There are thousands of carbon calculators out there on the internet, all giving different results to the same inputs, largely due to the different assumptions, methodology and data adopted and the targeted level of accuracy. WWF wanted to produce a carbon footprint calculator that was closely matched to the lifestyles and facilities available for Hong Kong residents giving users a first look into their carbon footprint and helping them make a first stab at reducing it. Many carbon calculators that are built in other countries are not appropriate because, for example, they are applicable to cooler climates, or because the power stations use different fuels. The WWF Climateers specifically uses data gathered in Hong Kong to build a carbon calculator that reflects Hong Kong living.
Our goal has been to create a simple yet decent enough calculator that can be completed in less than five minutes in a coffee shop. The latest version, launched in early 2009, covers more aspects of our daily life than most Asian carbon calculators, including emissions from water usage, public buses and waste.
The calculator totals the amount of carbon dioxide (CO2) produced from different lifestyle activities, with the exception of the aviation footprint which is more complex. CO2 is the main greenhouse gas responsible for global warming.
The simplest cases are when we buy fuel directly, for instance buying petrol for cars or gas for our apartments. Different fuels produce very different quantities of CO2, for instance liquefied petroleum gas is far cleaner than diesel fuel.
It becomes more complex when we talk about emissions from electricity. HK's power companies use a different mix of coal, gas and nuclear (and even a tiny amount of wind), and have power plants of different ages and with varying efficiencies. Also, electricity usage is highly seasonal, for example because air conditioning is used less in winter, and we make an estimate of how electricity usage changes through the seasons. So once we know the date, your location (therefore your electricity producer) and your electricity bill, we can work out with a good accuracy the CO2 contribution from your electricity consumption for that month and make an estimate for the whole year.
More approximations were involved when estimating emissions for people without their household bills. We started with figures released by the Hong Kong Government Electrical and Mechanical Services Department (EMSD) that provide a breakdown of how energy is used in HK's homes-- for instance, the proportion of home energy that is used in lighting, air conditioning and heating water. We make some judgments about how the average energy use changes with home size and number of people, for instance, that the energy used in lighting increases with the area of the apartment, but that hot water use per individual is the same whatever size apartment you live in. We then apply assumptions about the fuels used in the generation of this energy to derive the carbon footprint estimate.
Although water usage accounts for a relatively small part of an individual's carbon footprint, we have decided to include it in the calculation to highlight the importance of this resource. In fact, the process of getting water to your home is more complex in Hong Kong than in many countries. Around three quarters of the fresh water is piped from the mainland, and then treated and pumped around a series of reservoirs before coming through the taps. All these processes use energy. With energy usage data and average household consumptions of fresh and sea water, published by the Water supplies Department, we benchmark users' water usage habit against the average and produce an estimated footprint figure.
The major energy impacts of household waste are: useful sources of energy that can be recycled are thrown away, forcing new product to be manufactured and the release or collection of greenhouse gasses from landfill sites. The first of these is most important, and by asking how much of three major trash grouped people recycle, combined with values for the energy required to manufacture products from new, we can estimate the energy savings from recycling.
Rubbish buried in landfill sites slowly decomposes, releasing greenhouse gasses which need to be collected if they are not to contribute to climate change. According to the Environmental Protection Department's Waste facilities Group, most landfill gas is currently being captured and flared. Ideally the gas is processed and reused, but flaring it is still a big improvement. Lacking adequate data needed to reasonably estimate the volume of greenhouse gas produced from a typical tonne of domestic rubbish, the current calculator does not deal with emissions from landfills.
For all the public transport (ferry, bus, minibus and MTR), due to the complexity of the routing and pricing mechanism used by different service providers, we have adopted a simplified approach taking the total energy usage and divided it by the time or cost of the journey based upon data supplied by the companies respectively.
For air travel we break flights down by flight length in order to make it easier for people to remember and enter which trips they have taken. These flight lengths are then multiplied by a standardised figure for CO2 emissions per passenger km. In addition the aviation calculator uses a multiplier (a 'Radiative Forcing Index' of 2.7) to reflect the fact that the greenhouse gas emissions from aviation cause more damage at altitude, than if they were released at the ground level. Because of the long distances involved and the multiplier factor, people who fly a lot will find that aviation is often the dominant part of their carbon footprint.
The whole point of finding out one's carbon footprint is that one can take relevant actions to reduce our impact on climate change. Through the interactive pledges presented by the carbon calculator at the end of the journey, users can choose what actions they plan to take and to what extent they want to take up those carbon reducing lifestyle changes. Together, all users' pledges would amount to a collective carbon emissions reduction per year, convertible to carbon storage capacity of trees, showing how cumulated small actions can make a big impact!
By registering on Climateers, users will be able to save their carbon footprint whenever they have re-calculated the latest carbon footprint and track their footprint trends. With a Climateers account, the emissions spread among your home, transport and air travel and your projected footprint reduction from your pledged actions will also be kept in your account history. You can recall the saved data through logging in.
In addition to the approaches calculating personal emissions in the home, for travel and for flights the calculator adds on 2.7 tonnes of CO2 per year to everyone's footprint. The Hong Kong add-on represents emissions from HK's industrial, commercial and government sectors that provide goods and services to HK's people, but still leave a carbon footprint. For example shopping malls, government offices, construction and other sources outside the individual's control are all included in this figure. We include this figure because we want to capture the fact that not everything is covered by the carbon calculator. As this project expands we hope to provide more data about other parts of people's lives that carry a carbon footprint - and where they can take action.