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June 2011 Archives

'Contesting the future of Nuclear power'
Benjamin Sovacool, World Scientific

As someone who has been very critical of nuclear power, I was not expecting to be surprised by this book, which, according to the Introduction, sets out to prove that 'the basic premise behind a nuclear renaissance is wrong, whether one looks at it technically, economically, environmentally, or socio-politically'.

However I was surprised: I had not appreciated just how strong the case against nuclear power has become. Certainly if the nuclear lobby's relentless counter arguments have lulled you into a resigned acceptance that not everything about nuclear was bad, this book should provide a wake up call.

Following through the phases of the nuclear fuel cycle, it was good to be reminded just how much radioactive contamination uranium mining produced, including the tailings left behind. In terms of the uranium fuel production process, it was helpful to have the figures for carbon intensity. It has been said that 'nuclear power needs climate change more than climate change needs nuclear', but many people had no doubt presumed that, if we did accept a few new plants, they would at least avoid some carbon emissions. That expectation is dashed by this book- Sovacool claims that, as reserves of high grade uranium are depleted, there will be more carbon emissions from the fossil-energy powered nuclear fuel production process than from some directly fossil-fuelled plants.

In terms of plant operation, we are also often told that nuclear plants are relatively safe- and that this is confirmed by the fact that, for example, the Three Mile Island accident in 1979 did not lead to any serious emissions, much less deaths. But then Sovacool points out that this was a lucky fluke: 'It had a double containment shell capable of containing a hydrogen explosion only because the commercial flight path to Harrisburg Airport passed over the plant'. We were not so lucky with Fukushima, where, as Sovacool reports in a devastating postscript chapter, thin outer containment buildings were blown apart by hydrogen explosions.

Major accidents like this catch the headlines. Sovacool reports that 21 deaths have so far been linked to Fukushima - 7 from first responders and plant operators, and 14 elderly people who died during the evacuation process. None of these were due to radiation exposure, but he notes that 160 people have so far been exposed to 'hazardous' levels of radiation. Hopefully the final outcome will be less than the thousands of early deaths that followed Chernobyl - Sovacool quotes the low IAEA-WHO estimate of 4000, but also points to other studies, which suggest 93,000 early cancer deaths. But away from the media spotlight, there are claimed to be continuing deaths and disease as a result of routine emissions and occasional leaks from nuclear facilities: Sovacool quotes 3,780 premature deaths and 1,253 cancers globally per annum.

Of course it's not just people that have to be buried, but also nuclear waste. The back end of the nuclear cycle is probably its worst aspect- unless you are concerned about the prospects of terrorist attacks, the illegal diversion of nuclear material, or the proliferation of weapons making capacity. The latter issues relate to current geo-political conflicts, but the waste issue takes us beyond that into the far future. Sovacool quotes Alvin Weinberg's comment that, in terms of guarding and managing nuclear wastes, humanity seemed to have a ' remarkable belief that it can devise social institutions that are stable for periods equivalent to geological ages'.

All this for what Sovacool depicts as very expensive energy. While some of his explorations on nuclear power problems in terms of safety, security and so on, may be familiar to anyone who has followed the nuclear debate over the years, his treatment of the contemporary economic issues may introduce a new -and potentially conclusive- aspect to the case against nuclear. He quotes Amory Lovins' view that 'governments can have only about as many nuclear plants as they can force taxpayers to purchase', and presents chapter and verse on the ever-escalating costs of nuclear power- in some cases up to £10000/kW and rising.

In which case, why is anyone still backing it? Especially when, as Sovacool points out, there are a range of alternative options which are better - energy efficiency, cogeneration/CHP and the various renewables. Part of the answer seems to be that we have become locked in to a high tech nuclear path and seem to see anything else as unviable. For example he suggests that Japan could have focused on renewables instead of nuclear. He notes that, in total, it currently has 290 GW of conventional/nuclear power plant capacity in place, but has a total of 342GW of achievable potential in the form of onshore and offshore wind turbines (222GW), geothermal power plants (70GW), additional hydroelectric capacity (26.5GW), solar energy (4.8GW), and agricultural residue (1.1GW). However instead of developing this, it has built 50GW of nuclear and imported massive amounts of fossil fuel.

Sovacools chapter on alternatives does not duck the problems that some of them face, for example in terms of land-use conflicts, or the need to balance locally variable availability. But the sheer scale and variety of the renewables resource, and the rapidly falling costs of exploiting it, comes across very clearly.

