Individual Carbon Footprint
What is a carbon footprint? According to Wiedmann and Minx
(2008), “There is no consensus on how to measure or quantify a carbon
footprint. The spectrum of definitions ranges from direct CO2 emissions to full
life-cycle greenhouse gas emissions and not even the units of measurement are
clear.” The authors test the concept with a series of questions, asking whether
greenhouse gases other than CO2, such as methane, can be components of a carbon
footprint, and even those which, like nitrous oxide, contain no carbon. They
question whether the carbon footprint of a “product, process or person” should
be confined to direct emissions, or whether it should “reflect all life-cycle
impacts of goods and services used”. After illustrating a range of definitions found
in publications in 2006-7 the writers propose their own: "The carbon
footprint is a measure of the exclusive total amount of carbon dioxide
emissions that is directly and indirectly caused by an activity or is
accumulated over the life stages of a product."
As an example of a carbon footprint calculation, they cite a
report on UK households, which suggested that the carbon footprint of an
average UK household was 20.7 tonnes of CO2 in 2001. This comprised emissions
resulting from private cars; direct fuel use in the home; electricity in the
home; aviation and public transport; recreation, leisure and tourism; food,
drink and catering; household appliances; clothing and footwear; health,
hygiene and education; other goods and services. Heating and car use
represented direct emissions, and indirect emissions were “the emissions that
occur during the generation of electricity and the production of goods and
services” whether produced in the UK or elsewhere.
Birnik (2013) wrote that while “carbon calculators can play
an important educational role in increasing public awareness, a key challenge
at present is that there does not exist any standard or consensus regarding how
personal carbon footprints should be calculated.” He defined a carbon footprint
as amounting to “the greenhouse gas emissions generated by a person or household
within a specified time period”, and proposed a set of principles to which a personal
carbon footprint calculator should conform. These include requirements that emissions
estimates should account for methane and nitrous oxide as well as carbon dioxide,
and be based on 100-year global warming potential (GWP) conversion factors; consumption-based
footprints should be made regardless of where goods and services are produced; estimates
should take into account the user’s income or consumption and the household
size rather than using national averages, and should model housing emissions in
detail, noting energy use, goods, repairs and maintenance, food and transport;
and calculations should be based on up-to-date and geographically specific emission
factors. Birnik evaluated and rated a range of carbon calculators, providing
detailed notes on each. He commented on a number of typical shortcomings:
documentation is generally very poor; most fail to provide comprehensive carbon
footprints including most greenhouse gas emissions of a user; none appeared to
have based their estimations on consumption based data; and most did not adjust
for income or consumption and for the number of people living in a household.
Further, the popularity of the calculators did not appear to be correlated with
the quality ranking as defined in his paper.
Birnik’s principles helped guide the basis of comparison
used by Mulrow et al. (2019) in a study on publicly available carbon footprint
calculators that focus on the individual. The authors noted that the simplest
calculators only consider energy-related activities; others consider lifestyle,
consumption, food and travel, and some offer advice on reducing carbon
emissions. As well as input categories
such as home energy, transport, food and water, the depth of measuring inputs
was examined, for example by reference to green energy options, flight categories
and food emissions. User engagement was evaluated through the display of
emission values by category, country and world averages, and final value, and
calculators were rated on outputs such as advice for lowering emissions, likely
consequent carbon reduction, and on educational value. The results of
evaluations on 31 calculators, assessed by 15 criteria, are discussed and results
displayed as radar plots. The highest scores were for calculators by Carbon
Independent, with Carbon Footprint Ltd and Cool Climate Network second and
third; other calculators with notable high performance measures were WWF, ISCFC
and Carbotax. A survey of users showed
that while more than half had used a carbon footprint calculator previously,
only a minority could recall their calculated footprint measure. About three
quarters of participants reported knowing little about their home energy use,
and few could relate quantities such as 1 kg of CO2 or 1 kWh of energy to daily
activity. The writers believed that there is much work to be done in improving
carbon footprint calculators’ approach to user interaction and behaviour
change, perhaps by better integrating with mobile phone/sensor technologies,
and that calculators could easily move beyond simply calculating carbon
emissions, to include economic, social and environmental metrics.
A study by Barendregt, Biørn-Hansen and Andersson (2020)
moves beyond “traditionally calculated emissions based on user input about …
food, heating, and traveling”, by using data derived from their transactions. A
novel carbon calculator, called Svalna, “aims to provide users with a detailed
insight into their GHG emissions based on their consumption by making use of
transaction data from bank statements” thus simplifying and automating data
collection. Data from the user’s bank is “paired with data on GHG emissions per
monetary unit … estimated using Environmental Extended Multi Regional Input Output
analysis (EE-MRIO) for Swedish conditions.” Data on fuel type and consumption and annual mileage
is found from the Swedish Transport Agency using the car’s registration number,
and the National Board of Housing, Building and Planning provides data on
average energy use from the user’s home address. The user supplies data on dietary
choices, food waste, physical activity, and commuting habits. While many users were willing to connect their
bank account, others “perceived safety risks in doing so” and had limited
confidence in “the correctness of the estimated greenhouse gas emissions.” Further
work is planned to investigate “whether Svalna causes users to reduce their
emissions significantly.”
