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.

NASA is cultivating renewable energy?

You may wonder what's the relationship between NASA and renewable energy.
In fact, according to Jonathan Trent, the lead scientist at NASA Ames Research Center, " we are not passengers on spaceship Earth, we are the crew." Imagine we are astronauts going into space towards Mars, where will take at least 3 years to reach. And we have to bring life necessities and manage to use resources in a more sustainable way to accomplish missions and, most of all, survive. Living in a resources-limited Earth is much the same scenario as in a spaceship, which is what inspired NASA's "Sustainable Energy for Spaceship Earth" project.  Among this project, producing biofuels from algae has become main interest. Why? Economics. Last blog, I mentioned some second-generation biomass like Switchgrass which can yield 500 GJ/ha/yr (≒240 Gcal/acre-yr). While some microalgae can produce over 5000 Gcal/acre-yr, that is, 2,000 gallons of oil per acre per year. You can easily make a comparison of microalgae with other biomass from the following figure.

Source: TEDxSanJoseCA -Jonathan Trent, PhD - Can We Cultivate Energy?

Although two pilot land-based methods, open ponds and closed bioreactors, have been used to grow freshwater algae, there are some inevitable freshwater and land resources problems. Growing algae in open ponds needs sustainable water supply to prevent evaporation influencing steady growth conditions. While in closed bioreactors, evaporation won't be a disturbance, yet the computer-monitored systems are extremely expensive.

Bioreactors. Source: NASA 

To overcome these obstacles, NASA scientists have developed an ingenious system, ' Offshore Membrane Enclosure for Growing Algae (OMEGA)'. OMEGA is designed to commercially produce  carbon-neutral biofuel, yet it can at the same time clean waste water. In addition, cultivating algae in offshore doesn't compete with agriculture for land, freshwater or fertilizers. How does it achieve lots of advantages? Are there any potential effects on environments?

source: NASA

The idea is straightforward, nonetheless, state of the art techniques are needed. In OMEGA,  freshwater  algae are grown in semi-permeable membranes(plastic bags), filled with sewage providing growth nutrients. The algae can clean up the waste water while growing, meanwhile, clean water can pass  naturally into ocean via membranes (osmosis). The 'forward-osmosis membranes' can retain the algae and nutrients while release freshwater. In addition, algae absorbs carbon dioxide from the air and release oxygen after photosynthesis. Hence, biofuels produced from the algae are carbon-neutral, i.e. , the same amount of CO2 is fixed by the algae and burned using biofuels , no additional CO2 is released. These membranes also provide some marine habitats for aquaculture.

Now you may think what if this system is leaked and the algae is released to the ocean? According to Trent, OMEGA won't cause any environmental problems. The freshwater algae will either become a  part of food chains or die in the ocean.

Compared to the other land-based biomass, which consuming water and fertilizers and requiring land usage, OMEGA seems to be quite a solution to the resources depleting world.

References:
NASA OMEGA

TEDxSanJoseCA - Jonathan Trent, PhD- Can We Cultivate Energy?

Second generation bioenergy

Rapeseed and Sorghum/Photo taken in Quemoy, Taiwan

"A new generation of biofuels could meet almost half of Britain’s renewable transport needs, but without them the UK will miss its 2020 target, a new Government-commissioned report warns." [1]

What's 'a new generation of biofuels' about?

We've heard  news about first-generation bioenergy - bioethanol, produced mainly from food-based crops, like sugarcane and corn. And the food v.s. fuel competition has driven concerns in terms of food security. Whether subsided bioenergy has influence on food price and caused political unrest around developing countries is debatable [2]. 

While second-generation bioenergy, might be less controversial, converted from inedible part of plants- leaves, stalks, stems etc. and can avoid turning food into fuel. There are several processing platforms for producing different biofuels, among these routes, lignocellulosic biomass for ethanol has some promising perspectives [3].  There are four types of lignocellulosic biomass, including  agricultural residues, dedicated energy crops, wood residues, and municipal paper waste [4]. S. Yuan et al.[3] used net energy balance (NEB) as an indicator to examine whether a biofuels platform is environmentally and economically sustainable. A high positive NEB means higher energy output than input for biomass production and processing. For instance, ethanol from some popular lignocellulosic feedstocks in Europe, Switchgrass, and Miscanthus can yield 150-500 GJ/ha/yr and 250-550 GJ/ha/yr respectively. Compared with some first-generation biofuels platforms, NEB of maize and sugarcane is 10-80 GJ/ha/yr and 55-80 GJ/ha/yr respectively. They also proposed that if the hurdle of efficient convention into ethanol from lignocellulosic biomass can be overcome, then a NEB of  up to 600 GJ/ha/yr will be a plausible expectation [3]. In addition to higher energy gain and lower production costs,  poplar and switchgrass have a negative carbon balance, which means more carbon dioxide is fixed by the plants than emitted from production and usage of bioenergy [3]. If more carbon is sequenced by biomass crops, then bioenergy can be a feasible solution and mitigation to global warming.      

References

1.Greenwise

2.Bioenergy: Fuelling the food crisis?

3.S. Yuan et al., Plants to power: bioenergy to fuel the future, 2008, Trends in Plant Science.

4.Wikipedia: Lignocellulosic biomass

Carbon Capture and Storage: false hope or real mitigation?

I've posted a brief introduction of Carbon Capture and Storage (CCS), now let's have a follow-up discussion about if CCS is a double-edged sword.

