What Is The Greenhouse Effect?

Greenhouse gases trap some of the sun's energy within our atmosphere and increase the temperature of Earth's surface. This is called the greenhouse effect. (Source: Shutterstock)

Our atmosphere is but a thin layer of gas around a huge bulky planet. This gaseous outer ring and its greenhouse effect make life on Earth possible–and could destroy life as we know it.

The sun is the Earth’s primary energy source, a burning star so hot that we can feel its heat from over 150 million kilometers away.

About one third of this solar energy is reflected back into the universe by shimmering glaciers, water and other bright surfaces. Two thirds, however, is absorbed by the Earth, thus warming land, oceans, and the atmosphere.

Much of this heat radiates back out into space, but some of it is stored in the atmosphere. This process is called the greenhouse effect. Without it, the Earth’s average temperature would be a chilly -18 degrees Celsius, despite the sun’s constant energy supply.

In a world like this, life on Earth would probably have never emerged from the sea. Thanks to the greenhouse effect, however, we enjoy a comfortable average temperature of 14 degrees Celsius.

So, how does it work?

Radiator in space
Only about half of all solar energy that reaches the Earth is infrared radiation, which causes warming. The other half only translates into heat once it hits Earth and is reflected back into space as infrared radiation.

This transformation of solar radiation into infrared radiation is crucial, because infrared radiation can be absorbed by the atmosphere. Like a radiator in the middle of a room, our atmosphere radiates this heat in all directions.

How is this radiation absorbed?

Sunrays enter a greenhouse, heat up the ground, which, in turn, heats up the air inside the greenhouse. The glass roof and walls trap that warm air and temperatures increase.

Earth has no glass walls, but it does have the atmosphere, and within the atmosphere it has greenhouse gases.

Ninety-eight percent of the Earth’s atmosphere is made up of nitrogen, oxygen, and argon. But they do not absorb much infrared radiation, and don't contribute to the greenhouse effect.

Greenhouse gases like water vapour, carbon dioxide, ozone, methane, nitrous oxide, and chlorofluorocarbons do absorb heat, and thus increase atmospheric temperatures.

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Studies indicate that until some 2.7 billion years ago, there was so much carbon dioxide (CO2) and methane in our atmosphere that average temperatures on Earth were as high as 70 degrees Celsius.

But bacteria and plants slowly turned CO2 into oxygen and the concentration of CO2 in our current atmosphere dropped to just about 0.038 percent or 383 parts per million (ppm).

Minuscule changes, global impact
Slight changes in the amounts of carbon dioxide in the atmosphere are already changing the way our planetary heating system works.

Measurements of carbon dioxide amounts from Mauna Loa Observatory in Hawaii show that CO2 has increased from about 313 ppm in 1960 to about 375 ppm in 2005.

That means for every million particles in our atmosphere, there are now 62 CO2 particles more than in 1960. Even if this does not seem like much, scientists say this increase—most probably caused by human activities—is mainly responsible for rising global temperatures throughout the last decades.

Even if the term “greenhouse effect” is somewhat of a misnomer, it still might be a useful handle from which the public can grasp an otherwise intricate natural process.

Most people can relate to how hot and stuffy a greenhouse can get. Now that the Earth has started to heat up, we realize that our own global greenhouse has no window that we can open to catch some fresh air.

Source : http://knowledge.allianz.com

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CO2: Endless Warming

Protestors dressed in CO2 molecule costumes, demonstrate in Essen, Germany, as part of the initiative 'ByeBye CO2' against carbon dioxide pollution (Source: Reuters)

Carbon dioxide is the number one reason for man-made climate change. But what is carbon dioxide, actually? Where does it come from? And why are governments and businesses now scrambling to reduce their carbon dioxide emissions?

Contribution to Human-Induced Climate Change: 70 percent

Global Warming Potency (100 years): 1 (benchmark to other gases)

Carbon dioxide is the second most important greenhouse gas behind water vapor, but the most important contributor to anthropogenic climate change. Methane and ozone are more potent, but have less effect on climate change due to their smaller atmospheric concentrations.

The amount of carbon dioxide (CO2) in the atmosphere has been in flux throughout the Earth’s history, but the United Nations Intergovernmental Panel on Climate Change (IPCC) estimates that in pre-industrial times CO2 made up around 280 ppmv (parts per million volume) of the Earth’s atmosphere.

