A carbon offset is a financial instrument representing a reduction in greenhouse gas (GHG) emissions. Although there are six primary categories of greenhouse gases, carbon offsets are measured in metric tonnes of carbon dioxide - equivalent (CO2 e). One carbon offset represents the reduction of one metric tonne of carbon dioxide, or its equivalent in other greenhouse gases (GHG).

Offsets are typically generated from emissions - reducing projects. The most common project type is renewable energy, such as wind farms, solar energy, or hydroelectric dams. Other common project types includes energy efficiency projects, the destruction of industrial pollutants or agricultural by-products, destruction of landfill methane, and forestry projects. Purchase and withdrawal of emission trading credits also occurs, which creates a connection between the voluntary and regulated carbon markets.

Buying carbon offsets is only part of the solution to global warming. We must also reduce the amount of activity that creates excessive carbon dioxide and other greenhouse gases (GHG) such as methane. Here's a computation that all of us can implement:

At Home

Step 1
Replace 75-watt incandescent light bulbs with 25-watt ENERGY STAR Lights i.e. compact fluorescent lights (CFL)

You'll get the same amount of light for less energy and lower monthly bills. By replacing the five most frequently used lights in your home with ENERGY STAR qualified lighting, you can save about Php 2,880 each year in energy costs.

Formula:

Emission reduction = number of 75-watt incandescent light bulbs replaced x annual KWH savings per lamp x electricity emission factor

Assumptions:

Emission factor (lbs CO2/KWH) = 1.37
Annual KWH savings per lamp = 73

Sample Computations:
For 5 pcs 75-watt incandescent light bulbs replaced

Emission reduction = 5 pcs lamps x 73 KWH annual savings/lamp x 1.37 lbs CO2/KWH = 500 lbs CO2/year

Compute for percentage emission reduced based from total emissions lbs CO2/year = 13,803.52 lbs CO2/year

% Emissions Reduced = (Emissions Reduction / Total Emissions) x 100

% Emissions Reduced = (500 lbs CO2/year / 13,803.52 lbs CO2/year) x 100 = 3.6 %

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Step 2
Replace your old refrigerator with an ENERGY STAR model. Will you take this action?

Formula:

Emission reduction = (average KWH/year old fridge - average KWH/year new fridge) x electricity emission factor

Assumptions:

Emission factor (electricity/KWH) = 1.37
Annual KWH savings = 380
Average KWH/year old fridge = 820
Average KWH new fridge = 440

Sample Computations:
For old fridge replaced with new fridge model.

Emission reduction = (820 - 440) KWH/year x 1.37 lbs CO2/KWH = 520.6 lbs CO2/year

% Emissions Reduced = (520.6 lbs CO2/year / 13,803.52 lbs CO2/year) x 100 = 3.77%

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Step 3
Turn up your air conditioner thermostat by degrees F (air conditioners becomes colder if you lower the temperature thermostat settings). If your air conditioner has no thermostat dial it means that it has automatic thermostat dial complimented with low, medium cool, and high cool settings. You can choose the medium cool settings with this regard.

Formula:


Assumptions:

Percent of total electricity emissions accounted for by air conditioning = lbs CO2/year electricity x % of total electricity emissions

Lbs CO2/year electricity = 6,395.16
Percent of total electricity emissions = 0.16
Percent emission reduction per degree = 0.05
Assumed percentage of the year air conditioner is in use = 0.42

Sample Computations:

If you turn up your thermostat dial by 10 degrees F:

Emissions reduction = 6,395.16 lbs CO2/year x 0.16 x 0.05/degrees F x 10 degrees F x 0.42 = 215 lbs CO2/year

% Emissions Reduced = (215 lbs CO2/year / 13,803.52 lbs CO2/year) x 100 = 1.56%

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On The Road

Option 1
Are you in the market for a new car? Buy a vehicle that gets more miles per gallon than your current one. The Fuel Economy Website (http://www.fueleconomy.gov) can help you find efficient vehicles.

Formula:


Assumptions:

Annual emissions from vehicles = 4,338.95 lbs CO2/year
Let's assume that you changed your previous car with a sub-compact car (Toyota Yaris) to increase mileage from 26 MPG to 29 MPG (Source: http://www.fueleconomy.gov/FEG2009.pdf). If driven 17 kms (10.62 miles) from Valenzuela to Manila back and forth from monday to friday.
Lbs of CO2 emitted per gallon = 19.4
Emissions of greenhouse gases other than CO2 = 100/95 = 1.053

Sample Computations:

% Emissions reduced = (448.86 lbs CO2/year / 13,803.52 lbs CO2/year) x 100 = 3.25%

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Option 2
Give your car a break. Reduce the number of miles you drive.

Formula:

Assumptions:


Lbs CO2 emitted per gallon = 19.4
Emissions of greenhouse gases other than CO2 = 100/95 = 1.053

Sample Computations:

If you give your car 1 day break and retain your old car:
Emission reduction = (10.62 mile x 2 / day x 1 day / week x 52 weeks / year) / 26 miles /gal x 19.4 lbs CO2/gal x 1.053 = 2.08 lbs CO2/year

% Emission reduced = (2.08 lbs CO2/year / 13,803.52 lbs CO2/year) x 100 = 0.015%

Option 3

Walking, biking, carpooling, telecommuting, and using mass transit are best options.