Renewable Energies are the Future

Renewable Energies are the Future

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By José Santamarta

Renewable energy will solve many of the environmental problems, such as climate change, radioactive waste, acid rain and air pollution. But this requires political will and money.

The Stone Age did not end for lack of stones, and the age of fossil fuels will not end due to the depletion of oil, natural gas and coal.

Renewable energy will solve many of the environmental problems, such as climate change, radioactive waste, acid rain and air pollution. But this requires political will and money.

In 2003, world energy consumption exceeded 10,500 million tonnes of oil equivalent (Mtoe): 2,400 Mtoe of coal, 3,600 Mtoe of oil, 2,300 Mtoe of natural gas, 610 Mtoe of nuclear, 590 Mtoe of hydroelectric and close to 950 Mtoe of biomass, mainly firewood, and still small amounts of geothermal, solar and wind.

The production, transformation and final consumption of such an amount of energy is the main cause of environmental degradation. Consumption is very unevenly distributed, since the OECD countries, with 15% of the world's population, consume 60% of the energy, the latter factor to be taken into account when distributing responsibilities for the environmental crisis.

Primary energy consumption in Spain has gone from 88 Mtoe in 1990 to 132.6 Mtoe in 2003 (a 50.7% increase), the year in which energy dependence reached 78%, despite the fact that in National production includes nuclear energy for highly debatable methodological reasons. If the forecasts of the previous PP government are met, carbon dioxide emissions from energy sources will increase by 58% between 1990 and 2010, in the most favorable scenario, which makes it mathematically impossible to comply with the Kyoto Protocol.

The production, transformation and final use of such an amount of energy also in Spain is the main cause of environmental degradation: 9 nuclear power plants in operation and one permanently closed, a serious problem of unresolved radioactive waste, about a thousand reservoirs that they have irreversibly flooded 3,000 square kilometers, and greenhouse gas emissions, which represent 77.73% of the total. In addition, 2.4 million tons of sulfur dioxide and 1.3 million tons of nitrogen oxides are emitted.

At the current rate of extraction, the estimated reserves of coal will last 1,500 years, those of natural gas 120 and those of oil no less than 60 years. The improvement of the extraction technologies will increase the duration of the reserves, by accessing the deep sea areas. There is no problem of fossil fuel depletion on the immediate horizon, although current consumption is 100,000 times faster than its rate of formation; the real issue is that of sinks, such as the atmosphere, where carbon dioxide and other greenhouse gases accumulate, with subsequent warming. High oil prices aggravate the situation, although it should be remembered that they are much lower than those of 1980, the year in which they reached 80 dollars a barrel at current prices, the dollar going from then to today's, taking inflation into account.

The serious environmental crisis, the depletion of resources and the imbalances between the North and the South are factors that make it necessary to undertake a new energy policy. In the short term the priority is to increase energy efficiency, but this has economic and thermodynamic limits, so that in the longer term only the development of renewable energies will allow to solve the great challenges of the future. Renewable energies are the only sustainable solution, and nuclear energy, fission or fusion, would only aggravate the situation and lead to a dead end, of nuclear proliferation and generation of radioactive waste.

What are renewable energies?

Under the name of renewable, alternative or soft energies, a series of energy sources are included that are sometimes not new, such as firewood or hydroelectric plants, nor renewable in the strict sense (geothermal), and that are not always used in a way soft or decentralized, and their environmental impact can be significant, such as dams for hydroelectric uses or monoculture biofuels. Currently they supply 20% of world consumption (statistics do not usually reflect their real weight), their potential being enormous, although difficulties of all kinds have delayed their development in the past.

With the exception of geothermal energy, all renewable energies derive directly or indirectly from solar energy. Directly in the case of light and heat produced by solar radiation, and indirectly in the case of wind, hydraulic, tidal, wave and biomass energy, among others. Renewable energies, throughout history and well into the 19th century, have covered practically all of man's energy needs. Only in the last hundred years have they been surpassed, first by the use of coal, and after 1950 by oil and to a lesser extent by natural gas. Nuclear power, with 441 nuclear power plants in 2003, with an installed capacity of 360 GW, covers a negligible part of world consumption, and despite some optimistic forecasts, its role will always be marginal.

