Biochar Quality Research Articles

Microwave-assisted catalytic pyrolysis of refuse-derived fuel (RDF) to improve pyrolysis performance and biochar properties

This paper investigated the feasibility of microwave-assisted catalytic pyrolysis (MACP) of refuse-derived fuel (RDF) to produce high quality biochar for the first time. Two main catalysts, K2CO3 and K3PO4, and their combination with bentonite or clinoptilolite were selected to mix with RDF in a fixed bed reactor exposed to microwave radiation. By comparing heating rate and biochar properties, the promising catalyst was identified as 20 wt% K2CO3 + 10 wt% bentonite due to its high heating rate (163 °C/min) and large specific surface area (264 m2/g) of biochar obtained under relatively low temperature (500 °C) and short microwave radiation time (30 min), much higher than previously reported values of RDF derived biochar (6–25 m2/g). K2CO3 showed higher heating rate and larger specific surface area of biochar than that of K3PO4 due to its prominent activation effect. Synergistic effect was observed when bentonite or clinoptilolite was added into K3PO4 which significantly improved microwave heating rate. Biochar produced from K2CO3 acts as a potential sorbent for retaining heavy metals in the biochar and soil due to its better porosity, while K3PO4 remaining in the biochar serves as essential nutrients for plant growth.

BIOCHAR IN CATTLE FARMING: AN INNOVATIVE SOLUTION FOR SOIL FERTILITY AND CATTLE PRODUCTIVITY

Biochar as a soil amendment is increasingly popular in agricultural sector in the past few years. The production and application of biochar is increasing in a constant rate to meet farm requirements. Biochar is similar to charcoal and activated charcoal, which are pyrogenic carbonaceous matter derived from organic carbon rich matter through pyrolysis. The primary products generated by pyrolysis are biochar, syngas and bio-oils depending on biomass and pyrolysis conditions. The quality of biochar is according to primary biomass source, pyrolysis temperature and time which ultimately effects on variations in physicochemical properties such as porosity, carboncontent, elemental composition, surface area, retention capacity and overall applications. While biochar has been receiving attention as a restorative soil amendment, innovative dimensions for this ultra-porous material are cropping up all over the industrial landscape. In recent times, biochar has been gaining attention in agricultural productivity not as a soil fertility agent, but as an animal feed and animal husbandry applications. Biochar a carbonized biomass similar to charcoal is utilized for treating animals for centuries. An enhanced utility of biochar as cattle feed globally, to improve animal health, increased nutrient intake efficiency and thus productivity. Since biochar is enriched with nitrogen rich organic compounds during the digestion process, the excreted biochar manure acts as a valuable organic fertilizer causing lower nutrient losses and green house gas emissions during storage and soil application. The use of biochar as feed additive has the ability for general body fitness of animals, increased feed efficiency, minimize nutrient losses and greenhouse gas emission, increase the soil organic matter content and thus soil fertility as applied to soil. It can maintain blood cell contents, increase egg, milk and meat productivity and able to resist pathogens in gastrointestinal tract and reduce methane emission from animals. Moreover, the high sorption capacity of biochar removes the pollutants and toxins from the gastrointestinal tract of animals. However, current awareness on effectiveness of biochar in animal production is less, which should be explored more. The challenges such as safety, dosages, contaminations, cost and awareness among farmers need to be addressed. The review highlights the potential benefits of biochar as animal feed in all possible dimensions

Classifying the potential of biochars from agricultural and industrial waste for the recovery of Fe and Mn mining tailings

Various types of agricultural and industrial waste have been used for biochar production. However, a consistent method of biochar stratification for agronomic and environmental purposes is still lacking. The aim of this study was to propose and evaluate a method of stratification based on physical and chemical properties. A set of biochar samples was produced by pyrolysis and co-pyrolysis from two agricultural wastes (poultry litter - PL and swine manure - SM) and three industrial wastes (construction wood - CW, tyres - TR and PVC plastic - PVC) at a wide range of pyrolysis temperatures (300–700 °C). The proposed stratification considered the following criteria in order: (i) construction of a biochar viability indicator (BVI); (ii) classification of biochar potential based on fixed carbon, ash and volatile matter; (iii) joint use of biochar quality criteria and those established in the literature (e.g. International Biochar Initiative - IBI); and (iv) the restrictive conditions of the environment where the biochar might be applied, in this case mining tailings, aiming at plant development. Using the proposed method of stratification, PL+CW pyrolysed at 300 °C was chosen for the recovery of Fe and Mn mining tailings due to its intermediate fertility level and extremely low risk of environmental pollution. The proposed method allowed the identification of restrictions on biochar use, and most importantly, highlighted the potential of the most viable biochars for conditioning mining tailings, which hinder plant growth. However, despite being useful and efficient in biochar selection, the proposed methods are still dependent on the physico-chemical characteristics of the biochars.

