Biomass Drying Research Articles

Effect of drying and extraction conditions on the recovery of bioactive compounds from Chlorella vulgaris

Microalgae and especially green algae are microorganisms that are used in a wide range of industrial applications of high economic interest, such as fish farming, food, cosmetics, pharmaceuticals, and biofuel. In this study, the green microalga Chlorella vulgaris was examined as raw material for the recovery of bioactive compounds and the production of multifunctional extracts. Firstly, the drying of raw biomass, which is a crucial pre-treatment stage, was examined with freeze-drying having the best performance. Ultrasound assisted extraction (UAE) applying various solvent systems was studied under optimized conditions. For the untreated microalgal biomass, ethanol was indicated as the preferable solvent, whereas on dried samples, water was a more suitable solvent. UV-Vis spectrometry and high-performance liquid chromatography (HPLC) were used for the determination of total carotenoid, chlorophyll, and protein content in the raw materials, extracts, and extraction residues. Moreover, the suitability of drying technique and extraction solvent system was evaluated according to the obtained antiradical activity of the relevant treated biomass and extraction samples using the DPPH method.

Design and optimization of solar-assisted conveyer-belt dryer for biomass

Biomass, as a renewable source of energy, can be used in many industries to reduce their dependence on fossil fuels. However, due to the significantly high and varied moisture content of biomass, its use has several drawbacks, such as low total efficiency and process instability. Drying biomass before combustion or gasification can eliminate these drawbacks. Besides these benefits, there are several environmental advantages of removing moisture from organic materials before disposal. In this study, a solar-assisted conveyer-belt dryer was designed to remove moisture from biomass. Economic optimization was conducted under different economic conditions to find the optimum performance of the designed dryer. The results indicated that depending on the economic condition, drying biomass with the designed dryer costs between 4 and 7 cents per kilogram of biomass. Under optimum economic operation, the solar fraction is less than 6% in both scenarios. On the other hand, by ignoring economic constraints and reducing the dryer’s capacity, solar fraction increases to more than 55%, and in this case, the drying cost will be about 11 cents per kilogram of biomass.

A comparative analysis of biogas upgrading technologies: Photosynthetic vs physical/chemical processes

Two biogas upgrading technologies, viz. an innovative algal-bacterial photobioreactor and a conventional activated carbon filter coupled with a water scrubber, were comparatively evaluated in terms of environmental, economic and social performance by using the IChemE Sustainability Metrics. The upgrading of 300Nm3/h of biogas generated from the anaerobic digestion of mixed sludge in a wastewater treatment plant was used as a model scenario for the comparative analysis. Despite the algal-bacterial photobioreactor entailed 1860 times higher land requirements, the two-stage physical/chemical technology exhibited ×3.8 higher energy consumptions and larger environmental impacts in terms of material and water consumption and greenhouse gas emissions (the latter by a factor of ~45). The investment cost for the algal-bacterial photobioreactor was 1.6 times higher than that of its physical/chemical counterpart due to the biomass drying unit required to produce an algae-based fertilizer. However, the operating cost of the physical/chemical technology was ~7 times higher due to the frequent replacement of the activated carbon. A further analysis of the net present value (NPV 20) revealed that photosynthetic upgrading would yield revenues from year 5 of operation mainly due to the sale of the algal bio-fertilizer produced, even without tax incentives for bio-methane.

Bioethanol production from acidic and enzymatic hydrolysates of mixed microalgae culture

Mixed microalgae cultures are considered as an attractive research area compared to traditional pure culture to dominate cultivation contamination risk and enhance economic feasibility of large-scale biofuel production. However, pre-treatment and bioethanol production from mixed microalgae culture has not been reported yet. Therefore, this study was aimed to evaluate the effect of different pre-treatment strategies including acidic, alkaline, and enzymatic hydrolysis on the sugar extraction from mixed microalgae. Besides, the effects of MgSO4 and CaCl2 as lewis acids in acidic pre-treatment on reducing sugar yield were studied.Results showed that the mixture of dilute sulfuric acid and MgSO4 exhibited a higher sugar yield than dilute acid. Among all pre-treatments used, the enzymatic treatment with thermostable enzymes showed the highest recovery of 0.951g extracted glucose/g total sugar. Moreover, the enzymatic pre-treatment of wet microalgae was compared with dried ones at identical operational conditions and dried biomass concentration of 50g/l, similar sugar yields were achieved which would be advantageous to reduce the need for drying of the microalgae biomass. Fermentation of the acidic and enzymatic treated samples to ethanol using Saccharomyces cerevisiae showed yield of 0.38 and 0.46g/g glucose, corresponding to 76% and 92% of the theoretical values, respectively. The obtained results revealed that bioethanol yield after enzymatic hydrolysis of mixed microalgae culture are higher than those of acid hydrolysis.

