survey was discussed in Section 2.2. The results are
emissions of contrails. The other databases do not pro- summarized in Figs. 4 and 5.
vide such estimates. The black solid line corresponds to All in all, from 2015 to 2020, a total of 170 tCO2 e
the average value calculated from the 4 databases, which were emitted for all categories in the survey sample.
is used in our emission estimates for one-legged trips. As discussed in section 4.1, an overall factor of 3 is
We have not provided uncertainty estimates for this aver- applied to global estimates obtained using the survey,
age value as only the ADEME database provides some. in order to account for the whole panel of collaborators.
It is worth mentioning that the average emission factors Using this multiplication factor, the total greenhouse
are respectively between 5 and 10 % greater when consid- gas emissions of GRAND for the 2015 − 2020 period
ering respectively two or three legs instead of one-legged amounts to 510 tCO2 e.
long haul trip. Most of the emissions stem from academic travel
(99%) and only 1% are generated by commuting, as
4.3. Commuting shown in Figure 4. Interestingly, among the travel cat-
In order to compute the emissions due to daily com- egories, on-site missions constitute the dominant item.
mutes, we first need to estimate the number of days This seems to be consistent with a nascent experiment
worked by the GRAND collaboration members. For which requires to perform site surveys, as well as tests
this purpose, questions were asked in the survey about and hardware deployment in remote areas in China. As
the percentage of worked days dedicated to GRAND, a benchmark figure, one Paris-Dunhuang flight emits
the percentage of days worked remotely from home, the approximatively 1.7 tCO2 e (Dunhuang, Gansu Province,
country of residence (which gives the number of working China, being the closest airport to the experimental site
days per year in the country) and the number of years of GRANDProto300).
the collaborator has been working for GRAND. Figure 5 presents the trends of the travel emission
The number of kilometers travelled for commuting sources over the years for the survey sample. One can
for each type of travel was computed using the number clearly see the experiment taking off in 2018 − 2019,
of days worked per person annually and the number with maximal yearly levels of ∼ 114 tCO2 e, due to the
of kilometers travelled per person per day by mode of development of the prototype GRANDProto300, which
travel. was planned to be deployed in 2020. The emissions in
2020 pertain only to the months of January and February,
2 The emission factors from ADEME were retrieved from the after which the Covid-19 pandemic froze most academic
database prior to the June 2020 update by ADEME. travels, in particular to China. The proportion between
62020* 42% 16% 42% ity (e.g., smart grids, connected mobility...) are presented
as a way to reduce energy consumption. However, as
2019 31% 31% 38%
reported for example by the Shift Project [18], digital
2018 55% 13% 32%
technologies have a non-negligible environmental im-
2017 72% 18% 10% pact. Carbon footprint assessments often neglect the
2016 27%
digital contribution, and the impact of the digital equip-
73%
ment is largely underestimated by its users.
2015 55% 33% 12%
Digital technologies are used in every aspect of the
0 20 40 60 80 100 120 GRAND project: e.g., for simulations, data analysis,
Greenhouse gas emissions [tCO2e] data storage and transfer, and communication. It is hence
On-site missions Collaboration meetings Conferences etc…
necessary to evaluate the digital impact on greenhouse
gas emissions, in order to compare it to the other emis-
Figure 5: Trends of travel emissions over the years based on the
survey responses corrected to an overall factor of ∼ 3. The percentage sion sources. For such a study, defining the scope is
attributed to three travel categories (on-site missions, collaboration essential. A focus has been made on four categories,
meetings, other) is indicated on each histogram. *The emissions for which we present in the following sections: electronic
2020 are restricted to the first two months of 2020. devices, communication & data exchanges, numerical
simulations, and data transfer, processing and storage.
Strong
5.1. Electronic devices
Mod
Among the electronic devices owned by GRAND
Light
members, laptop, desktop computers and screens are
most prominently used for the GRAND project. A lim-
0,0 0,5 1,0 1,5 2,0 2,5 ited number of collaborators work on a digital tablet
Emissions per person per year [tCO2e] and the percentage of smartphone usage dedicated to the
project is on average negligible compared to the laptop
Figure 6: Average travel emissions per year for the three types of and desktop computers.