Interactions between biochar, arbuscular mycorrhizal fungi and photosynthetic processes in potato (Solanum tuberosum L.)

Pyrolyzed biomass, generating biochar for use as soil amendment, is recognized as a promising strategy for carbon sequestration. Current understanding of the interactions between biochar, arbuscular mycorrhizal (AM), and plant photosynthesis, in terms of biochemical processes and CO2 uptake, is fragmentary. The aim of this study was to investigate the effects on photosynthesis in potato including maximum rate of carboxylation by Rubisco (Vcmax), maximum rate of electron transport rate for RuBP-regeneration (Jmax), mesophyll conductance (gm) and other plant traits. Four types of biochar (wheat or miscanthus straw pellets pyrolyzed at temperatures of either 550 °C or 700 °C) were amended into low phosphorus soil. Potato plants were inoculated with the AM fungus Rhizophagus irregularis (M+) or not (M−). The results showed that four types of biochar generally decreased nitrogen and phosphorus content of potato, especially the biochars pyrolyzed at high temperature. This negative effect of biochar on nutrient content was alleviated by AM. It was found that Vcmax was limited by low plant nitrogen content as well as leaf area and phosphorus content. Plant phosphorus content also limited Jmax, which was mutually constrained by Vcmax of leaves. Low gm was an additional limiting factor for photosynthesis. The gm was positively correlated to nitrogen content, which influenced the leaf anatomical structure by alteration of leaf mass per area. In conclusion, the influence of interactions between quality of biochar and AM symbiosis on photosynthesis of potato seems to relate to effects on plant nutrient content and leaf structures. Accordingly, a model for the dependence of Vcmax on nitrogen and phosphorus content and their interactive effect exhibited a high correlation coefficient. As potato plants form AM symbiosis under natural field conditions, the extent and interaction with the quality of amended biochar can be a determining factor for plant nutrient content, growth and yield.

Upgrading biochar by co-pyrolysis of heavy bio-oil and apricot shell using response surface methodology

In this study, heavy bio-oil (HB) and apricot shell (AS) were used as raw materials to produce biochar by co-pyrolysis in a tube furnace. Three operational factors were assessed, namely pyrolysis temperature (400–700 °C), residence time (5–20 min) and percentage of HB (0–100%), with the effects on the yield and properties of biochar comprehensively investigated using a response surface methodology. Results showed that the mass yield, fixed carbon content, carbon content, and high heating value (HHV) of co-pyrolysis biochar (550 °C, 12.5 min, and an AS/HB mass ratio of 1:1) were 29.33%, 81.84%, 82.91%, and 32.97 MJ/kg, respectively. The experimental values for the co-pyrolysis biochar were 1.52%, 5.30%, 1.82%, and 1.12 MJ/kg higher than their corresponding theoretical values, respectively. However, the oxygen content of co-pyrolysis biochar was 1.71% lower than the theoretical value. Meanwhile, the C/H ratio of biochar improved with increasing pyrolysis temperature, residence time and percentage of HB, indicating higher biochar aromaticity. The evolution of surface functional groups indicated that an increase in pyrolysis temperature and residence time reduced the intensity of CO and C–O absorption peaks, while an increase in the percentage of HB enhanced the intensity of the C–O absorption peak of biochar. In general, compared to the pyrolysis of HB and AS alone, co-pyrolysis of HB and AS exerted a synergistic impact, improving the mass yield and fuel quality of biochar. Finally, the relationships between properties (mass yield, element content, proximate analysis parameters, and HHV) and the three varied factors were established, providing guidance for effective upgrading of biochar by co-pyrolysis of HB and biomass.

Exhausted Grape Marc Derived Biochars: Effect of Pyrolysis Temperature on the Yield and Quality of Biochar for Soil Amendment

The present study focuses on the valorisation of winery industry wastes through slow pyrolysis of exhausted grape marc (EGM). The optimal pyrolysis parameters were firstly identified by small scale experiments carried out using thermogravimetric analysis. Nine pyrolysis temperatures were tested and their influence on the decomposition of the EGM residue and biochar yield was evaluated. Then, biochar production was conducted in a pilot plant at three chosen temperatures (450, 500 and 550 °C) at which the biochar was shown to be stable. The effects of biochar application to soil with respect to plant (ryegrass) growth was also evaluated. Pyrolysis of EGM at the 450–550 °C temperature range has been shown to generate thermally stable and nutrient-rich biochars, but only the biochar produced at 450 °C showed a marked benefit effect of ryegrass growth.