Optimization of direct solvent lipid extraction kinetics on marine trebouxiophycean alga by central composite design – Bioenergy perspective

This present work compares various pretreatment techniques, single/binary solvent system, biomass drying methods and biomass particle sizes to ascertain effective lipid extraction process for marine trebouxiophycean microalga Chlorella vulgaris BDUG 91771. Of the tested methods, homogenization or direct solvent extraction (DSE) pretreatment, chloroform/methanol binary solvent system, and ≤600µm particle size extracted maximum lipid of 22.1% irrespective of different biomass drying methods. Further, considering low energy consumption and industrial feasibility, optimization of DSE process kinetics was performed by central composite design. According to central composite design, high lipid recovery was attained with 2:1 chloroform/methanol ratio, 1:5 dry cell weight/solvent ratio, 65°C temperature, 120min reaction time, and it was highly validated by regression analysis, coefficient determination, F-value, coefficient variation, desirability ratio of the models. It is noteworthy that, the optimized DSE process was compatible with another trebouxiophycean alga Picochlorum sp. BDUG 91281 through biological and technical replicates. In a bioenergy outlook, fuel properties of C. vulgaris BDUG 91771 biodiesel such as degree of unsaturation (69.03), long chain saturation factor (2.49), cold filter plugging point (−9.75°C), cloud point (8.1°C), pour point (0.66°C), saponification value (248.2mg KOH/g), acid value (0.51mg KOH/g), ash content (0.019%), insoluble impurities (0.022g/kg) and viscosity (4.1 cSt) comply ASTM D6751, EN 14214 and ISO 15607 standards.

6-2-3 自己熱再生によるバイオマス乾燥技術の開発(6-2 エネルギーシステム,Session 6 省エネルギー,研究発表)

6-2-3 自己熱再生によるバイオマス乾燥技術の開発(6-2 エネルギーシステム,Session 6 省エネルギー,研究発表)

3-11-3 自己熱再生によるバイオマス乾燥の省エネルギー化(3-11 粉砕・乾燥,Session3 バイオマス等,研究発表)

3-11-3 自己熱再生によるバイオマス乾燥の省エネルギー化(3-11 粉砕・乾燥,Session3 バイオマス等,研究発表)

Low-cost Biodiesel Production

Use of fossil fuel after about 200 years of its dominance the world’s primary source of energy has caused many environmental problems of which increase in air pollution and climate change are the major ones. Biodiesel production from microalgae is a renewable and bio-friendly source of energy recognized worldwide than fossil fuel. Unfortunately, the major challenge hindering biodiesel production at pilot scale is the high cost of production. This study, therefore, discusses some important steps taken to lower the cost of biodiesel production which includes a choice of lipid extraction methods, biomass drying methods, biodiesel conversion methods and choice of cultivating media. The cheap and effective method of lipid extraction, biomass drying and biodiesel conversion was identified and discussed. The use of natural media such as Palm Oil Mill Effluent (POME) for the cultivation of microalgae to produce biomass, which can be used as feedstock for biodiesel production was highlighted. The identification of the major strategies for up-scaling biodiesel production is a step forward in making biodiesel production economically viable.