GRAND collaboration members as described in Section 2.2: strongly To assess the carbon footprint of electronic devices,
involved, moderately involved, lightly involved. we use the online tool Ecodiag developed by the
CNRS [19]. It allows us to compute the emissions related
the various categories of travel fluctuate as a function to various electronic devices such as laptop, desktop com-
of the need for on-site missions (e.g., a large site survey puters, etc., for given lifetimes, as presented in Table 1.
campaign was conducted in 2017 − 2018), and of the Each device has a carbon footprint corresponding to its
location of the annual collaboration meeting (e.g., the production phase and its utilization phase. As the carbon
meeting of 2019 took place in Dunhuang, China, hence footprint of keyboards, mouses, headphones and other
the increased emissions). accessories are negligible compared to the contribution
As discussed in section 2.2, the level of involvement of computers, we do not take the former into account.
in the collaboration results in different traveling profiles. The emission factor for the electricity consumption of
This is illustrated in figure 6, where the emission for the devices is the European one, retrieved from [13] 3 .
three typical members stemming from the three involve- As the devices are not used only for GRAND-related
ment populations (light/moderate/strong) are presented. projects, the percentage of each member’s total work
These results were estimated from the survey. Strongly days dedicated to GRAND is taken into account. For
involved members emit on average over 3 times more example, for a member working x% of the time for
than moderately involved members. Theses figures, com- GRAND on two personal computers, the GHG emis-
bined with a potential future distribution of the different sions associated to those devices will be computed as x%
populations, will enable us to derive emission projections of the total emissions associated to the devices.
for the next steps of the GRAND experiment.
3 The fraction of European collaboration members prevails at the
current stage of the GRAND experiment (& 50%), although the fraction
5. Digital technologies of members from China (with a higher electricity emission factor) is
steadily growing (∼ 25%). The presence of several members from
Digital technologies are often proposed as a solution Brazil (∼ 15%), a country with low electricity emission factor, also
for climate change mitigation: automation and connectiv- balances the overall factor.
72020
Device Lifetime Emissions
[years] [kgCO2e/yr]
2019
3 130.2
2018 MacBook Pro 15”
4.5 93.2
Year
2017 4 154.4
Average desktop
2016 6 129.4
2015 5 115.4
Average screen
7.5 86.4
0,0 5,0 10,0 15,0
Greenhouse gas emissions [tCO2e] Table 1: Devices and their overall greenhouse gas emissions, including
Desktop Laptop Screen production and utilization phases. The emission factor used for the
electricity consumption is the European one
Figure 7: Cumulative greenhouse gas emissions related to the use . Emissions are listed for two typical lifetimes. Source:
of electronic devices by collaboration members, computed from the Ecodiag-CNRS [19].
answers to the survey. An overall factor of 3 is applied to the emission
levels in order to correct for the survey-sampling bias.
2015. To estimate the number of days worked for
We assess emissions related to electronic devices GRAND per person, we assumed an average number
based on the responses from the survey detailed in Sec- of days worked annually per country, and for each mem-
tion 4.1 concerning the involvement level of each mem- ber of the collaboration, we weighted this number with
ber. Our calculations assume that a collaboration mem- the percentage of time worked for GRAND.
ber uses: one laptop (MacBook Pro 15” –a large fraction The Shift Project estimated that sending an email with
of GRAND members are Apple users), one mid-range a 1 MB attached file (a conservative hypothesis in our
desktop and one screen4 . For the lifetime, we chose the case) leads to an electricity consumption of 1 Wh [18].
shorter lifetimes listed in Table 1. Figure 7 presents the Using the emission factor of the European electricity
emissions related to the use of devices since the begin- consumption [13], as explained in section 5.1, the total
ning of the collaboration. These emissions correspond emissions amount to 74 kgCO2 e for the whole period
to the emissions of the whole collaboration, a factor of 3 2015−2020. With a higher rate of 20 emails per working
was applied to the results of the survey. One can see that day sent by each collaboration member during the time
the emissions are consistently proportional to the growth working for GRAND, which is a conservative hypothesis,
of the collaboration. the emissions amount up to ∼ 0.5 tCO2 e for 2015 − 2020.
