What is gasification?
The reality is that the creation of synthetic natural gas (syngas- SNG) is a technology based on coal gasification for the majority of power plants that use gasification technologies worldwide. Gasification to produce SNG can also use natural gas, municipal waste, other biomass, or petroleum, as the primary feedstock.
Clean energy-based gasification is used efficiently in synergy with carbon capture and storage (CCS), integrated gasification combined cycle (IGCC), anaerobic digestion (AD), combined heat & power (CHP, a.k.a. cogeneration), district heating (DH), and waste-to-energy technologies. These are clean energy technologies that use the syngas created through gasification, natural gas, and other renewable (and non-renewable) energy sources. These technologies are also used to create even more renewable energy than just energy created during the various unique technological processes (this is explained further below).
Gasification uses fossil fuels or organic based carbon materials to create the gases which make up syngas (by combining one of the feedstocks listed above and oxygen at extremely high temperature, after which the gas undergoes a clean-up process).
Lignite, a brownish type of coal, is the type of coal often used as a fuel source in the process of creating syngas in much of the world.
The process of gasification is when coal, gas, or another feedstock, along with steam and oxygen, is used to create syngas. The syngas goes through a clean-up process (methanation); and can then be burned directly to generate electricity and/ or heat for homes and businesses.
The syngas can be processed to create products including methanol, nitrogen-based fertilizers, other chemicals and compounded materials, or hydrogen for oil refining and transportation fuels (as is the dominant use of hydrogen productionworldwide today). Coal gasification, especially in the cases of integrated gasification combined cycle and/ or with CCS technology, is sometimes called a “clean coal” technology because it can create energy with less harm to the environment than traditional fossil fuel use. Gasification to produce SNG can be less polluting and a more efficient, versatile use of energy than the direct use of fossil fuels for energy.
CCS & IGCC, CHP, AD, and DH – clean energy technologies used in combination with syngas
Is gasification truly a “green” or a “clean” energy production technology? It is clean-er energy production, when gasification is used in conjunction with CCS, or a low carbon technology like IGCC. IGCC is a fairly new technology that uses a gasifier in converting organic raw material (lignite, biomass, etc…) into syngas.
When syngas is created using biomass, the technology is certainly “greener” than just burning a fossil fuel. Producing SNG with gasification can also be used in conjunction with a number of clean energy technologies, such as CHP, AD, and DH.
Creating bio-syngas with biomass by gasification
The energy production (SNG, energy/ heat in CHP and DH, hydrogen) created with gasification technologies is only renewable energy when the fuel source for gasification are biomass or municipal waste. More environmentally-friendly versions of gasification than with the use of fossil fuels as a feedstock, are available with biomass energy production, or waste-to-energy (discussed below).
However, municipal waste is renewable, so waste-to-energy is a renewable energy technology. The syngas created in the waste-to-energy process, or any of the other gasification energy generating processes described below, is energy that can be used in municipal energy grids, to heat homes, or can be converted into liquefied natural gas (LNG) or compressed natural gas (CNG) for use in the transportation sector.
A significantly more environmentally friendly, cost-effective and efficient, version of gasification than coal use, is available in biomass and waste-to-energy. Biomass gasification uses feedstocks like: agricultural residues (such as wheat and straw), energy crops (like switchgrass), forestry residues and urban wood waste (for example, from construction sites). Agricultural waste, along with other waste, can also be used in the gasification process. The resulting product is known as bio-syngas (bio-SNG).
Waste-to-energy in gasification
Waste-to-energy is the least complex situation in which gasification is used to create renewable energy. Waste-to-energy refers to a viable current technique for producing syngas through gasification technologies. Incineration in combination with gasification uses municipal waste as a fuel; combustion of it forms methane, CO2, and other gases, which can be captured and processed into SNG.
In a waste-to-energy plant that uses incineration, these hot gases are used to make steam, which is then used to generate electricity. As the process also creates heat, which might otherwise just be waste heat, waste-to-energy is also ideal to be used in CHP plants, and for district heating. Incineration of municipal solid waste has been practiced for almost 150 years as a technique to produce energy, and reduce landfill waste.
The leading region in the world for syngas production is Asia, in particular China. China mostly uses coal for its syngas production, relying on their vast coal deposits, thus still producing significant quantities of greenhouse gas emissions. China is trying to rely more on domestic sources for gas and less on importing liquefied natural gas. A large number of gasification plants are also found in India, South Korea, Taiwan, and Singapore.
The Africa/ Middle East regions also produce a significant quantity of syngas, more than Europe, or the United States. However, production of syngas in Europe uses a wider selection of feedstocks, technologies and products than other regions. The coal-based units in Europe primarily utilize IGCC technologies.
A fairly new gasification plant in Swindon, England illustrates the advancements that European nations are making with gasification. Methanation is used to transform gasified biomass into grid-quality syngas in the Swindon plant, the biosynthetic natural gas (bio-SNG) then providing power to the grid.
Most syngas production in North America lies within the United States. These plants include: natural gas facilities that primarily produce chemicals, and coal and petroleum based plants that produce either power, chemicals and fertilizers or syngas, including a couple of IGCC plants. In Canada, gasification is also used to produce hydrogen and power to upgrade synthetic crude oil from the tar sands.
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