Mathematical modeling of drying behavior of cashew in a solar biomass hybrid dryer

The main objective of this study is to analyze the drying behavior of cashew nut experimentally in a solar biomass hybrid dryer using mathematical models. Suitability of fifteen different mathematical drying models available in the literature is used to describe the drying characteristics of cashew. Experimental data of moisture ratio, temperature and relative humidity obtained from different dryer conditions were fitted to the various empirical drying models. The performance of the drying model was compared based on their correlation co-efficient (R2), Root Mean Square Error (RMSE) and Reduced Chi-Square (χ2) between the observed moisture ratios. The two terms and Midilli models showed the best fit under solar drying. Page model was found to be the best model for describing the thin layer drying behavior of cashew for biomass drying and hybrid drying.

Development of Solar Biomass Drying System

The purpose of this paper focuses on the experimental pre-treatment of biomass in agricultural site using solar energy as power source and contribution of common use and efficiency solar dryer system for consumer. The main purpose of this design for solar cabinet dryer is to dry biomass via direct and indirect heating. Direct heating is the simplest method to dry biomass by exposing the biomass under direct sunlight. The solar cabinet dryer traps solar heat to increase the temperature of the drying chamber. The biomass absorbs the heat and transforms the moisture content within the biomass into water vapour and then leaves the chamber via the exhaust air outlet. This problem however can be solved by adopting indirect solar drying system. High and controllable temperatures can be achieved as a fan is used to move the air through the solar collector. This project has successfully created a solar cabinet dryer that combines both direct and indirect solar drying systems and functions to dry biomass as well as crops effectively and efficiently with minimal maintenance. Hence, it is indeed a substitution for conventional dryers which are affordable to local farmers.

Aplicação de glyphosate na dessecação do sorgo biomassa

O sorgo biomassa é uma alternativa para a geração de energia renovável pela queima em caldeiras, destacando-se por sua alta produtividade e possibilidade de mecanização de todos os seus processos agrícolas. Uma alternativa comum para a redução da umidade de culturas é a aplicação de herbicidas dessecantes, contudo, não há pesquisas que elucidem a perda de umidade da massa colhida de sorgo com a aplicação de dessecantes na parte aérea, antes da colheita. Assim, o objetivo deste trabalho foi avaliar aplicação de glyphosate na dessecação do sorgo. O delineamento experimental utilizado foi em blocos inteiramente casualizados, no esquema fatorial 2x5x4, constituídos por: duas cultivares de sorgo (BRS 716 e CR 1342); cinco doses de glyphosate (0, 720, 1.440, 2.160 e 2.880 g ingrediente ativo ha-1) e quatro épocas de coleta das plantas (7, 14, 21 e 28 dias após a aplicação), com 4 repetições. Durante as diferentes épocas de coleta das plantas foram realizadas as avaliações da biomassa fresca e seca dos colmos e folhas e porcentagem de biomassa seca dos colmos e das folhas. A aplicação do glyphosate não foi eficaz no processo de dessecação das plantas de sorgo biomassa BRS 716 e CR1342.

Lipid extraction from wet Chaetoceros muelleri culture and evaluation of remaining defatted biomass

Microalgae-based lipids are considered a good feedstock for various applications, including biodiesel and omega-3-rich oil production. However, developing new lipid extraction and recovery techniques are required to make microalgal oil a more economically competitive feedstock. To avoid the costly process of complete drying of algal biomass, extraction from wet slurry was improved. Potentially cost-effective and scalable processes were investigated and developed that enable total rupture of nutrient-starved microalgal cells to facilitate lipid recovery directly from wet algal slurry, including pretreatments (thermal treatment, UV-C light radiation and osmotic shock) and the use of a solvent mixture. Using hexane and ethanol on UV-C and thermally pre-treated algal slurries led to more than doubling of the total extractable lipids and total transesterifiable lipids, compared to biomass that was not pretreated and when hexane only was used as the solvent. Lipids (25% w/dry weight), triacylglycerol (13%) and fatty acid methyl esters (17%) were recovered from UV-C pre-treated algal slurry (1000mJ/cm2 UV-C). The residual defatted biomass was analysed for further applications and contained carbohydrates (≈15% w/dry weight) that may be suitable for bioethanol production through fermentation.

