**1.3 Methane emissions from the gas industry**

The debate of climate change has shifted from merely considering CO2 to also methane, where a significant fraction of the emissions is associated with oil and gas production. These methane emissions can reduce or even completely offset the greenhouse gas benefits of using gas instead of the more carbon-intense fuels coal and **oil.** The "2021 Oil & Gas Benchmarking Report "[12] with a focus on the USA reads: *"EPA-estimated methane emissions from crude oil and refined oil product systems decreased 28% from 1990 to 2015. However, emissions estimates remain uncertain"* [13], see also **Figure 10**.


#### **Figure 10.**

*Sources of methane emissions in the USA in 2015, as estimated by the Environmental Protection Agency (EPA). Source: [13].*

#### **Figure 11.**

*"Well-to-city-gate" greenhouse gas intensities of natural gas supplies to China from >100 different fields. In the depiction, the colors represent emissions by individual processes. The confidence intervals are 90% (error bars). X-axis: Number of gas field; Y-axis: kg of CO2 equivalent per MJ [14].*

*Value-Added Products from Natural Gas Using Fermentation Processes: Fermentation of Natural… DOI: http://dx.doi.org/10.5772/intechopen.103813*

In the US, it is estimated that enteric fermentation, e.g., from cattle, accounts for ¼ of anthropogenic methane emissions. Landfills are responsible for 1/5 of the emissions, on the same level as manure. Approx. 1/3 of man-made methane emissions are attributed to natural gas and petroleum systems, with high uncertainty (and recent evidence that this fraction will be higher).

Recent work has assessed the well-to-city-gate greenhouse gas intensities of natural gas in a Chinese setting, see **Figure 11**.

We can see from that study that there are huge differences in the negative climate effects of natural gas. Domestic natural gas from domestic sources is slightly better, on average, than overseas LNG, but can be a factor of 10 better than international pipeline-derived natural gas. Natural gas can be lost in pumping stations or at the end user, e.g., as unburnt fuel, which all adds up to the radiative forcing.
