Read through any article about green living, and sooner or later, you’re likely to come across the term “carbon footprint.” The phrase comes up so often that it’s pretty clear the authors think your carbon footprint is something you need to be concerned about. But what they don’t always bother to explain is just what your carbon footprint is, and why it’s so important.
The first question is pretty simple to answer: Your carbon footprint is the sum of all the greenhouse gas emissions you produce through your day-to-day activities. It’s called a carbon footprint because the main greenhouse gas involved in global warming is carbon dioxide, or CO2.
However, the second question is a bit more complicated. The short answer to why it’s so important is that your carbon footprint shows how much you personally contribute to global warming, and it points toward steps you could take to reduce your impact on the climate. But more generally, your carbon footprint is also a rough indicator of how much energy and other natural resources you use. So your carbon footprint is a good measure of how green your lifestyle is in general.
Understanding Your Carbon Footprint
The term carbon footprint is a variant of “ecological footprint,” a more general measure of how much of the planet’s resources you use. Your ecological footprint is expressed as the number of Earths it would take to support everyone on the planet if we all used resources at the same rate you do. For most Americans, that number is more than three Earths, according to Global Footprint Network.
A carbon footprint is a specific type of ecological footprint, one that focuses on greenhouse gases. This is useful because greenhouse gas emissions are closely tied to energy use. By calculating the carbon footprint for a group of people – a household, a business, a town, or even a whole country – you can get an idea of how much energy that group uses, and how it compares to the footprint for other similar groups. This information makes a good starting point for a plan to cut energy use.
How Your Carbon Footprint Is Measured
Your carbon footprint is usually measured in tons of “CO2 equivalent,” meaning that in addition to CO2, other gases are also measured. That’s because although CO2 is the main gas that contributes to global warming, other gases, such as methane, also have a strong effect. There’s much less of these other gases in the atmosphere, but it only takes a small amount to produce the same effect as a larger volume of CO2.
When you calculate your carbon footprint, you take the amount of these other gases you produce and convert it to the amount of CO2 it would take to create the same impact on the Earth’s temperature. Then you add that figure to your actual CO2 emissions to come up with your total carbon footprint. So your carbon footprint isn’t really just about CO2 – it’s actually a measure of all gases that affect the climate. Expressing it in tons of carbon equivalent is just a handy way of adding the impact of all the different types of greenhouse gas together.
What Contributes to Your Carbon Footprint
The easiest part of your carbon footprint to measure is your direct emissions. These are the greenhouse gases you produce personally, such as the exhaust that comes out of the tailpipe of your car or the chimney of your furnace. All you have to do to calculate these direct emissions is figure out how much fuel you used, in gallons of gasoline, gallons of oil, or therms of natural gas. Then you simply multiply that number by the amount of CO2 each gallon or therm produces when burned, and add it all up.
However, direct emissions make up only a fraction of your total carbon footprint. For many Americans, a much bigger portion comes from indirect emissions: the greenhouse gases produced to make the things you use. Nearly every object in your home, from your shoes to your TV set, had to be produced in a factory and shipped to the store where you bought it, and every stage in that process emits CO2. So each of your belongings has its own carbon footprint, and all of them together contribute to yours.
Even the food you eat factors into your carbon footprint. For example, beef comes from cattle, which produce methane, a potent greenhouse gas, in their digestive tracts. On top of that, the grain that’s fed to the cattle produces carbon emissions from the chemicals used to grow it and the gasoline burned to transport it. Transporting the cattle to the slaughterhouses and shipping their meat to stores piles on still more carbon emissions.
All this makes meat one of the most carbon-intensive foods you can eat. A 2014 British study published in the journal Climatic Change found that a meat-heavy diet produces more than seven kg of CO2 equivalent each day, while a vegetarian diet produces less than four kg daily, and a vegan diet less than three kg. This means that a vegan driving a gas-guzzling SUV could actually have a smaller footprint than a steak lover in a fuel-sipping hybrid vehicle.
Why Your Carbon Footprint Matters
When you calculate your carbon footprint, you learn several things. First, you can see how much greenhouse gas you personally put into the atmosphere – and more importantly, where those emissions are coming from. This means you can figure out which of the activities you do each day contribute most to global warming, and what you could do to reduce your personal impact on the climate.
But the benefits of calculating your carbon footprint don’t stop there. Since your carbon footprint is also a good indicator of your energy use, it can show you which of your everyday activities use the most energy, in the form of gasoline, electricity, or heating fuel. So any steps you take to shrink your carbon footprint are likely to shrink your energy bills as well, saving you money.
