2007 US greenhouse gas emissions: cement, limestone, natural gas, and other industries

The Energy Information Administration (EIA) has released a report on U.S. greenhouse gas (GHG) emissions in 2007 (Note: ftp link).

What attracted my attention was the "other sources" category, of which cement contributed ~46 million metric tons (MMT) of CO2/year in 2007 (~0.8% of total U.S. greenhouse gas emissions). The next highest contributor was lime-making, which involves limestone calcination. Aluminium (3.8 MMT) production contributes much lesser to U.S. GHG emissions compared to cement production. Additionally, iron and steel production likely contributes ~45 MMT CO2/year. On the other hand, recent high-gas prices partly contributed to higher natural gas production (and higher CO2 co-produced from natural gas). CO2 emissions from natural gas-flaring in the U.S. were not projected to change from 2006 (7.8 MMT CO2/year). In the figure, the values for natural gas show a spike in 1995, from my data it appears to be due to significantly higher natural gas flaring, than CO2 production from natural gas.