Microbial Exploitation of Biofertilizer, Pullulan and Biochar from Floral Waste

In diversified India, there are different traditions and cultures and their spirituality to believe in God is unconditional. People used to go temple and offer several things to God, and mainly the item they offer is the flower. Heaps of flowers flooded in temples are served as waste in nearby areas, or they dumped it into water. Flower waste has abundant properties with several nutrients (macro as well as micro) in them. In this article, we have emphasized the production and application of fertilizer, Pullulan and Biochar with the help of microbes present on floral waste enriched samples. Test samples were collected in the nearby areas of the temple, and after collection, serial dilution of the enriched sample was prepared. 1mL of each serial dilution were outspread on sterile nutrient agar plates, and bacterial isolation was done. Properties of degradation of soil isolates were evaluated. Flowers collected were then dried, and 1% was then transferred in minimal medium (without C source). Streaking was carried out, and isolated possessing tremendous growth was choosen for the development of the consortium. Different combinations of soil isolates were used. Five per cent inoculum of various consortia was spread on flower waste chambers. It was incubated aerobically. Degradation was analyzed after a specific time interval. The microbial consortium supports minimizing the time required for degrading an enormous amount of flower waste. With this perspective, we can prepare good quality Biopolymer Pullulan and Biochar without causing any harm to the environment.

Effect of sewage sludge biochar on the soil nutrient, microbial abundance, and plant biomass: A sustainable approach towards mitigation of solid waste

Soils functions, fertility, and microbial abundance may alter in various ways by the biochar amendments to the soil. This study revealed the way of pyrolysis temperature influences the biochar quality and its addition for improving soil properties. The SS biochar was synthesized via pyrolysis and characterized by SEM and FTIR for studying surface images and chemical functional groups. The biochar upon addition with soil was studied for physiological parameters of plants like seed germination index, root length, shoot length, biomass, metal (loid) analysis of soil, SS and SS biochar, total organic content, C: N ratio, NPK values, etc. Besides, combinations of biochar: soil {1:3 (25% + 75%), 1:1 (50% + 50%), and 3:1 (75% + 25%)} ratios were used for studying the effect of biochar on soil microbial community. The 16S rRNA metagenomic analysis revealed the dominance of phyla: Proteobacteria, Actinobacteria, and Acidobacteria that influence the soil nutrient cycle when applied at ratio 1:3. This study highlights the valorization of SS into biochar and studied the effect of biochar augmentation with soil; its impact on soil nutrients, microbial abundance, and plant biomass enhancement. The greener approach also mitigates and helps in the sustainable management of solid wastes, thus reducing GHGs emissions and improves nutrient cycling.

Optimization of biochar quality and yield from tropical timber industry wastes.

The conversion of timber industry waste to biochar was investigated, based on residues from local tropical hardwoods in Cameroon. Closed and flow reactors, loaded with few grams of the sample and fluxed with different inert gases, were used with the aim of converting these wood residues to a safe and efficient solid fuel that can be exploited by the local community for cooking purposes. The pyrolysis temperature had the highest impact on the process up to approximately 700°C as biochar yields decreased from 87 to 23.5% while increasing the temperature. A significant concentration of carbon required temperatures greater than 500°C for the biochar to become a good solid fuel, approaching the heating value of coal. The role of heating rate appeared marginal even in a broad range: 0.1 to 70°C/min. The dwell time (in the range 0.5 to 5h) at maximum temperature revealed to be of little influence on the charring which occurred mostly during the first few minutes of the isothermal phase. Thus, actual production time can be <1h/batch (up to 500°C at 10°C/min). Stepwise heating revealed a sequence of devolatilization reactions following their activation energies. Use of CO2 as inert gas increased the char yield. The inert gas flow rate had two contrasting effects on the biochar yield, in relation to volatile components residence time and the biomass temperature. The reactivity of biochar in combustion suggests a trade-off between heating content and reactivity. Charring in a closed, pressurized reactor produced biochar of low value as fuel, with tars absorbed in the porous solid residue.

