text: co2Emissions = massCO2PerDistance * distance * passengers;
  returnValues.putValue('CO2', 'kg',null, co2Emissions);
  
  try {
    var c = massCH4PerDistance;
    ch4GWP = parseFloat(dataFinder.getDataItemValue('planet/greenhousegases/gwp','gas=CH4','GWP')); //global warming potential for CH4
    massCH4PerDistance /= 1000.0;
    ch4Emissions = massCH4PerDistance * distance * passengers;
    returnValues.putValue('CH4', 'kg',null, ch4Emissions);
    returnValues.addNote('comment', 'CH4 emissions converted to CO2e using a global warming potential of '+ch4GWP);
  } catch(error) {
    ch4Emissions = 0;
    ch4GWP = 0;
    returnValues.putValue('CH4', 'kg',null, ch4Emissions);
    returnValues.addNote('comment', 'CH4 emissions not available for this item');
  }
  
  try {
    var n = massN2OPerDistance;
    n2oGWP = parseFloat(dataFinder.getDataItemValue('planet/greenhousegases/gwp','gas=N2O','GWP')); //global warming potential for N2O
    massN2OPerDistance /= 1000.0;
    n2oEmissions = massN2OPerDistance * distance * passengers;
    returnValues.putValue('N2O', 'kg',null, n2oEmissions);
    returnValues.addNote('comment', 'N2O emissions converted to CO2e using a global warming potential of '+n2oGWP);
  } catch(error) {
    n2oEmissions = 0;
    n2oGWP = 0;
    returnValues.putValue('N2O', 'kg',null, n2oEmissions);
    returnValues.addNote('comment', 'N2O emissions not available for this item');
  }
  
  co2eEmissions =  co2Emissions + (ch4Emissions * ch4GWP) + (n2oEmissions * n2oGWP);
  returnValues.putValue('CO2e', 'kg',null, co2eEmissions);
  returnValues.setDefaultType('CO2e');
  