sexta-feira, 27 de janeiro de 2012

A comparison between reflective and green roofs as tools for Adaptation to Global Warming

Reflective roofs are atractive as a tool to deal with the climate change, with the increasing temperatures the world is abide to brace. They have a high level of solar reflectance, thus presenting a low level of solar energy absorption. Reflective roofs today are built by covering the roof with a highly reflective seamless coat.
The thermal properties of the reflective roofs are equivalent to those of the green roofs. As the data provided by the U.S. Department of Energy Building Technologies Program shows for the reflective roofs, there is a broad thermal equivalence between green roofs and reflective roofs.

The leaves reflect 20 to 30% of the visible radiation received from the sun. But most of the radiation they absorb is used to their metabolic work, bringing water from the soil and doing their photosynthesis, by which they absorb carbon to grow. This way they do not allow the soil temperature to increase.

The reflective roofs presents a much higher level of reflectance, absorbing the energy that it does not reflect. Both types of roof decrease the roof temperature by broadly equal level thus protecting the user of the rooms immediately under the roof from high temperatures or from high electricity bills, a benefit appropriated by users. Both protect from high themperature variations the part of the building structure that is most sensitive to temperature variations. This represent a benefit appropriated by owners. These first two benefits, the reduction of the temperature for the floor under the roof and the protection of the structure, are private benefits.

Having treated the aspects under which the reflective roofs and the green roofs are equivalente, let us go to aspects under which they work producing very divergent effects. If someone in the second floor of a two floor building take a look through the window may be exposed to be uncomfortably hit by the glare of the one level building neighbor roof solar reflection. Instead of this, a green roof would provide a nice view. The green roof would provide some sense of tranquility. The reflective roof provide some contribution to take someone more far way from his inner equilibrium. A world where a passer-by is circundated by reflective roofs is an arid world. This is a negative public good effect.

A comparison of effects should not miss another unfriendly aspect of the reflective roofs. By reflecting solar energy to the neighboring buildings fachades, it may increase their temperatures. This is another negative public good effect.

Another difference incides on the relation to the flash floods. Green roofs retard the time a strong precipitation becames a flash flood. It is a service they provid to the county community. Reflective roofs do not do so. More yet than ordinary roofs, they allow the water run promptly to the streets. This is other kind of negative public good.

By least, think about being prudent. Small airplanes do not approch landing by navigation instruments. Nowadays even for the smallest of them, the pilots are guided by GPSs. Now suppose the GPSs are out of order, because a high solar radiation episode. Or, what is more probable to happen, an airplane GPS becames out of order. The pilot needs to find the airport by focusing the green and white airport lighthouse. But how can the pilot find the green and white airport lighthouse if the roofs are reflecting the powerfull sun rays in his eyes? Who would like to be in such airplane. Who would like to be in a city under it?

One may conclude that in matters of private benefit, green roofs and reflective roofs are equivalent as a tool for adaptation to global warming. But in matters of public goods effects green roofs are very superior.

quarta-feira, 18 de janeiro de 2012

Green roof as an universal tool for Adaptation to Global Warming


A green roof, a nordic tradition , with present use with germans as leaders, is a roof of a building that is partially or completely covered with vegetation. There is consensus that a growing medium, planted over drainage, an irrigation system and a waterproofing membrane on top of a building is a green roof. Container gardens on roofs where plants are maintained in pots may produce the same benefits and represent very beautiful instances of roofs covered by green. But there is contention if the expression green roof also includes roofs looking green by this way. There is no contention that covering streets with treetops does not make green roofs as some Brazilians say.

Usually we find in the literature, conventional or in electronic media, lists of green roof benefits not discriminating the benefit nature, if relative to Adaptation to Global Warming, if connected with mitigation.

Lets display these relations.

The benefit which most emphasis is given goes about the cool relief, on a hot day, for the offices immediatly under the roof, given to the high thermal insulation capacity of the green roofs. To those with air conditioning the smaller absorption of heat by the structure of the building is translated into smaller electricity bills. This is so because the waterproofing membrane, the drainage system and the growing medium work as insulators. The vegetation leaves reflect more than the ordinary tiles, absorbing less solar heat. But there is more. Most of the solar energy that the leaves absorb are not transformed into heat as the tiles do. They use this energy to their metabolic work, and more important yet, to bring water from the soil (their growing medium in the green roofs case), which evaporate keeping down their temperature. To keeping down the roof temperature in a hot day, when the hot days are forecasted to be more frequent and more hot, the green roofs works as an Adaptation to Global Warming effect, appropriated by the building users, mainly by those directly under the roof.

On hot or cold days the vegetation leaves, the growing medium, the drainage system and the waterproofing membrane compose a sound absorbtion system protecting the ears of the building occupants. This is a benefit appropriated by the building users, also mainly by those directly under the roof.

To the building owners there is a benefit related to the life span of the building and to its maintainance costs. The green roofs reduce the expansions and contractions of concrete roofs just the place in the buildings where those variations are more severe, mainly because they have sinergy with deformations caused by winds that bend the structure in a way as more accentuated as more high one is. As the winds are forecasted to be more strong with the Global Warming, this property of the green roofs work as an Adaptation to Global Warming that benefit the building owners.

Now two Adaptation to Climate Change effects brougth by the green roofs that work as public goods at a county level. By decreasing the solar thermal energy absorption by buildings, also decrease the thermal energy dissipated in the air, thus decreasing the inconvenient heat island effect. In addition green roofs decrease the water flow, thus helping to prevent floods.

Finally, in this rol that is far from being exhaustive, one may say that as all vegetation, green roof absorb carbon dioxide. It produces, then, a mitigation effect. It is a public good at all mankind level, benefiting all people in this moment and as far way in the future as the human horizon can see.