Even today, for more than two billion people in the countries of the South, the main energy source is firewood, affected by a real energy crisis, caused by deforestation and rapid population growth. Biomass, and mainly firewood, supplies 14% of world consumption, a figure that in the countries of the South rises to 35% globally, although in Tanzania it reaches 90% and in India it exceeds 50%; in the richest country, the United States, it represents 4% of global consumption, a percentage higher than that of nuclear energy, in the European Union 3.7% and in Spain 3%.

In 1999, the Plan for the Promotion of Renewable Energies in Spain was approved, setting the objectives for 2010. Given the current development, the Plan will not be met, although the IDAE has revised the objectives upwards and tries to create the conditions that allow you to make up for lost time. Renewable energies in 2003 represented 6% of primary energy consumption, a figure very far from the 12% that is to be achieved in 2010. The 1999 Plan and Directive 2001/77 / EC foresee producing 29.4% of the total electricity in 2010 with renewables.

The sun shines for everyone

The solar energy absorbed by the Earth in a year is equivalent to 20 times the energy stored in all the fossil fuel reserves in the world and ten thousand times higher than the current consumption. The sun is the only source of organic matter and vital energy on Earth, and although it sometimes goes unnoticed, today we are already using solar energy massively, in the form of food, firewood or hydroelectric energy. The same fossil fuels, whose burning is at the origin of environmental deterioration, are nothing more than solar energy stored over millions of years. Photosynthesis is today the most important use of solar energy, and the only source of organic matter, that is, food and biomass.

Although all energy sources, except geothermal and nuclear, come from the sun, in the current sense the term solar has a meaning restricted to the direct use of energy from the sun, either in the form of heat or light. The sun rises for everyone every day and will continue to send us amazing amounts of heat and energy, oblivious to the use we can make of it. Its greatest virtue is also its greatest defect, as it is a diffuse and poorly concentrated form of energy, and hence the difficulties involved in the direct use of solar radiation, in a society in which energy consumption is concentrated in a few few industrial factories and large metropolises.

The distribution of solar radiation registers large geographical variations, ranging from two kWh per m2 per day in northern Europe to 8 kWh per m2 in the Sahara desert. Equally important are the daily and seasonal variations in solar radiation, and its two components, direct and diffuse radiation. Direct radiation is that received from the sun when the sky is clear, and diffuse radiation is that which results from being reflected in the atmosphere and clouds. Some teams use both, and others only the direct one, as is the case of tower plants.

The use of solar energy can be indirect, through wind (wind) and water evaporation (hydraulic), among other ways, or direct, through active or passive thermal capture and through photon capture. An example of the latter is the photochemical capture carried out by the plants, and the photoelectric effect, the origin of current photovoltaic cells.

The only negative impacts could be in the hypothetical case of large solar plants in space, and to a lesser extent in central tower plants, due to the use of potentially polluting substances used for the accumulation and transmission of heat. Another possible effect is the use of the territory, due to the large surfaces required, although a country like Spain could meet all its electricity needs with just 1,000 km2, 0.2% of its territory.


Hydrogen production is still a technologically immature and costly process, so huge investments in research will be required. When hydrogen is produced commercially, within 10 or 20 years, and based on factors as abundant as water and solar and wind energy, the energy and environmental problems will be solved, since hydrogen, unlike other fuels, it is not polluting. Hydrogen is produced by electrolysis, a process that requires large amounts of electricity, which can be obtained thanks to photovoltaic cells and wind turbines, thus storing solar and wind energy.

In any case, in the coming decades we will enter an economy based on hydrogen as a secondary fuel or energy vector; its combustion hardly pollutes. The primary energy for obtaining it will be solar and wind, and the conversion will be made into fuel cells, which will mean a great revolution. By 2020, most of the vehicles are expected to run on fuel cells.

From ancient Greece to today

The passive use of solar energy began in the very distant past. In ancient Greece, Socrates pointed out that the ideal house should be cool in summer and warm in winter, explaining that "in houses facing south, the sun penetrates the porch in winter, while in summer the solar arc described rises above our heads and above the roof, so there is shade. " In Roman times, the guarantee of rights to the sun was incorporated into Roman law, and thus, the Justinian Code, collecting previous codes, stated that "if an object is placed in a way to hide the sun from a heliocaminus , it must be affirmed that such an object creates shadow in a place where sunlight is an absolute necessity. This is so in violation of the right of the heliocaminus to the sun.