However, energy isn’t the only resource that’s tied to your carbon footprint. Many activities that produce CO2 and other greenhouse gases also use other natural resources, such as water, land, and raw materials. Shrinking your footprint is almost guaranteed to reduce your use of these other resources as well, preserving more of them for future generations. So by reducing the size of your carbon footprint, you don’t just help slow global warming – you also tread more lightly on the Earth in general.
Measuring Your Carbon Footprint
An accurate measurement of your carbon footprint has to include both your direct and indirect emissions. Direct emissions are fairly easy to calculate, but figuring out your indirect emissions is much more complicated. It’s pretty much impossible to calculate the exact carbon footprint of every single object in your house, so you have to figure out some way to estimate these emissions instead.
There are a wide variety of online calculators for finding your carbon footprint. However, each one uses a slightly different method to estimate your indirect emissions, and some are more precise than others about calculating direct emissions. For instance, the EPA and Carbon Footprint calculators ask you to input actual numbers for your home energy bill and your car’s gas mileage, while the calculators from the Nature Conservancy and the Center for Climate and Energy Solutions ask only general questions about what kind of home and car you have.
As a result, you can check your carbon footprint on different calculators and get widely differing results. For example, when I used the calculators listed below to find my carbon footprint, the results ranged from 6 to 17 tons. However, the last two calculators on the list, which are more accurate than the others, narrowed the range to between 7.3 and 9.5 tons.
Here’s how several online carbon footprint calculators stack up against each other:
- EPA. The calculator designed by the U.S. Environmental Protection Agency (EPA) estimates your carbon footprint based on three factors. It calculates your direct emissions from home energy use and transportation, and it uses the amount of waste your household produces to estimate your indirect emissions. In each section, the site lists steps you could take to reduce your emissions and shows how much they would shrink your carbon footprint. It also shows how your personal carbon footprint compares to the U.S. average. If you know a few basic facts about your household, such as your average monthly energy bill and your car’s gas mileage, you can complete this calculator in just a few minutes. However, because the only measure of indirect emissions is how much waste you recycle compared to the average U.S. household, the results aren’t that accurate.
- Nature Conservancy. This calculator from The Nature Conservancy uses the same categories as the EPA’s, plus an additional category for food and diet. However, instead of asking you to input actual numbers for things like home energy use and fuel efficiency, it asks general questions such as how big your car is and whether you have taken steps to heat and cool your home efficiently. This makes the calculator quick and easy to use, but not very precise in its results. The final page of the calculator compares your carbon footprint to the average for both the United States and the world as a whole.
- Center for Climate and Energy Solutions. The Center for Climate and Energy Solutions, a research organization, offers a carbon footprint calculator that gives you a very quick, rough estimate. It asks a series of short, general questions about your home, your car, and your use of other forms of transportation, but it doesn’t go into details like what you eat or whether you use renewable energy. You can see your results instantly, but to compare them with the average for people in your area, you must first register with the site and provide your e-mail.
- Carbon Footprint. The calculator from Carbon Footprint, an environmental consulting firm, is more thorough than most others. It has separate sections for your home, car, and other transportation, and it covers secondary emissions by asking questions about your diet, shopping habits, and use of services. At the end, it compares your carbon footprint to the average for your country, the industrialized nations, the whole world – and the target number each person in the world would have to achieve to contain global warming. Because this calculator is more detailed than others, it takes a bit longer but gives a more accurate result.
- CoolClimate. The CoolClimate Network at the University of California at Berkeley, has one of the most flexible carbon calculators. It asks questions about your travel, housing, food, and shopping habits, and you can adjust the questions to be more or less specific and detailed. At each stage, it shows how you compare to other households in your area with the same income and number of people, and at the end, it lists steps you can take to reduce your carbon footprint. This calculator’s results can be very precise or only approximate, depending on how much you personalize the questions.
Shrinking Your Carbon Footprint
Once you know what your carbon footprint looks like, you can start taking steps to shrink it down to size. You can reduce your footprint directly by taking steps to cut your CO2 emissions, such as driving less or eating lower on the food chain. However, it’s pretty much impossible to shrink your carbon footprint to zero this way. So after you’ve reduced your emissions as much as you can, you can offset the rest: Cancel them out by doing things that have a positive effect on the atmosphere, such as planting trees.
Reducing Your Carbon Footprint
Most carbon footprint calculators offer personalized tips on ways to reduce your greenhouse gas emissions – both direct and indirect. As a bonus, most of these carbon-cutting tips are also energy-saving tips that can save you money. Here are some of the strategies they recommend:
- Drive Less. The easiest way to reduce your car’s carbon footprint is to drive less. You can make short trips on foot or by bicycle, and for longer ones, you can carpool to reduce the amount of gas used – and carbon emitted – per person. You can also cut down on the miles you drive by combining multiple errands into a single car trip whenever possible. In some cases, you can avoid a trip altogether – for instance, by shopping online or working from home one or two days a week.
