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Polyhydroxyalkanoates (PHAs) attract considerable attention as sustainable "green plastics" with a real potential to replace their petrol-based competitors in some applications in the not-too-distant future. To reach this goal PHAs must be able to compete with the established petrol-based plastics in both technical and economic terms. The current PHA production is based on prized substrates of high nutritional value such as sucrose, starch or vegetable oils. An alternative, carbon-rich industrial waste can be used as a suitable feedstock. This would contribute to making PHAs economically competitive and would avoid the conflict with human nutrition or animal feeding. Consequently, the decision about the location of the PHA-production facilities depends on the preferable in-house availability of such waste streams. The issue of competitive, large-scale PHA production in Europe was the topic of the ANIMPOL and the WHEYPOL projects. Both intended to develop novel processes for the transformation of abundant, locally available, renewable wastes. In the ANIMPOL case, waste lipids from slaughterhouses are converted to glycerol and a mixture of saturated and unsaturated fatty acid esters (FAEs), better known as biodiesel. The production of saturated FAEs is 50 000 t per year in Europe, decreasing the biodiesel performance as an engine fuel. However, within the project it was demonstrated that they can be efficiently metabolized to PHAs. In the WHEYPOL project attention was focused on 1.4 x 10sup8 t per year of whey from dairies. This waste is of limited use and causes environmental concern. However, lactose, the main carbohydrate found in whey, can be used as a substrate in the WHEYPOL bioprocesses. These strategies demonstrate the feasibility of making "green plastics" competitive by integrating their manufacturing directly into the existing production lines, where the convertible waste streams accrue. Polihidroksialkanoati (PHA) vzbujajo posebno pozornost kot trajnostna "zelena plastika" z realno možnostjo, da nadomestijo svoje tekmece, ki temeljijo na nafti, za določene namene uporabe v bližnji prihodnosti. Za dosego tega cilja morajo biti PHA sposobni tekmovati tako po tehničnih kot po ekonomskih vidikih z uveljavljenimi plastikami na osnovi nafte. Sedanja proizvodnja PHA temelji na dragih podlagah z veliko hranilno vrednostjo, kot so saharoza, škrob ali rastlinska olja. Kot alternativna surovina se lahko uporabi z ogljikom bogate industrijske odpadke. To bi prispevalo k bolj ekonomični izdelavi PHA in bi preprečilo konflikt s prehrano ljudi in krmo živali. Posledično je odločitev o lokaciji izdelave PHA odvisna od razpoložljivosti in virov takih odpadkov. Vprašanje konkurenčne proizvodnje PHA v velikih količinah v Evropi je bila tema projektov ANIMPOL in WHEYPOL. Oba sta imela namen razviti nove postopke predelave obilnih in lokalno razpoložljivih obnovljivih odpadkov. V primeru ANIMPOL-a so bili odpadni lipidi iz klavnic pretvorjeni v glicerol in mešanico estrov (FAE) nasičenih in nenasičenih maščobnih kislin, bolj poznani kot biodizel. Proizvodnja nasičene FAE v Evropije 50 000 t na leto in zmanjšuje zmogljivost biodizla kot pogonskega goriva. Projekt je pokazal, da jih lahko pretvorimo v PHA. Pri projektu WHEYPOL je bila pozornost usmerjena na 1,4 x 10na8 t na leto sirotke iz mlekarn. Ta odpadek ima omejeno uporabo in povzroča okoljske skrbi. Vendar pa se laktoza, glavni ogljikovodik v sirotki, lahko uporabi kot osnova pri WHEYPOL-bioprocesih. Te strategije kažejo, da je mogoča proizvodnja konkurenčne "zelene plastike" z vključitvijo njihove izdelave neposredno v proizvodne linije, kjer se vredni odpadki pojavljajo. |