Archimedes, 212 years before Christ, according to legend, used incendiary mirrors to destroy the Roman ships that besieged Syracuse. Roger Bacon, in the thirteenth century, proposed to Pope Clement IV the use of solar mirrors in the Crusades, because "this mirror would fiercely burn whatever it was focused on. We must think that the Antichrist will use these mirrors to set fire to cities, fields and weapons". In 1839, the French scientist Edmund Becquerel discovered the photovoltaic effect and in 1954 the Bell Telephone developed the first photovoltaic cells, later applied by NASA to the Vanguard and Skylab space satellites, among others.

The so-called bioclimatic architecture, heir to the knowledge of popular architecture, is the adaptation of the building to the local climate, considerably reducing the cost of heating and cooling, compared to the current building. It is possible to achieve, with minimal consumption, comfortable buildings and with very small temperature fluctuations throughout the year, although the climatic variations are very marked outside. The design, the orientation, the thickness of the walls, the size of the windows, the construction materials used and the type of glazing, are some of the elements of passive solar architecture, heir to the best architectural tradition. Investments that rarely exceed five percent of the cost of the building, allow energy savings of up to 80% of consumption, quickly amortizing the initial extra cost.

The use of solar energy in buildings presupposes the disappearance of a single construction typology, used today from the cold latitudes of northern Europe to Ecuador. If the house is not built adapted to the climate, heating or cooling it will always be a serious problem that will cost large amounts of energy and money.

The solar collector

The flat solar collector, used since the beginning of the century to heat water to temperatures of 80 degrees Celsius, is the most common application of the sun's thermal energy. Countries like Germany, Austria, Japan, Israel, Cyprus or Greece have installed several million units.

The basic elements of a flat solar collector are the transparent glass cover and an absorbent plate, through which water or other heat transfer fluid circulates. Other components of the system are the insulation, the protective box and an accumulator tank. Each square meter of collector can annually produce an amount of energy equivalent to about eighty kilograms of oil.

The most widespread applications are the generation of hot water for homes, swimming pools, hospitals, hotels and industrial processes, and heating, jobs in which heat is required at low temperatures and which can represent more than a tenth of consumption. Unlike conventional technologies for heating water, the initial investments are high and require a payback period of between 5 and 7 years, although, as it is easy to deduce, the fuel is free and the maintenance costs are low.

More sophisticated than flat collectors are vacuum collectors and concentration collectors, which are more expensive, but capable of achieving higher temperatures, which allows covering large segments of industrial demand and even producing electricity. The linear concentration solar collectors are parabolic trough mirrors, which have a conduit in the focal line through which the heat transfer fluid circulates, capable of reaching 400 degrees centigrade. At such temperatures electricity and heat can be produced for industrial processes. In the United States, more than one hundred thousand square meters of linear concentrators operate, and the company "Luz Internacional" installed six plants in California to produce electricity, with a power of 354 MW of electricity (1 MW = 1,000 kW), and satisfactory yields. The cost of the kWh amounts to 15 cents, still higher than the conventional one, but interesting in many areas far from the distribution network that have good insolation. The prospects are promising, despite some failures, as proved by Luz's bankruptcy in 1991 and its subsequent sale, and today there are several projects underway in Spain and India, among other countries. The government's plan foresees producing 180 ktoe in 2010 of solar thermoelectric power, with an installed power of only 200 megawatts and a production of 458.9 GWh / year.

The point collectors are parabolic mirrors in whose focus a receiver is arranged, in which the transfer fluid is heated, subsequently sent to a centralized turbine, or a motor is installed directly. The so-called central tower solar plants consist of numerous large surface mirrors (heliostats) which, thanks to constant orientation, concentrate the solar radiation on a vapor receiver located at the top of a tower. The development of low-cost heliostats, using new materials such as polyester, fiberglass or tensioned graphite fiber membranes and more reliable and efficient receivers, opens up new possibilities for the use of solar energy to obtain electricity.

