Gunnarsson, Ingólfur Bragi

Et bioraffinaderi har potentiale til at fortrænge fossile brændstoffer og olie-baserede produkter. I et bioraffinaderi kan en række forskellige produkter fremstilles af biomasse, herunder fødevarer, foder, biokemikalier og biobrændstoffer. Hvilke produkter der produceres, er i høj grad afhængig af den kemiske sammensætning af den specifikke biomasse, samt hvilken forbehandling, saccharificeringsprocesser, gæring og udvindingsteknikker der anvendes. Desuden vil biologiske processer der integrerer effektivt forbrug af CO2, med produktion af biokemikalier blive stadig vigtigere. En sådan procesintegration kan i væsentlig grad forbedre bæredygtigheden af de overordnede processer i et bioraffinaderi.I denne undersøgelse blev ukonventionelle lignocellulære og akvatiske biomasser undersøgt som bioraffinaderi-biomasser. De undersøgte biomasser var jordsskokke, industrihamp og makroalgearten Fingertang. Den kemiske sammensætning af biomasserne blev bestemt for at demonstrere deres potentiale i et bioraffinaderi. Bioethanol, biogas og ravsyre var de undersøgte bioprodukter, mens potentiel produktion af andre forbindelser også blev undersøgt.Forskelle og ændringer i biomassen sammensætning og produktivitet af elleve forskellige jordskokke-kloner blev undersøgt ved tre høsttidspunkter. Udbytte på op til 35 t ha-1 tør lignocellulose blev opnået, men mængden af cellulose var i mange tilfælde mindre end 50% af, hvad der blev observeret i fx hamp. Planternes rødder indeholdte høje mængder kulhydrater (≤88% af tørvægt) og gav op til 6 t ha-1 tørstof af yderligere kulhydrater. Kulhydratindholdet i L. digitata viste sig at være usædvanlig høj (77.6% af tørvægt).Forskellige metoder til forbehandling og saccharificering af biomasse blev anvendt afhængig af typen af biomassen. L. digitata krævede ingen anden forbehandling end formaling og tørring før enzymatisk hydrolyse. Forbehandlinger med H2SO4, NaOH og H2O2 ved forskellige betingelser blev anvendt til at forbehandle hamp før enzymatisk hydrolyse, mens jordskokke-knolde blev behandlet med 0.2% H2SO4 i kombination med varmebehandling som en direkte hydrolysemetode.Bioethanol blev produceret af industrihamp-hydrolysater. Ethanoludbytte i området 74-92% af det teoretiske udbytte blev opnået, mens ethanol koncentrationer var op til 10.0 g L-1. Produktion af ravsyre fra denne type af hydrolysat resulterede i meget højere koncentrationer og substratudnyttelse i forhold til ethanolfermentering, delvist fordi A. succinogenes er i stand til at fermentere både glucose og xylose til ravsyre.Jordskokke-knolde, industrihamp og L. digitata viste alle stort potentiale som råvare til ravsyreproduktion. Den maksimale ravsyreproduktion varierede mellem 21.9 og 47.4 g L-1. Den højeste ravsyrekoncentration blev opnået med gæring af jordskokke hydrolysat, mens det maksimale ravsyre udbytte (86.5%) blev opnået ved gæring af L. digitata hydrolysat. Med rodknolde-biomasse blev vist, at knolde let kunne hydrolyseres uden enzymer og fermenteres uden tilsætning af næringsstoffer, hvilket påviser, at anvendelsen af dette råmateriale potentielt kunne reducere omkostningerne for ravsyreproduktion.Det biokemiske metanpotentiale for L. digitata, PHSR (e. post hydrolysis solid residue) og fermenteringsvæsken efter ravsyregæring blev også bestemt. I et bioraffinaderi er biogasproduktion vigtig for energiudvinding samt for at minimere spild og skabe et ekstra produkt i form af gødning. Energiudnyttelse af PHSR og fermenteringsvæske gennem anaerob nedbrydning svarede til 298 og 285 NmL CH4 g-1 VSadded, hhv.Ved yderligere integration af de forskellige processer i bioraffinaderikonceptet blev en ny biogas-opgraderingsteknologi udviklet. Fremgangsmåde var baseret på CO2-fiksering af A. succinogenes samtidig med produktion af ravsyre og CH4 af høj renhed. Systemet var i stand til at opnå 95.4% CH4, hvilket svarer til renhedsgraden som kommercielle biogas- opgraderingteknologier leverer.Resultater opnået i denne undersøgelse er den første rapport for udnyttelse af makroalger, hamp og jordskokke-knolde som biomasse til fermentativ ravsyreproduktion. Det blev vist, at de tre biomasser er attraktive biomasseråstoffer til ravsyreproduktion, hovedsagelig på grund af deres høje indhold af kulhydrat. Et casestudie af et bioraffinaderikoncept med makroalger beskriver potentialet af PHSR til fremstilling af en lang række yderligere produkter, såsom ω-3 og ω-6 fedtsyrer, biodiesel, protein, foder, biogas og gødning, og kan dermed diversificere bioraffinaderiets produktportefølje.Biorefinery has the potential of displacing fossil fuels and oil-refinery based products. Within the biorefinery a palette of marketable commodities can be produced from biomass, including food, feed, biochemicals and biofuels. Which bioproducts are produced is largely dependent on the chemical composition of the specific biomass feedstock, as well as which