Gas-solid mixing and mass transfer in a tapered fluidized bed of biomass with pulsed gas flow

Improvement in fluidization quality and mass transfer rate was made to the pulsed fluidized bed for the fluidization of biomass particles without the need of inert bed materials by modifying the rectangular cross-section to a tapered bottom section to eliminate the dead-zones. Batch biomass drying tests were performed as an indirect indicator of gas-solid contact efficiency and mass transfer performance. Compared to the original design, biomass particles were able to be fluidized in the tapered column at a wider range of gas pulsation frequencies with significantly reduced channeling and gas bypassing. Faster drying and improved mass transfer were also observed and confirmed by measured instantaneous drying rate and final moisture content of the biomass sample. A model based on two-phase theory for biomass drying in fluidized bed verified such findings, where under the same operating condition fluidized bed with tapered bottom showed higher effective diffusion coefficients than the original design.

Thermochemical and physical evaluation of poplar genotypes as short rotation forestry crops for energy use

Short rotation plantations of fast-growing species provide a promising way to produce heat and electricity from renewable sources. The thermo-chemical and physical properties of different genotypes of poplar in short rotation forestry crops grown at three locations with different climatic and edaphic characteristics as well as planting density, have been determined in order to characterize the most appropriate biomass in terms of energy potential. The planting density was 6666 or 13,333trees/ha (depending on the location) in a rotation of three-four years and the analysis was carried out at the end of the first rotation. For all the genotypes, experimental tests to quantify the moisture content, particle size distribution, bulk density, heating value, ash content and composition as well as the volatile matter were performed. In addition, natural air drying of biomass (stem and branches) was studied in two locations with the aim of determining the humidity loss during raw storage. A significant effect of the genotype and the planting density on the biomass properties was observed. The results obtained indicate that ‘Monviso’ and ‘Viriato’ are the most suitable genotypes. No operational problems related to ash fouling and deposition in combustion devices are expected for any of the genotypes studied.

Technical difficulties and solutions of direct transesterification process of microbial oil for biodiesel synthesis.

Microbial oils are considered as alternative to vegetable oils or animal fats as biodiesel feedstock. Microalgae and oleaginous yeast are the main candidates of microbial oil producers' community. However, biodiesel synthesis from these sources is associated with high cost and process complexity. The traditional transesterification method includes several steps such as biomass drying, cell disruption, oil extraction and solvent recovery. Therefore, direct transesterification or in situ transesterification, which combines all the steps in a single reactor, has been suggested to make the process cost effective. Nevertheless, the process is not applicable for large-scale biodiesel production having some difficulties such as high water content of biomass that makes the reaction rate slower and hurdles of cell disruption makes the efficiency of oil extraction lower. Additionally, it requires high heating energy in the solvent extraction and recovery stage. To resolve these difficulties, this review suggests the application of antimicrobial peptides and high electric fields to foster the microbial cell wall disruption.

An Experimental Study on Natural Convection Biomass Dryer with Different Sensible Heat Storage Materials

The state Odisha of India is mainly an agro based state and maximum percentage of population of the state depends on cultivation. Rice is the main cultivation crop here. Post harvesting losses are more due to lack of proper knowledge of farmers. Farmers used to dry paddy with open solar drying technique before storing. The main problem in this technique is that there is no control in the amount of heat transferred to the items which gradually leads to cracking of grains. One of the best possible solution is to dry the grain by using biomass grain dryer. In the present research work, an efficient and effective biomass burner with fins is designed and fabricated at SOA University in city of Bhubaneswar, Odisha to dry the paddy by using sensible heat storage materials. Two different sensible heat storage materials pebble and concrete have been used to dry 10 kg of paddy in a batch wise drying process. The average moisture content of fresh paddy of 29.2% was dried to 14.8% in 240 minutes by using pebbles and by using concrete time taken to reach desire moisture content is in 210 min. The time taken by this process is less than the conventional drying without storage materials. The temperature near the paddy tray was maintained in a range of 50– 58 °C which is a comfortable temperature for paddy drying. The efficiency of the dryer with pebbles and concrete also calculated and better efficiency is observed with concrete as sensible heat storage material.

