Waste Handling: Anaerobic digestation and Esterification
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Anaerobic digestation
Anaerobic digestation is a way to change waste into heat and biogas. As a contrast to fermentation where a specific microbe is used to produce a particular product like ethanol, here we do not know how many or tens of microbes participate to produce biogas. At least some 50 metadogen populations are known today. It is used mainly for wet waste.
It is used to treat livestock manure, slurry etc in farms. It is also standard technology for stabilization of sewage sludge for treatment of organic industrial waste and organic waste from municipal solid waste
Farms are looking for anaerobic digestation to process their own livestock manure to produce own power and heat. This saves money, reduces greenhouse emissions, reduces the odors coming with manure and produces digestate that can be used as a fertilizer.
A farm scale unit would have some kind of holding unit that feeds the manure at adjustable speed to the main digester. The main digester is the place the microbial activity happens producing biogas.
This biogas can be used for example to directly drive an aggregate producing electricity for the farm. If there is excess electricity, it can be even sold to the grid operator.
The digestate needs its own storage unit. A farm scale digestation unit also needs a control unit. Various parameters need to be measured like the amount of biogas being produced, electricity generation amount etc. These measurements need to be processed in some computing unit that is either local or a cloud service and resulting insight visible via some kind of user interface so the process can be controlled.
Esterification
Esterification can be used to turn oils into biodiesel and other valuable end products. The process can use for example vegetable oils, yellow grease, used cooking oils, or animal fats.
The process is called transesterification. In it oil is reacted with alcohol like methanol or ethanol in the presence of a catalyst - usually sodium hydroxide (NaOH) or potassium hydroxide (KOH). This produces methyl, ethyl or propyl ester (biodiesel). As co-product it produces glycerin. Glycerin is a sugar commonly used in the manufacture of pharmaceuticals and cosmetics.
Biodiesel is usually blended with petro-diesel (normally less than 10%) as most engines would require medication to run on pure biodiesel. Biodiesel blends can also be used as heating oil.
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