In Spain much remains to be done in solar energy. Whereas in 2002 we only had 522,561 square meters of solar collectors, in Germany, with much less sun and less surface area, they had 3,365,000 square meters already in 2000! In Greece they had 2,460,000 square meters and in Austria 2,170,000 square meters. The objectives are to reach 336 ktoe in 2010, installing a total of 4,500,000 additional square meters. The new municipal regulations, which require the installation of solar collectors in all newly built homes or major renovations, will allow the relaunch of a market with a huge future. Potentially met demand with flat solar collectors amounts to 6.1 Mtoe.

Solar cells

The production of electricity from photovoltaic cells is still six times more expensive than that obtained in coal plants, but just two decades ago it was twenty times more. In 1960 the cost of installing a single watt of photovoltaic cells, excluding batteries, transformers, and other ancillary equipment, was $ 2,000; in 1975 it was only $ 30 and in 2004 it goes from $ 2.62 to $ 4.25, depending on the amount and type of installation. If in 1975 the kWh cost more than 7 euros, the current price is between 0.3 and 0.6 euros, which allows the use of photovoltaic cells to produce electricity in places far from the distribution networks and to compete with the alternatives existing, such as electric generators from oil.

Today, in the United States the production of a kWh costs 4 to 8 cents in a coal plant, 4 to 6 in wind farms, 5 to 10 in an oil plant, 12 to 15 in a nuclear power plant and 25 to 40 cents using photovoltaic cells. In the coming years it is expected to reduce the cost of kWh to 12 euro cents before 2010 and to 4 cents by 2030. Of course, the previous costs do not include the results of the deterioration caused to the environment by the different ways of producing electricity. electricity.

The photovoltaic effect, discovered by Becquerel in 1839, consists of the generation of an electromotive force in a semiconductor device, due to the absorption of light radiation. Photovoltaic cells convert light energy from the sun into electrical energy, with only one drawback: the still very high economic cost for centralized production. However, photovoltaic cells are already competitive in all those places away from the grid and with low demand, such as villages and houses without electrification, television repeaters, beacons, agriculture, lighthouses, calculators and other consumer goods. Throughout the decade, the photovoltaic market grew at annual rates of over 40%, and there are already more than 2,500 megawatts installed worldwide. It is estimated that another 85,000 MWp will have to be installed, investing some 50,000 million euros, to make photovoltaics competitive in the market, which implies a price of 1 euro per watt. To obtain a 20% price reduction, production must be doubled, depending on the experience or learning curve.

Currently most photovoltaic cells are made of high purity monocrystalline silicon, a material obtained from sand, very abundant in nature. Silicon purification is a very expensive process, due to the dependence on the electronic components market, which requires a purity (electronic grade silicon) higher than that required by photovoltaic cells. Obtaining solar grade silicon, directly from metallurgical silicon, whose purity is 98%, would considerably lower costs, as would the production of cells from amorphous silicon or other procedures, today in an advanced state of research and whose results they may be decisive in the next decade. The multinational BP produces high-performance cells at its factory in Madrid, the so-called Saturno. Institutional support, opening new markets, can shorten the time necessary for the full competitiveness of photovoltaic cells.

The occupied surface does not pose problems. In the Mediterranean area, 90 million kWh per year could be produced per square kilometer of surface covered by photovoltaic cells, and before the year 2010, with the expected yields, 150 million kWh per km2 will be reached. As regards storage, the production of hydrogen by electrolysis and its subsequent use to produce electricity or other uses, may be an optimal solution.

The government's objective was to have 143.7 MWp (peak megawatts) installed in 2010, of which 135 MWp new, of which 61 MWp should be installed before 2006 (15% in isolated facilities and 85% in connected facilities to network). Between 1998 and 2001 only 6.9 MWp were installed. While in Germany they had 87.5 MWp (seven times more than in Spain), thanks to the 100,000 solar roofs program, which plans to install 300 MWp between 1999 and 2004. Even the Netherlands, with little sun and surface area, had more installed power (12, 2 MWp). The price of the photovoltaic kWh, with the premiums, amounts to 0.397 euros (maximum) and 0.217 euros (minimum), compared to 0.72 and 0.35 in Austria, 0.48 in Germany and 0.39 and 0.23 in Portugal. In Spain, 50.85 MWp of photovoltaic cells were manufactured in 2002 (36% of European production), almost 90% destined for export. The two largest manufacturers are Isofoton and BP Solar, although 182 companies operate in the sector, employing more than 4,000 people. The prices of photovoltaic modules have fallen considerably, from 7.76 euros / Wp in 1990 to 3.3 euros / Wp in 2000. In Spain, with a daily solar radiation higher in almost the entire territory at 4 kWh per meter square, the potential is immense. Only 180 TWh could be produced annually on the roofs of Spanish houses. In the world, according to the report? Solar Generation? from the European Photovoltaic Industry Association and Greenpeace, it should reach 276 TWh in 2020, with annual investments of 75,000 million euros.