The case for a change-over seem very strong and of course it is now happening. Following Fukushima, it seems unlikely that Japan will ever build any more nuclear plants. Germany certainly wont, and is phasing out its existing ones, while ramping up renewables rapidly, as is Switzerland and most of the rest of Europe, including now Italy- after 94% of those who voted in the recent Italian national referendum opposed the governments plan to build nuclear plants. China may well throttle back on its nuclear programme and expand its already very much larger renewable programme. It seems set to beat the USA and the EU in this regard, and certainly now has the economic power to do so.

Sovacool does not try to predict what is going to happen, but simply concludes that ' any effective response to electricity demand in a world facing climate change involves enormous expansion in our use of renewable technologies and a steady abandonment of nuclear power'.

Not everyone will agree, and some might ask for more discussion of new nuclear options including fast breeders, mini nuclear units and thorium based systems, while some will dismiss this book as just anti-nuclear propaganda. But it does present a well argued and wide ranging case that has to be faced.

"It is a dark day for Europe's leading role in tackling climate change", said the British energy secretary Chris Huhne. Poland had just rejected to sign on the Commission's "Roadmap for moving to a competitive low-carbon economy in 2050". According to this roadmap, indicative intermediate target for 2020, 2030 and 2040 would have been set, e.g. suggesting but not mandating a 25% reduction target for 2020 below 1990 levels. However, even the indication was not bearable for Poland, risking increased friction to other EU member states just before taking over the EU presidency.

Indeed, this is not the first time that Poland applies the brakes on EU climate policy, balking at previous allocations of emission certificates. The reason is not hard to identify: Poland is dependent on brown coal, the most polluting of fossil fuels.

It is clear that the EU has to offer Poland ways out of this dependency, e.g. providing support in to build-up an alternative infrastructures and energy saving measures. And in fact, it is likely that such a deal was part of the negotiations – but to no avail.

David Vincent from the British Carbon Trust has done a more thorough analysis of the Polish situation. In brief, the Polish elite does not yet see the benefits of a low-carbon economy; the coal lobby (coal companies but also miners' unions and allies in government) is traditionally strong while the environmental voice is rather quiet. Possibly, a Carbon Trust for Poland, supporting business in implementing low-carbon solutions, but also more activity from civil society could contribute to a mental change and subsequent policy change.

After Fukushima, the nuclear industry is facing some serious problems. Some are simply plugging on ahead, but adding promises that they will upgrade existing reactor safety and operations, but others are looking to new technology. High on the list of new ideas is the use of thorium as a new fuel, with one favourite being the molten flouride salt thorium reactor. This allegedly will generate fewer wastes and might even be able to burn some of them up.

The attraction of thorium is that there is three times more of it in the world than uranium, but its disadvantage, at least as a reactor fuel, is that it is not fissile. You have to supply neutrons- the options being to use a particle accelerator as a source or to use uranium/plutonium fission. One idea is to have a blanket of thorium around a plutonium core. But you could also mix them up, possibly using this mix as a fuel in conventional reactors, or dissolve them in molten form- as in the liquid fluoride molten salt concept, with the liquid acting as both fuel and coolant. Doing it all in one reactor would be ideal- then, arguably, there would be less risk of illegal diversion of plutonium, or the production of weapons material.

India has been looking at thorium for some while, since, as a non signatory to the Nuclear Proliferation Treaty, it has faced problems importing uranium for its nuclear programme- whereas it has plenty of thorium. But they have approached it in a different way.

WNN reported that 'The long-term goal of India's nuclear programme has been to develop an advanced heavy-water thorium cycle. The first stage of this employs the pressurized heavy-water reactors and light water reactors, to produce plutonium. Stage two uses fast neutron reactors to burn the plutonium and breed uranium-233 from locally mined thorium. The blanket around the core will have uranium as well as thorium, so that further plutonium is produced as well. In stage three, AHWRs burn the uranium-233 from stage two with plutonium and thorium, getting about two thirds of their power from the thorium.' Pretty complicated then, with several stages.

However , earlier this year, but before Fukushima, China announced that it would be developing a molten fluoride salt thorium system. Whether that, and China's High Temperature helium cooled Pebble Bed modular reactor project, survived the post Fukushima review of nuclear policy remains to be seen- all new projects were temporarily halted.

The UK nuclear industry does not seem very interested in thorium,- it's seen as a very long shot. Instead it is pinning its hopes for expansion on upgrades of the conventional pressurised water reactor- the French EPR and the US AP1000, even though neither of these have yet been built or operated yet.

