Biogas production by anaerobic co-digestion using byproducts of first- and second-generation bioethanol production process.

Programa de P?s-Gradua??o em Engenharia Ambiental. N?cleo de Pesquisas e P?s-Gradua??o em Recursos H?dricos, Universidade Federal de Ouro Preto.Neste trabalho foi avaliada a co-digest?o anaer?bia (AcD) dos subprodutos da biorefinaria da cana-de-a??car, especificamente, hidrolisado hemicelul?sico (HH) (obtido pelo pr?-tratamento hidrot?rmico do baga?o da cana (SB)), vinha?a (gerada durante o processo de produ??o de etanol de primeira gera??o), extrato de levedura (YE) (que pode ser obtidos a partir de leveduras descartadas) e cinzas volantes de baga?o de cana (SBFA), usando experimentos de potencial bioqu?mico de metano (PBM). As melhores condi??es experimentais da AcD em batelada (propor??o de mistura de 25-75% de HH-vinha?a; 1,0 g L-1 YE; 15 g L-1 SBFA e 100-0% de HH-vinha?a, 1,5 g L-1 YE; 45 g L-1 SBFA) levaram ? produ??o de 0,279 e 0,267 Nm3 de CH4 por kg de demanda qu?mica de oxig?nio (DQO) removida com um excedente de energia de 0,43 e 0,34 MJ kg SB-1, respectivamente. Realizaram-se experimentos de adsor??o utilizando SBFA mostrando que ? poss?vel adsorver at? 61,71 e 58,21 mg g-1 de 5-hidroximetil-2- furfuralde?do e 2-furfuralde?do, reduzindo assim a toxicidade do substrato e melhorando a produ??o de biog?s durante a AcD dos subprodutos mencionados. Posteriormente, dois sistemas anaer?bios mesof?licos alimentados continuamente com a mistura de HH e vinha?a e inoculados com SBFA e YE foram utilizados para validar os dados obtidos em batelada. Um novo reator anaer?bio de leito estruturado de est?gio ?nico (nSBR) foi comparado com um sistema acidog?nico-metanog?nico de dois est?gios, formado por um reator acidog?nico de leito estruturado (ASTBR) seguido por um reator metanog?nico UASB. A carga org?nica (OLR) (de 0,9 a 10,8 g COD L-1 d-1) aplicada em estes sistemas foi atingida pela fixa??o do tempo de reten??o hidr?ulica (HRT) nos reatores (17,5 h em nSBR; 6 h no ASTBR e 19,9 h no UASB) e a altera??o da concentra??o de DQO da alimenta??o por meio de dilui??o. Os resultados mostraram a viabilidade do uso de um sistema de dois est?gios (ASTBR / UASB) no tratamento de uma mistura HH-vinha?a, levando a uma remo??o global de DQO superior a 80% e um rendimento de metano de 0,245 Nm3 CH4 kg de COD-1r. Por sua vez, o sistema de est?gio ?nico (nSBR) levou a 65% da remo??o da DQO e 0,205 Nm3 CH4 kg de COD-1r de rendimento de metano. An?lises da comunidade microbiana do lodo coletado dos reatores anaer?bios em diferentes condi??es operacionais mostraram mudan?as estruturais e relacionais entre as comunidades microbianas dominantes, pertencentes aos g?neros Clostridium, 8 Bacteroides, Desulfovibrio, Lactobacillus, Lactococcus, Longilinea, Methanosaeta, Pleomorphomonas e Syntrophus, e as condi??es cin?ticas, hidrodin?micas e de performance dos sistemas anaer?bios. Ambos sistemas, ?nico (nSBR) e duplo (ASTBRUASB) estagio, exibiram estabilidade a longo prazo de opera??o (240 dias) com baixo ac?mulo de AGV (m?dia de 550 mgL-1 no nSBR e 625 mgL-1 no UASB). Finalmente, para cen?rios que consideram uma biorrefinaria de cana-de-a??car integrada, uma avalia??o t?cnico-econ?mica e ambiental foi realizada mostrando que o rendimento de metano ? o par?metro mais sens?vel. O melhor cen?rio mostrou, que usando um sistema anaer?bio de dois est?gios para o substrato estudado e considerando o uso de 50% do excedente do baga?o para a produ??o de etanol, foi poss?vel atingir uma taxa interna de retorno (TIR), um retorno sobre o investimento (ROI) e um per?odo de payback de 26%, 89,05% e 5,36 anos, respectivamente. Indicadores de impacto ambiental como pegada de carbono, que variou de 12,3 a 50,02 g CO2/MJ e % de redu??o de emiss?es (de 42,7 a 85,9%) para etanol 2G e processo de produ??o de biog?s foram obtidos em todos os cen?rios. Assim, os resultados evidenciaram a import?ncia do investimento em P&D e da implementa??o de Pol?ticas de Biocombust?veis, principalmente para produ??o de etanol 2G (baga?o dispon?vel), e tamb?m para a co-digest?o anaer?bia de subprodutos buscando atingir objetivos de economia circular e viabilidade global da bioferinaria de cana de a??car integrada.In this thesis anaerobic co-digestion (AcD) of sugarcane biorefinery