High Ash Biomass Research Articles

The impact of hydrothermal-acid infusion pretreatment on the pyrolytic behaviors of high-ash biomass

A coupling pretreatment on high-ash content biomass, namely rice straw (RS), followed by slow pyrolysis has been proposed to yield high-quality bio-oil and value-added chemicals. Hydrothermal pretreatment was combined to acid infusion to pretreat rice straw, and the physico-chemical properties and pyrolytic behavior of the pretreated rice straw were investigated. After the mentioned pretreatment, the thermal degradation temperature of pretreated RS decreased from 359 °C to 281 °C while the crystalline of cellulose decreased from 67.1% to 63.1%. The catalytic effect of alkali and alkaline earth metals in RS has been passivated with decreased amount of H2SO4, showing in the increment of bio-oil yield from 39.8 wt% to 47.0 wt%. Furthermore, the yield of levoglucosenone (LGO) from pretreated RS increased from 0.06 wt% to 8.4 wt% and the yield of monophenol products decreased from 4.8 wt% to 1.4 wt%. The present study offers an effective and sustainable method for processing agro-industrial waste with high content of ash, which enables the production of high-yield and quality bio-oil.

Impact of biomass ash content on biocomposite properties

Owing to its low cost and sustainable nature, lignocellulosic biomass has been utilized for reinforcing polymers, but it is crucial to understand the impact of high-ash concentrations in biomass on composite strength and processing. Biomass is not only desirable for biofuel production but could also have a strong market, if high-ash biomass is acceptable, for biocomposites. In this work, natural fibers (switchgrass and corn stover) were used to reinforce polylactic acid (PLA) to produce biocomposites. Natural fibers were pretreated to obtain fibers that contain different percentages of ash. The mechanical properties (such as Young's modulus, tensile strength, failure strain, storage modulus) of corn stover/PLA composites remained largely unaffected by the ash concentration of the biomass fibers, despite the large range of ash contents (2.2–11.9 wt%). However, the tensile strengths of switchgrass/PLA composites were slightly negatively affected by the ash concentration of the switchgrass fibers (0.7–2.1 wt%). Both the switchgrass/PLA and the corn stover/PLA composites exhibited a high-enough tensile strength (49–57 MPa) and suitable complex viscosity (2.0−7.0 kPa·s at the frequency of 3.2 rad/s). They are expected to be 3D-printable through an extrusion-based additive manufacturing process.

Downdraft co-gasification of high ash biomass and plastics

Co-gasification is gaining attention as a sustainable chemical recycling technology for the conversion of plastic waste and biomass into producer gas. Experimental study of the co-gasification of low density polyethylene waste plastic and garden waste biomass is performed in a downdraft gasifier to understand the viability of using plastic waste with high ash biomass (ash content above 10% w/w) as a feedstock and to investigate the quality of the gas obtained. By increasing the plastic content in the feedstock from 0 % wt. to 25 % wt., an increase of temperature is observed in all zones of the gasifier, improving the lower heating value of the gas produced from 3.5 MJ/Nm3 to 4.7 MJ/Nm3 and increasing the cold gas efficiency from 43.8% to 61.8%. It has also reduced the clinker formation from 3 % wt. to 0.65 % wt. in terms of the feedstock and slightly decreased the tar yield from 8.1 g/Nm3 to 5.7 g/Nm3. Further, by changing the equivalence ratio during the co-gasification, the effect on heating value, energetic yield and gas yield obtained is also reported.

CO2 Gasification Reactivity of Char from High-Ash Biomass

Biomass char produced from pyrolysis processes is of great interest to be utilized as renewable solid fuels or materials. Forest byproducts and agricultural wastes are low-cost and sustainable biomass feedstocks. These biomasses generally contain high amounts of ash-forming elements, generally leading to high char reactivity. This study elaborates in detail how chemical and physical properties affect CO2 gasification rates of high-ash biomass char, and it also targets the interactions between these properties. Char produced from pine bark, forest residue, and corncobs (particle size 4–30 mm) were included, and all contained different relative compositions of ash-forming elements. Acid leaching was applied to further investigate the influence of inorganic elements in these biomasses. The char properties relevant to the gasification rate were analyzed, that is, elemental composition, specific surface area, and carbon structure. Gasification rates were measured at an isothermal condition of 800 °C with 20% (vol.) of CO2 in N2. The results showed that the inorganic content, particularly K, had a stronger effect on gasification reactivity than specific surface area and aromatic cluster size of the char. At the gasification condition utilized in this study, K could volatilize and mobilize through the char surface, resulting in high gasification reactivity. Meanwhile, the mobilization of Ca did not occur at the low temperature applied, thus resulting in its low catalytic effect. This implies that the dispersion of these inorganic elements through char particles is an important reason behind their catalytic activity. Upon leaching by diluted acetic acid, the K content of these biomasses substantially decreased, while most of the Ca remained in the biomasses. With a low K content in leached biomass char, char reactivity was determined by the active carbon surface area.

