ABE fermentation from microalgae-derived carbohydrates after lipid extraction

Although lignocellulosic biomass is an abundant substrate, major challenges in their pretreatment and digestion remain a serious limitation for large scale second generation biofuel production. First generation feedstocks which are primarily starchy substrates like corn have much more favourable economics as they are simple to mash. However, concerns related to the use of water and land for the production of biofuel crops have generated a need for alternative biomass sources for renewable biofuel production from a non-food crop. One biomass which satisfies all of these concerns is microalgae. Many strains are capable of growing in waste water, can accumulate carbon intracellularly as starch, are not eaten as food in any significant amount, and also have the added bonus of fixing CO2 during photosynthetic growth. However, production of microalgae biomass has its own particular challenges such as the high cost of dewatering and drying microalgal biomass. In order to demonstrate a possible biofuel production strategy using microalgal biomass, Chlorella vulgaris was cultivated at the pilot scale (100 L) and harvested using centrifugation. Lipids were extracted for biodiesel production using either a water compatible ionic liquid based process or using traditional (non water compatible) solvent based process. The residual biomass containing proteins and carbohydrates was recovered from both processes and designated either ionic liquid extracted algae (ILEA) or hexane extracted algae (HEA). To convert these micro-algal carbohydrates into solvents (ABE), HEA and ILEA was either acid hydrolysed into glucose before fermentation or directly fermented as it is. The highest butanol titers (8.05 g/L) was obtained with the fermentation of acid hydrolysates of HEA, which however required detoxification to support solvent production while ILEA did not. Interestingly, both ILEA and HEA can be fermented directly without any additional steps and resulted in a butanol titer of 4.99 and 6.63 g/L, respectively, which significantly simplified the LEA to butanol process. Further study has shown that butanol titers close to the toxicity limits are possible with higher substrate loadings, however a a fed-batch approach is required in order to mitigate increased culture viscosity issues during direct fermentations. These results indicate that lipid extracted microalgae are a readily consumed substrate for biofuel production. Please click Additional Files below to see the full abstract

Application of Advanced Oxidation Process in the Food Industry

Wastewater in the food industry contains recalcitrant organic compounds and a certain degree of toxicity. Present wastewater treatment plants are insufficient in dealing with the increasing complexity of effluents from modern food industries. Improperly treaded wastewaters can lead to spoil soil and are threads to aquatic life. The reaction of these recalcitrant chemicals with reactive radicals is an efficient treatment strategy. Researchers have proposed advanced oxidation processes (AOPs) that generate reactive radicals including ozonation, UV irradiation, (photo-) Fenton process, etc. This chapter reviews laboratory-scale and pilot-scale AOPs to incorporate with conventional pre-treatment methods and to evaluate their effectiveness and factors including operation condition and catalysts to optimize the process. Further research related to novel catalyst synthesis and cost evaluation of pilot-scale study is suggested

Anaerobic digestion of the aqueous pyrolysis condensate

Fractional condensation of biomass pyrolysis vapors allows the segregation of different pyrolysis fractions and a separation of an aqueous pyrolysis condensate from an organic rich dry bio-oil fraction. Aqueous pyrolysis condensate is often referred at as “wood vinegar” or “pyroligneous acid” since it contains 70-80% water together with 10-20% acetic acid, and smaller quantities of acetone and methanol mixed with hundreds of other chemicals in small concentrations. Such aqueous pyrolysis condensate cannot be easily disposed of, and it may represent a valuable resource. For example, the significant percentage of acetic acid offers the opportunity to attempt its conversion into methane by anaerobic digestion. Aqueous pyrolysis condensate produced by fractional condensation of vapors generated from the pyrolysis of birch bark at 500 °C has been characterized (elemental composition, pH, COD, volatile fatty acids (particularly acetic acid), ammonia, hydrogen sulfide, minerals, and phenolics), inoculated with a consortium of bacteria from an organic waste anaerobic digestor, and digested over several weeks. Biogas production has been progressively monitored and methane and CO2 concentrations experimentally measured. We performed a large number of experiments to investigate the effects of (a) dilution of the aqueous pyrolysis condensate, (b) nutrients addition, and (c) addition of bio-char on the production of biogas and on its methane concentration. The results clearly show that the anaerobic digestion of aqueous pyrolysis condensate is possible and leads to the production of biogas and on the reduction of the COD of the original feedstock to make it suitable for disposal. However, the high phenolic content of the condensate, together with possibly other chemical species, creates considerable inhibition of microbial methane production. Such inhibitory effects, however, can be mitigated by gradual adaptation of the bacteria population to the feedstock composition. The result show that 50 to 60 days are required before significant biogas production is observed when raw anaerobic pyrolysis condensate is processed. The addition of bio-char to the process is beneficial in shortening the lag phase to approximately 20 days and is triggering a higher volume of biogas production with an increased methane content, compared to similar conditions without bio-char. This is attributed to the ability of bio-char to adsorb inhibitory compounds as well as to create more favorable environmental conditions for the digestion process. Similarly, but less effectively, the addition of selected nutrients is shown to benefit the anaerobic process by shortening the lag phase to 40 days