byproducts, i.e. hemicelluloses hydrolysate (HH) (obtained by hydrothermal pretreatment of sugarcane bagasse), vinasse (generated during 1G ethanol production process), yeast extract (YE) (which can be obtained from spent/excess yeast) and sugarcane bagasse fly ashes (SBFA), was optimized by means of biochemical methane potential (BMP) experiments. The best experimental conditions of AcD (25-75% HH-to-vinasse mixture ratio; 1.0 g L-1 YE; 15 g L-1 SBFA and 100-0% HH-to-vinasse; 1.5 g L-1 YE; 45 g L-1 SBFA) led to the production of 0.279 and 0.267 Nm3 of CH4 per kg of chemical oxygen demand (COD) removed with an energy surplus of 0.43 and 0.34 MJ kg SB-1, respectively. Adsorption experiments using SBFA were carried out and showed this residue could adsorb up to 61.71 and 58.21 mg g-1 of 5-hydroxymethyl-2-furfuraldehyde and 2-furfuraldehyde, thereby reducing toxicity and improving biogas production during AcD of the aforementioned byproducts. Subsequently, two mesophilic anaerobic systems fed continuously with the mixture of HH and vinasse and inoculated with SBFA and YE were used in order to validate batch data. A single stage novel structured bed anaerobic reactor (nSBR) was compared with a two-stage acidogenic-methanogenic system formed by an acidogenic structured-bed reactor (ASTBR) followed by an UASB methanogenic reactor. The organic loading rate (OLR) (from 0.9 to 10.8 g COD L-1 d-1) applied to these systems was attained by fixing the hydraulic retention time (HRT) in the reactors (17.5 h in nSBR; 6 h in the ASTBR and 19.9 h in the UASB) and changing the influent COD concentration by means of dilution. The results showed the feasibility of applying the two-stage system (ASTBR/UASB) to treat a HH-vinasse mixture, leading to a global COD removal higher than 80% and methane yield of 0.245 Nm3 CH4 kg CODr-1. In its turn, the single stage (nSBR) system led to 65% of COD removal and 0.205 Nm3 CH4 kg CODr-1 of methane yield. Microbial community analyses of sludge collected from the single (nSBR) and twostage system (SBR/UASB) at different operational conditions revealed structural changes and the relation among the main genus found (Clostridium, Bacteroides, Desulfovibrio, Lactobacillus, Lactococcus, Longilinea, Methanosaeta, Pleomorphomonas and Syntrophus) with processes performance, kinetic and hydrodynamic parameters. Both systems (single nSBR and ASTBR-UASB) exhibited a stable long-term operation (240 days) with low VFA accumulation (average of 550 mg/L at nSBR and 625 mg/L at UASB). Finally, for scenarios that consider an integrated sugarcane biorefinery, technical-economic and environmental assessment was realized showing that methane yield is the most sensitive parameter. The better scenario showed, that using a two-stage anaerobic system for byproducts and considering the use of 50% of bagasse surplus for ethanol production, was possible achieve the internal rate of return (IRR), return on investment (ROI), and payback period of 26%,89.05% and 5.36 years respectively. Environmental impact indexes such as carbon footprint, which varied from 12.3 to 50.02 g CO2 /MJ and % of emission reduction (from 42.7 to 85.9 %) for 2G ethanol and biogas production process was obtained in all scenarios. Thus, the results evidenced the importance of investment in R&D and the implementation of Biofuel Policies especially in 2G ethanol production (available bagasse) but also in the anaerobic co-digestion of byproducts for attain its global feasibility

Sustainable production of fuel bioethanol from switchgrass in Uruguay

Sustainability concerns due to long-term depletion of fossil fuels and climate change are responsible for a renewed interest on biofuels and biorefineries. Fuel bioethanol produced from lignocellulosic materials using modern technology could lead to high greenhouse gases (GHG) emissions savings. Biorefineries integrate the production of materials, chemicals, fuels, and energy. This could maximize the value obtained from biomass and minimize environmental impacts. Switchgrass (Panicum virgatum L.) is considered a good source of biomass because of its high productivity, longevity, high efficiency in water and nutrient use, and low production cost. Although several works have studied bioethanol production from switchgrass, a complete analysis