Since the beginning of the Industrial Revolution, however, the average amount of carbon dioxide in the atmosphere has increased by nearly 40 percent from an estimated 280 to more than 380 ppmv.

Sources of CO2
Carbon dioxide has always been with us. Scientists say Earth’s earliest atmosphere was made up mostly of steam, carbon dioxide, and ammonia from volcanic eruptions.

Today, carbon dioxide is naturally produced by the combustion of organic matter like coal, oil, and wood, and the fermentation or respiration processes of living organisms.

People are another source. The air we exhale is made up of about 4.5 percent CO2. Bacteria in the soil release CO2 when they digest leaves and carcasses. Even plants that usually absorb CO2 'exhale' it at night.

CO2 is one of the most important substances on Earth. Besides providing warmth to the world, it is the world’s most important fertilizer.

Plants, phytoplankton, and algae need the gas for their photosynthesis to produce sugar and to grow. While doing so they absorb and bind carbon dioxide and produce oxygen. That is why forests are one of the world’s most important absorbers of CO2, otherwise known as 'carbon sinks'.

There are a number of artificial uses of carbon dioxide, in fire extinguishers, as dry ice and, as the food additive E290, CO2 adds the fizz to soft drinks and sparkling water.

Human-induced increase
The increase in CO2’s share of the atmosphere is mostly due to anthropogenic (man-induced) factors, such as burning fossil fuels, deforestation, and industrial production.

Most anthropogenic CO2 is produced by energy production and transport. Cement production is just one among many chemical processes that release the gas. Rotting organic materials release CO2, and so landfills are big CO2 contributors too.

In total, humans emit around 32 gigatons of carbon dioxide each year. Half of this stays in the atmosphere; the rest is absorbed by oceans and vegetation.

But with sharp increases in man-made CO2 emissions, the natural CO2 cycle has been thrown out of balance: vegetation can no longer transform the same proportion of CO2 into oxygen, and oceans are steadily reaching saturation level.

Theoretically, rising CO2 levels should be compensated for by plants and algae. Up to a certain concentration, more CO2 means more photosynthesis and more growth.

Unfortunately, under hot and dry conditions many plants close their pores to prevent the loss of water and switch to a process called photorespiration during which they consume oxygen and produce carbon dioxide. Only areas with enough precipitation and fertile soils will see increased growth as a result of rising CO2 levels.

The result is an enhanced greenhouse effect and, subsequently, climate change. While CO2 is only responsible for 20 percent of the natural greenhouse effect, it accounts for about 60 percent of the anthropogenic greenhouse effect that is causing the current global warming.

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Netralisasi pada pengolahan limbah cair

Sebagian besar limbah cair dari industri mengandung bahan bahan yang bersifat asam (Acidic) ataupun Basa (alkaline) yang perlu dinetralkan sebelum dibuang kebadan air maupun sebelum limbah masuk pada proses pengolahan, baik pengolahan secara biologic maupun secara kimiawi, proses netralisasi tersebut bisa dilakukan sebelum atau sesudah proses equalisasi.

Untuk mengoptimalkan pertumbuhan microorganisme pada pengolahan secara biologi, pH perlu dijaga pada kondisi antara pH 6,5 – 8,5, karena sebagian besar microb aktif atau hidup pada kondisi pH tersebut. Proses koagulasi dan flokulasi juga akan lebih efisien dan efektif jika dilakukan pada kondisi pH netral.

Netralisasi adalah penambahan Basa (alkali) pada limbah yang bersifat asam (pH 7).Pemilihan bahan/reagen untuk proses netralisasi banyak ditentukan oleh harga/biaya dan praktis-nya, Bahan (reagen) yang biasa digunakan tersebut adalah :

Asam :

Sulfuric acid ( H2SO4 )
Hydrochloric acid ( HCI )
Carbon dioxide ( CO2 )
Sulfur dioxide
Nitric acid

Basa :

Caustic soda (NaOH) Ammonia (NH3)
Soda Ash (Na2CO3) Limestone (CaCO3)

Ditulis oleh Suparni Setyowati Rahayu dari Chemistry.org

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