Rivers of energy

Hydropower is generated by passing a stream of water through a turbine. The electricity generated by a waterfall depends on the amount and speed of the water that passes through the turbine, whose efficiency can reach 90%. The electrical use of water does not produce a physical consumption of it, but it can conflict with other agricultural or urban supply uses, and above all, large power plants have a great environmental impact. Hydroelectric plants themselves are not polluting; However, its construction produces numerous alterations of the territory and of the fauna and flora: it hinders the migration of fish, river navigation and the transport of nutritious elements downstream, it causes a decrease in the river flow, modifies the level of the water table , the composition of the dammed water and the microclimate, and originates the submergence of arable land and the forced displacement of the inhabitants of the flooded areas. In most cases it is the cheapest way to produce electricity, although the environmental costs have not been seriously considered.

The untapped electrical potential is enormous. Only 17% of the potential is used worldwide, with a great disparity between countries. Europe already uses 60% of its technically usable potential. Third world countries only use 8% of their hydraulic potential. In Spain, the additional technically developable potential could double current production, reaching 65 TWh per year, although the environmental and social costs would be disproportionate. Mini hydroelectric plants cause less damage than large projects, and could provide electricity to large areas that lack it.

The Development Plan sets a target of 720 new MW, up to 2,230 MW. Between 1998 and 2001, 95.4 MW were put into operation, so the target will not be achieved at the current rate, mainly due to administrative barriers and environmental impact. In 2001, the power of hydroelectric plants with less than 10 MW amounted to 1,607.3 MW and production reached 4,825 GWh, and in large hydro plants the power was 16,399.3 MW and production was 39,014 GWh. It must be remembered that 2001 was exceptional, as it rained much more than usual.

Wind power

Wind energy is a variant of solar energy, as it derives from the differential heating of the atmosphere and the unevenness of the earth's surface. Only a small fraction of the solar energy received by the Earth is converted into kinetic energy from the wind and yet this reaches enormous figures, several times higher than all current electricity needs. Wind energy could provide five times more electricity than the total consumed worldwide, without affecting the areas with the highest environmental value.

The power that can be obtained with a wind generator is proportional to the cube of the wind speed; When the wind speed is doubled, the power is multiplied by eight, and hence the average wind speed is a determining factor when analyzing the possible viability of a wind system. Wind energy is a highly variable resource, both in time and place, and can change a lot in very short distances. In general, coastal areas and mountain peaks are the most favorable and best equipped for harnessing the wind for energy purposes.

The conversion of wind energy into electricity is carried out by means of wind turbines, with sizes ranging from a few watts to 5,000 kilowatts (5 MW). Wind turbines have developed intensively since the oil crisis in 1973, with more than 150,000 machines having been built since then. Installed capacity was 40,000 MW in 2003, concentrated in Germany, Spain, the United States and Denmark.

In 2004 electricity production was already competitive in places where the average wind speed exceeded 4 meters per second. It is expected that within a few years also large machines installed at sea will become profitable. Wind energy does not pollute and its environmental impact is very small compared to other energy sources. Hence the need to accelerate their implementation in all favorable locations, while trying to reduce the possible negative repercussions, especially on birds and the landscape, in some locations.

Coal, and later electricity, ruined the use of the wind until the energy crisis of 1973, the year in which oil prices soared and the rebirth of a source began whose contribution in the coming decades could reach cover 20 percent of the world's electricity needs without changes in the management of the distribution network.

