Seguimos con más noticias sobre algas, aunque en este caso traemos un artículo que proviene de Estados Unidos donde han llegado a conclusiones interesantes. La primera de ellas nos la muestra el título del artículo original, que USA tiene capacidad para reconvertir el consumo de petróleo en consumo de bioenergía producida por algas. Podría llegar a sustituir hasta el 17 % del petróleo importado para transporte. Los autores hicieron un estudio detallado de las necesidades de tierra y de aguas para esa cantidad y las cifras que arrojaron son altas: se necesita una extensión de tierra similar a Carolina del Norte, que tiene unos 83.000 km2, una sexta parte de España, que es mucha extensión. Además las necesidades de agua son elevadas también partiendo de 350 galones de agua necesarios por cada galón de petróleo producido. Por ello se pusieron a analizar donde podría ser más eficiente su producción y los criterios de selección óptimos se determinaron en base a dos parámetros, uno la humedad ambiental y el segundo la disponibilidad de sol, necesaria para que crezcan las algas. Si se conjugan de forma adecuada esos factores se consigue reducir de forma drástica la necesidad de agua, aunque siempre considerando a cielo abierto y además agua dulce y teniendo en cuenta las tecnologías actuales. Encontraron que se necesitaba entre 8,6 y 50,2 galones de agua (cada galón es 3,875 litros) por cada milla recorrida y que esa variación dependía de las tecnologías utilizadas y de dónde crecían las algas, cifras que ofrece menos oscilación que el etanol producido por el maíz, que llama la atención por la dispersión de resultados entre 0,6 y 61,9 galones de agua por cada milla recorrida. Estas cifras demuestran la escasa viabilidad ambiental de la generación de biocombustibles con las tecnologías actuales, ya que hoy por ello las cifras resultan desproporcionadas. Este es precisamente uno de los puntos débiles de las microalgas, aunque es cierto que todavía es demasiado incipiente las investigaciones para sacar conclusiones. Según estos estudios, en la banda alta de cifras, si consumiéramos 50 galones por milla recorrida, supondría el consumo de 11760 litros a los 100 km cifras que hoy serían disparatadas. El consumo mínimo de agua según estas variables serían 2.022 litros cada 100 km, números realizados para un vehículo normal. Es cierto que los estudios están hechos para agua dulce y entornos abiertos, situación que podría cambiar con estudios de agua salada y en espacios cerrados. Sabemos que las algas tienen un gran futuro como recurso energético y su especial contribución está en la necesidad de CO2 para crecer por lo que se está investigando ubicar plantaciones de algas para procesar el CO2 que emiten otras industrias más contaminantes. Que duda cabe que la ciencia avanza deprisa pero ver escritos estos datos, realmente asustan. De todas formas y para tranquilidad de los lectores, el uso de microalgas está vinculado a otros aspectos como la producción de medicamentos y la producción de alimento especialmente para la acuicultura, que sí son aplicaciones de mucho mayor valor añadido. En España hay instalaciones experimentales en ubicaciones que cumplen esas características de luz y humedad, situándose plantas para producción de algas cerca de zonas costeras y en zonas húmedas. Además tal y como indica el artículo, pueden ser utilizadas aguas residuales para su cultivo ya que estas aguas son ricas en nitratos y fósforo necesarias para el crecimiento de las algas.
El tema es apasionante y como todo asunto que tiene futuro siempre al principio crea muchas dudas. No obstante seguimos recordando la apuesta firme de algunas empresas petroleras por esta vía de investigación. Parece ser que zonas con luz y abundancia de agua marina como zonas costeras en el Norte de África pueden llegar a ser un escenario ideal, si la investigación va más por el uso de aguas marinas. El enlace original lo publica la página Renowable Energy World y la puede encontrar en este enlace.
Study: Algae Could Replace 17% of U.S. Oil Imports
Richland, Washington, USA -- High oil prices and environmental and economic security concerns have triggered interest in using algae-derived oils as an alternative to fossil fuels. But growing algae — or any other biofuel source — can require a lot of water.
However, a new study shows that being smart about where we grow algae can drastically reduce how much water is needed for algal biofuel. Growing algae for biofuel, while being water-wise, could also help meet congressionally mandated renewable fuel targets by replacing 17 percent of the nation's imported oil for transportation, according to a paper published in the journal Water Resources Research.
