Post by davidm on Aug 9, 2012 0:03:29 GMT 9.5
Over the previous 5 years the US cut its CO2 emissions significantly. Some folks attribute this principally to the substitution of natural gas which increased considerably during this time due in large part to lower price made possible by fracking. Mostly this is wrong or misleading according to this article.
As it turns out increased hydro and wind played a significant role in this decline.
Then there appears to be a kind of Jevon's Paradox effect.
Finally when you are talking about total ghg effect, natural gas is as toxic as coal despite its lower CO2 emission per unit of energy produced. The joker in the deck is natural gas partially leaks in its original uncombusted form as methane, a ghg with a much higher greenhouse trapping effect than CO2.
To sum it up.
*I assume by this he is referring principally to efficiencies.
Because natural gas generates just over half the CO2 emissions of coal per unit electricity, it is considered cleaner. CFR Senior Fellow for Energy and the Environment Michael Levi made the point in this quarter’s edition of Foreign Policy. Natural gas’s lower carbon intensity and rising use has been lauded by the International Energy Agency (IEA) and in serious outlets like The Economist and the Financial Times as the reason US CO2 emissions declined in the five years between 2006 and 2011.
As it turns out increased hydro and wind played a significant role in this decline.
Emissions dropped at a rate a 1.56% per year in the 5 years up to 2011, dropping from 5,919 to 5,473 million metric tons. If the 50 million metric tons of CO2 savings from natural gas were excluded from this calculation, emissions would have dropped 1.38%. That 0.18% change is within any reasonable margin of error. Shale gas has indeed contributed to CO2 reduction, but trivially compared to other factors.
Then there appears to be a kind of Jevon's Paradox effect.
when the price falls as it did during the shale gas boom, consumption of natural gas gets a boost across all sectors—not just electricity generation. Sixty-six million metric tons, or 47%, of the increase in CO2 from natural gas occurred in commercial, residential and industrial sectors (Exhibits 7, 8 & 9) where natural gas isn’t necessarily displacing a dirtier fuel like coal. The 50 million tons it saved from substituting coal generation by virtue of its low price came at the cost of generating 66 million additional tons of CO2 from other sectors.
Finally when you are talking about total ghg effect, natural gas is as toxic as coal despite its lower CO2 emission per unit of energy produced. The joker in the deck is natural gas partially leaks in its original uncombusted form as methane, a ghg with a much higher greenhouse trapping effect than CO2.
Once we add in methane leakages to its CO2 emissions, natural gas could surpass coal in terms of its overall impact on our climate (Wigley 2011 and The New York Times 2011). And, just like coal, natural gas from shale rock also has a variety of local environmental impacts. When you combine these impacts —global and local, natural gas looks more and more like coal.
To sum it up.
Natural gas cannot be credited with the reductions in the US CO2 emissions observed in the last half-decade. Most reductions, nearly 90%, were caused by the decline in petroleum use, displacement of coal by mostly non-price factors*, and its replacement by wind, hydro and other renewables. Where low price of natural gas saved some CO2 by displacing coal, it was quickly offset by its increased use in other sectors—highlighting the pitfall of justifying the current market for natural gas as a “bridge” or an interim phase of transition towards clean energy.
*I assume by this he is referring principally to efficiencies.