These estimates are conservative, as we systematically This is still negligible relative to the other sources of
choose the higher emission ranges for the devices used emissions.
by each member of the collaboration. Monthly collaboration meetings, regular core-team
meetings and other discussions are held via video-
5.2. Online exchanges conferencing. The environmental cost of video-
Online exchanges can take different forms: email, conferencing is highly dependent on several factors,
video call, team communication platforms, cloud. These such as the meeting duration, the technologies used, etc.
media do not have the same impact on carbon emissions, The emissions associated to video conferencing are es-
and have to be compared to other solutions, as, for exam- timated to be 7% of the ones from in-person meetings
ple, gathering everyone in the same room. [20]. Refs. [21, 22] estimated differences in emission
Assuming that each member of the collaboration sends of several orders of magnitude (∼ 3000) between large-
3 emails every working day during the time working for scale conferences held online or in person, in astronomy
GRAND, it amounts up to 180 000 emails sent since and in geophysics respectively. Although the scales of
these conferences gathering several hundreds of partici-
4 This can be viewed as a conservative assumption, as many mem- pants are different to the smaller-scale (∼ 30 participants)
bers with Apple laptops do not use a desktop. However, more and meetings mentioned here, these estimates confirm that,
more members use two screens (one at the office and one at home), and compared to the other emission sources, the impact of
this is a growing trend with the incentive to work remotely, due to the the use of video-conferencing in the collaboration can
Covid-19 situation. The emissions of a screen correspond roughly to
that of a desktop, hence our calculation remains valid. A more precise
be neglected. Note that this technology is also often
investigation of the average computing devices owned by physicists presented as a greener option than in-person meetings,
would require a dedicated study. and its use could be considered for the GRAND annual
82020 3.5m CPU hours for GRANDProto300, using the same emission factors
2019 2.1m CPU hours as for simulations. Data analysis is comparatively one
2018 2.2m CPU hours order of magnitude less emitting than the simulations
2017 3.7m CPU hours run during the preparatory phases.
2016 510k CPU hours Here we did not take into account the analysis required
2015 170k CPU hours to work on the Radio Astronomy science case, and fo-
cussed on the primary science case of GRAND, which
0,0 5,0 10,0 15,0
Greenhouse gas emissions from numerical simulations is the detection of ultra-high energy astroparticles.
[tCO2e]
Electricity consumption Other (construction, staff…) 5.4. Data transfer
In this study, we focus on the data transfer related to
Figure 8: Emissions from numerical simulations run for GRAND. the first prototype of GRAND, GRANDProto300, which
Emissions are separated in two categories in order to understand the
impact of electricity consumption and other sources of emissions. is being currently developed. The projections for the
next phases are discussed in Section 7.2.
On the GRANDProto300 experimental site, data will
collaboration meetings (see Section 7.1). be collected by the radio antennas deployed . The data
collected will be sent to the nearest city via Ubiquiti Air-
5.3. Numerical simulations and data analysis Fiber [25]. The raw data will amount roughly to 10 TB
Numerical simulations are essential at all stages of per day. Assuming that the data acquisition will take
the project, and particularly for the preparatory phases. place over 300 days a year (due to weather conditions,
Over the last four years, about 2 million CPU hours were maintenance, etc.) during 5 years, about 15 × 103 TB of
used on various superclusters (principally at CCIN2P3 in data will be collected during the whole experiment. We
Lyon, ForHLR at the Karlsruhe Institute of Technology, calculate the GHG emissions that would be produced if
and UFRJ in Rio de Janeiro). Using the emission factors this data were to be transferred via the Internet to a data
from Ref. [23], we computed the emissions associated center in Beijing and then transferred across the world
to simulations from 2015 to 2020, as presented in Fig. 8. to a few data centers harbored by GRAND institutes.
