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Greenhouse – Solutions
Since the start of the Industrial Revolution in the late 1800’s the atmospheric concentration of carbon dioxide (CO2) has increased approximately 40% (110 µL/L). Most of this increase has occurred since 1945 and levels are continuing to rise at an alarming rate. Burning fossil fuels such as coal and petroleum is the main cause of increased man-made CO2. Deforestation is the second major cause, followed by the use of other gases such as methane. Around 24,000 million tonnes of CO2 are released per year worldwide, equivalent to about 6500 million tonnes of carbon a year. For the problems of the greenhouse phenomenon to be addressed we must aim to reduce CO2 emissions to pre-industrial levels. In order to achieve this, we will need to look at alternatives to burning fossil fuels, as well as finding ways to stop future CO2 emissions and to remove existing CO2 from the atmosphere. There is no single solution to the greenhouse problem, so it must be attacked on several fronts if CO2 levels are to be effectively reduced and future increases avoided. Some of the methods most likely to make a positive impact are the use of renewable resources; nuclear power; geo-engineering; and carbon sequestration - both natural sequestration by trees and the oceans, and artificial sequestration such as geo-sequestration. According to the Intergovernmental Panel on Climate Change (IPCC), it is necessary to reduce world CO2 emissions by 8 billion tons by 2015, by 15 billion tons by 2030 and by 27 billion tons by 2050 in order to stabilize the concentration of atmospheric CO2 at 550ppm. Renewable Energy Renewable energy is the term used to describe any source of energy that can be used without depleting its reserves. Examples of renewable energy resources are: hydro dams, geothermal means and, increasingly, wind farms and solar power. These methods of producing electricity are efficient and do not create CO2 as a by-product. Other types of renewable energy, such as ethanol, do in fact produce CO2, but at much lower levels than are associated with the burning of fossil fuels. In this way we can still reduce our emissions by a small percentage. Renewable energy is one of the fastest growing industries in the world. It provides a commercially viable, readily available solution to our energy needs and can reduce greenhouse gas emissions by a significant amount. With sufficient political will and financial support it will be possible to shift from using fossil fuel-based power to renewable-based energy in the near future. Nuclear Power 
Nuclear power has the potential to provide a solution to the greenhouse problem because the energy-producing process does not burn fossil fuel, and so does not create carbon dioxide. However, there are several problems with nuclear power that would need to be addressed before it could be considered a viable option. In the first instance, building nuclear power stations is extremely expensive, and enormous financial investment would be required to replace coal-fired power stations. Other significant problems with this form of power generation include waste disposal, reactor accidents, threats to public health, nuclear weapons proliferation and vulnerability to terrorism. It has also been suggested that nuclear power may be ineffective in combating greenhouse warming because it only provides electricity, which accounts for just one-third of fossil fuel use. In addition, the construction and maintenance of nuclear power stations alone would generate a significant quantity of CO2. Carbon Sequestration Carbon sequestration is the term used to describe the process whereby CO2 is captured from the atmosphere and placed somewhere else. It is a different approach to the greenhouse problem as it does not attempt to produce less CO2 or stop the consumption of fossil fuels which are driving increases in greenhouse gases. Instead, this method tries to prevent CO2 from entering the atmosphere, in effect removing CO2 from our industrial emissions and putting it somewhere else. A variety of different means of artificially capturing and storing CO2 are being explored, including geo-sequestration, as well as maintaining and enhancing natural sequestration processes, all of which are intended to help reduce greenhouse levels and mitigate global warming. Enhancing natural sequestration processes Sequestration of CO2 occurs naturally within the environment. Enormous amounts of carbon are naturally stored in forests and in the oceans. Forests 
