Negative emissions

The United Nations Framework Convention on Climate Change (UNFCCC) calls for setting a  2℃ or even lower target to avoid dangerous climate change, which needs to stabilize atmospheric greenhouse gas concentration in certain level.  According to recent released The Emissions Gap Report 2012 [1], "Current global emissions are already considerably higher than the emissions level consistent with the 2℃ target in 2020 and are still growing.". Indeed, current global gas emission are estimated at 50.1 GtCO2e, which is 14% higher than the emission level  in 2020 with a likely (>66%) chance to achieve 2 degree target [1].  It implies that stricter action and country pledges should be carried out immediately, or "net negative emissions", i.e., more greenhouse gases are removed than emitted ― should be achieved.

In previous posts, I've talked about some basic ideas about CCS and biomass energy(1,2), and now why not  combining these two mitigation strategies to create a greater effect in terms of emission reduction.  Here comes the BioCCS (or BECCS)  ―  the combination of CO2 Capture and Storage (CCS) with bioenergy production ― a process can reach a net removal of CO2 from the atmosphere [2]. The critical step towards carbon negativity is that after we extract the oil from biomass stock, if we can trap and store the residue for good then it won't decompose and return CO2  to the atmosphere. In this way, more CO2 is removed than the biofuel burns and emits [3]. In fact,  recent scenario surveyed in the IPCC Special Report on Renewable Energy Sources and Climate Mitigation indicate that BioCCS may become a feasible medium-term mitigation option[4].

source: International Energy Agency

References
1. The Emissions Gap Report 2012 , UNEP, 2012. http://www.unep.org/publications/ebooks/emissionsgap2012/

2. Biomass with CO2  capture and storage (Bio-CCS)-The way forward for Europe, ZEP & EBTP, 2012.
http://www.zeroemissionsplatform.eu/library/publication/206-biomass-with-co2-capture-and-storage-bio-ccs-the-way-forward-for-europe.html

3. The feasibility of low CO2concentration targets and the role of bio-energy with carbon capture
and storage (BECCS), Azar et al., Climatic Change, 2010.
DOI 10.1007/s10584-010-9832-7

4.IPCC Special Report on Renewable Energy Sources and Climate Mitigation, IPCC, 2011.
http://srren.ipcc-wg3.de/report

Shale gas : good gas or bad gas

George Osborne, the Chancellor of the Exchequer of the UK, just announces "Gas Generation Strategy" on 5^th December. This plan will partly provide tax incentives for shale gas production companies, which critics believe will lock Britain in to a high-carbon future, according to the Guardian. [1]

Shale gas by definition is nature gas trapped in shale rocks. Nature gas, although is cleaner than coal (less pollutant after burning), the drilling process of shale gas has been a highly controversial issue. 

Shale formations, source: U.S. Energy Information Administration

Shale gas used to be uneconomical to produce, while during last decade the U.S. have invented a method, hydraulic fracturing aka fracking, to drill shale gas out in a commercial scale. Since 2005 shale gas production in the states has been booming; now it accounts for one third of the total nature gas production. And shale gas surge has not only led to a drop in gas price for households, but also a switch to cheap gas from coal in power plants. The latter did have a influence on  the nation's CO₂ emission, which in 2010 were lower than in 2005 by 7 percent. [2]  Many countries including China and UK, now want to explore its own shale gas reservoirs to "not miss out on the opportunities being enjoyed in the U.S"[1].

At first glance, shale gas seems to be a good alternatives to fossil fuels. However, shale gas has two accompanying potential problems. One is the nature of gas, methane is a powerful greenhouse gas having 25 times global warming potential than CO₂. We'll come to this point later. The other danger is coming from the hydraulic fracturing  process.   

To mine out shale gas, first, a hole is drilled down to the shale layer, which is hundreds of meters wide but only ten meters thick, so the wellhole is turned horizontally. Then a mix of vast amounts of water, sand and chemicals is injected under high pressure into the well, creating tiny fissures in the shale rocks, through which the natural gas flows into well.       

Fracking process, source: http://www.propublica.org

So why is fracking so controversial?

Water contamination is one of major hazardous problems. When shale layer is beaneth aquifers, if mismanaged, the water-chemical mixture ― which may contain toxic chemicals (benzene, lead etc.) ― and methane as well can be released into the aquifer by leaks and faulty wells [3].  According to ProPublica, "water contamination has been reported in more than a thousand places where drilling is happening" [4]. In addition, fracking process is related to some small-scale earthquakes and seismic activity. Moreover, Howarth et al. indicate that the emissions of shale gas are greater than conventional gas, coal or oil over a short term time scale (20 years) [5]. On the other hand, other studies suggest that greenhouse gas footprint of shale gas is lower than coal; higher than conventional gas [6]. And a recent report for European Commission proposes that if emissions from shale gas are not controlled, the greenhouses gas emissions from domestic shale gas will be greater than utilizing imported conventional gas [7].      

In summation, keeping on investment in shale gas may undermine developments in  renewable energy. With these potential costs to the environments and contaminants to drinking water, the U.S. EPA is currently carrying out a study of the fracking, while New York state has bloked fracking. Meanwhile, in Europe, France and Bulgaria have banned shale gas fracking. It seems like the U.K. may be a little bit 'avant-garde' in exploiting shale gas.       

References

1. Gas strategy unveiled by George Osborne, the Guardian, 2012.

2. Good gas, bad gas, National geographic report, 2012.

3. What is shale gas and why is it important?U.S. Energy Information Administration, 2012.

4. Gas Drilling: The Story So Far, ProPublica, 2010.

5. Methane and the greenhouse-gas footprint of natural gas from shale formations, Howarth et al, Climate change, 2011. DOI 10.1007/s10584-011-0061-5

6. A commentary on “The greenhouse-gas footprint of natural gas in shale formations” by R.W. Howarth, R. Santoro, and Anthony Ingraffea, M. Cathles et al., Climatic Change, 2012. DOI 10.1007/s10584-011-0333-0

7. Climate impact of potential shale gas production in the EU, EC DG Climate Action, 2012.