Energy from waste is a process by which discarded materials are converted into fuel or electricity. This can be achieved in many ways. Gasification, Incineration, Landfill and methane capture are just a few of the options. Others can make use of plastic waste. The end result is clean, renewable energy that is both sustainable and friendly for the environment.
Gasification
Gasification is an efficient and environmentally friendly way to transform waste energy. The process can produce as much as 1,000 kilowatts per hour of electricity from a single ton (MSW) of municipal solid waste. It can also produce chemicals and methanol which are the base of many fertilizers. The process reduces the need for landfill space and reduces methane emissions.
One example is plasma gasification, which makes use of extremely high temperatures in an oxygen-starved atmosphere to convert waste material into simple compounds. Although it is similar to pyrolysis in that it produces high-temperature plasma gases, it is not. This process produces syngas, molten steel, and vitrified slate.
Incineration
Incineration of waste is a process which reduces waste's mass and produces heat and flue gases. The ash, mostly composed of inorganic waste materials, is then recovered and the heat generated is used to generate electricity. Incineration is a cost-effective way to generate renewable energy. It is used often to offset the landfill costs. Incineration can reduce the mass of waste by as much as 96%. However, incineration is not meant to replace landfills.
Incinerators can also be used for certain waste types that cannot go to landfills. Because they can heat waste to high temperatures, they can destroy pathogens and toxins. They are also ideal for treating wastewater from chemical multiproduct plants which produce a large amount of toxic material. These toxins are not compatible with conventional wastewater treatment facilities. Burning piles and pits is one of the oldest methods of disposing of waste. However, this method can lead to high levels of pollution.
Landfill methane capture
Landfill methane (or landfill gas) can be captured to make energy. It is created when organic waste in a landfill breaks down. The gas is mostly composed of methane and carbon dioxide with trace amounts of other gases. Landfill methane can also be captured for energy and heat production.
The anaerobic method captures methane in a landfill. Afterwards, the landfill gas is collected by perforated pipes placed throughout the capped landfill. The pipes are designed to permit the gases to rise vertically without flowing toward buildings. The gases are then burned or vented into air. The methane is captured and converted to a renewable energy source, which is then sold at a profit.
Conversion of plastic waste
The process of converting plastic waste into energy is a recent development. It uses hydrothermal liquidification and efficient separation. This technology can produce new fuels and be used as a source of feedstock for other chemical products. It could also be used for the production of specialty solvents or monomers. The world could use it to supply up to 4% of its fuel needs. Next, the technology must be scaled up to greater scales.
RES Polyflow is a company which plans to process 100,000 tons plastic each year. It also converts the energy into fuel oil and naphtha for the production of polymers. The company has already made a deal for BP to acquire the output of this plant. It is due to open in 2011.
Conversion of agricultural waste
Agricultural waste is a valuable resource and if properly converted, can be used to generate renewable energy sources such as biogas and bio-oil. It is expensive to collect, transport and store agricultural waste. Traditional methods of disposing of this waste are still used by many countries. They release toxic gases that can pose a danger to the environment as well as human health. Energy conversion of agricultural waste can help countries manage waste and develop renewable energy resources.
Pretreatment processes are used to reduce agricultural waste into a variety of components. Microwave pyrolysis, which creates biochar, oil, and syngas, is one of the most common thermochemical transformation methods. In developing countries, biomass residues don't get treated. Instead they are left to decompose or burned.