No-one serioulsy questions that renewable energy offers global environmental benefits over the alternative of fossil-fired power stations, as a means of generating the power we need.

 

These global benefits, however, often come at a price that has to be paid at the local level, in terms of the ecological and environmental damage associated with specific projects.

 

This “global gain versus local cost” issue is set to gain prominence with the proposal to build a barrage across the Severn estuary. A recent report by the Sustainable Development Commission (SDC) has noted that the barrange could “supply 4.4% of UK electricity supply from the second greatest tidal range resource in the world, generating electricity for over 120 years. Developing a Severn barrage would result in significant climate change and energy security benefits.”[1]

 

The SDC noted, however, that securing these benefits would have “a major impact on the local environment, with the loss of up to 75% of the existing intertidal habitat, which is internationally protected. There would also be a number of impacts on local communities and the regional economy, and a high risk that unsustainable ancillary development would take place alongside any barrage project.”

 

The recent announcement of Government support for this project ahead of the SDC’s report has galvanised opposition to the project. Dr Mark Avery, Conservation Director at the RSPB, said: "Its construction will cause the emission of ten million tonnes of carbon. Greenhouse gas savings will be substantial in the long run, but those savings could be too late to avert the damage of climate change…It would be far better to spend the £15 to £20 billion the barrage will cost on measures that will cut emissions more quickly. The Severn estuary is an irreplaceable refuge for wildlife”[2]

 

This view was supported by Natural England: "The mudflats, sandbanks, rocky platforms and saltmarsh of the Severn Estuary comprise one of the largest mosaics of habitat of their type in Britain, supporting important populations of waterfowl, invertebrates and large numbers of migratory fish."[3]

 

The environmental damage that is brought about by large hydro-electric schemes has long been a cause of concern. The Three Gorges dam in China has long been accused of causing major ecological harm: “The Three Gorges Dam is the world’s most notorious dam. The massive project sets records for number of people displaced (at least 1.3 million), number of cities and towns flooded (13 cities, 140 towns, 1,350 villages), and length of reservoir (more than 600 kilometers). The project has been plagued by corruption, spiraling costs, technological problems, human rights violations and resettlement difficulties…Erosion of the reservoir and downstream riverbanks is causing landslides, and threatening one of the world’s biggest fisheries in the East China Sea. Scientists estimate that annual catches may be reduced by one million tons due to the decline in fresh water and sediment reaching the sea”

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The RSPB’s comment that the Severn Barrage construction would cause “the emission of ten million tonnes of carbon” may seem surprising, but it’s not the first time that hydro-electric projects have been criticised from a carbon-saving viewpoint. In 2000, the World Commission on Dams concluded: "All large dams and natural lakes in the boreal and tropical regions that have been measured emit greenhouse gases… some values for gross emissions are extremely low, and may be ten times less than the thermal option. Yet in some cases the gross emissions can be considerable, and possibly greater than the thermal alternatives"[5].

 

You may conclude from all this that the problem is restricted to hydro power, but this is far from the case. Wind farms may seem a benign way of generating power, but even these can give rise to environmental and ecological concerns.

Research into the local weather effects of wind farms carried out by scientists at Princeton University in 2004 found they could cause a drying and warming effect in the morning when turbines push warm air across moist and cool overnight soil. “Unaddressed, the severity of the local weather impact induced by large wind farms would fall somewhere between the environmental costs of deforestation and global warming,” lead researcher Baidya Roy said.[6]

 

 The culprit in local climate impacts is the turbulent air left in the wake of each turbine's rotors. This artificially energized air stirs up horizontal layers of air near the surface more than normal, leading to more vertical mixing of the atmosphere.

 

“To reduce the global climate effects, engineers could install wind farms in ways that their effects counteract one another globally. ..Engineers could reduce the turbulence by designing rotors and farms differently so they produce less wake, possibly by turning rotors up to the sky like helicopter blades or a ceiling fan”, Roy said.

 

Measuring the net effects of growing biomass crops for energy use is not straightforward, either. Crops can be converted to energy either by being processed into liquid fuel for the transport sector (biofuels) or by being burnt in power plants (biomass). Effectively, producing energy from biofuels or biomass could be seen as ‘recycling’ CO2.

 

However, this rosy picture is over-simplistic. “Bioenergy production is never a neutral process when it comes to “greenhouse gases”… In fact, life-cycle analyses of bioenergy production have shown that with poor management methods, production can actually result in a net increase in the emission of greenhouse gases.”[7]

 

“The rush to produce bio-energy crops is alarming for biodiversity. Some of the most promising crops for producing biofuels are oil palm and soy, two rapidly expanding tropical monocultures which are amongst the chief causes of tropical deforestation. A huge surge in demand for biodiesel could drive even further the large scale clearing of forests in key biodiversity hotspots such as Indonesia or the Brazilian Cerrado.”

 

Perhaps the source of renewable power with the greatest claim to call itself “green” is solar power.  Fuel cells are made from silicon, one of the most abundanct elements on the planet. Even its production may have side benefits, with IBM announcing in 2007 “an innovative new manufacturing technique for turning waste silicon generated during the manufacture of computer chips into silicon capable of being used in solar panels.” [8]

 

The company said that the process, which it intends to share with the rest of the semiconductor manufacturing industry, will “help slash the energy footprint of solar panel manufacture by up to 90 per cent and help tackle the current silicon supply crunch being experienced by many solar panel manufacturers.”

 

It may be that the only answer is to cut our usage. "We have to stop emitting carbon dioxide or we'll mess up the climate, but any of the alternatives -- be it nuclear energy, fossil fuels with carbon sequestration, or wind power -- will also have environmental risks and will create other side effects. That is a fact of being as large and power-hungry civilization."[9]