Pyrolysis of polyethylene-lined waste paper cups

Fractional condensation of biomass pyrolysis vapors allows the segregation of different pyrolysis fractions and a separation of an aqueous pyrolysis condensate from an organic rich dry bio-oil fraction. Aqueous pyrolysis condensate is often referred at as “wood vinegar” or “pyroligneous acid” since it contains 70-80% water together with 10-20% acetic acid, and smaller quantities of acetone and methanol mixed with hundreds of other chemicals in small concentrations. Such aqueous pyrolysis condensate cannot be easily disposed of, and it may represent a valuable resource. For example, the significant percentage of acetic acid offers the opportunity to attempt its conversion into methane by anaerobic digestion. Aqueous pyrolysis condensate produced by fractional condensation of vapors generated from the pyrolysis of birch bark at 500 °C has been characterized (elemental composition, pH, COD, volatile fatty acids (particularly acetic acid), ammonia, hydrogen sulfide, minerals, and phenolics), inoculated with a consortium of bacteria from an organic waste anaerobic digestor, and digested over several weeks. Biogas production has been progressively monitored and methane and CO2 concentrations experimentally measured. We performed a large number of experiments to investigate the effects of (a) dilution of the aqueous pyrolysis condensate, (b) nutrients addition, and (c) addition of bio-char on the production of biogas and on its methane concentration. The results clearly show that the anaerobic digestion of aqueous pyrolysis condensate is possible and leads to the production of biogas and on the reduction of the COD of the original feedstock to make it suitable for disposal. However, the high phenolic content of the condensate, together with possibly other chemical species, creates considerable inhibition of microbial methane production. Such inhibitory effects, however, can be mitigated by gradual adaptation of the bacteria population to the feedstock composition. The result show that 50 to 60 days are required before significant biogas production is observed when raw anaerobic pyrolysis condensate is processed. The addition of bio-char to the process is beneficial in shortening the lag phase to approximately 20 days and is triggering a higher volume of biogas production with an increased methane content, compared to similar conditions without bio-char. This is attributed to the ability of bio-char to adsorb inhibitory compounds as well as to create more favorable environmental conditions for the digestion process. Similarly, but less effectively, the addition of selected nutrients is shown to benefit the anaerobic process by shortening the lag phase to 40 days

Anaerobic digestion of aqueous pyrolysis condensate enhanced by biochar: a circular economy approach

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Comparison of ethanol production from corn cobs and switchgrass following a pyrolysis-based biorefinery approach

Background One of the main obstacles in lignocellulosic ethanol production is the necessity of pretreatment and fractionation of the biomass feedstocks to produce sufficiently pure fermentable carbohydrates. In addition, the by-products (hemicellulose and lignin fraction) are of low value, when compared to dried distillers grains (DDG), the main by-product of corn ethanol. Fast pyrolysis is an alternative thermal conversion technology for processing biomass. It has recently been optimized to produce a stream rich in levoglucosan, a fermentable glucose precursor for biofuel production. Additional product streams might be of value to the petrochemical industry. However, biomass heterogeneity is known to impact the composition of pyrolytic product streams, as a complex mixture of aromatic compounds is recovered with the sugars, interfering with subsequent fermentation. The present study investigates the feasibility of fast pyrolysis to produce fermentable pyrolytic glucose from two abundant lignocellulosic biomass sources in Ontario, switchgrass (potential energy crop) and corn cobs (by-product of corn industry). Results Demineralization of biomass removes catalytic centers and increases the levoglucosan yield during pyrolysis. The ash content of biomass was significantly decreased by 82–90% in corn cobs when demineralized with acetic or nitric acid, respectively. In switchgrass, a reduction of only 50% for both acids could be achieved. Conversely, levoglucosan production increased 9- and 14-fold in corn cobs when rinsed with acetic and nitric acid, respectively, and increased 11-fold in switchgrass regardless of the acid used. After pyrolysis, different configurations for upgrading the pyrolytic sugars were assessed and the presence of potentially inhibitory compounds was approximated at each step as double integral of the UV spectrum signal of an HPLC assay. The results showed that water extraction followed by acid hydrolysis and solvent extraction was the best upgrading strategy. Ethanol yields achieved based on initial cellulose fraction were 27.8% in switchgrass and 27.0% in corn cobs. Conclusions This study demonstrates that ethanol production from switchgrass and corn cobs is possible following a combined thermochemical and fermentative biorefinery approach, with ethanol yields comparable to results in conventional pretreatments and fermentation processes. The feedstock-independent fermentation ability can easily be assessed with a simple assa

The nucleoporin RanBP2 tethers the cAMP effector Epac1 and inhibits its catalytic activity

Direct interaction between the catalytic domain of Epac1 and the nuclear pore component RanBP2 blocks Epac1 catalytic activity and downstream cAMP signaling