In 2004, wind power in Spain will exceed 7,000 MW. The price of kWh in Spain was 0.0628 euros in the fixed price system or 0.066 in the most incentive pool (0.037 in the so-called pool price and 0.0289 in compensation), compared to 0.09 in Germany, and is one of the lowest in the European Union, but the price support system has proven its worth in Germany and Spain. From 1996 to 2002 the price of the wind tariff for producers covered by Royal Decree 2366/94 has fallen by 36.94%. The costs of wind are already competitive with those of conventional energies: about 900 euros per installed KW.

In 2010 in Spain we will reach 20,000 MW, and in 2040 we can reach 100,000 MW without problems, producing much of the electricity we consume, and also hydrogen, but for this, certain difficulties must be overcome to integrate wind power into the electricity grid, and overcome irrational opposition to new wind farms. Each kWh of wind would save one kilogram of CO2, among other polluting substances. Wind power is the cheapest way to reduce polluting emissions and move towards sustainability.

Geothermal energy

The thermal gradient resulting from the high temperatures in the center of the Earth (above a thousand degrees Celsius) generates a heat current towards the surface, a current that is the source of geothermal energy. The average value of the thermal gradient is 25 degrees Celsius for each kilometer, being higher in some seismic or volcanic areas. Los flujos y gradientes térmicos anómalos alcanzan valores máximos en zonas que representan en torno a la décima parte de las tierras emergidas: costa del Pacífico en América, desde Alaska hasta Chile, occidente del Pacífico, desde Nueva Zelanda a Japón, el este de África y alrededor del Mediterráneo. El potencial geotérmico almacenado en los diez kilómetros exteriores de la corteza terrestre supera en 2.000 veces a las reservas mundiales de carbón.

La explotación comercial de la geotermia, al margen de los tradicionales usos termales, comenzó a finales del siglo XIX en Lardarello (Italia), con la producción de electricidad. Hoy son ya 22 los países que generan electricidad a partir de la geotermia, con una capacidad instalada de unos 8.000 MW, equivalente a ocho centrales nucleares de tamaño grande. Estados Unidos, Filipinas, México, Italia y Japón, en este orden, son los países con mayor producción geotérmica.

Actualmente, una profundidad de perforación de 3.000 metros constituye el máximo económicamente viable; otra de las limitaciones de la geotermia es que las aplicaciones de ésta, electricidad o calor para calefacciones e invernaderos, deben encontrarse en las proximidades del yacimiento en explotación. La geotermia puede llegar a causar algún deterioro al ambiente, aunque la reinyección del agua empleada en la generación de electricidad minimiza los posibles riesgos.

Los países con mayores recursos, en orden de importancia, son China, Estados Unidos, Canadá, Indonesia, Perú y México. El potencial geotérmico español es de 600 ktep anuales, según una estimación muy conservadora del Instituto Geominero de España. Para el año 2010 se pretende llegar a las 150 Ktep. Los usos serían calefacción, agua caliente sanitaria e invernaderos, no contemplándose la producción de electricidad.


La utilización de la biomasa es tan antigua como el descubrimiento y el empleo del fuego para calentarse y preparar alimentos, utilizando la leña. Aún hoy, la biomasa es la principal fuente de energía para usos domésticos empleada por más de 2.000 millones de personas en el Tercer Mundo. Los empleos actuales son la combustión directa de la leña y los residuos agrícolas y la producción de alcohol como combustible para los automóviles en Brasil. Los recursos potenciales son ingentes, superando los 120.000 millones de toneladas anuales, recursos que en sus dos terceras partes corresponden a la producción de los bosques.

¿Es la biomasa una energía alternativa? A lo largo y ancho del planeta el consumo de leña está ocasionando una deforestación galopante. En el caso del Brasil se ha criticado el empleo de gran cantidad de tierras fértiles para producir alcohol que sustituya a la gasolina en los automóviles, cuando la mitad de la población de aquel país está subalimentada. Por otra parte, la combustión de la biomasa es contaminante. En el caso de la incineración de basuras, la combustión emite contaminantes, algunos de ellos cancerígenos y disruptores hormonales, como las dioxinas. También es muy discutible el uso de tierras fértiles para producir energía en vez de alimentos, tal y como se está haciendo en Brasil, o el empleo de leña sin proceder a reforestar las superficies taladas.