- Drive More Efficiently. You probably can’t eliminate all car travel, but you can reduce the amount of gas you use for each trip. For starters, you can improve your car’s gas mileage by keeping it tuned up, inflating the tires fully, and doing all scheduled maintenance on time. More efficient driving techniques, such as driving slowly and smoothly, also keep your fuel consumption down. Finally, when it’s time to replace your car, you can look for one that gets good ratings for fuel efficiency.
- Fly Less. Air travel is one of the most carbon-intensive activities there is. You can eliminate some plane trips by taking the train instead or by combining multiple trips into one. When flying is your only choice, look for nonstop flights, which produce less greenhouse gas emissions than connecting flights.
- Heat and Cool Your Home Efficiently. You can save energy on both heating and cooling by keeping systems tuned up and improving your home’s insulation, and weather-stripping to seal up air leaks. You can also adjust the thermostat a few degrees higher in the summer and lower in the winter. If that’s too uncomfortable for you, try using a programmable thermostat to adjusting the temperature only during times when you’re not home.
- Save Electricity. If you haven’t already upgraded your old incandescent light bulbs to more efficient CFL or LED bulbs, it’s high time to do it – especially since the old-school bulbs have mostly disappeared from the market by now, so you can’t buy new ones when yours burn out. Use a power strip to shut off electronic devices, such as TV sets, when you’re not using them; even in their “standby” mode, they still draw a steady trickle of electricity. And when it’s time to replace appliances or electronic devices, look for new ones with an Energy Star rating.
- Eat Carbon-Light. Eating lower on the food chain reduces your carbon footprint. Chicken produces less carbon than beef, and beans produce less than chicken. Adding just a couple of meatless meals to your diet each week can make a big dent in your carbon footprint.
- Reduce Waste. Pretty much any step you take to reduce waste, from composting to cutting out junk mail, also reduces your carbon footprint. Of the “three R’s” – reduce, reuse, and recycle – reducing waste is the most efficient, because most products use energy at every stage of their life cycle, from production through disposal. Reducing waste at the source cuts out extra energy use at every stage, while recycling only cuts it at the end of the product’s life cycle. Seemingly small steps have disproportionate impact, such as swapping disposable plastic bottles for a reusable, BPA-free sidekick like Reduce’s 40-ounce Axis bottle.
Offsetting Your Carbon Footprint
Cutting back on energy use is a good start, but the only way to reduce your carbon footprint all the way to zero is with carbon offsets. When you buy carbon offsets, you’re basically canceling out your carbon emissions by funding projects that reduce emissions somewhere else, such as reforestation and renewable energy. There are numerous companies that sell carbon offsets for both businesses and individuals.
- Carbon Footprint. Offset options at Carbon Footprint Ltd include reforestation in Kenya, planting new trees in Britain, and a variety of renewable energy projects around the globe. The cost of these offsets ranges from around $10 to $20 for each ton of CO2 equivalent.
- Carbonfund.org. Carbonfund.org invests in three types of carbon offset projects: It invests in renewable energy, such as wind farms and burning captured landfill gas; it invests in energy efficiency; and it works to conserve and restore forests. You can spend anywhere from $11.33 to offset the cost of a single airplane flight, to $960 to offset the carbon footprint of a whole family for a year. The site also offers a program wherein if you invest a certain dollar amount in planting trees, you get a Restaurant.com e-gift card for at least twice that amount.
- The Carbon Neutral Company. The Carbon Neutral Company sells carbon offsets for businesses only, not individuals. Its offsets fund a huge variety of programs, from Amazon rainforest conservation, to wind farms in India, to efficient cook stoves in rural Mexico.
- Native Energy. Carbon offsets from Native Energy go to fund the Ghana Clean Water Project. It provides clean filtered water for the people of Ghana’s Greater Accra Region so that they no longer need to boil their water to make it safe to drink. You can make a one-time donation of $14 per ton to offset your carbon footprint for the year or spread it out over a series of ongoing monthly donations.
- TerraPass. TerraPass offers a choice between a one-time offset and a monthly subscription. Its carbon offsets support clean energy programs, including wind farms and captured methane from landfills, coal mines, and animal waste. These projects offer a double benefit, since they keep heat-trapping methane out of the atmosphere and turn it into a fuel source. TerraPass offsets are also cheaper than most, at $5.95 per 1,000 pounds.
The saying “nobody’s perfect” is particularly true when it comes to your carbon footprint. It simply isn’t possible to live in the modern world without producing some greenhouse gases. However, it is possible to shrink your carbon footprint considerably – and even, with the help of offsets, wipe it out completely. Then you can feel confident that you really are doing everything you can do, at least on an individual level, to fight global warming and keep the Earth livable for generations to come.
What contributes most to your carbon footprint?