The process of making energy from waste involves the conversion of discarded materials into fuel or electricity. This can happen in many different ways. Gasification, Incineration, Landfill Methane Capture are some methods. Other methods can make use plastic waste. The end result, no matter what the process may be, is clean and renewable energy.
Gasification
The environmentally sound and cost-effective way to convert waste into energy is gasification. One ton of municipal solid refuse (MSW) can be converted to electricity, producing up to 1,000kilowatt-hours. 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.
This method uses high temperatures and oxygen-starved environments to convert waste materials into simple compounds. Plasma gasification is an example. Although it is similar to pyrolysis in that it produces high-temperature plasma gases, it is not. It produces syngas and molten metal as well as vitrified slag.
Incineration
Incineration of waste is a process which reduces waste's mass and produces heat and flue gases. The ash, made mostly of inorganic material waste, is then reclaimed and used to create electricity. The incineration process is often used to offset the costs of fossil fuels and landfills, and is an efficient way to produce renewable energy. Incineration can reduce waste volumes by as much 96%. It is not an alternative to landfills.
Incinerators can be used to dispose of certain wastes that are not allowed in landfills. Incinerators are capable of heating waste to high temperatures which can destroy pathogens or toxins. They are an ideal solution for wastewater treatment from chemical multi-product plants. These plants produce a range of toxic substances. These toxins can not be treated at standard wastewater treatment facilities. One of the oldest forms of waste disposal is by burning piles or burning pits. However, this method can lead to high levels of pollution.
Landfill methane capture
Landfill methane can be used to generate energy. It is formed when organic waste is broken down in landfills. Methane and carbon dioxide are the main components of the gas, but there are small amounts of other gases. The gas can be captured and used to make heat and energy.
The process to capture methane from a landfill begins by capturing the methane during the anaerobic process. Perforated pipes are then used to collect the gas from the capped landfill. The pipes are designed to permit the gases to rise vertically without flowing toward buildings. The gases collected are either emitted into the atmosphere, burned, or passed through a flame. Once captured, the methane is converted to a renewable fuel, which is sold at a profit.
Plastic waste recycling
Recently, a new conversion process uses hydrothermal liquefaction with efficient separation to make energy from plastic waste. This technology can produce renewable fuels, and it can be used to make other chemicals. It could also produce specialty solvents, monomers, and other chemicals. It could potentially meet up to 4% world fuel requirements. Next is scaling the technology to bigger scales.
RES Polyflow will process 100,000 tons annually of plastic and transform the energy into gasoline and naphtha that are used to make polymers. The company already has a deal with BP to purchase the output from the plant. It is expected that the plant will open in 2011.
Conversions of agricultural waste
Agricultural waste is valuable and can be used for renewable energy sources such biogas, bio-oil and other forms of energy if it is properly converted. It is expensive to collect, transport and store agricultural waste. Many countries still use traditional methods to dispose of their agricultural waste. These releases harmful gases which pose a risk to the environment and people's health. Renewable energy can be created from agricultural waste. This will help countries manage their waste better.
Pretreatment can help to break down agricultural waste into different components. The most common thermochemical method for converting agricultural waste is microwave pyrolysis. This produces biochar and bio-oil or syngas. In developing countries, biomass residues are usually not treated and are left to decompose naturally or are burnt.