Mass methane emissions top expectations: Study

Methane emissions in eastern Massachusetts are about six times higher than the state estimates and about half of the methane in the air associated with natural gas is coming from end users, according to a study published on 25 October by the Proceedings of the US National Academy of Sciences (PNAS).

There was no change in emissions over eight years despite efforts from the state to repair leaks from natural gas pipelines. The study found that about 2.5pc of natural gas going into Boston is lost.

The state measures emissions coming from natural gas pipelines, which are generally kept at a constant pressure all year. Emissions should not vary with different consumption levels through the seasons but PNAS found methane emissions were higher in the winter, when customers use natural gas to heat homes and buildings. The study suggests that higher winter emissions are because of leaks within those homes and buildings. This further suggests that pipeline leaks are not the main source of methane emissions, as previously thought.

Methane, a greenhouse gas, is the largest component of natural gas, which heats half of the homes in the state and supplies 70pc of the region's energy needs. Gas pipelines in the state are some of the oldest in the US, according to the Gas Leaks Allies report. Each year, about 14,000 new gas leaks are identified in the state.

Governor Charlie Baker signed a climate bill in March 2021 for Massachusetts to reach net zero emissions by 2050. The plan includes intermittent goals such as a 50pc reduction in emissions in the state from 1990 by 2030, and a 75pc reduction by 2040.

Burning natural gas should release less CO2 molecules into the atmosphere than burning coal. The impact of leaking natural gas in addition to burning is equivalent to the emissions released when burning coal, the study said.

Fixing natural gas leaks in pipelines is already a priority in many cities including Boston, but policy makers may need to expand regulations to address leaks in homes and buildings previously not accounted for.

By Nola Z Valente