of techno-economic and environmental sustainability for the current technology and conditions in Uruguay is necessary to promote the sustainable national production of bioethanol. In this work, switchgrass was evaluated as a feedstock for the production of bioethanol in a biorefinery located in Uruguay using a liquid hot water (LHW) pretreatment. Material and energy use was determined for different scenarios and process configurations through process modeling. Material and energy results were used in a techno-economic model to analyze the effect of different parameters and configurations on the economics of the process. The minimum ethanol selling price (MESP) obtained for ethanol in a facility producing only ethanol and electricity was within the expected price range for advanced alcohol fuels and could compete with oil prices above 100 $/ barrel. Working on a biorefinery scenario producing furfural, acetic acid, and formic acid as high-value co-products, decreased the MESP. The MESP was sensitive to plant size and to switchgrass composition. Enzyme dosage, solids content, and hydrolysis and fermentation efficiencies are the operating parameters with higher impact on MESP, experimental information on how they are related (e.g. efficiency vs solids content) is necessary for more reliable assessments. Experimental assays were performed to evaluate the cellulose enzymatic hydrolysis of LHW pretreated switchgrass at high solids content. LHW pretreatment (200ºC, 5 min) proved to be a suitable alternative for a biorefinery approach. It was found that the washing of solids and initial pH had a significant effect on hydrolysis efficiency. The effect of solids content, enzyme dosage, and partial cellulase substitution by xylanase, were studied experimentally. Glucose concentration and hydrolysis efficiency were significantly affected by solids content and enzyme dosage. Very high glucose concentrations (189 g/L) were achieved. High hydrolysis efficiencies were found even for high solids content (>90dosage (40-70 mgprotein/gglucan). Experimental results were combined with the process and techno-economic models. Maximizing glucose concentration or hydrolysis efficiency did not directly correlate to minimizing the MESP. Enzyme dosage and solids content had a significant effect on MESP and it was found that an enzyme dosage of 37 mgprotein/gglucan and a solids content of 21 MESP. A life cycle assessment (LCA) was performed to evaluate GHG emissions and non-renewable fossil energy consumption associated with the production of fuel bioethanol in Uruguay using results from material and energy balances previously obtained. GHG emissions for bioethanol produced in all the scenarios analyzed were lower than the reference emissions for fossil fuel. The biorefinery scenario was better than the ethanol and electricity facility in terms of the environmental impacts and the biofuel produced there could meet GHG reduction requirements. All the factors analyzed (switchgrass composition, enzyme dosage, fermentation and hydrolysis efficiency and solids content) had a significant effect on the environmental performance of fuel bioethanol, enzyme use being the most significant factor. When compared with other works for Uruguay, the ethanol from the scenario with only electricity as co-product had a worst environmental performance than ethanol from sugarcane and sorghum grain. However, the ethanol from the biorefinery scenario performed better. Otherscenarios analyzed (e.g. low enzyme dosage) also had a good environmental performance. Optimal conditions for both economics and GHG emissions were found from models based on experimental data. These conditions (21 environmental performance (well to tank: -68 5 gCO2eq/MJethanol, GHG emissions) and good process economics (MESP of 0.84$/L). Therefore, environmentally sustainable production of ethanol from switchgrass on a biorefinery located in Uruguay (in terms of GHG emissions and fossil energy use) could be possible with the technology and yields currently available. Economic sustainability for current technology and yields depends on oil prices and/or policies (carbon taxes). Scale-up of the experimental results obtained and appropriated industrial equipment are critical aspects of the technical feasibility.Existe un