What can we do about future methane emissions?
So far, we have only looked at past methane concentrations. Future projections, however, might be more urgent to look at. Methane emissions are projected to increase in the future (fig. 1), mainly due to continued fossil fuel use and agricultural activities.
According to the business-as-usual scenario (RCP8.5), methane levels are projected to be ~3750ppb at the end of this century. Taking a GWP of 28, this amount would equal ~105ppm CO2 emissions. To put that into context, CO2 levels are projected to be around 1000ppm by 2100. Methane is thus not as big a threat as CO2, but still substantial.
A seminar by professor Viv Jones set me to think about geo-engineering. The seminar adressed the potential of mitigation of climate change by capturing CO2 from the atmosphere and storing it, for example, under ground. Would such a technique be possible for atmospheric methane? Will it be necessary?
Atmospheric capturing is, I think, less suited to methane emissions than it is for CO2. Whilst CO2 circulates between reservoirs, methane breaks down. This destruction not only results in a shorter lifetime of methane than of CO2, it also means that it is possible to influence methane's lifetime. Methane sinks break down a larger fraction of methane emissions, when less methane is emitted. According to the IPPC AR5, methane's lifetime will decrease under RCP2.6 and RCP4.5, will remain constant under RCP6.0 and increase under RCP8.5. Thus, my thoughts about geo-engineering were nonsense - we should just reduce emissions. Opportunities for reduction lie in the realms of industry and agriculture.
The industry leaves room for improvement in tackling fugitive emissions, by upgrading equipment. When this methane is captured from, for example, coal mines or landfills, it can be used again for energy production (arguably more sustainable than diesel fuel).
There would be one simple solution for reducing methane emissions in agriculture: less consumption of beef. However, is not easy to make people change their diet. Therefore, more and more studies focus on reducing emissions from cows by altering their feed composition (Maia et al., 2016; Meale et al., 2014; Martin et al., 2016; Penn State University, 2015). Some projects go even further in their aims to reduce emissions by trying to modify the cow's genome, mainly by selective breeding.
One way or the other (or preferable all ways together), methane emissions should be reduced. Because of methane's relatively short lifetime, it is possible to decrease atmospheric levels and bring the methane cycle into equilibrium again.
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| Figure 1 | Projected methane emissions for this century for the four different RCPs. Top: Anthropogenic methane emissions in Mt/yr. Bottom: Total methane concentrations in ppb. Pre-industrial levels were ~700 ppb. RCP& are rescaled values, according to updated AR5 values. The small uncertainty in the figure actually surprised me as we have seen that there is still a lot unknown about the relative contribution of methane sources. The shown uncertainties arise from uncertainties in emissions from land use change, agriculture, the atmospheric lifetime for each scenario and in chemical feedbacks (although, remember that permafrost methane emissions are not included in these uncertainties). |
A seminar by professor Viv Jones set me to think about geo-engineering. The seminar adressed the potential of mitigation of climate change by capturing CO2 from the atmosphere and storing it, for example, under ground. Would such a technique be possible for atmospheric methane? Will it be necessary?
Atmospheric capturing is, I think, less suited to methane emissions than it is for CO2. Whilst CO2 circulates between reservoirs, methane breaks down. This destruction not only results in a shorter lifetime of methane than of CO2, it also means that it is possible to influence methane's lifetime. Methane sinks break down a larger fraction of methane emissions, when less methane is emitted. According to the IPPC AR5, methane's lifetime will decrease under RCP2.6 and RCP4.5, will remain constant under RCP6.0 and increase under RCP8.5. Thus, my thoughts about geo-engineering were nonsense - we should just reduce emissions. Opportunities for reduction lie in the realms of industry and agriculture.
The industry leaves room for improvement in tackling fugitive emissions, by upgrading equipment. When this methane is captured from, for example, coal mines or landfills, it can be used again for energy production (arguably more sustainable than diesel fuel).
There would be one simple solution for reducing methane emissions in agriculture: less consumption of beef. However, is not easy to make people change their diet. Therefore, more and more studies focus on reducing emissions from cows by altering their feed composition (Maia et al., 2016; Meale et al., 2014; Martin et al., 2016; Penn State University, 2015). Some projects go even further in their aims to reduce emissions by trying to modify the cow's genome, mainly by selective breeding.
One way or the other (or preferable all ways together), methane emissions should be reduced. Because of methane's relatively short lifetime, it is possible to decrease atmospheric levels and bring the methane cycle into equilibrium again.
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