The emission factors take into account all the stages The computation of the emissions is based on the elec-
related to performing simulations in a data center: server tricity intensity of Internet data transmission which rep-
manufacturing, electricity consumption, and emissions resents the amount of electricity consumed per amount
generated by the staff running the data center. In our of data transmitted. This quantity can vary much accord-
calculations, we used the electricity-specific emission ing to the way it is computed: the system boundaries,
factor of the countries hosting the superclusters where the assumptions made, and the year to which the data
the simulations were run (France, Germany and Brazil, apply, significantly affect the estimates. Reference [26]
see Appendix A). provides an estimate of 0.06 kWh/GB for 2015. Using
The scope chosen has a great impact on the results this number along with the estimation of the quantity
of the greenhouse gas assessment. In order to see the of data transferred as given above, we evaluate the total
impact of every stage, we present the emissions related consumption of data transmission to about∼ 900 MWh.
to electricity consumption only, and to the larger scope The emissions related to this energy consumption de-
including staff interventions, server manufacturing and pend on the emission factor chosen for electricity con-
the like. sumption. For example, the European electricity emis-
The storage of the results of the simulations also have sion factor is 0.42 kgCO2 e/kWh while the Chinese one is
a cost in terms of GHG emissions. The percentage of the 0.766 kgCO2 e/kWh [13], due to different energy mixes
energy use in data center for data storage is around 10% to generate electricity. In order to choose an emission
of the emissions of simulations [24]. We thus estimated factor as close as possible to reality, we take into ac-
the energy consumption related to the storage of the re- count the distribution of data center locations across
sults of the simulations at around 10% of the one related the world, as the data will travel around the globe to
to simulations. reach the various GRAND institutes. We assume that the
Once experimental data has been collected (see next data centers are located in the same country as the data
sections), it will be analyzed. For GRANDProto300, transmission network equipment. The countries hosting
each year over 5 years, between 200k CPU hours and the largest number of data centers are the United States
400k hours will be needed to analyze the astroparticle (38% of the centers), along with five other countries
data. This amounts to 0.9 tCO2e to 1.7 tCO2e per year which host together 55% of the data centers in the world
9(see Appendix B). The emission factor is calculated
as the weighted average of the emission factors of these
countries, based on the proportion of data centers hosted.
Note that this calculation does not account for the size
of the data centers, which can vary from one country to
another. The emission factor obtained yields an emission
of 0,518 kgCO2 e/kWh.
Finally, we calculate that the total electricity con-
sumption needed for the raw data transmission for
GRANDProto300 emits 470 tCO2 e. This amount
assumes that the data collected is only transferred once.
If we assume that 10 institutes will transfer the data from
the central data center in Beijing, emissions amount to
4700 tCO2 e.
Interestingly, for the primary scientific scope of the
experiment, i.e., radio-detection of astroparticles, the rel-
evant data could be efficiently reduced on-site down to
Figure 9: GRANDProto300 prototype antenna.
100 GB per day, leading to 150 TB of data transmitted
during the whole experiment. The transmission of this
limited volume of data would imply 2 orders of mag- cycle assessment of the hardware equipment is out of the
nitude less emissions, leading to a total of 4.7 tCO2 e scope of this work, and will be evaluated in a subsequent
emitted via data transfer at the GRANDProto300 stage. study. Still a rough assessment of the carbon footprint of
The choice of keeping only this limited data reduces how- the detection units can already initiate discussions about
ever the science case of the GRAND experiment. For the impact of the hardware on the carbon footprint of the
the prototyping stage, it also appears cautious to keep all collaboration.
the available data. In Section 7.2.3, we give strategies to Each detection unit consists in a radio antenna with
reduce the overall data amount for the later phases of the a mechanical support setup (made primarily of 75 kg of
experiment. stainless steel), data acquisition electronics (the material
of the Print Circuit Board is MEGTRON [28]), several
5.5. Data storage cables of 6-meter length in total, a solar panel (poly-
The data collected will be stored in cloud servers. cristalline module) and a battery (see Fig. 9).