A report from the UK's National Nuclear Labs (NNL), based at Sellafield, was pretty dismissive of the thorium option- it would take years to develop land there weren't many obvious benefits, given that uranium was plentiful.

NNL estimated that it would be likely to take '10 to 15 years of concerted R&D effort and investment before the Thorium fuel cycle could be established in current reactors and much longer for any future reactor systems'. It went on 'Thorium fuel concepts which require first the construction of new reactor types (such as High Temperature Reactor (HTR), fast reactors and Accelerator Driven Systems (ADS)) are regarded as viable only in the much longer term (of the order of 40+ years minimum)'.

What about the thorium breeder concept? NNL says 'The use of thorium in place of U-238 as a fertile material in a once-through fuel ...only yields a very small benefit over the conventional U-Pu fuel cycle. For example it is estimated that the approach of using seed-blanket assemblies (the blanket being the surrounding fertile thorium material) in a once-through thorium cycle in PWRs, will only reduce uranium ore demand by 10%. This is considered too marginal to justify investment in the thorium cycle on its own.'

And on the alleged avoidance or reduction of proliferation risks NNL says 'Contrary to that which many proponents of thorium claim, U-233 should be regarded as posing a definite proliferation risk. For a thorium fuel cycle which falls short of a breeding cycle, uranium fuel would always be needed to supplement the fissile material and there will always be significant (though reduced) plutonium production'.

On the economics, NNL says that 'while economic benefits are theoretically achievable by using thorium fuels, in current market conditions the position is marginal and insufficient to justify major investment. There is only a very weak technical basis for claims that thorium concepts using seed-blanket PWR cores will be economically advantageous. The only exception is in a postulated market environment of restricted uranium ore availability and thus very high uranium prices. This is not considered very likely for the foreseeable future.'

It's not totally dismissive though. It says that 'claims that thorium fuels give a reduction in radiotoxicity are justified. However, caution is required because many such claims cite studies based on a self-sustaining thorium cycle in equilibrium. More realistic studies which take account of the effect of U-235 or Pu-239 seed fuels required to breed the U-233 suggest the benefits are more modest. NNL's view is therefore that thorium fuel cycles are likely to offer modest reductions in radiotoxicity. It is considered that the realistic benefits are likely to be too marginal to justify investment in the thorium fuel cycle'.

So there is some faint praise, but otherwise it's a pretty damning review. Moving to perhaps even more exotic ideas, some see sub-critical particle accelerator driven systems ('ADS') as being useful, in that they could also possibly transmute some nuclear wastes, but that too is seen as a long shot option. A 2002 OECD/NEA study noted that ADS would require 'fuel cycles with multiple recycling of the fuel and very low fuel losses' and concluded that 'the full potential of a transmutation system can be exploited only if the system is utilised for a minimum time period of about a hundred years'

And more recently UK Energy Minister Charles Hendry has noted that 'As yet, industry has not indicated that they would be looking to develop and deploy sub-critical nuclear reactor designs in the UK in the near term future'.

Overall then it doesn't look too good for thorium based systems, at least in the UK. Some work is going on in the USA on ADS under the Generation IV programme. For example, Aker Solutions, is developing a subcritical 600MWe fast neutron reactor which sustains a chain reaction in thorium and MOX fuel by using an accelerator to shoot a beam of protons into the molten lead coolant. The theory is that if anything went wrong the beam could be shut down instantly, halting fission. It's a scaled-down version of Rubbia's Energy Amplifier idea, developed as a concept at CERN some years ago, but with a smaller, cheaper, accelerator. But that means it runs closer to criticality- with safety implications.

There is also some US work on high temperature / fast neutron reactors, which could use thorium, with a degree of waste burn up possibly being achieved. Some novel mini-reactors are also being developed. But in terms of utility scale projects, it seems that the US programme is some decades away from a practical commercial reactor. That will surely also be true of the Chinese programme- although small prototypes may emerge before then, a 20 year timeframe was mentioned. But a 10MW Japanese Fuju project is claimed to be likely to be ready within 5 years.

Basically, possible fast track break throughs like this aside, for the moment we are stuck with what we have got- uranium pressurised water reactors.

For more optimistic views, see: and Also And

There is clearly a significant lobby in the USA, including, notably, US climate scientist Dr. James Hansen, and there has been some positive UK media coverage, including from the Guardian:

But it probably didn't help the case for thorium that British National Party leader Nick Griffin MEP, backed the liquid fluoride thorium concept strongly in a recent speech to the Europarliament.


