PORTLAND (AP) – Maine ranks 33rd in the nation for overall emissions per capita, but is No. 1 for residential pollution per capita, according to government data.

The high rating for residential emissions is because Mainers are so reliant on oil for their heating needs. Seventy percent of Maine homes use oil as their primary heating source, the highest proportion in the country.

A relatively large number of Mainers also burn wood in their homes. About a third of all Maine residences burn wood, primarily as a secondary heating source in wood-burning stoves or in fireplaces.

To generate 1 million Btu, natural gas emits 117 pounds of carbon dioxide, while heating oil releases 162 pounds and wood releases 240 pounds, according to David Wright of the Maine Department of Environmental Protection.

In other emissions categories, Maine was fourth in the nation for commercial emissions per capita. Commercial emissions includes those from non-industrial businesses in their day-to-day work.

But Maine ranked low in other categories.

For output of coal-fired power, Maine was 46th. It ranked 44th for industrial emissions per capita and 41st for electric power generation emissions.