Renewables – The Downside
Phase out fossil fuels, move to 100 percent renewables and save the planet. Sounds good, if a little expensive at first. Unfortunately, things aren’t quite that simple. While renewable sources of energy, whether wind, solar, hydro, biomass or geothermal, are certainly less polluting than coal or natural gas, they are not entirely pollution free, and while the accelerating adoption of renewables has many advantages, the disadvantages must also be considered.
Wind is perhaps the least polluting of any renewable source; it uses less land than other renewables per kilowatt-hour and hardly interferes with either grazing or crops. Its construction costs can be recovered in just three months and it has a long operating life, as long as 25 years. Greenhouse gas emissions and pollution resulting from construction and installation of wind farms are minimal, and noise, an early concern, is being minimized. A significant concern about wind farms is their impact on birds and bats. The danger to birds is certainly exacerbated when turbines are located in migratory paths or upwind slopes, but fossil-fueled plants are also dangerous to avians, particularly in their affect on climate, which is altering weather patterns and significantly impacting avian habitats, and because of collisions, especially with the cooling towers of nuclear plants. So while wind farms pose some dangers to birds and bats, it’s by no means clear that these exceed or even equal the dangers already posed by other forms of generation. What’s more, new research suggests that birds actually learn to take account of wind farms.
Photo voltaic installations are, perhaps second only to wind, the most environmentally friendly of renewable sources. PV systems are noiseless and cause no pollution while operating. While the manufacture of PV modules involves a number of chemicals, air stack emissions are minimal; they do, however, require considerable energy both for manufacture and transportation to their final sites. Large solar installations can have an impact on the fauna and flora of the land where they are located, and since solar arrays require periodic cleaning there is the possibility of some water pollution, but that too can be easily minimized.
On the other hand, solar thermal power plants, in which water is heated and the rest of the plant operates on the classic steam-powered model, can have significant negative impacts. They occupy large areas and, in this respect, the potential effects on plant and animal life are similar to those of PV solar arrays, and they also require great amounts of water for cooling or as a working fluid. This introduces the possibility of ground water pollution and the disruption of nearby water sources.
Geothermal plants raise even more serious environmental concerns, although, again, these can be mitigated by careful planning and monitoring. Their large-scale construction and drilling operations are noisy, and the waste that results can have negative impacts on the local environment and economies. The fluids can carry a mixture of various gases, including carbon dioxide, hydrogen sulfide, methane and ammonia, which can contribute to global warming and acid rain if they are released into the atmosphere. Geothermal plants with adequate emission-control systems are, however, far less polluting than fossil fuel plants. Detailed plans must be drawn up ahead of operation to address concerns about air and water quality, waste disposal, geologic issues (including, in rare instances, earthquakes) noise and the biological impact on surrounding farm land.
Hydropower, with just over a 70 percent share, is the world’s largest source of renewable energy. It can meet base-load requirements and, by incorporating pumped-storage technology, peak and unexpected demand. It’s also the world’s oldest source of power; moving water has been used since prehistoric times in all but desert societies. While early uses of hydropower, such as water mills, had virtually no environmental impacts, today’s plants often do. They can be extremely costly to build, and they can negatively affect natural river systems, fish and other wildlife. Their environmental impact depends on where they are located and on how large they are. A big, shallow installation which destroys large fields of vegetation can result in greenhouse gas emissions, including carbon dioxide and, much more seriously, methane. Fish habitats can be altered or destroyed as can whole towns, potentially displacing thousands of people. The most negative impact can be the flooding of an entire area. When water stored in a dam is suddenly released, either intentionally or because of heavy rain, the river downstream can suddenly flood, resulting in large-scale destruction.
While biomass is considered a renewable energy source, it can have very harmful environmental impacts, often quite similar to those of fossil fuels. When the feedstock is animal based or municipal and industrial waste there can be substantial greenhouse gas emissions, including methane. Whatever the fuel source, there are serious global warming emissions associated with growing, harvesting and transporting biomass feedstock. While some biomass feedstocks, such as sustainably-harvested wood and forest residues and energy crops that do not compete with food crops for land may be somewhat more benign, the environmental impact of most biomass generation is not substantially more positive than traditional fossil fuel sources.
Clearly, then, there is no getting around the fact that whatever the source, renewable fuels have some negative impacts on the world’s natural environment. That is not to say that renewable sources, with the possible exception of biomass, are not extremely important tools in halting environmental destruction. But replacing fossil fuel with renewables takes planning and careful monitoring if their full advantages are to be realized.