interés renovado en biocombustibles y biorefinerías debido a problemas de sustentabilidad asociados al agotamiento a largo plazo de combustibles fósiles y al cambio climático. El bioetanol combustible producido a partir de materiales lignocelulósicos con tecnologías modernas podría reducir significativamente las emisiones de gases de efecto invernadero (GEI). Las biorrefinerías integran la producción de materiales, químicos, combustibles y energía. Esta integración podría maximizar el valor obtenido de la biomasa y minimizar los impactos ambientales. El switchgrass (Panicum virgatum L.) es considerado una buena fuente de biomasa debido a su alta productividad, longevidad, alta eficiencia en el uso de agua y nutrientes y bajos costos de producción. Aunque existen varios trabajos sobre la producción de bioetanol a partir de switchgrass, es necesario un análisis completo de la sustentabilidad técnico-económica y ambiental para la tecnología disponible y las condiciones de Uruguay para promover la producción nacional de bioetanol combustible. En este trabajo, se evaluó el uso de switchgrass como materia prima para la producción de bioetanol combustible en una biorrefinería localizada en Uruguay. Se estudió el uso de materiales y energía para diferentes escenarios y configuraciones mediante el modelado del proceso. Los resultados de los balances de materia y energía se utilizaron en un modelo técnico-económico, con el objetivo de analizar el efecto de diferentes parámetros y configuraciones en la economía del proceso. El precio mínimo de venta de etanol en una planta que produce solamente etanol y electricidad estuvo en el rango esperado para alcoholes combustibles de avanzada y podría competir con precios de petróleo superiores a 100 US$/ barril. Producir furfural, ácido acético y ácido fórmico como co-productos de alto valor agregado en un concepto de biorrefinería, redujo el precio mínimo de venta del etanol. El precio mínimo de venta fue sensible a la escala de producción y a la composición del switchgrass. Las eficiencias de hidrolisis y fermentación, el contenido de sólidos y la dosis de enzima son los parámetros operativos con más impacto en el mínimo precio de venta. Información experimental sobre cómo se relacionan (ej. eficiencia vs contenido de sólidos) es importante para obtener resultados más confiables. Se realizaron ensayos experimentales para evaluar la hidrolisis enzimática de la celulosa a altos contenidos de sólidos obtenidos luego de un tratamiento de auto-hidrólisis. El pretratamiento de auto-hidrólisis (200ºC, 5min) fue una alternativa adecuada para el enfoque de biorefinerías. El lavado de los sólidos pretratados y el pH inicial tuvieron un efecto significativo en la eficiencia de hidrólisis. Se estudió experimentalmente el efecto del contenido de sólidos, dosis de enzima y sustitución parcial de celulasas por xilanasas. Tanto la concentración final de glucosa como la eficiencia de hidrólisis se vieron afectadas por contenido de sólidos, y por la dosis de enzima. Se obtuvieron concentraciones altas de glucosa (189 g/L). Se encontraron eficiencias de hidrólisis elevadas incluso para contenidos de sólido altos (>90para 25resultados experimentales se utilizaron en el modelo del proceso y en el modelo técnicoeconómico. Se encontró que maximizar la concentración de glucosa o la eficiencia de hidrólisis no se correlaciona directamente con una reducción del precio mínimo de venta. La dosis de enzima y el contenido de sólidos tuvieron un efecto significativo sobre el precio de venta, una dosis de 37 mgprotein/gglucan y un contenido de sólidos de 21 invernadero y el consumo de energía fósil no renovable asociados a la producción de bioetanol combustible en Uruguay, utilizando los resultados de los balances de materia y energía obtenidos previamente. En todos los casos estudiados el bioetanol combustible presentó emisiones de GEI menores que las de referencia para combustibles fósiles. La biorrefinería presentó un mejor desempeño ambiental que la planta que produce etanol y electricidad, y el etanol producido allí podría cumplir con los requerimientos de reducciones de GEI. Todos los parámetros estudiados (composición del switchgrass, dosis de enzima, eficiencias de hidrolisis y fermentación, y contenido de sólidos) tuvieron un