First, from Greenpeace's points of view[1],
'The technology (CCS) is highly speculate, risky and unlikely to be technically feasible in the next twenty years.'
The reason being,

1. CCS cannot deliver in time to avoid dangerous climate change.The earliest commercial CCS equipped power plant is not expected before 2030, whilst climate scientists suggest that we should cut global greenhouse gas emission by at least 50% by 2050, compared to 1990 level to avoid climate crisis.
2.  CCS waste energy. Capturing and storing carbon are pricey and need lots of energy. In addition, power plants with capture technology will need more freshwater than those without. 
3. Storing carbon underground is risky. There is always a risk of leakage after injecting carbon into geological sites. Even as low as 1% of continuous leakage will undermine the mitigation efforts. Not to mention CO2 leakage can have a potential threat to ecology systems and  health.
4. Funding CCS is at expense of  real solutions like renewable energy. Moreover, according to Greenpeace's Energy [R]evolution [2], using renewable energy combined with energy efficiency is sufficient to cut global emission by almost 50% and at the same time deliver half the world's energy need by 2050.

On the other hand, R. Stuart Haszeldine, a professor of University of Edinburgh, has published a review article[3] and proposed urgent action is required to overcome hurdles of CCS developments, providing that CCS plays a role in mitigating climate change. Here are some of his viewpoints which are not necessary against Greenpeace's.  

1.  CCS pilots and experiments are already operating, and can be increased to cost-effective commercial size by 2020. This depends on not only a pricing carbon market but also additional policy levers to provide revenue to realize large investments and enforce developments .
2. Technical challenges from carbon capture to transport and storage can be progressively  resolved, but the road to rapid commercial deployment is less certain. For example, all three kinds of carbon capture technologies(i.e., precombustion, postcombustion and oxyfuel combustion) have different pros and cons. It will be much slower to replicate each other with competitions between three types rather than only one type of capture is dominant.   
3. CCS can be responsive on a renewable electricity grid. For instance, at extreme period of no wind, which is not rare, then backup fossil fuel generation will be needed.

What do you think?

Actually, I worked in an environmental consultant company in Taiwan before my current studies at UCL climate change program, and last year I had participated in organization of a CCS seminar and press conference which announced the commencement of Taiwan CCS projects. In other words, I used to have some positive recognition of CCS. Nonetheless, after I read the reports above-mentioned, I start to think about whether CCS is a real mitigation for tackling climate change. Moreover, simply look at the following quotation from Haszeldine's report [3],

'Several commercial developments(CCS) seen likely to operate before 2015 in the U.S; Alberta, Canada; Queensland, Australia; U.K., and Abu Dhabi, United Arab Emirates.'

I just sensed some unusual relationship between these nations CCS developments and their fossil fuel 

industrial giants...

References

1.False hope: Why carbon capture and storage won’t save the climate, 2007, Greenpeace International.http://www.greenpeace.org/usa/en/media-center/reports/false-hope-why-carbon-capture/

2.The Energy [R]evolution, 2012, Greenpeace International, Greenpeace International and European Renewable Energy Council. http://www.greenpeace.org/international/en/publications/Campaign-reports/Climate-Reports/Energy-Revolution-2012/

3. Carbon Capture and Storage: how green can black be, 2009, R.Stuart Haszeldine, Science, vol 325.

Carbon Capture and Storage: a brief intro.

Source: awards.earthjournalism.org

From the International Energy Agency (IEA) to the Intergovernmental Panel on Climate Change (IPCC) have recognized  Carbon Capture and Storage/Sequestration (CCS) as a feasible technology to reduce CO2 emission from coal or gas fired power planets.  The idea is straightforward, first, CO2 emission can be captured at a specific installation and pressurized to liquid, then liquified CO2 can be transported to a storage site, such as exploited oil field, saline formation or below the seabed.  Moreover, future monitoring plans will be needed to prevent and remediate deficient storage.

source: IPCC, 2005

In principle, there are three methods of carbon capture[1, 2],

1. Postcombustion, in other words, the CO2 is removed after combustion of the fossil fuel.  This technology uses chemical solvents to separate CO2 and is currently applied  to power plants as well as other industrial applications.
2. Precombustion, i.e., the fossil fuel is partially oxidized, and H2 and carbon are separated before combustion taking place. 
3. Oxyfuel combustion, coal or gas are burned in oxygen instead of air to yield CO2 and water.

Likely, there are two main storage options are being considered, geological storage and mineral storage. The former method involves directly inject CO2 into underground geological formations, for example, oil fields, gas fields and saline formations etc.. In the latter one, the CO2 is reacted with metal oxides, which in turn produces stable carbonates. However, according to IPCC, a power plant equipped with CCS using mineral storage will need 60-180% more energy than one without CCS.

So far so good? One may start to worry about the safety issues accompanying this so-called mitigation technology. Moreover, the concern can be put in this way, does it sound more like an excuse of keeping on the track of using fossil fuels? Or does it can help to achieve Kyoto protocol targets without sacrificing a 'civilized' living standard? We may need more research and scientific evidence to make a plausible conclusion.  I'll address more about these considerations of applying CCS in the present and future commercial scale power stations in my following blogs.

References:
1.Wikipedia: CCS
2. R.Stuart Haszeldine, Carbon Capture and Storage: how green can black be, science, 2009.
 

The opening

 Photo taken in Taitung, Taiwan.

The Royal Society held a seminar, Towards a low carbon future in 2008, the key conclusion arising  from the meeting was that 'there is no single best solution in moving towards a low carbon future : an integrated approach making best use of all available technologies is required.'.  In the meeting's summary report,  several issues addressed regarding how to achieve a low carbon economy in terms of short, medium and long-term developments. Following are some addressed topics:

• Decarbonization of the electricity supply (including renewable energy and bioenergy)
• Major gains in energy efficiency and energy savings (including energy storage and green architectures)
• Decarbonization of transport and agricultural sector
• A coherent portfolio of policy measures and specific mechanisms

In this Blog, I'll explore among these above-mentioned issues and review related scientific news and papers, hope you'll enjoy it in a low carbon way.