Garbage Power

A Montgomery-based brick making company, Jenkins Brick Co., set up its $56 million new manufacturing plant, on an excavated hillside near Birmingham, because of its easy access to a source of cheap, abundant energy — a municipal landfill. The company uses more than 300 million cubic feet of gas a year generated by a landfill in a small city nearby.

Why should I be aware of this?

The trash that we toss into the garbage can now not only power our bulbs, computers and washing machines but also helps run industries.

About 30 years ago it was unthinkable that junk and sewage could be cost-effectively turned into a valuable commodity. Methane emerging from buried trash, which earlier used to escape into the atmosphere as a potent greenhouse gas, is now captured in some landfills. Solar Hydrogen Energy Corporation (SHEC Labs) has developed a process which converts methane into hydrogen with the help of solar energy. With the help of this technology they hope to compete with the cheapest source of hydrogen within 5 years.

Garbage power and environment

Methane's effect on climate change is considered at least 20 times worse than carbon dioxide, the most common greenhouse gas. It is about 23 times more potent over a 100-year time frame and it also has an atmospheric lifetime of 9-14 years.

There are many important energy, safety, economic, and environmental benefits from reducing methane emissions. As it is both a potent greenhouse gas and has a short atmospheric lifetime, methane reductions can produce significant near-term results. Producing energy from landfill gas can avoid the use of higher-emission traditional fossil-energy resources such as wood, coal or oil. Landfill gas generates fewer air pollutants during combustion than burning an equivalent amount of energy in the form of coal or oil.

The use of LFG provides environmental and economic benefits, and users of LFG have achieved significant cost savings compared to traditional fuel usage due primarily to the fact that LFG costs are consistently lower than the cost of natural gas.

All about garbage power

Several approaches are being developed, and some of them commercially, to turn garbage and sewage into electricity. Microorganisms that live in organic materials such as food wastes, paper or yard clippings cause these materials to decompose. This produces landfill gas (LFG), typically comprised of roughly 60 percent methane and 40 percent carbon dioxide with some additional trace compounds and can burn in virtually any application with minor adjustments to air/fuel ratios.

If landfill gas is left uncontrolled, it can create odor problems in the atmosphere and create global climate change. It can also cause health and safety concerns. The process of converting landfill gas into energy is relatively simple. To convert it as an energy source, landfill gas is typically extracted from landfills using a series of wells and a blower (or vacuum) system. The collected gas is then directed to a central point where it can be processed and treated, depending upon the ultimate use for the gas. From this point, the gas can be simply flared or used to generate electricity or to replace fossil fuels in industrial and manufacturing operations.

Methane and landfill gas

Methane produced in landfills, is a valuable energy resource that can be used in place of natural gas or propane. Burning, or destroying, methane gas as a source of energy is a low-cost, reliable alternative to fossil fuels. Methane is also a potent greenhouse gas with a 100-year global warming impact estimated at 23 times that of pure carbon dioxide alone.

Methane typically makes up about half of the total gas extracted from the landfill. The bulk of the remainder is carbon dioxide, but small amounts of other compounds are commonly found as well.

Landfill capacity

Energy producing capacity of a landfill is generally in the range of 3 to 8 megawatts, depending on its size and age. Generators at landfill-gas sites are very reliable and operate almost year-round with little downtime. So a 6-megawatt plant would produce approximately 47 million kilowatt-hours per year, enough to supply about 3,200 homes.

At smaller landfills there are several options for constructively using methane. Methane from landfills are used as an energy source for many development of many communities, such as fueling a pottery kiln and glass furnace, or to heat greenhouses or generate electricity for the landfill operations. Landfill methane can also be piped to nearby industrial users to partly offset their use of natural gas.

Plasma garbage conversion

Another method, and a highly effective on too, is to use a high intensity electrical arc to turn the incoming waste into plasma state in which the inflow is broken down to its elemental components -- individual atoms. The result is a burnable gas and an inert solid that can be used for things like pavement, bricks, and other building materials.

At a simple level plasma waste conversion involves application of a plasma torch to garbage. A plasma torch uses a gas and powerful electrodes to create plasma, an ionized gas with free-roaming electrons that carries a current and generates a magnetic field. Natural displays of plasma can be seen in lightning. A plasma torch can generate a temperature higher than 6,000 degrees C.

The molecules unable to stand this temperature, break down in a process called molecular dissociation. Left behind are the elemental components of the molecules. With cyanide, for example, you’ll end up with atoms of carbon and nitrogen. The carbon-based molecules become volatilized, or turn into gases, which after proper cleaning, can be used as a fuel source.

All types of waste, including the difficult ones like medical waste, can be treated with plasma waste converters. Only heavy radioactive material, such as the rods used in a nuclear reactor, cannot be broken down by a plasma converter.

Waste-to-energy plants

Waste-to-energy plants have been set up in many countries to capture the energy in their trash. Waste-to-Energy Plants function mostly like coal-fired power plants except that it uses garbage—not coal—to fire an industrial boiler. Otherwise the process is the same

• The fuel is burned, releasing heat.
• The heat turns water into steam.
• The high-pressure steam turns the blades of a turbine generator to produce electricity.

Out of 100 pounds of typical garbage, consisting of paper, plastics, and yard waste, more than 80 pounds can be burned as fuel to generate electricity at a power plant. About 525 kilowatt-hours (kWh) of electricity can be generated from a ton of waste, enough to heat a typical office building for one day.

Most of the waste in a waste-to-energy plant is burnt in a high-temperature incinerator.

90 degrees

One disadvantage to landfill gas is that though it's cheaper than natural gas, it has less than about half the heating capacity.

References

• Earth News/ Water To Energy
• Waste To Energy
• Water Management World
• How Plasma Converters Work