Cloud servers allow all the collaborators to easily have Here we focus on three major parts of the detection
access to the data and to process them with virtual ma- units: the antenna with its mechanical setup, the solar
chines. The collaboration envisions that the data be panel and the battery. We also focus on the hardware
stored at 3 different locations to provide back-up. The already designed for the prototyping phase GRAND-
peak consumption of cloud storage is around 11.3W/TB Proto300. The projections for the further stages of the
of data [27]. For one TB of data for a year, this leads to experiment are presented in Section 7.2.4.
99 kWh of electricity consumption. Assuming the same Note that for each of these items, recycling has not
emission factor of 0.518 kgCO2 e/kWh as above, it leads been taken into account in the GHG emissions. A re-
to an estimate of 51.2 kgCO2e for one TB of data stored cycling plan has not been elaborated yet within the
for a year. Each year, GRANDProto300 stores 3,000 GRAND collaboration, although it will clearly be an
TB of data, which leads to around 153.6 tCO2e/yr for important line of action (see Section 7.2.4).
GRANDProto300.
6.1. Antennas
6. Hardware equipment In order to evaluate the carbon footprint of the anten-
nas, we focused on the 75 kg of stainless steel composing
In the GRAND project, the hardware equipment will the arms, the frame, and the pole. The emission factor
be dominated by the radio detection units. The units will of stainless steel varies from ∼ 2.2 kgCO2 e/kg [13] to
be deployed in large numbers (200 000), hence their en- 6.8 kgCO2 e/kg [29] in the literature, depending on the
vironmental impact cannot be neglected. A complete life assumptions on the production methods and the country.
10References before 2010 tend to indicate higher emission account in terms of metal depletion and fossil fuel deple-
factors (see also Ref. [30]). Recent estimates of stainless tion5
steel production in China (where the first 10’000 units In terms of GHG emissions the impact of the pro-
will likely be produced) give an emission factor as low as duction of lead-acid batteries per kilogram of battery
1.76 kgCO2 e/kg. We choose to take a mid-range value of is 0.9 kg CO2 e [33]. The batteries used for GRAND-
2.9 kgCO2 e/kg for this emission factor, closer to recent Proto300 weigh 51 kg, which yields an emission of
estimates, that correspond for example to the estimates 13.7 tCO2 e for the whole array.
documented in Ref. [31]. As already mentioned, no recycling plan has been
One antenna has therefore a carbon footprint of elaborated yet by the collaboration, but this will be care-
217 kgCO2 e. For the 300 units of GRANDProto300, fully discussed in the future. Indeed, the recycling of
this yields 65 tCO2 e, and for the last stage of the project lead-acid batteries in China is a great concern for public
43,400 tCO2 e. health, as lead is classified as one of the top heaviest
It seems important to remind here that even if this metal pollutants in China. However, sodium-ion batter-
figure appears to be high, it should be compared to sim- ies are a potential alternative to lead-acid batteries, and
ilar infrastructures. Indeed, compared to other metals, they are promising in terms of environmental aspects
stainless steel has a low emission factor. For example, [34].
aluminum has an emission factor of 35.7 kgCO2 e/kg
[29]. However, the environmental impact of stainless 6.4. Hardware transportation
steel depends on many external factors, that can lead
The production of hardware will not take place on-
to changes in its environmental impact. For example,
site, hence the emissions due to their transportation have
the ore grade, electricity energy source, fuel types, and
to be taken into account. We assume that the detection
material transport as well as process technology influ-
units, which weigh approximately 126 kg, will travel ap-
ence the environmental impact of the extraction of this
proximately 1700 km from the factory (located in Xi’An,
metal [29]. These factors can vary in time, and by 2035
Shaanxi Province, China) to the final site (close to Dun-
the emission factors used here to compute the emissions
huang, Gansu Province, China). The exact type of ve-
for GRANDProto300 could be completely different for
hicle to be used has not been decided yet; however, as
GRAND200k.
