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Pyrolysis
Pyrolysis is the thermal decomposition of organic wastes in the absence of oxygen. It is the fundamental chemical reaction that is the precursor of both the combustion and gasification processes and occurs naturally in the first two seconds. The products of pyrolysis include fixed carbon char, oils and gases including methane, hydrogen, carbon monoxide and carbon dioxide. Depending on the thermal environment and the final temperature, pyrolysis will yield mainly char at low temperatures, less than 450 degrees Celsius, when the heating rate is quite slow and mainly gases at high temperatures, greater than 800 degrees Celcius, with rapid heating rates. At an intermediate temperature and under relatively high heating rates, the main product is oil.
Pyrolysis can be performed at relatively small scale and at remote locations which enhance energy density of the waste resources and reduce transport and handling costs. Heat transfer is a critical area in pyrolysis as the pyrolysis process is endothermic and sufficient heat transfer surface has to be provided to meet process heat needs. Pyrolysis offers a flexible and attractive way of converting solid wastes into easily stored gases which can be successfully used for the production of heat, power and chemicals.
A wide range of waste feedstocks can be used. The pyrolysis process is very dependent on the moisture content of the feedstock, which should be at or below 10%. High-moisture waste streams, such as sludge and meat processing wastes, require drying before subjecting to pyrolysis.
Waste pyrolysis has been attracting much attention due to its high efficiency and good environmental performance characteristics. It also provides an opportunity for the processing of agricultural residues, wood wastes and municipal solid waste into clean energy. In addition, carbon sequestration could make a big difference in fossil fuel emissions worldwide and act as a major player in the global carbon market with its robust, clean and simple production technology.
Link to Biochar document.
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