The role of catalytic iron in enhancing volumetric sugar productivity during autothermal pyrolysis of woody biomass

Passivation of naturally occurring AAEM in biomass enhances sugar yields from the fast pyrolysis of biomass by preventing these metals from catalyzing the fragmentation of pyranose rings in cellulose and hemicellulose. However, because AAEM also catalyzes lignin depolymerization, its passivation can be accompanied by undesirable char agglomeration. Pretreatment of biomass with ferrous sulfate both passivates AAEM and substitutes ferrous ions as lignin depolymerization catalysts. This pretreatment has been particularly successful for high ash biomass like corn stover, but of limited value for low ash biomass like wood. This study explores the reasons for this discrepancy and offers a combined pretreatment of ferrous sulfate and ferrous acetate pretreatment to overcome char agglomeration in wood. This new pretreatment increased sugar yields from 4.4 wt% to 15.5 wt% and 5.4 wt% to 19.0 wt% for hardwood and softwood biomasses, respectively. This pretreatment produces an iron-rich biochar that catalyzes oxidation of the biochar under the oxygen-rich conditions of autothermal pyrolysis, which is preferentially consumed to provide the enthalpy for pyrolysis, preserving bio-oil as a more desirable energy product. Instead of producing carbon monoxide, which dominates oxidation of biochar from untreated biomass, the iron catalyzes oxidation to carbon dioxide, producing more energy per mole of oxygen consumed. In fact, oxygen demand to support autothermal pyrolysis of red oak and southern yellow pine was reduced 15% by the presence of iron in the biochar.

Effects of pyrolysis temperature and feedstock type on particulate matter emission characteristics during biochar combustion

Aiming to reduce the emission of particulate matter (PM) during biomass combustion, we investigated the effects of pyrolysis temperature and feedstock type on the chemical properties of biochar and PM emission characteristics during subsequent combustion. Wood- and manure-based char samples were prepared at pyrolysis temperatures ranging from 200 to 500 °C and combusted in a laboratory-scale tube furnace at 850 °C. Due to the removal of volatile matter (VM), the total PM emission factor (EF) of the wood char decreased with increasing pyrolysis temperature, becoming negligible with pyrolysis at temperatures over 400 °C. For manure char, although pyrolysis removed VM and reduced the total PM EF from 12.5 ± 2.7 to 5.8 ± 2.9 mg/g-fuel, the high ash content precluded any effect on the emission of ash-derived PM. The occurrence of ash-derived PM resulted from release of Na, Mg, K, and Ca and was enhanced at higher combustion temperatures. We demonstrated that the pyrolysis of low-ash biomass effectively reduces the risk of PM emission. However, the efficacy of thermal treatment of high-ash biomass is limited but might be improved with further treatment, such as ash removal.

Production of activated carbons from four wastes via one-step activation and their applications in Pb2+ adsorption: Insight of ash content.

Natural biomass is a renewable source for precursors of porous carbon. Four agriculture wastes of corn cob (CC), wheat bran (WB), rice husk (RH), and soybean shell (SS) were applied to produce activated carbons (ACs) via one-step activation by sodium hydroxide. The effects of ash contents and NaOH dosage ratio (1-5) on surface area for ACs were investigated. Owing to ash etching, the high ash precursor (like RH) exhibited less alkali consumption and larger surface area than low ash one (like CC). All four ACs expressed developed pore structure and outstanding surface area of ∼2500m2g-1. During adsorption of lead ions in simulated wastewater, RH-based AC revealed superior capture capacity of 492±15mgg-1. One-step activation had the potential to deliver savings around 1/3 of energy consumption, enabling the cost performance of high ash RH-based AC reaching 194±12gPb2+$-1, 76% larger than low ash CC-based AC. High ash biomass is a promising candidate to obtain eco-friendly carbon products.

A green route for pyrolysis poly-generation of typical high ash biomass, rice husk: Effects on simultaneous production of carbonic oxide-rich syngas, phenol-abundant bio-oil, high-adsorption porous carbon and amorphous silicon dioxide

Rice husk is a widespread agriculture waste in rice-farming country. High silica content in rice husk prevent its efficient utilization. So in this work, concept of poly-generation was introduced to improve its utilization value. This study provided CO-rich syngas, phenol-abundant bio-oil, high-adsorption porous carbon and amorphous SiO2 as four end products for first time via combination of acid washing and activated carbon catalyst. Specifically, acid washing effectively decreasedsoluble ash, which altered pyrolysis paths, increased volatiles release and reduced impurities in bio-char. After catalytic pyrolysis, phenol content of 65.56% and CO of 56.09 vol% were detected in bio-oil and syngas from AWRH. For solid products, acid washing benefited both bio-char and silica. A low-cost porous carbon with developed pores and rich surface functional groups was prepared for water absorption. And high purity amorphous SiO2 was recycled from alkali etching solution. Finally, a green process with no waste emission was proposed.