there is no major infrastructure for freight transportation
connecting these cities except road, the transportation
6.2. Solar panels
will most likely happen by truck. We chose an emission
Each antenna is fueled by a 1 m2 poly-crystalline solar
factor of 0.07 kgCO2 e/tkm for truck transportation. This
panel. GHG emissions from photovoltaics show high
is an average value from the ADEME Carbon Data Base
variations even for photovoltaic systems from the same
[13] and only serves as an order of magnitude estimate.
year. The current GHG footprint is estimated at around
For GRANDProto300, the total weight is 37.8 t. The
∼ 20 gCO2 e per kWh for 1 m2 poly-Si photovoltaic sys-
total transportation of GRANDProto 300 will emit
tems [32]. The values used here refer to standardised
around 4.5 tCO2 e.
conditions. The yield of a solar panel is usually 13%,
which leads to an annual production of 221 kWh per 1 m2 .
Using the emission factor presented above, one 1 m2 7. Emission projections of the whole GRAND
solar panel emits 4.42 kgCO2 e per year. For GRAND- project
Proto300, this represents 1.3 tCO2 e per year. However, a
clear decrease in the environmental footprint of photo- In the previous sections we presented the emissions
voltaic systems over time has been observed: the GHG over the period 2015 − 2020 in order to define the main
footprint of photovoltaic systems were divided by 7 over sources of GHG emissions of the GRAND project. In
24 years [32]. Following this trend, it is likely that the this section, we present the estimates for the upcoming
GHG footprint of solar panels will decrease over the next years and the next stages of the project. The estimates
decades. are computed in a Business as usual scenario, assuming
that no specific actions are taken by the collaboration
6.3. Batteries
The batteries chosen for GRANDProto300 are lead- 5 The environmental impact of lead-acid batteries is negative in case
acid batteries. Here we only focus on their GHG emis- of grid-connected systems [33], but such a setup is inapplicable to
sions, but it should be pointed out that the environmen- our study, as our experiment is carried out in a remote area without
tal cost of lead-acid batteries should also be taken into electricity supply.
11to reduce its carbon footprint, and that the number of number of members are needed for on-site missions,
collaborators in GRAND increases as presented below, whatever the stage of the project (GRANDProto300,
and in Fig. 1. This scenario allows us to compare the GRAND10k or GRAND200k). For on-site missions,
impact of different actions that could be implemented to the emissions are more influenced by the different ex-
mitigate the GHG emissions. perimental stages: in particular by the number of units
The projections bear large uncertainties, and should be deployed , the number of sites, and their distance from
viewed as order-of-magnitude estimates. Besides, even one to the other. On-site missions are also expected to
though we try to reflect the reality of the evolution of the have a higher impact on the carbon footprint at later
experiment, unforeseen changes may occur in the future. stages as the different sites for GRAND200k might be
In the projection calculations, two types of emis- located on different continents. Due to the current high
sion sources stand out: those depending on the number uncertainty related to the future location of the site, we
of GRAND collaboration members (e.g., collaboration chose not to take that effect into account.
meetings, electronic devices), and those depending solely We estimate yearly emissions of on-site missions by
on the project (e.g., hardware, data transfer). averaging the emissions calculated over the years 2015 −
The growth of the GRAND collaboration is foreseen 2019. The yearly rate corresponds to 51.3 tCO2 e/year for
to reach & 400 − 1000 members (see Section 2.1). As we the collaboration. In order to derive projections for the
see in the following section, we find that these numbers three stages of GRAND, we assume that this benchmark
only have a limited influence on the total GHG emis- rate will remain constant during the years of operation
sions of the GRAND project. We thus present the upper of GRANDProto300, will double during GRAND10k,
limits derived from the 400 member-scenario in the next and will be multiplied by 10 during GRAND200k. The
sections. GRAND10k phase will roughly be an extension of the
The three main stages of the experiment, GRAND- existing GRANDProto300 site, hence no drastic increase
Proto300, GRAND10k, GRAND200k, as pictured in in on-site missions is expected . At the final stage of the
Fig. 1, are assumed to last for 5, 10 and 10 years respec- project, about half of the 10 − 20 sub-arrays will be de-
tively. This last figure is conservative, as most large-scale ployed in China and the rest will be deployed worldwide.
ground experiments run for more than 10 years (e.g., the Adequate experimental sites will have to be searched,
Pierre Auger Observatory [35]). In our calculation of the implying a large increase in on-site missions.
emissions for each stage, we only take into account the These assumptions lead to the proportions presented
emissions due to the deployed hardware and the emis- in the first row of Fig. 10. One can notice that each of
sions occurred during the years of operation. The yearly the three travel purposes take up about 1/3 of the travel
emissions from the collaboration members prior to 2021 emissions for the first two phases of the project, whereas
are not taken into account. on-site missions prevail in the last phase.