efecto significativo en el desempeño ambiental del bioetanol combustible, siendo el uso de enzima el más significativo tanto en las emisiones de GEI como en el uso de energía fósil. Comparado con otros estudios realizados para Uruguay el etanol de la planta que sólo produce etanol y electricidad tuvo un peor desempeño que el etanol de caña de azúcar y sorgo grano. Sin embargo, el etanol producido en la biorrefinería tuvo un mejor desempeño ambiental. Otros escenarios analizados también presentaron un buen desempeño ambiental. Se encontraron las condiciones que optimizan simultáneamente las emisiones GEI y la economía del proceso a partir de los modelos basados en datos experimentales. Estas condiciones (21 (“cuna a tanque”: -68 5 gCO2eq/MJetanol, emisiones GEI) y económico (precio de venta 0.84 US$/L). La producción ambientalmente sustentable de etanol a partir de switchgrass en una biorrefinería ubicada en Uruguay, podría realizarse con la tecnología y rendimientos actuales. La sustentabilidad económica en estas condiciones depende del precio del petróleo y de las políticas (ej. bonos de carbono). El escalado y el diseño de equipos industriales es un aspecto crítico de la viabilidad técnica del proceso

Comparative techno-economic assessment of sugarcane biorefineries producing glutamic acid, succinic acid, levulinic acid and xylitol from A-molasses and lignocellulosic biomass

Thesis (MEng)--Stellenbosch University, 2021.ENGLISH ABSTRACT: The financial sustainability of the South African sugar industry is currently threatened by difficult economic conditions, including external factors such as low sugar prices by new global competitors, and increased production costs. Because of these challenges, some of the sugar mills face potential closure in the future because they are no longer profitable. With this in mind, it has been proposed that sugar mills should valorise by-products to increase profitability. Molasses and lignocelluloses (bagasse and trash) biomasses are the two by-products of the sugar mill as the potential first-generation (1G) and second-generation (2G) feedstocks, respectively, for valorisation in a biorefinery context. These feedstocks are promising carbon sources for the prominent global bio-based economy, owing to their low cost, high content of the fermentable sugars, and relative abundance. The global demands, technological maturity, and potential to penetrate new markets support the section of the product of interest: glutamic acid (GA), levulinic acid (LA), succinic acid (SA), and xylitol for investigation in a biorefinery context as a way to diversify products in a sugar mill, thereby increasing revenues. An overall aim of this study was to determine if the profitability of sugarcane biorefineries producing GA, LA could be further improved from the previously attained profitable scenarios that utilised the second-generation (2G) feedstock (lignocelluloses), by further considering 1G feedstock (A-molasses). Considered as a cleaner raw material, 1G results in the elimination of the costly pretreatment and enzymatic hydrolysis processes. Furthermore, the integration of feedstocks (1G and 2G) was investigated to evaluate the economies of scale benefits through a sole production of GA, LA, and SA. Thereafter, multi-production of the aforementioned with xylitol was considered. Literature data were used to design and develop the process flow sheets for detailed AspenPlus® process simulation models considering feed capacities of 25.4 t/h A molasses and 113.5 t/h of lignocellulose. The generated mass and energy balances data were used for techno economic analysis for a yearly operation if 5000 hours. With reconfigurations on the sugar mill, 1G biorefineries can benefit from utilising the existing CHP facility or incorporating low-cost, low-pressure boiler in the 1G biorefineries. As a result, 1G biorefineries showed better economic performances than their 2G biorefinery counterpart. The integration of feedstocks in 1G2G designs showed the economies of scale benefits, compared to 1G-only scenarios. This was demonstrated by the decrease in minimum selling price (MSP) from $2950/t to$2102/t in 2G LA and 1G2G LA scenario, $2237/t to$1745/t in 2G SA and 1G2G SA, and $2969 to 2205 for 2G GA and 1G2G GA scenarios, respectively. Comparatively, multiproduct