Burgui-Burgui and Chuvieco (2020) note the shortcomings of carbon
calculators highlighted by previous authors, and describe their Carbon
Footprint Observatory, named CO2web. This was intended to promote citizens’
awareness about personal GHG emissions and encourage “behavioral change though
focused recommendations”. It presents the scientific basis of climate change,
the concept of CF and its calculation, and explores lower emission alternatives
to habitual behaviour regarding food, transportation, clothing, hygiene, home
appliances, IT/devices and pets; it also includes a personal CFC, preceded by
an explanatory section. Users are offered “the possibility of comparing the
results with people of similar characteristics”, by age, sex, work, place of
residence, level of studies; and gives an “analysis of the reasons that could
explain why their emissions were higher or lower than the average values” for
their group. Initial results indicate that the first version of the site can be
used directly for educational purposes in schools and universities, and future
work “will focus primarily on evaluating the response of users, as well as the
changes experienced regarding their awareness and actions taken towards a
low-carbon life.”
Children do not appear in the list of categories found in a
typical carbon calculator, but the difficult, highly personal and emotive issue
of offspring is addressed by Murtaugh and Schlax (2009), who consider the
future environmental consequences of the reproductive choices of an individual.
They note that “should the offspring reproduce, additional impacts could
potentially accrue over many future generations” and they attempt to quantify
these impacts “by tracing a single female’s genetic contribution to future
generations and weighting her descendants’ impacts by their relatedness to
her”. The carbon emissions of descendants, thus weighted, are then reckoned as
the responsibility of their ancestor. A parent’s genetic material “propagates
through subsequent generations”, and multiplying its amount by the “per-capita
rate of carbon emissions over time” allows a value to be estimated for the
carbon legacy of an individual.
The calculations clearly depend upon life expectancy,
fertility, and expected carbon emissions per person, and so will vary greatly
from region to region. Estimates were made for eleven countries, using three different
emission scenarios: optimistic, with global emissions falling to 0.5 t CO2 per
person per year by 2100; constant, with emissions remaining at the 2005 global
average figure of 4.31 t per person per year; and pessimistic, with emissions
rising to 1.5 times their 2005 value by 2100, and continuing to rise
thereafter. The scenarios all assume the figure for fertility projected by the
United Nations in 2007. Since these converge for all nations to 1.85 children
per woman by 2050, the genetic contribution of a single individual declines in
later generations, allowing a finite emissions legacy to be calculated. The
largest average legacy figure per individual on the constant emissions scenario
is found in the USA, at 9441 t CO2 (5.7 times the life time emissions of the
ancestor); Bangladesh has the smallest average legacy figure, at 56 t CO2.
These figures are compared, for the USA, with the lifetime emissions savings
possible from measures such as reducing travel and improving home energy
efficiency: having one fewer child far outweighs such savings in the constant
and pessimistic emissions scenarios, and is somewhat greater even in the
optimistic scenario. The authors point out that this comparison does not reduce
the urgent need cut present emissions.
References
Barendregt, W., Biørn-Hansen, A. and Andersson, D., (2020), Users’ Experiences
with the Use of Transaction Data to Estimate Consumption-Based Emissions in a
Carbon Calculator, Sustainability 2020,
12(18), 7777
Available at https://www.mdpi.com/2071-1050/12/18/7777
Birnik, A., (2013), An evidence-based assessment of online
carbon calculators, International Journal
of Greenhouse Gas Control, Volume
17, September 2013, Pages 280-293
Accessed from https://www.academia.edu/
Carbon Footprint Ltd calculator
https://www.carbonfootprint.com/calculator.aspx
Carbon Independent calculator
https://carbonindependent.org/
Carbotax calculator
Cool Climate Network calculator
https://coolclimate.berkeley.edu/calculator
CO2web Carbon Footprint Observatory
ISCFC calculator
https://depts.washington.edu/i2sea/iscfc/calculate.php
Mulrow J., et al. (2019), The state of carbon footprint
calculators: An evaluation of calculator design and user interaction features, Sustainable Production and Consumption
Volume 18, April 2019, Pages 33-40
https://doi.org/10.1016/j.spc.2018.12.001
Murtaugh, P., and Schlax, M., (2009), Reproduction and the
carbon legacies of individuals, Global
Environmental Change 19 (2009) 14–20
http://sites.science.oregonstate.edu/~murtaugp/files/gec-2009.PDF
Wiedmann, T. and Minx, J. (2008), A Definition of 'Carbon
Footprint. In: C. C. Pertsova, Ecological
Economics Research
Trends: Chapter 1, pp. 1-11, Nova Science Publishers, Hauppauge NY, USA.
Published as ISAUK
Research Report 07-01, available at http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.467.6821&rep=rep1&type=pdf
WWF calculator
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