These pie charts show the importance of taking ac-
7.1. Travel tions on all three items in order to reduce the impact of
travelling. The logistics should also be carefully planned
The emissions related to collaboration meetings and in the global GRAND200k stage, in order to minimize
"other" purposes (e.g. participation to conferences, vis- the number of on-site missions.
its) identified in Section 4) will grow roughly propor-
tionally to the size of the collaboration. We estimate the 7.2. Digital technologies
yearly emissions per person in the collaboration for col-
laboration meetings and “other" purposes, by calculating The emission projections presented in this section are
the average emissions per person and per year over the highly dependent on technological change. We present
period 2015−2019. Emissions due to travelling to collab- the proportions of emissions related to the different dig-
oration meetings and other purposes amount respectively ital sources for the three main stages of the GRAND
to 0.6 tCO2 e/person/yr and 0.5 tCO2 e/person/yr . Those project, in the middle row of Fig. 10. Below, we men-
numbers are calculated on average and take into account tion the assumptions made in order to calculate these
every collaborator of GRAND. The emissions for the projections.
three main stages of the experiment can then be calcu-
lated by multiplying these rates by the corresponding 7.2.1. Electronic devices
number of members and the number of years. Projections for electronic devices are proportional to
The emissions related to on-site missions do not de- the size of the collaboration. For projections, we use
pend on the number of collaborators, as only a limited the emission factors presented in Part 5. In the Business
12GRAND200k - Travel
965 tCO2e/yr
22,5 % 24,3 %
GRANDProto300 - Travel GRAND10k - Travel GRAND200k - Travel
130 tCO2e/yr 328 tCO2e/yr 965 tCO2e/yr
29,1 %
22,5 % 24,3 % GRAND200k - Digital
31,5 % 33,0 % 35,7 % 5985 tCO2e/yr
53,2 %
1%
7,2 %
53,2 % Collaboration meetings
9,0 %
On-site missions
39,4 % 31,3 %
Conferences etc.
GRANDProto300 - Digital GRAND10k - Digital GRAND200k - Digital52 %
338 tCO2e/yr 422 tCO2e/yr 6007 tCO2e/yr
31,3 %
4,2 % 9,6 % 1%
7,1 %
22,2 % 9%
36,5 %
45,7 % 25,4 % GRANDProto300 - Hardware
0,3 % 51,4 %
46 tCO2e/yr
Devices
31,2 % Simulations
6,4 %
27,7 % Data analysis
22,1 % Data transfer
Data storage
25,1 %
GRANDProto300 - Hardware GRAND10k - Hardware GRAND200k - Hardware
18 tCO2e/yr 322 tCO2e/yr 6435 tCO2e/yr
5,9 %
4,6 % 2,9 % 66 %
4,9 % 4,6 %
15,3 % 14,3 % 14,3 %
7,4 % 13,7 % 13,7 %
67,4 % 67,4 % Stainless steel
72,4 % Solar panels
Ba.eries
Hardware transporta2on
Figure 10: Projected distribution of GHG emissions related to transportation (top), digital (middle), hardware (bottom) for GRANDProto300,
GRAND10k and the full GRAND array. The title of each graph indicates the total amount of emissions due to each source and each experimental
stage. These emission rates should be viewed as orders-of-magnitude estimates due to the large uncertainties inherent to projections and to emission
factor estimates.