pretreatment, saccharification, fermentation and extraction techniques are used. Furthermore, integrating biological processes into the biorefinery that effectively consume CO2 will become increasingly important. Such process integration could significantly improve the sustainability indicators of the overall biorefinery process.In this study, unconventional lignocellulosic- and aquatic biomasses were investigated as biorefinery feedstocks. The studied biomasses were Jerusalem artichoke, industrial hemp and macroalgae species Laminaria digitata. The chemical composition of biomasses was determined in order to demonstrate their biorefinery potential. Bioethanol and biogas along with succinic acid production were the explored bioconversion routes, while potential production of other compounds was also investigated.Differences and changes in biomass composition and productivity of eleven different Jerusalem artichoke clones was examined at three harvest times. Yields of up to 35 t ha-1 of dry lignocellulose matter was reported, nonetheless the amount of cellulose in many cases was less than 50% of what was observed in e.g. hemp. However, the underground tubers which the plant produces, contained high amounts carbohydrates (≤88% of dry weight) and yielded up to 6 t ha-1 dry matter of additional carbohydrates. The carbohydrate content found in L. digitata was also shown to be exceptionally high (77.6% of dry weight) compared to other studies.Diverse methods for pretreatment and saccharification of biomass were used depending on the type of biomass. L. digitata did not required any pretreatment before enzymatic hydrolysis other than milling and drying. Pretreatments using H2SO4, NaOH and H2O2 at different conditions were used to pretreat hemp prior to enzymatic hydrolysis, while Jerusalem artichoke tubers needed 0.2% H2SO4 in combination with heat-treatment as a direct hydrolysis method.Bioethanol was produced from industrial hemp hydrolysates. Ethanol yields in the range of 74-92% of theoretical yield were reported, while ethanol concentrations amounted up to 10.0 g L-1. However, the production of succinic acid from this type of hydrolysate resulted in much higher product titer and substrate utilization compared to ethanol fermentation, partially because A. succinogenes is able to ferment both glucose and xylose into succinic acid.Jerusalem artichoke tubers, industrial hemp and L. digitata all showed considerable potential as feedstock for succinic acid production. The maximum succinic acid production from the different feedstocks ranged between 21.9 and 47.4 g L-1. The highest succinic acid titer was reached when fermenting Jerusalem artichoke hydrolysate, while the maximum succinic acid yield (86.5%) was reached when fermenting L. digitata hydrolysate. In the case of tuber biomass it was shown that tubers could be readily hydrolyzed without enzymes and fermented without any addition of nutrients, which clearly indicates that utilization of this feedstock could potentially lower the costs for succinic acid production.The biochemical methane potential of L. digitata, post hydrolysis solid residue (PHSR) and fermentation broth after succinic acid fermentation was also determined. In a biorefinery, biogas production is important for energy recovery as well as for minimizing waste and generating an additional product in the form of fertilizer. Energy recovery of PHSR and fermentation broth through anaerobic digestion corresponded to 298 and 285 NmL CH4 g-1 VSadded, respectively. To further increase the integration of the different processes in the biorefinery concept, a novel biogas upgrading technology was developed. The approach was based on the CO2 fixation abilities of A. succinogenes to simultaneously produce high purity CH4 and succinic acid. The system was able to reach 95.4% CH4 content, which is similar purity as commercial biogas upgrading technologies deliver.Results obtained in this study constitute the first report for utilization of macroalgae, hemp and Jerusalem artichoke tuber biomass for fermentative succinic acid production. It was demonstrated that all biomasses are attractive biomass feedstocks for succinic acid production mainly due to their high carbohydrate content. A case study of a proposed macroalgae biorefinery concept highlighted the potential of post hydrolysis solid residue (PHSR) for the production of numerous additional products such as ω-3 and ω-6 fatty acids, biodiesel, protein, feed, biogas and fertilizer, thereby diversifying the biorefinery product portfolio.<br/

Online Research Database In Technology

Unconventional biomasses as feedstocks for production of biofuels and succinic acid in a biorefinery concept

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Unconventional biomasses as feedstocks for production of biofuels and succinic acid in a biorefinery concept

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