| The rapid development of the agriculture and livestock industry promotes economic growth,but it also leads to an increase in demand for energy and generated wastes are being the major problem regarding the increase in serious environmental pollution.Both problems can be solved through the implementation of proper treatment technology able to recycle these wastes to produce fuel,feed,and fertilizer.One important challenge for using agricultural byproducts such as crop residues to produce biofuels is the low digestibility of these materials.In addition,there are millions of tons of livestock manure is produced annually and is not properly utilized in a valueadded way.Meanwhile,during storage and handling of livestock manure being produced GHG emissions that cause global warming.Therefore,the effective bioconversion and high-value utilization of agricultural byproducts could be realized by the integration of biotechnological treatments.In this thesis,we attempt to explore the effective bioconversion mechanism of crop straw and poultry manure.Also,we studied the effect of different bioconversion parameters on the characteristics of products and biofuels based on the application of technologies of anaerobic digestion and black soldier fly(Hermetia illucens).Moreover,we developed new cascading waste biorefinery systems to improve the biofuels and protein production as well as achieve more reduction of GHGs emissions.The main results are summarized as follows:1)Anaerobic liquid digestates for pretreatment of rice straw: A holistic approach for efficient biomethane production and nutrient recyclingIn this study;the potential of acidogenesis digestate rich in volatile fatty acids(Bio-DAcid)and methanogenesis digestate rich in ammonia(Bio-DMeth)as green method for the pretreatment of rice straw and biomethane production.After pretreatment with Bio-DMethfor 48 h,a maximum hemicellulose reduction of 22.4%was recorded,while 48 h of Bio-DAcid showed the lowest reduction of 15.7%.In addition,pretreatment for 48 h with Bio-DMethand Bio-DAcid showed significant removal of lignin by 16.6 and 11.0%,respectively.SEM and FTIR confirmed major increase in straw porosity and degradation after all applied pretreatments.The highest significant biomethane content of 71.2% was recorded in 24 h Bio-DAcid-pretreated straw.However,the highest significant yield of 249.1 Lkg-1 VS was recorded from the 48 h Bio-DMethpretreated straw,which was 9.8,19.6,and 27.0% higher than 24 h Bio-DMeth-,24 h Bio-DAcid and 48 h Bio-DMeth-treated straw,respectively.Importantly,pretreatment with Bio-DMethfor 24 h showed the highest estimated net bioenergy output of 7.37 GJ ton-1 dry straw,which represented 28.6 and 0.13 % increase over that of the control and 48 h Bio-DMeth-pretreated straw,respectively.In addition,the relative CO2 emission of 24 h Bio-DMeth-pretreated rice straw was 0.69 kg CO2m-3 biogas,which represented 17.9% lower than the control.The present study suggested application of Bio-DMeth for 24 h as an efficient eco-friendly pretreatment method for efficient AD of rice straw.2)A novel integrated approach of waste-free biofuel production from agricultural wastes based on anaerobic digestion and black soldier fly(Hermetia illucens)In the present study,a novel biorefinery route for efficient conversion of chicken manure(CM)mixed with rapeseed straw(RS)was investigated through anaerobic codigestion with digestate recycling.The liquid digestate fraction was used for straw pretreatment,while solid fraction was utilized for rearing of the oleaginous black soldier fly larvae(BSFL).Anaerobic digestion(AD)of raw straw resulted in 144.2 L kg-1 VS,while the pretreatment enhanced biomethane yield to 227.6 L kg-1 VS.SEM images and FTIR analysis confirmed substantial changes in morphological fiber structure and functional groups of cellulose,hemicellulose and lignin.Co-digestion of the pretreated straw with chicken manure at different ratios of 1:1,1:3,and 3:1 increased the biomethane yield to 323.5,349.6,and 262.3 L kg-1 VS,respectively.In addition,biomethanation efficiency(EB)increased from 33.9% by digestion of raw straw to 53.3% for the pretreated straw,reaching its maximum value of 76.5% by codigestion at a ratio of 1:3.BSFL was grown on different ratios of solid digestate/larva(D/L)of 0.25,0.50,0.75 and 1.00,where it showed higher growth and faster development by increasing the solid digestate ratio.In addition,protein and lipid contents significantly increased by increasing the digestate ratio,reaching the maximum values of 36.1 and 31.8 dw%,respectively,at 1.00 D/L.Therefore,the highest FAMEs recovery of 301.8 mg g-1 dw was recorded at the highest applied digestate ratio,with significant increase in the saturation degree.The suggested integrated approach using a mixture of 1:3 pretreated straw: manure for dual production of biogas and biodiesel enhanced the gross bioenergy yield(GBY)by 95.7%,24.6%,and 38.7% over the conversion of raw rapeseed straw,pretreated straw,or chicken manure,respectively.The present study demonstrates a novel waste-toenergy approach that will have a significant impact on the future of biofuel industry.3)Bioconversion of rapeseed straw mixed with chicken manure to biodiesel via Hermetia illucens: Innovative approach for enhanced biodiesel production from rapeseed plantAlthough rapeseed plant is currently one of the main feedstocks of biodiesel,the efficient utilization of the huge amount of rapeseed straw(RS)wastes has not been fully exploited.The present study evaluated the indirect conversion of RS(mixed in different ratios with chicken manure)into biodiesel using the oleaginous black soldier fly larvae(BSFL)in an innovative biorefinery concept.Results showed that 20% RS ratio effectively enhanced the biodegradation of RS fibers,biomass production and lipid accumulation in BSFL.The lipid produced from larval biomass grown on 800 kg of chicken manure could be converted into 17.2 kg of biodiesel at a conversion rate of 91.8%.However,adding200 kg of RS improved the biodiesel yield to 32.8 kg at a conversion rate of 94.4%.Interestingly,the saturated fatty acid content of the produced biodiesel at 20% RS(74.1%)was much higher than that reported for the biodiesel produced currently from rapeseed oil,which results in higher cetane number and oxidative stability of the BSFL-RS derived biodiesel.Based on the current biodiesel industry from rapeseed oil,a total dry RS of 4.2 ton can be obtained annually from 1 ha of rapeseed,that can be used to additionally produce 689.4 kg of biodiesel using BSFL.In addition,the potential application of BSFL technology could reduce the CO2 emissions by 10.42 ton per ha.In conclusion,the results of this study suggested the BSFL as a promising mini-livestock for innovative RS management through conversion of lignocelluloses into biodiesel. |
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