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Carbon is a Ruby API client and command-line console for the Brighter Planet impact estimate web service, which is located at By querying the web service, it can estimate the carbon emissions, energy usage, and other environmental impacts of many real-life objects, such as cars and houses, based on particular characteristics that they may have.

Full documentation: RDoc

Build Status

Quick start 1: experimenting with the console

You'll need a Brighter Planet API key. See the "API keys" section below for details.

First get the gem:

$ gem install carbon

Then start the console:

$ carbon

Provide your key:

carbon-> key '123ABC'
  => Using key 123ABC

Start a flight calculation:

carbon-> flight
  => 1210.66889895298 kg CO2e

Start providing characteristics:

flight*> origin_airport 'jfk'
  => 1593.46008200024 kg CO2e
flight*> destination_airport 'lax'
  => 1766.55536727522 kg CO2e

Review what you've entered:

flight*> characteristics
  => origin_airport: jfk
     destination_airport: lax

See how the calculation's being made:

flight*> methodology
  => emission: from fuel and passengers with coefficients
     [ ... ]
     cohort: from t100

See intermediate calculations:

flight*> reports
  => emission: 1766.55536727522
     [ ... ]
     cohort: {"members"=>262}

Generate a methodology URL:

flight*> url

And when you're done:

flight*> done
  => Saved as flight #0

You can recall this flight anytime during this same session:

carbon-> flight 0
  => 1766.55536727522 kg CO2e
flight*> characteristics
  => origin_airport: jfk
     destination_airport: lax

For more, see the "Console" section below.

Quick start 2: using the library in your application

You'll need a Brighter Planet API key. See the "API keys" section below for details.

Carbon works by extending any Ruby class to be an emission source. You include Carbon and then use the emit_as DSL...

# see Carbon::ClassMethods#emit_as for more details
class MyFlight
  def airline
    # ... => MyAirline(:name, :icao_code, ...)
  def aircraft
    # ... => MyAircraft(:name, :icao_code, ...)
  def origin
    # ... => String
  def destination
    # ... => String
  def segments_per_trip
    # ... => Integer
  def trips
    # ... => Integer
  include Carbon
  emit_as 'Flight' do
    provide :segments_per_trip
    provide :trips
    provide :origin, :as => :origin_airport, :key => :iata_code
    provide :destination, :as => :destination_airport, :key => :iata_code
    provide(:airline, :key => :iata_code) { |f| f.airline.try(:iata_code) }
    provide(:aircraft, :key => :icao_code) { { |f| f.aircraft.try(:icao_code) }

See RDoc on Carbon::ClassMethods#emit_as for all the details.

The final URL will be something like[iata_code]=MSN&destination_airport[iata_code]=ORD&airline[iata_code]=UA&aircraft[icao_code]=B737

When you want to calculate impacts, simply call MyFlight#impact.

?> my_flight =[...])
=> #<MyFlight [...]>
?> my_impact = my_flight.impact(:timeframe => => 2009))
=> #<Hashie::Mash [...]>
?> my_impact.decisions.carbon.object.value
=> 1014.92
?> my_impact.decisions.carbon.object.units
=> "kilograms"
?> my_impact.methodology
=> "[...]"

See RDoc on Carbon#impact for all the details.

API keys

You should get an API key from and set it globally:

Carbon.key = '12903019230128310293'

Now all of your queries will use that key.

Gotcha: timeframes and 0.0kg results

You submit this query about a flight in 2009, but the result is 0.0 kilograms. Why?

$ carbon carbon-> flight [...] flight*> date '2009-05-03' => 0.0 kg CO2e flight*> url =>

It's telling you that a flight in 2009 did not result in any 2011 emissions (the default timeframe is the current year).

flight*> timeframe '2009' => 847.542137647608 kg CO2e flight*> url =>

So, 850 kilograms emitted in 2009.


This library includes a special console for performing calculations interactively. Quick Start #1 provides an example session. Here is a command reference:

Shell mode

help : Displays a list of emitter types.

key yourkey : Set the developer key that should be used for this session. Alternatively, put this key in ~/.brighter_planet and it will be auto-selected on console startup.

emitter : (e.g. flight) Enters emitter mode using this emitter type.

emitter num : (e.g. flight 0) Recalls a previous emitter from this session.

exit : Quits.

Emitter mode

In Emitter mode, the prompt displays the emitter type in use. If a timeframe has been set, the timeframe is also included in the prompt.

help : Displays a list of characteristics for this emitter type.

characteristic value : (e.g. origin_airport 'lax') : Provide a characteristic. Remember, this is Ruby we're dealing with, so strings must be quoted.

timeframe : Display the current timeframe in effect on the emission estimate.

timeframe timeframe : (e.g. timeframe '2009-01-01/2010-01-01' or just timeframe '2009') Set a timeframe on the emission estimate.

emission : Displays the current emission in kilograms CO2e for this emitter.

lbs, pounds, or tons : Display the emission using different units.

characteristics : Lists the characteristics you have provided so far.

methodology : Summarizes how the calculation is being made.

reports : Displays intermediate calculations that were made in pursuit of the emission estimate.

url : Generates a methodology URL suitable for pasting into your browser for further inspection.

done : Saves this emitter and returns to shell mode.

Copyright (c) 2012 Brighter Planet.