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Image by RaeA via Flickr

by Julia Römer and Felix Creutzig

Walking constitutes a particularly low-impact mode of transportation. While pedestrians can cover only relatively short distances, walking can have a high modal share and even substitute car trips if mixed-use and accessibility conditions enable neighborhood shopping and satisfaction of service demand.

What particular conditions are favorable for pedestrians? Here we summarize some insights from a recent report on Pedestrian Quality Needs in Europe (Methorst et al., 2010).

First, the safety of a pedestrian path network is a major factor because of its huge impact on use or avoidance of sidewalks. Safety includes two dimensions: traffic safety - being save from accidents and motorised vehicles; and subjective feeling of safety. Measures that reduce motorised traffic, lower motorised traffic speed or reduce crossing times of pedestrians increase traffic safety.One example is the implementation of so called Home Zones with reduced speed limits of 10 miles an hour. To improve the subjective feeling of safety the sidewalk's design has to be pedestrian-friendly. An adequate illumination of a sidewalk at night is an example for improvement.

Second, a pedestrian path network has to give pedestrians the chance to get to their destination as quickly as possible. Barriers, needless detour or waiting time leads to modal shift to less environmentally-friendly modes. Measures that improve the directness of a pedestrian path network, the connection with public transport or reduce waiting time therefore make sense. Examples are the implementation of scramble signals on large intersections, or same level pedestrian networks.

Third, walking has to be more attractive compared to other transport modes. Important indicators for the attractiveness of a pedestrian path network are accessibility and land-use. Pedestrian networks can be made more attractive by diverse design of the built environment, a multitude of options for pedestrian use, and active street life.

The report on Pedestrian Quality Needs brings together crucial insights on pedestrians. Nonetheless, scientific analysis is still far away from operationalizing pedestrian demand and supply in a systemic perspective.

Methorst R., Monterde i Bort H., Risser R., Sauter D., Tight M. & Walker J. (Eds.) (2010) Pedestrians' Quality Needs. Final Report of the COST project 358, Cheltenham: Walk21.

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Solar energy has been the focus of research effort for decades now, and some interesting new technologies have emerged. Most of the effort has been going into improving cell efficiency, using new materials or configurations, but there have also been some novel developments based on completely new concepts. For example, as reported in New Scientist last year (20/12/10), the US Dept of Energy's Idaho National Lab has developed a device that works on infra-red radiation - which accounts for about half of the available energy in the solar spectrum. Moreover IR is re-emitted by the Earth's surface after the sun has gone down, so the device can capture some energy at night. Lab tests have suggested that a complete system could have an overall efficiency of 46%; much higher than the best silicon cell at 25%. And they would not be so directionally sensitive. The new device doesn't rely on photons liberating electrons in semi conductors, as in conventional solar cells. Instead it uses tiny nano-scale antennas which resonate when hit by light waves, generating an alternating current at very high frequency. That has to be rectified to be useful- tricky it seems at nano-scale.

There are also some other clever new technologies on the horizon. For example A US team led by a North Carolina State University researcher have developed solar cell with a water-based gel infused with light-sensitive molecules - the researchers used plant chlorophyll in one of the experiments and have shown that water-gel-based solar devices can produce electricity.

The researchers say "We do not want to over-promise at this stage, as the devices are still of relatively low efficiency and there is a long way to go before this can become a practical technology. However, we believe that the concept of biologically inspired 'soft' devices for generating electricity may in the future provide an alternative for the present-day solid-state technologies."

Just as intriguing, New Energy Technologies Inc. has developed a room temp 'spray-on' solar PV coating for glass windows, using nano-particles 4 times smaller than a grain of rice . It's claimed to cut solar cost/kW by a third and leaves windows translucent.

Meanwhile, MIT has developed transparent organic PV cells, which can be used in windows. They only use near infra red wavelengths- the rest passes through:

Even more exotic, and moving beyond PV electricity production, is the prototype solar device that has been developed by researchers at CALTEC and in Switzerland which uses a quartz window and cavity to concentrate sunlight into a cylinder lined with cerium oxide, also known as ceria, which exhales oxygen as it heats up and inhales it as it cools. If, as in the prototype, hydrogen and/or water are pumped into the vessel, the ceria will rapidly strip the oxygen from them as it cools, creating hydrogen and/or carbon monoxide. The hydrogen produced could be used to fuel hydrogen fuel cells, while a combination of hydrogen and carbon monoxide can be used to create "syngas" for fuel.