13as usual scenario, we suppose that the lifetime of the GRANDProto300 (see Section 5.3) to the GRAND10k
devices is still the shortest presented in Table 1. The and GRAND200k phases.
middle row of Figure 10 shows that the contribution
of electronic devices remains limited among the digital 7.2.3. Data transfer and storage
emission sources. This stands even when assuming a As shown in Section 5 data transfer and storage is
strong increase in the collaboration size. an important source of GHG emission for the GRAND
project, especially if raw data is transferred and stored.
The data volume in the future will mainly scale with the
7.2.2. Simulations and data analysis number of detection units that will be deployed, which
Projections for numerical simulations and the related are already defined for each step of the project (300, 10k,
use of CPU time are difficult to make as they are depen- 200k for GRANDProto300, GRAND10k, GRAND200k
dent on the way scientists carry out research. Making respectively). This yields a gigantic volume of 2 EB/yr
projections for future years is highly hypothetical and (exabytes/yr) of raw data to store and transfer for the
uncertain. Moreover, the electricity intensity of Internet 200k antenna stage.
data transmission is dependent on the year, as digital Starting from the 10k phase, a data center will be built
technologies are changing fast. Therefore emissions on-site in order to directly process and reduce the data
computed in 2020 will have to be revised later in order storage. For instance, for the radio-astronomy data, by
to have a more accurate estimate, as the project will be adding the signals incoherently over the antennas (as
fully deployed in the 2030s. opposed to performing heavy Fast-Fourier-Transform-
There are several factors that can influence the future type operations to phase the signals) and storing only the
use of CPU time for simulations: the number of local sum (as opposed to keeping the individual signal for each
groups that run simulations for their own research, the antenna), we can divide the volume of data by the number
first results from GRANDProto300 that will call for more of antennas, and expect to gain 4 orders of magnitude
simulations (or not), the level of accuracy needed for the in volume for GRAND10k. For GRAND200k, the gain
simulations, the number of people that will work on would also be of 4 orders of magnitude, as it is limited
those simulations, etc. by the size of each sub-arrays (of ∼ 104 antennas each),
The current members involved in the GRAND simula- over which the information can be added.
tions estimate that about 6 M hours CPU will be needed As done in other radio experiments with large amounts
overall for GRANDProto300. For the next phases, it of data processing, the data will be classified according
is likely that the same library can be used, resorting to the treatment they have undergone. Raw data (D0)
for instance to interpolation and semi-analytical tools will be quickly processed and erased after a few months.
that are being developed [36, 37]. How much CPU A class of data with a first layer of reduction (D1) will
will be used (as well as how many new simulations be stored in a cloud until the end of a given observation
will be needed) would then depend more on how many program, and another class will be archived (D2). The
studies are being pursued (i.e., how many people work reduction from D0 to D1 will thus happen on-site, D1 to
on the project) rather than on the number of antennas D2 will be done in a nearby data center, in the country
in the array. We will hence start from the hypothesis of each 10k sub-array, and only D2 will be transferred
that the GHG emissions from simulations correspond worldwide.
to 26.9 tCO2 e (6 M hours CPU) for GRANDProto300 In practice, D2 will mostly correspond to the data
and scale with the size of the collaboration for the next "necessary for astroparticles" that were mentioned at
stages. More discussions can be found in Section 8.2.2. the end of Section 5.4. The data to be transferred and
stored will then be considerably reduced to 1 PB/yr for
For data analysis on the other hand, one expects that GRAND10k and 20 PB/yr for GRAND200k compared
the volume of data to be analyzed would scale along with to a simple scaling from GRANDProto300 emissions.
the size of the experiment (i.e., the number of antennas). We calculated our estimates for the GRAND10k and
Indeed, the signal extraction requires the full data to be GRAND200k stages of the project assuming that the
scanned and the corresponding CPU-time will scale with reduced data will be transferred and stored in 3 different
the data volume. The further layers of more "science- places.
driven" data analysis would scale with the number of Figure 10 shows that even with data reduction at
collaboration members, but this can be considered as a GRAND10k and GRAND200k stages, data transfer and
second-order effect. In order to make projections, we storage are the major sources of GHG emissions among
have scaled the GHG emissions from data analysis in the digital emissions.
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