It is important to notice that as the problem of heating the roof structure of buildings is literally of all latitudes, the benefits of green roofs can be harvested in literally all latitudes. But as the conditions vary substantially betweem different places, and native vegetation is recomended, there his for resaerch about them in all latitudes.

For all this, it seems that green roofs should be universally incentivated.

In Brazil there are resaerchs about green roofs going on the Southern states. But the other area, covering the majority of the extension of the country resaerch on this topic is missing. So are unkown to be research going on other latinamerican countries. And there is no information about incentives to green roofs on this part of the world.

quarta-feira, 11 de janeiro de 2012

Nueva tecnología de alimentación animal para convivencia con la sequía y adaptación al calentamiento global

Aquellos que buscan en la Internet alguna información sobre la alimentación animal con el fin de adaptación al cambio climático llegan a sitios que relacionan la criación animal a la produción de gases invernaderos y no los informa sobre lo que buscan.

Los ganaderos que viven con períodos de sequías prolongadas, que el avance del cambio climático promete más intensas y prolongadas, están preocupados por la forma en que pueden alimentar a sus animales para sobrevivir de la mejor manera posible, un problema de adaptación al calentamiento global. Ahora tenemos una nueva tecnología para la alimentación del ganado en la sequía. Son las tabletas o bloques multinutricionales. Se componen de una mezcla de melaza, urea, ganado, sal, minerales, fibra de caña de azúcar, junto con hojas encontradas a nivel local.

Desarrolladas en la Empresa Estatal de Investigación Agrícola de Paraíba - Brasil (EMEPA), las tabletas proporcionan nutrientes esenciales como proteínas, energía y minerales durante el período cuando el forraje es de mala calidad. Mejoran la multiplicación microbiana, aumentando así la digestión de las fibras, el principal componente del forraje en épocas de sequía.



segunda-feira, 9 de janeiro de 2012

Pensando na convivência com a seca e trazendo uma nova tecnologia de alimentação animal como adaptação ao aquecimento global

Criadores que convivem com períodos de estiagens prolongadas, que com o avançar das mudanças climáticas se prometem mais intensas e mais prolongadas, dispõem de nova tecnologia para alimentar gado na estiagem. São os tabletes nutritivos ou blocos multinutricionais. Consistem numa mistura de melaço, uréia pecuária, sal comum, minerais, bagaço de cana, juntamente com folhas encontradas localmente.

Desenvolvidos na Empresa Estadual de Pesquisa Agropecuária da Paraíba (Emepa), os tabletes fornecem nutrientes essenciais como proteína, energia e minerais durante o período em que as forrageiras estão com baixa qualidade. Melhoram o ecossistema ruminal para a multiplicação microbiana, assim incrementando a digestão das fibras, principal componente da forragem durante épocas de estiagem.

sexta-feira, 6 de janeiro de 2012

Centrais nucleares são indispensáveis

Hoje a atenção está dirigida à localização de centrais nucleares. 
Certamente que serão necessárias para o futuro. Até mesmo para que se tenha uma diversidade de fontes de energia que produza uma situação de robustez face às incertezas que o futuro apresenta. E como o futuro tem as incertezas aumentadas pelo Aquecimento Global, pode-se dizer que dotar o eferta de energia elétrica de um razoável componente de origem nuclear é uma medida de Adaptação às Mudanças Climáticas.
Digamos que um estudo locacional para a instalação de uma central nuclear leve em conta a disponibilidade de água, o investimento para interligação à rede elétrica existente, o investimento na construção (que varia com a localização), o custo de aquisição do terreno, as perdas pelo transporte da energia até os usuários, etc.
Digamos que este belo estudo locacional indique um local ótimo algumas centenas de quilômetros a montante da foz de um rio, o qual provê a disponibilidade de água para a central nuclear.
Agora adicione-se um ponto. Digamos que um dia, contrariando o desejo de todos, algo saia muito errado nesta central. Alguém pode dizer: impossível. Também assim um dia haviam dito para Three Mile Island. Também assim haviam dito para Chernobyl (há sempre quem diga. Ah!, aquilo era um galpão. Mas não foi por isto que estourou) . Pode-se arguir em relação a Fukushima (Ah!, não temos maremotos. o que até o momento é verdade. Também diziam que seria impossível furacões na América do Sul).
O ponto a adicionar é o que se ensinava nas escolas de engenharia: mesmo que você faça tudo certo, a probabilidade de algo dar errado nunca será exatamente zero. Sempre haverá aquele incomodo resíduo de probabilidade, que se faz tender para zero, mas, desgraçadamente, nunca é exatamente zero. Agora junte-se outro elemento ao raciocínio. Se a probabilidade de um acontecimento não é exatamente zero, um dia ele vai acontecer. O construtor pode não estar na Terra para ver, mas isto é irrelevante para a sociedade. Junte-se outra informação. Se um dia, que se deseja nunca venha a existir, por um acidente vazar água radioativa do reator e chegar ao rio, não poderá haverá o comprometimento dele a jusante da central nuclear, até a sua foz? Então não seria mais racional que fosse a central localizada cerca da foz? De qualquer forma a foz estaria comprometida. Mas, se estaria poupando problemas causados por radiação na extensão entre a melhor localização que não leva em conta o desastre “impossível” (desastre este que se sabe “relativamente impossível”, não “absolutamente impossível”) e a localização cerca da foz (que, qualquer for a localização da central, acabará comprometida). Quanto custa a mais hoje poupar uma área adicional de ser exposta? O poupar à exposição não vale o custo adicional?