Crude glycerol

Biodiesel is chemically known as methyl esters, which is produced through transestrification reaction by reacting a vegetable oil or animal fat with an alcohol under a strong base catalysis environment [104]. Along with biodiesel, such transestrification reaction produces significant

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quantity of glycerol (also called as glycerin), which is normally collected with other ingredients such as catalysis, water and unreacted alcohol and it is termed as crude glycerol [105]. Normally biodiesel industries utilize excess amount of methanol as required for the completion of reaction, which leaves unreacted methanol to the glycerol after the reaction. With every 3 gallons of biodiesel, 1kg of crude glycerol is produced and it shows very low value because of its impurity [106]. As the global biodiesel production increases exponentially, the resulting crude glycerol is extensively high and become issues due to their disposal or effective utiliza­tion. On the other hand, pure glycerol has found a wide range of applications that includes food, cosmetics, and drugs. In order to upgrade the crude glycerol to those high end applica­tions, it should undergo various purification stages such as bleaching, deodoring, and ion exchange. Normally, this is not affordable nor economically feasible for most of the small/

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Figure 7. World protein meal consumption(milliontonnes)in2011(drawnfromdata reportedin[97]).

medium ranged industries. Hence, it is necessary toinvestigatethevalue-addedusesofcrude glycerol in various applications.

Prior to that, it is necessary to understandldierelationship between time oilfeedstosk end tha eouife glycerol. Thompson and He [105] performed a research on the characterization of crude glycerol samples from various feedstocks. Theirresearchsho ws that the compositions of different crude glycerol are highly varying wirh rheir feedstocks. Shieereates thechallenge le ados>tauniver — sal protocol to fabricate value-added arodunCffsom oruaeglyrerolfrom vae-Ges Seedstacke. Crude glycerol has been ueed to produce varioui prnduots mcludingl-3/l, a-propenediol, dihydroxyacetones, polyestenr andOydrogen [і.7]. Mu el: aS. —i(rn] repoeted tha r^jmSCtef:^гз1Гl, iCn propanediol using crude glyeerel produced during biodfeselptepapationrheough fermenta­tion process using Klebsiell apneumoma. Theyusedtirecruda gtyoero1 nbtained °uring soybean oil-based biodiesel producttongmolooingalkalicatolysis. Tgeyulfimatelycompepedtheproduct of 1,3-propanediol obtainedbrometirefdyt-erolanafoundthaeiheyarecimiSar toaachnthor]aeaC. Soares et al. [109] demonstr afeg thegenerationofseerthenii gaeorsgngar (hydrooen andcasdng monoxide) from glycerol at vaoy low temperatuiebeeween225-300 °С emploningaPd-nared catalyst. Further it can be converted into nuelrOchemicalcbyPisohae-Trons tli mathano! son-he. sis. They also suggest this paneess fos ahe effettive utilizationotvarloue cmaegiyrerca Ceed — stocks for the fabrication of high vatue fuefe/chemfealr. Mothec e — ai.[r dOt repocendl the synlherlc of poly (3-hydroxybutyrate) ^HB. uaingcrudegiycesol (ropeseldoil-barodiar She feedstockvia biotechnological process empioyind Peracoscue demlrillcanr anl Cupriaoldusnecatoemi — crobes. They compared the propertiecof hre eyntiraeized йгогпРігоіИіїєгєп1 feedetocke add

found that the properties areviryalmi lnr:ZhoueCeLiniO(rev-ewedtheehemn-peleetiveox idslion of crude glycerol into various prodncts suchacgleoeric add, Sydroaypyenvio асЮ grid meeoox, alic acid which can be used a sprecurrnrforvariourfmerhemicalrandpoh^iericmaterialr. Theso reports indicate the emergm. oppostumtierfor erude glnceroeforoaciousapnUcahonomclud — ing chemical, fuel and mate rials.

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