The BBC web site reported that 'the prototype is grossly inefficient, the fuel created harnessing only between 0.7% and 0.8% of the solar energy taken into the vessel. Most of the energy is lost through heat loss through the reactor's wall or through the re-radiation of sunlight back through the device's aperture. But the researchers are confident that efficiency rates of up to 19% can be achieved through better insulation and smaller apertures. Such efficiency rates, they say, could make for a viable commercial device'.

However, in terms of even more radical large-scale developmental concepts, University of Tokyo researchers have launched a Sahara Solar Breeder project, aiming to use desert sand to produce PV solar units and desert sun to ultimately generate 50% of the planet's electricity, by distributing solar energy globally through a superconducting supergrid.

As I mentioned in my previous Blog, the idea is that power generated by the first wave of plants would be used to "breed" more silicon manufacturing and solar energy plants, which would in turn be used to breed yet more in a "self-replicating" system.

The initiative is funded by Japan's Ministry of Education, Culture, Sports, Science and Technology (JST) and the Japan International Cooperation Agency (JICA) under the auspices of the International Research Project on Global Issues, which will fund the project to the tune of 100 million Yen ($1.2 million USD) annually for five years.

The aim of this initial five-year phase will be to demonstrate the possibility of manufacturing high quality silicon from desert sand and of building a high-temperature superconducting long-distance DC power supply system. But they suggest that it should be possible to generate 50% of global electricity globally with solar by 2050 .

Clearly many of these ideas will take some time to develop to be viable options, and some won't succeed. But the pace of change in the solar world is quite dramatic. There is already over 40GW (peak) of conventional PV capacity in place globally and rapid growth continues, with new technologies and applications feeding in. For example over 20 MW of large-scale concentrator photovoltaics (CPV) systems are now connected to the grid, and CPV should reach GW level in the next 5 years, according to the European Photovoltaic Industry Association. Module efficiency in current power plants has reached 25-27% and is expected to grow to 30% by 2012. One of the attractions of CPV is the simple fact that, at present, mirrors, for focussing sunlight, are less expensive than PV cells.

New cheaper, light weight scratch resistant mirror materials are also emerging for use with concentrating solar (thermal) power (CSP) systems: That could make CPV, as well as CSP, more competitive. But even without that, focussed solar heat CSP seems to be booming. Some are hybrid systems with gas fired back-up/parallel generation, but with molten salt heat stores being added to some projects to allow for continued solar generation overnight.

Currently there is around 3 MW of CSP capacity in place globally and over 50 MW of new large-scale projects is being deployed around the world, mainly in Spain and the USA, but also in N Africa and the Middle East (see my last Blog). However, some say CPV will overtake CSP. Either way solar electricity generation looks likely to prosper, with much talk of price parity with conventional power sources within the next few years.

*For an interesting series of youtube videos on the many solar innovation projects in the USA, many of them seeking to copy/adapt phototsynthsis, see:

PV 'cheaper than oil' in Gulf

Falling costs of photovoltaic (PV) technology mean that solar energy is already a more economically attractive option for domestic electric power generation in the Gulf Cooperation Council Region (GCC) when compared to oil-fired electricity production. So said a White Paper published by Bloomberg New Energy Finance, which modeled the use of a 100MW PV project built in 2011 to displace oil-fired power generation, freeing that oil to be sold at world market prices.

The central scenario for PV capital cost was based around the 2010 global lowest price of $3.14 per Watt, but that will fall, with, it's suggested, the cheapest bankable systems in 2011 likely to be developed and built for $2.73/W with prices falling further thereafter, according to the established 'experience curve' for PV technology.

It was calculated that a PV project in the GCC would generate a real internal rate of return (IRR) of 9.4% if oil prices rise to $163/bbl (in real 2010 terms) by 2030. Even in the case of flat real oil prices to 2030, the project would generate a rate of return of 4.6%.

Michael Liebreich, Bloomberg New Energy Finance CEO, commented 'This exercise demonstrates the clear argument for large-scale deployment of PV in the Middle East region. The continued cost decline of PV will open up electricity markets in the Gulf extremely quickly.'

The study concluded that GCC states should be replacing the use of oil-fired electricity generation with large-scale and distributed photovoltaics, and earmarking their oil for sale on international markets. But even there they may face new challenges.