Researchers at the Department of Energy's Pacific Northwest National Laboratory found that water use is much less if algae are grown in the U.S. regions that have the sunniest and most humid climates: the Gulf Coast, the Southeastern Seaboard and the Great Lakes.
"Algae has been a hot topic of biofuel discussions recently, but no one has taken such a detailed look at how much America could make - and how much water and land it would require — until now," said Mark Wigmosta, lead author and a PNNL hydrologist. "This research provides the groundwork and initial estimates needed to better inform renewable energy decisions."
Algal biofuel can be made by extracting and refining the oils, called lipids, that algae produce as they grow. Policy makers and researchers are interested in developing biofuels because they can create fewer overall greenhouse gas emissions than fossil fuels. And biofuels can be made here in the United States. In 2009, slightly more than half of the petroleum consumed by the U.S. was from foreign oil.
Wigmosta and his co-authors provide the first in-depth assessment of America's algal biofuel potential given available land and water. The study also estimated how much water would need to be replaced due to evaporation over 30 years. The team analyzed previously published data to determine how much algae can be grown in open, outdoor ponds of fresh water while using current technologies. Algae can also be grown in salt water and covered ponds. But the authors focused on open, freshwater ponds as a benchmark for this study. Much of today's commercial algae production is done in open ponds.
Crunching the Numbers
First, the scientists developed a comprehensive national geographic information system database that evaluated topography, population, land use and other information about the contiguous United States. That database contained information spaced every 100 feet throughout the U.S., which is a much more detailed view than previous research. This data allowed them to identify available areas that are better suited for algae growth, such as those with flat land that isn't used for farming and isn't near cities or environmentally sensitive areas like wetlands or national parks.
Next, the researchers gathered 30 years of meteorological information. That helped them determine the amount of sunlight that algae could realistically photosynthesize and how warm the ponds would become. Combined with a mathematical model on how much typical algae could grow under those specific conditions, the weather data allowed Wigmosta and team to calculate the amount of algae that could realistically be produced hourly at each specific site.
Water for Oil
The researchers found that 21 billion gallons of algal oil, equal to the 2022 advanced biofuels goal set out by the Energy Independence and Security Act, can be produced with American-grown algae. That's 17 percent of the petroleum that the U.S. imported in 2008 for transportation fuels, and it could be grown on land roughly the size of South Carolina. But the authors also found that 350 gallons of water per gallon of oil — or a quarter of what the country currently uses for irrigated agriculture — would be needed to produce that much algal biofuel.
The study also showed that up to 48 percent of the current transportation oil imports could be replaced with algae, though that higher production level would require significantly more water and land. So the authors focused their research on the U.S. regions that would use less water to grow algae, those with the nation's sunniest and most humid climates.
But the authors also found that algae's water use isn't that different from most other biofuel sources. While considering the gas efficiency of a standard light-utility vehicle, they estimated growing algae uses anywhere between 8.6 and 50.2 gallons of water per mile driven on algal biofuel. In comparison, data from previously published research indicated that corn ethanol can be made with less water, but showed a larger usage range: between 0.6 and 61.9 gallons of water per mile driven. Several factors — including the differing water needs of specific growing regions and the different assumptions and methods used by various researchers — cause the estimates to range greatly, they found.
Because conventional petroleum gas doesn't need to be grown like algae or corn, it doesn't need as much water. Previously published data indicated conventional gas uses between about 0.09 and 0.3 gallons of water per mile.
More to Consider
Looking beyond freshwater, the authors noted algae has several advantages over other biofuel sources. For example, algae can produce more than 80 times more oil than corn per hectare a year. And unlike corn and soybeans, algae aren't a widespread food source that many people depend on for nutrition. As carbon dioxide-consuming organisms, algae are considered a carbon-neutral energy source. Algae can feed off carbon emissions from power plants, delaying the emissions' entry into the atmosphere. Algae also digest nitrogen and phosphorous, which are common water pollutants. That means algae can also grow in — and clean — municipal waste water.
"Water is an important consideration when choosing a biofuel source," Wigmosta said. "And so are many other factors. Algae could be part of the solution to the nation's energy puzzle — if we're smart about where we place growth ponds and the technical challenges to achieving commercial-scale algal biofuel production are met."
Next up for Wigmosta and his colleagues is to examine non-freshwater sources like salt water and waste water. They are also researching greenhouse ponds for use in colder climates, as well as economic considerations for algal biofuel production.
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