Techno-economic analysis of ash removal in biomass harvested from algal turf scrubbers

Large-scale microalgae cultivation for biodiesel production is expected to be performed utilizing open air growth infrastructure that will inherently introduce ash into the system. High ash biomass represents a significant challenge for the production of biofuel as it increases processing capital and operational costs. This study assesses the economic viability of pretreatment to remove ash from biomass grown with an algal turf scrubber (ATS). An engineering process model of biofuel production was developed based on an ATS growth system followed by an ash removal process and conversion of the biomass to fuels through hydrothermal liquefaction. The model was validated with literature data for the growth and conversion processes and with experimental data for 14 de-ashing processes using water washing or alkaline extraction. The engineering process model was integrated with techno-economic modeling to investigate the impact of ash on biomass and fuel selling prices. Capital costs associated with biofuel conversion doubled as ash content increased from 0% to 70%, increasing fuel selling price by 21%. Integrating ash removal resulted in reduced conversion capital costs (14–42%) based on the reduction of total mass processed. However, only water washes scenarios at 25 °C and 50 °C were found to reduce overall fuel selling price, with alkaline extraction scenarios showing a significant increase. Operational expenses associated with alkaline extraction de-ashing including wastewater treatment, chemical costs, and heating the microalgae slurry were found to significantly increase the overall fuel selling price of the microalgae biofuel by 17–92% depending on the operational scenario.

Co-gasification of high ash biomass and high ash coal in downdraft gasifier

The present work studies gasification of high ash biomass (20–25% w/w), high ash coal (30–35% w/w), and their co-gasification in a downdraft gasifier developed in our earlier study (Siddiqui et al., 2018). TGA studies were performed to examine the change in performance due to the catalytic effect of inorganic content. The effect of biomass ratio (BR) was examined. Higher percentage of biomass increased the conversion to gas on carbon basis, and decreased the conversions to char and tar. The presence of coal enhanced the temperature and hence the rates of the reactions to certain extent. The respective cold gas and thermal efficiencies for BR0 are 33.06% and 49.38%, and for BR1 are 52.22% and 64.15%. BR0.75 gave the best performance with CGE of 57.5% and thermal efficiency of 72.63%. Finally, the clinker formation issue and the preliminary atmospheric emissions measurements are reported for gasifier.

Effect of temperature on product performance of a high ash biomass during fast pyrolysis and its bio-oil storage evaluation

Bio-oil from the fast pyrolysis of agro-residues still needs to contemplate different production scenarios to look for its feasibility. For this reason, in this work the effect of a range of fast pyrolysis temperature (450, 480, 510 and 550°C) processing rape straw biomass (with high K content) has been studied in a continuous bubbling fluidised bed reactor. It was found that the catalytic effect of the inorganic content was different at each fast pyrolysis temperature, with the lower temperatures resulting in the highest yield of bio-oil due to minor catalytic effect (up to 41.39wt%). It was also found that at 480°C the bio-oil presented the best combination of physico-chemical features such as non-separation phase and the lowest water content; yield (39.65wt%) and HHV (19.23MJ/kg), containing a high concentration of phenolic compounds. At the fast pyrolysis temperature of 510°C and 550°C, the conjunction effect of temperature and the catalytic effect provoked bio-oil separation into two phases and a higher gas yield than was expected. Then, the higher temperatures are not suitable for bio-oil production. Char is also an interesting co-product for all pyrolysis temperatures.

Production of biochar from rice husk: Particulate emissions from the combustion of raw pyrolysis volatiles

Increasing energy demands and waste management concerns have motivated agricultural producers to consider the decentralized conversion of agricultural by-products for energy and value-added product (biochar) generation. Due to the variability of fuel properties, direct combustion of agricultural by-products with high ash contents, such as rice husk, may suffer from increased fouling and slagging issues with high particulate matter (PM) emissions. Combustion of the raw pyrolysis volatiles (bio-oil and synthesis gas (syngas) mixtures) produced from pyrolysis with the inherent separation of ash in the biochar may potentially mitigate these issues. In this study, PM emissions from the combustion of the raw pyrolysis volatiles derived from the pyrolysis of rice husk were evaluated at laboratory scale by using a combined pyrolysis and combustion facility. Pyrolysis temperatures ranging from 400 °C to 800 °C were used to generate raw pyrolysis volatiles with differing bio-oil to syngas ratios which were then combusted at 850 °C. It was found that bio-oil dominated the higher heating value of the raw pyrolysis volatiles produced at low pyrolysis temperatures. The combustion of such raw pyrolysis volatiles with high bio-oil content substantially increased the yields of PM10 and PM2.1. Linear dependence was observed between PM emissions and bio-oil fraction in the raw pyrolysis volatiles. Nevertheless, the pyrolysis-combustion process, with >96% of the ash retained in biochar prior to combustion, is more favorable than direct combustion for high ash biomass as far as PM emissions are concerned.