Charcoal Production in a Continuous Operation Retort. Experimental Data Processing

The charcoal industry has recently regained the spotlight along with other renewable resources, not from its previous ill repute as a cause of deforestation but as one of the tools for climate change mitigation. In this paper a study with an experimental evaluation of a charcoal production technology is carried out in an industrial facility. The investigated technology is a state-of-the-art continuous operation automated retort which is comprised of a monitoring system continuously registering process characteristic temperatures. The raw material, biomass, passes through three different stages in the retort - biomass heating and drying, biomass carbonization, and charcoal cooling. These process sections are described and analyzed according to the relevant temperatures. The obtained data is processed using Statgraphics Centurion Statistical data analysis tool. This study draws attention to the importance of a scientific approach to charcoal production with optimized process parameters directing the charcoal industry towards the increase of production sustainability.

Biomass drying in a pulsed fluidized bed without inert bed particles

Batch drying was performed in the pulsed fluidized bed with various species of biomass particles as an indicator of gas–solid contact efficiency and mass transfer rate under different operating conditions including pulsation duty cycle and particle size distribution. The fluidization of cohesive biomass particles benefited from the shorter opening time of pulsed gas flow and increased peak pressure drop. The presence of fines enhanced gas–solid contact of large and irregular biomass particles, as well as the mass transfer efficiency. A drying model based on two-phase theory was proposed, from which effective diffusivity was calculated for various gas flow rates, temperature and pulsation frequency. Intricate relationship was discovered between pulsation frequency and effective diffusivity, as mass transfer was deeply connected with the hydrodynamics. Effective diffusivity was also found to be proportional to gas flow rate and drying temperature. Operating near the natural frequency of the system also favored drying and mass transfer.

Coupled reactor and particle model of biomass drying and pyrolysis in a bubbling fluidized bed reactor

A comprehensive single particle model of biomass drying and pyrolysis is coupled with an ideal reactor model of a bubbling fluidized bed with nitrogen as the fluidizing gas. To predict biomass pyrolysis products yield and composition under steady-state operation, a two-step biomass pyrolysis kinetic mechanism is adopted with primary pyrolysis described by two different reaction kinetic schemes: (a) Three parallel first-order reactions producing primary pyrolysis products (non-condensable gas, tar/bio-oil and char), and (b) a detailed solid state kinetics mechanism based on multiple reactions of lignin, cellulose, and hemicellulose contents of two specific types of biomass (poplar and lodgepole pine). Secondary pyrolysis is modeled by two parallel reactions describing homogeneous thermal cracking of tar to non-condensable gas and char. In addition to the yields of pyrolysis products often modeled as lumped species, this model addresses an existing gap of knowledge in predicting the proportions of major compounds in the pyrolysis gas based on a few simplifying assumptions and CHO elemental balances. This predictive model is a useful tool to relate biomass pyrolysis products yield and composition to process operating parameters such as biomass ultimate analysis, reactor temperature, gas residence time, mean solids residence time inside the reactor, as well as biomass particle size and moisture content. Model predictions for the two kinetic schemes are in good agreement with available experimental data from the literature.

Techno-economic assessment of poly-3-hydroxybutyrate (PHB) production from methane—The case for thermophilic bioprocessing

A major obstacle preventing the large scale production of polyhydroxyalkanoates (PHAs) has been the lack of a reliable, low cost, large volume feedstock. The abundance and relatively low price of methane therefore marks it as a substrate of interest. This paper presents a techno-economic assessment of the production of poly-3-hydroxybutyrate (PHB) from methane. ASPEN Plus was used for process design and simulation. The design and economic evaluation is presented for production of 100,000t/a PHB through methanotrophic fermentation and acetone-water solvent extraction. Production costs were estimated at $4.1–$6.8/kg PHA, which compares against a median price of $7.5/kg from other studies. Raw material costs are reduced from 30 to 50% of production for sugar feedstocks, to 22% of production for methane. A feature of the work is the revelation that heat removal from the two-stage bioreactor process contributes 28% of the operating cost. Thermophilic methanotrophs could allow the use of cooling water instead of refrigerant, reducing production costs to $3.2–5.4/kg PHA; it is noted that PHB producing thermophilic methanotrophs are yet to be isolated. Energy consumption for air compression and biomass drying were also identified as significant capital and operating costs and therefore optimisation of bioreactor height and pressure and biomass moisture content should be considered in future research.