Material properties and environmental potential of developing world-derived biochar made from common crop residues

Biochar is frequently made using high-tech, high-control methods which will no doubt better optimize the final material for its intended purpose and increase its value. In contrast, we used low-tech, low-control methods to produce a developing world biochar (DWB) from two common crop wastes, cottonseed (CS) and pecan shell (PS). We created DWB biochar using a top-lit updraft microgasifier (TLUD) made from paint cans, and compared it to a biochar created in a muffle furnace held at 450 °C (MF450). We first used modern material characterization methods (yield, BET, SEM/EDS, TGA, XRD, FTIR) to understand the difference in biochar production methods on the feedstock. We then used batch equilibrium adsorption with cationic and anionic dyes (methyl orange, MO and crystal violet, CV) to examine environmental performance. The TLUD method generally has a lower biochar production yield than MF450 because we believe much of the material in the TLUD achieves temperatures > 450 °C and is sometimes difficult to retain in the device. The higher temperatures in the TLUD device lead to a biochar which is more microporous, has greater surface area, has less surface functional groups, has greater ash content, is more carbonized, and has lower residual cellulose crystallinity.There were differences in adsorption performance whereby the MF450 biochar adsorbs CV more strongly than the TLUD. For MO, PS-TLUD is less effective at adsorbing the dye when compared to PS-MF450, while CS-TLUD has a much higher adsorption strength than CS-MF450. We are not certain why the two methods show opposite effects in different feedstock but speculate that it may have to do with the much higher mineral content in the PS-TLUD compared to its MF450 counterpart. Out of many isotherms examined Freundlich and Langmuir isotherms provide a best-fit to our data only about half the time. Sometimes an S-shaped isotherm was the best fit or still fit the data reasonably well. Comparing the dye adsorption to other studies, the DWB does not adsorb as well, yet it is still effective for removal at environmental dye concentrations of relevance. Overall, we conclude that DWB, made in this uncontrolled fashion, can make a reasonably high quality biochar based on material properties and environmental performance. We suggest that additional research be done on other low-tech biochar production methods to see how to scale-up and optimize them according a developing world community's intended use.

Pyrolysis of different wood species: influence of process conditions on biochar properties and gas-phase composition

The potential of biomass pyrolysis to mitigate climate change needs to be reconsidered. Thermogravimetric pyrolysis of beech, oak, and spruce wood was carried out to evaluate the course of pyrolysis, the conditions affecting the biochar yield, its fixed carbon content and yield, specific surface area, and gas phase composition. The thermal degradation of the main wood components occurred at the same temperatures with a comparable gas composition (30% H2O, 22% CO, 17% CO2 and 31% VOC + H2) determined by mass spectrometry. Several organic compounds were also confirmed. Lower temperatures, heating rates, and isothermal times favored higher biochar yields while lowering fixed carbon contents. Oak (> 24%) showed higher carbon sequestration potential than beech and spruce (about 21%). To obtain high specific surface area values (> 200 m2 g−1), pyrolysis should be operated in the temperature range of 500–700 °C. The isothermal time is not necessary at temperatures of 600 or 700 °C, but at 500 °C, it is essential that the biochar develops an internal surface. To achieve a high yield of quality biochar with high specific surface area and fixed carbon content, pyrolysis should be carried out at a low heating rate (4 K min−1) and in the temperature range of 500–700 °C, with the necessary isothermal stage at 500 °C. Using pyrolysis instead of combustion, CO2 emissions are reduced by almost half due to carbon sequestration through biochar formation. To obtain the same power output as in the case of combustion, virtually twice the biomass amount must be pyrolyzed.

Compost and Biochar Characteristics Test of Some Animal Manure Waste

This study aims to determine the quality of compost and biochar from some animal manure in improving soil properties and fruit yields of chili plants. This research was conducted in a greenhouse, with nesting experiments using a random block design. The treatment composition consisted of 6 types of fertilizer (cow compost, goat compost, chicken compost, cow biochar, goat biochar, chicken biochar), and three levels of fertilizer doses (5, 10, and 15 tons ha-1) and one treatment control. The results showed differences in fertilizer types differed significantly for N-total soil and weight of red chili and were significantly different from P-available in the soil. While the difference in compost fertilizer dose has a significant effect on P-available and K-available soil, cow dung compost has the lowest effect on soil properties. The number and weight of fresh red chili per plant, while compost goat manure tends to be highest. Biochar from chicken droppings and doses significantly influenced the total N, the highest available P and the lowest C/N, and the amount and weight of fresh red chili. From this study, it can be concluded that the type of raw material for livestock manure for compost and biochar affects soil properties and red chili production, where compost and biochar from goats and chicken manure are better than cow dung. This research's implication is the type of animal feed ingredients affecting the face of livestock and determining the quality of compost and biochar.