An expert group on future transport fuels presented a report to the European Commission showing that alternative fuels have the potential to gradually replace fossil energy sources and make transport sustainable by 2050. Expected demand from all transport modes could it said be met through a combination of electricity (batteries or hydrogen/fuel cells) and biofuels as main options. Synthetic fuels (increasingly from renewable resources) as a bridging option. Methane (natural gas and biomethane) as complementary fuel and LPG as supplement. The Bloomberg Paper is at

The next stage- exporting solar power

Using solar to replace oil for generating electricity in the Middle East is just the first step. Longer term they could be exporting it. PV is only part of the story. Several large Concentraing Solar Power (CSP) arrays are being built- e.g Egypt has a 150 MW Kuraymat hybrid solar- gas project. And more are planned. For example, Israel and Jordan have been developing CSP, the UAE is planning a 100MW project, and the Egyptian National Plan for 2012 includes a 100MW CSP plant in South Egypt, while the follow-up National Plan for 2018-2022 has 2,550 MW of CSP. Although most plants at present have gas-fired back up, molten salt heat stores can be used to capture some of the daytime solar heat to run the generators overnight- so offering 24/7 power.

Although, inevitably, oil still dominates their thinking, most oil-rich Middle Eastern countries have made commitments to energy diversification e.g. the UAE is aiming to get 7% of its electricity from renewable energy sources by 2020, while Egypt is aiming to get 20% of its power from renewables by 2020, much of which it has already achieved via large hydro (12%), but solar and wind are seen as the main new options.

Exporting power long distances (e.g. to the EU) via High Voltage Direct Current (HVDC) supergrid links is relatively efficient (energy losses are put at around 2% per 1000km) and there is a German led Desertec Initiative to link up CSP in desert areas in the Middle East and North Africa to the EU. It aims to get about 15% of the EU's power from such sources, with political links being made via the Med Unions 'Solar med' programme. Exporting power eastwards is also an option - to India and even China.


The Middle East has sun and oil. The first may soon begin to replace the last. It also has sand, and silica can be used to make solar cells. So the Middle East, along with North Africa, could become major producers of PV systems. The UAE's Masdar project has already established some PV cell production and this could grow rapidly as the world market for PV expands - it is one the fastest expanding areas in the energy field at present.

Indeed, there are plans for a 'Sahara Solar Breeder' project, aiming to use desert sand to produce PV solar units and desert sun , using the power generated by the first wave of plants to "breed" more silicon manufacturing and solar energy plants, which would in turn be used to breed yet more, in a "self-replicating" system.

It seems clear that the PV solar market is going to be big, and countries with plenty of sun, land and sand are a good place to exploit it. A big issue is whether the new political regimes emerging in many of these locations will see solar energy as a way forward- rather than just relying on oil.

The political turmoils in Middle East and North Africa may lead to the emergence of more progressive policies, but in the short term some see them delaying or undermining the case for 'Destertech' Concentrating Solar Power (CSP) electricity export projects- why would the EU want to become reliant on imported power from (another) politically unstable area? The counter view is that there is no need for the EU to become dependent on this source- all that was being suggested was around a 15% contribution and that could opportunistic i.e. when prices were low there and high in the EU e.g. matching their peak supply and EU peak demand times. In any case, CSP projects (and maybe Concentrating PV projects) are likely to go ahead locally anyway, since there are many local benefits, not just energy and jobs, but also the option of desalination of sea water.

Mapping forest carbon stocks

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biomass map.jpg

By James Dacey

The distribution of stored carbon across the globe is considered to be a major uncertainty in greenhouse gas emissions calculations. But this map could help to improve the situation by detailing the spread of biomass carbon stocks over 2.5 billion hectares of forests across three continents – encompassing all tropical forests.

The map was created by researchers in the US, the UK and Gabon, who combined satellite data and ground-based observations to calculate above- and below-ground biomass quantities to a resolution of 1 km. To calculate forest heights, the researchers collected more than 3 million lidar shots using an instrument aboard NASA's Ice, Cloud,and land Elevation Satellite (ICESat).

Presenting their map in a paper published online yesterday in Proceedings of the National Academy of Sciences, the researchers say that forests in the study region contained 247 GT of carbon. Forests in Latin America, sub-Saharan Africa, and south-east Asia accounted for 49%, 25% and 26% of the total carbon stock respectively.

The regions with the largest carbon biomasses are highlighted in deep red, while the zones with the least carbon are coloured in violet.

The researchers say that the new data and accompanying map could help developing countries in the study area to implement climate change mitigation policies relating to deforestation and degradation (REDD).