Fast pyrolysis char – Assessment of alternative uses within the bioliq® concept

Experiments with a process development unit for fast pyrolysis of biomass residues of 10kgh−1 have been performed to quantify the impact of two different product recovery options. Wheat straw, miscanthus and scrap wood have been used as feedstock. A separate recovery of char increases the organic oil yield as compared to a combined recovery of char and organic condensate (OC). Furthermore, it allows for an alternative use of the byproduct char which represents an important product fraction for the high ash biomass residues under consideration. The char produced shows little advantage over its biomass precursor when considered as energy carrier due to its high ash content. Significant value can be added by demineralizing and activating the char. The potential to increase the economic feasibility of fast pyrolysis is shown by an assessment of the bioliq® process chain.

An experimental study of combustion and emissions of biomass pellets in a prototype pellet furnace

This study presents combustion and emission results obtained using a prototype pellet furnace with 7–32kW capacity (designed for burning high ash content pellet fuels) for four biomass pellets: one grass pellet and three wood pellets. Fuel property, gas emissions and furnace efficiency are compared. In regard to fuel properties, proximate analysis, ultimate analysis and heating values are determined and emissions of carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), nitrogen oxides (NOx) and sulfur dioxide (SO2) are measured and compared. Scanning electron microscopy (SEM) was used for ash analysis. No ash agglomeration was observed and ash discharge was in the form of powder instead of lumped particles, which are usually observed for high ash biomass fuel. The results suggest that grass pellets can successfully be combusted with similar performance and emissions to that of other wood pellets if burned in appropriate combustion installations.

Modern approaches to the production of carbon materials from vegetable biomass

Recent trends in methods for the preparation of porous carbon materials (PCM) from vegetable biomass by physical and chemical activation methods are analyzed. Data on the effect of activating agents and also other parameters on the textural characteristics of PCMs were classified. A new direction for the production of PCMs was discovered in the use of high-ash biomass.

Texture and adsorptive properties of microporous amorphous carbon materials prepared by the chemical activation of carbonized high-ash biomass

Samples of microporous amorphous carbon materials with calculated BET specific surface areas of up to 3500 m2/g, pore volumes of up to 3.0 cm3/g, and micropore volumes of up to 1.9 cm3/g were prepared using the chemical activation of rice hulls carbonized in a fluidized-bed reactor with a copper-chromium catalyst for deep oxidation. The effects of various activation parameters (temperature, activating agents, etc.) were studied, and optimum parameters were chosen. The resulting materials exhibited sorption capacities of up to 6.3 and 41 wt % for hydrogen at liquid nitrogen temperature and 50 atm and for methane at 0°C and 60 atm, respectively. Because of this, they are promising for use in the purification, storage, and transportation of fuel gases. Moreover, some aspects of the mechanism of the interaction of an activating agent with a carbon-containing precursor are proposed.

“Texture and surface properties of carbon-silica nanocomposite materials prepared by the carbonization of high-ash vegetable raw materials in a fluidized catalyst bed”

A series of carbon-silica nanocomposite samples prepared by the carbonization of high-ash biomass (using rice husks as an example) in a fluidized-bed reactor with a deep oxidation catalyst at 450–600°C was studied by a set of physicochemical techniques (BET, IR spectroscopy, XPS, and TGA). The dependence of the chemical composition, texture characteristics, and main properties of the resulting materials on carbonization temperature was found.

Preparation and investigation of nanostructured carbonaceous composites from the high-ash biomass

Abstract The various pathways of high-ash biomass processing to the valuable carbonaceous composites are considered. From the rice husk carbon–silica composites and supermicroporous carbon materials (SMC) were prepared. In the new SMCs, the specific surface area A BET reaches 3460 m 2 /g while micropore volume V μ is up to 1.9 cm 3 /g at the total of pore volume, V Σ , as large as 3.0 cm 3 /g. These carbons were shown to absorb up to 41 wt% of methane at room temperature and 60 atm and more than 6 wt% of hydrogen under mild cryogenic conditions (at 77 K). Also methods for the synthesis of carbon–silica composites with A BET up to 710 m 2 /g and with average size of SiO 2 particles less 5 nm are proposed. The expected practical application of the obtained carbon–silica composites may be first of all reinforcing rubber extenders and bi-functional sorbents for the gas and liquid purification.