En España actualmente el potencial energético de los residuos asciende a 26 Mtep, para una cantidad que en toneladas físicas supera los 180 millones: 15 millones de toneladas de Residuos Sólidos Urbanos con un potencial de 1,8 Mtep, 12 millones de toneladas de lodos de depuradoras, 14 millones de t de residuos industriales (2,5 Mtep), 17 Mt de residuos forestales (8,1 Mtep), 35 Mt de residuos agrícolas (12,1 Mtep), 30 Mt de mataderos y 65 Mt de residuos ganaderos (1,3 Mtep). El reciclaje y la reutilización de los residuos permitirán mejorar el medio ambiente, ahorrando importantes cantidades de energía y de materias primas, a la vez que se trata de suprimir la generación de residuos tóxicos y de reducir los envases. La incineración no es deseable, y probablemente tampoco la producción de biocombustibles, dadas sus repercusiones sobre la diversidad biológica, los suelos y el ciclo hidrológico. A más largo plazo, el hidrógeno es una solución más sostenible que el etanol y el metanol.

El Plan de Fomento de las Energías Renovables en España prevé que la biomasa llegue a 10.295 ktep. Hoy apenas llegamos a 3.600 ktep (incluyendo los biocarburantes y el biogás), con un incremento ínfimo respecto a años anteriores. Y las perspectivas no son mucho mejores. Con las políticas actuales, en el año 2010 difícilmente se superará el 50% de los objetivos del Plan (poco más de 5 Mtep), y tampoco se debería hacer mucho más. Los restos de madera, como sostiene ANFTA (Asociación Nacional de Fabricantes de Tableros), son demasiado valiosos para ser quemados, pues constituyen la materia prima base de la industria del tablero aglomerado y sólo debe quemarse como aprovechamiento último, y España es muy deficitaria en restos de madera (se importan más de 350.000 m3), y en madera en general (se importa más del 50%). Además el CO2 se acumula en los tableros (cada metro cúbico de tablero aglomerado fija 648 kg de CO2), mientras que la quema lo libera, se genera más empleo en las zonas rurales, más valor añadido y se producen muebles de madera al alcance de todos. El reciclaje debe tener prioridad frente al uso energético y los únicos residuos de madera que se deberían incinerar son las ramas finas de pino, los restos de matorral, las cortezas y el polvo de lijado.

Los costes de extracción y transporte de las operaciones de limpieza del monte para las plantas de biomasa son de 0,16 euros por kg, a los que hay que añadir los de almacén, cribado y astillado, secado, densificación y el coste del combustible auxiliar. Hoy las centrales termoeléctricas de biomasa no son viables económicamente, y además esos residuos también son necesarios para el suelo (aporte de nutrientes, erosión).



Eficiencia Energética y Energías Renovables, boletín del IDAE. Números 1, 2, 3, 4, 5 y 6.
Energías Renovables
C.V. Revista internacional de energía y medio ambiente
Energética XXI
Era Solar
Energía. Ingeniería Energética y Medioambiental
World Watch

Libros y estudios
*IDAE (1999). Plan de Fomento de las Energías Renovables en España. Madrid.
*Ministerio de Economía (2002). Planificación de las redes de transporte eléctrico y gasista 2002-2011. Madrid.
*ANFTA (Asociación Nacional de Fabricantes de Tableros) (2002). Restos de madera: demasiado valiosos para ser quemados. Madrid.
*Johansson, T. B. et el (1993): Renewable Energy, Island Press, Washington; D. Deudney y C. Flavin: "Renewable energy: The power to Choose", New York, Norton, 1983.
*Goldemberg et al.: Energy for a sustainable world, John Wiley and sons, New Delhi, 1988.
*Ogden, J.M. et Williams R. H.: Solar Hydrogen. Moving Beyond Fossil Fuels, World Resources Institute, Washington, 1989.
*Maycock, P.: Photovoltaic thecnology, perfomance, cost and market forecast. PV Energy systems, Casanova, 2004.
*ASIF (2003): Hacia un futuro con electricidad solar. Madrid.

*José Santamarta Flórez es director de World Watch. Teléfono: 650 94 90 21