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

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/

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.