Trees and other plants absorb CO2 from the atmosphere as they grow, through the process of photosynthesis. They store the carbon as sugar, starch and cellulose, and subsequently release oxygen back into the atmosphere. A young forest composed of rapidly growing trees absorbs CO2 and acts as a sink where CO2 is stored. Mature forests made up of a mix of various aged trees, as well as dead and decaying matter may be carbon-neutral above ground, but CO2 can also be absorbed by the soil. When a tree dies or rots on the ground, nutrients are returned to the soil. The gradual build-up of slowly decaying organic material will continue to accumulate carbon, thereby acting as a sink by sequestering carbon at a rate that exceeds any soil carbon and other emissions. Carbon dioxide can also be released back into the atmosphere as the trees, timber or wood products are burned. Land plants can hold about three times as much carbon as the atmosphere. However, the rate at which forests sequester carbon is influenced by climate, topography and soils, as well as by the trees’ individual characteristics and how the forest is managed. Plantation forests have the potential to help existing forests to absorb CO2 from the atmosphere. They also provide a number of additional benefits including reduction of erosion, increased water capture, and economic benefits when sustainably harvested. Oceans Oceans can also act as natural sequestration sites for CO2. As the level of CO2 increases in the atmosphere, the level in the oceans also increases, creating potentially catastrophic acidic oceans. Ocean water can hold a variable amount of dissolved CO2 depending on temperature and pressure, but it has been estimated that it could absorb as much as 40 percent of our fossil fuel emissions. Phytoplankton are microscopic plants that are found in the ocean. Like trees, they use photosynthesis to extract carbon from CO2. Plankton and other marine organisms extract CO2 from the ocean water and convert it to the mineral calcite (CaCO3) to build their skeletons and shells. This removes CO2 from the water, allowing room for more to be absorbed from the atmosphere. These calcite skeletons and shells, along with the organic carbon of the organisms, eventually fall to the bottom of the ocean when the organisms die. One of the most promising ways to increase the carbon sequestration efficiency of the oceans is to add very small iron particles called hematite or iron sulphate to the water. This has the effect of stimulating growth of plankton. Iron is an important nutrient for phytoplankton, and increases in the numbers of plankton allow the oceans to sequester more carbon. It is also possible to grow plankton on a large scale away from the ocean, in systems similar to those used in aquaculture. In this scenario, large tanks of plankton are maintained to sequester CO2 from the atmosphere. Artificially capturing and storing carbon dioxide - Geo-sequestration 
There are several different methods used to store CO2 in a non-gaseous state. The most common method is geo-sequestration. Geo-sequestration is the process of capturing and storing CO2 underground. Geo-sequestration has been suggested as a method which would allow us to continue using fossil fuels for energy whilst ensuring a reduction of greenhouse gas emissions into the atmosphere. To prevent CO2 from entering the atmosphere the coal is burned and turned into a mixture of gases. The CO2 is removed from the gas mixture, and then captured and compressed into a liquid form. If the coal is burned in oxygen, higher concentrations of CO2 can be produced which are easier to separate. The liquid CO2 is then pumped deep underground into crevices and spaces that exist in solid rock formations, where it is secured and stored for thousands of years. Other potential storage sites include old oil and gas fields, coal beds or under the deep seafloor. The gas that remains after processing is CO2-free and can be used by the power station. Although geo-sequestration seeks to reduce CO2 admissions, thereby reducing greenhouse gas concentrations, there are many potential problems with this method. Almost all the existing power stations will require major modifications or will have to be replaced so they are able to capture the CO2. This will require major financial investment. The safety and security of storage also needs to be considered because of the potential for the CO2 to leak out of the rock it is stored in. Public acceptance is potentially the most challenging obstacle, as the community needs to be convinced of the benefits of geo-sequestration and support such an activity despite the cost and associated risk factors. Geo-Engineering Geo-engineering is an approach based on the artificial modification of the environment to try and solve the problem. It may provide additional time to address the economic and technological challenges faced by other solutions to the greenhouse problem. One geo-engineering approach is to try and reflect more sunlight back into space, thereby decreasing concentrations of sunlight and reducing the amount of greenhouse gas trapped in our atmosphere. Several different methods have been suggested to achieve this, including placing a reflective film over large deserts, floating white plastic islands on the world's oceans, placing a mirror 240km long between Earth and the Sun, as well as spraying tiny droplets of sea water onto clouds over the ocean to make them better mirrors for the Sun’s rays Another strategy, first proposed in the 1970s, is to inject sun-blocking sulphate particles, or aerosols, into the stratosphere every one to four years. Each ‘injection’ would, in theory, cool the climate for a year or more in much the same way that large volcanic eruptions create a global cooling effect. |