facilities achieved lower MSP than the sole product 1G2G configurations counterparts ($2205/t vs $1926/t for GA and$2600/t vs $1133/t for LA). Except 1G2G SA+Xylitol at$1745/t vs $1888/t. This can be accounted for by the reduction in sales for SA from when there was an upgrade from sole product to multiproduct. Since techno-economic evaluation alone does not fully justify the sustainability and competitiveness of the proposed biorefineries in the eyes of investors or decision-makers, a study on the Life cycle assessment considering the environmental and social impact of biorefineries could be further investigated.AFRIKAANSE OPSOMMING: Die finansiële volhoubaarheid van die Suid-Afrikaanse suikerindustrie word tans bedreig deur moeilike ekonomiese kondisies, insluitend eksterne faktore soos lae suikerpryse deur nuwe globale mededingers, en verhoogde produksiekostes. As gevolg van hierdie uitdagings, staar sommige van hierdie suikermeule potensiële sluitings in die toekoms in die gesig omdat hulle nie meer winsgewend is nie. Met hierdie in gedagte, is dit voorgestel dat suikermeule byprodukte moet valoriseer om winsgewendheid te verhoog. Molasse en lignosellulose (bagasse en afval) biomassa is die twee byprodukte van die suikermeule as die potensiële eerste-generasie (1G) en tweede-generasie (2G) voermateriale, onderskeidelik, vir valorisasie in ’n bioraffinadery-konteks. Hierdie voermateriale is belowende koolstofbronne vir die prominente globale bio-gebaseerde ekonomie, weens hul lae koste, hoë inhoud van die fermenteerbare suikers, en relatiewe volopheid. Die globale vereistes, tegnologiese rypheid, en potensiaal om nuwe markte te penetreer, ondersteun die deel van die produk in belang: glutamiensuur (GA), levuliniensuur (LA), suksiensuur (SA), en xilitol vir ondersoek in ’n bioraffinadery-konteks as ’n manier om produkte te diversifiseer in ’n suikermeul, en daardeur inkomste te verhoog. ’n Algehele doel van hierdie studie was om te bepaal of die winsgewendheid van suikerrietbioraffinaderye wat GA, LA produseer, verder kon verbeter uit winsgewende scenario’s wat voorheen verkry is deur die 2G-voermateriaal (lignosellulose) te gebruik, deur 1G-voermateriaal (A-molasse) verder te oorweeg. Oorweeg as ’n skoner rou-materiaal het 1G die eliminasie van die duursame voorbehandeling en ensimatiese prosesse tot gevolg. Verder, die integrasie van voermateriaal (1G en 2G) is ondersoek om die ekonomieë van skaal se voordele te evalueer deur ’n enkel-produksie van GA, LA en SA. Daarna is multi-produksie van die voorafgenoemde met xilitol oorweeg. Data uit literatuur is gebruik om die prosesvloeikaarte te ontwerp en ontwikkel vir gedetailleerde Aspen Plus®-prosessimulasiemodelle wat voerkapasiteite van 25.4 t/h A- molasse en 113.5 t/h lignosellulose oorweeg. Die gegenereerde massa- en energiebalanse se data is gebruik vir tegno-ekonomiese analise vir ’n jaarlikse bedryf van 5000 ure. Met hersamestellings op die suikermeule, kan 1G-bioraffinaderye voordeel trek deur die bestaande Gekombineerde hitte en krag (CHP) fasiliteite of die lae-koste, lae-druk ketel in die 1G-bioraffinaderye te inkorporeer. As ’n gevolg, het 1G-bioraffinaderye beter ekonomiese doeltreffendheid gewys as hul 2G-bioraffinadery eweknie. Die integrasie van voermateriaal in 1G2G-ontwerpe het die voordele van die ekonomieë van skaal gewys, in vergelyking met die 1G-alleenlik scenario’s. Hierdie is gedemonstreer deur die afname in (Minimum Verkoopprys) MSP van$2950/t tot $2102/t in 2G LA en 1G2G LA- scenario,$2237/t tot $1745/t in 2G SA en 1G2G SA, en$2643 tot $2794 vir 2G GA en 1G2G GA-scenario’s. In vergelyking het multi-produkfasiliteite laer MSPs teenoor die enkel-produk 1G2G-konfugirasies se eweknieë bereik ($2205/t vs. $1926/t vir GA en$2600/t vs. $1133/t vir LA). Buiten 1G2G SA+xilitol by$1745/t vs. $1888/t. Hierdie kan verduidelik word deur die reduksie in verkope vir SA vandat daar opgradering van enkel-produk tot multi-produk was. Aangesien tegno-ekonomiese evaluasie alleen nie die volhoubaarheid en mededingendheid van die voorgestelde bioraffinaderye ten volle regverdig in die oë van beleggers of besluitnemers nie, kan ’n studie op die lewensiklusassessering, wat die omgewings- en sosiale impak van bioraffinaderye oorweeg, verder ondersoek word.Master