Comparative Investigation of Yield and Quality of Bio-Oil and Biochar from Pyrolysis of Woody and Non-Woody Biomasses

This study investigated the quantitative and qualitative attributes of liquid product and biochar obtained from pyrolysis of woody biomass (rubberwood sawdust (RWS)) and non-woody biomasses (oil palm trunk (OPT) and oil palm fronds (OPF)). The prepared biomass was pyrolyzed at temperatures of 500 °C, 550 °C, and 600 °C by using an agitated bed pyrolysis reactor, and then the yields and characteristics of liquid product and biochar were determined. The results showed that liquid product and biochar yields were in the respective ranges of 35.94–54.40% and 23.46–25.98% (wt.). Pyrolysis of RWS at 550 °C provided the highest liquid yield. The energy content of the water free liquid product was in the range 12.19–22.32 MJ/kg. The liquid product had a low pH and it mainly contained phenol groups as indicated by GC-MS. The biochars had high carbon contents (75.07–82.02%), while their oxygen contents were low (14.22–22%). The higher heating value (HHV) of biochar was in the range 26.42–29.33 MJ/kg. XRF analysis revealed that inorganic elements had higher contents in biochar than in the original biomass. The slagging and fouling indexes of biochar were also different from those of the biomass. High carbon content of the biochar confirms potential for its use in carbon sequestration. The specific surface of biochar was lower than that of biomass, while the average pore diameter of biochar was larger than for raw biomass as revealed by BET and SEM. These results on liquid product and biochar obtained from RWS, OPT, and OPF demonstrate that they are promising feedstocks for biofuels and other value-added products.

RETRACTED: Optimization of Pyrolysis Parameters for Production of Biochar From Banana Peels: Evaluation of Biochar Application on the Growth of Ipomoea aquatica

Banana peels waste can be utilized to produce high quality biochar that can be incorporated into the soil for sustainable production of crops. This research analyzed several properties of the biochar produced from the banana peel at different temperatures, residence times and heating rates. This study focuses on the biochar yield and the EDX analysis of the biochar produced. Response surface methodology using central composite design (CCD) was used to optimize these parameters in the batch reactor pyrolysis system. These factors were operated in different ranges for banana peels, in which pyrolysis temperature (200 to 600°C), residence time (60 to 180 min) and heating rate (5 to 15°C·min−1) were varied using 20 experiments respectively. Quality of the biochar was determined based on the biochar yield and O/C ratio. The optimum biochar chosen from the CCD model was applied to several pots of Ipomoea aquatica in different biochar dosage levels of 0, 3, 9 and 15 g (0, 1, 3 and 5 wt% of soil) respectively. Pot experiment was conducted with completely randomized design (CRD) of one factor with five replications to correlate the average plant heights with the biochar dosage levels. Results showed that biochar dosage of 1% yields the highest average final Ipomoea aquatica plant height of 37.04 cm.

Effects of added calcium-based additives on swine manure derived biochar characteristics and heavy metals immobilization

Although pyrolysis is a promising way for treating animal manure, the application is restricted with some limitations of biochar. To improve the quality of biochar derived from swine manure and enhance the immobilization of heavy metals (Cu and Zn) in it, swine manure was mixed with four types of Ca-based additives (CaO, CaCO3, Ca(OH)2, and Ca(H2PO4)2) prior to pyrolysis at 300–700 °C. The thermogravimetric characteristics of swine manure were obviously influenced The addition of CaO, CaCO3, and Ca(OH)2 during the whole decomposition process. Furthermore, with the addition of CaO and Ca(OH)2, the emission of CO2 and CO was substantially decreased at 200–500 °C, whereas the formation of CO, H2, CO2, and CH4 was drastically increased at 600–800 °C. The biochar produced with CaO addition had the highest pH, surface area and carbon content. Moreover, by addition of Ca-based additives, except for Ca(H2PO4)2, the transformation of labile Cu and Zn to the stable fraction was promoted, and the leachability and environmental risk of them were simultaneously reduced. In contrast, CaO and Ca(OH)2 were more favorable for the immobilization of Cu and Zn than CaCO3. Our study indicated that the catalytic pyrolysis using CaO was an effective and valuable method of animal manure treatment.

A Review On The Comparison Between Slow Pyrolysis And Fast Pyrolysis On The Quality Of Lignocellulosic And Lignin-Based Biochar

In recent years, biochar has attracted considerable attention due to its unique characteristics and wide applications in agricultural and environmental areas. Biochar is recognized for its potential role in carbon sequestration, reduction of greenhouse gas emissions, soil amendment, bioenergy production and waste mitigation. The current review discusses on the utilization of various lignocellulosic and lignin-based feedstocks for the biochar production. However, the quality of biochar varies among different thermo-conversion technologies due to the differences in their key process parameters and the feedstock composition. This article aims to review two production technologies for lignocellulosic and lignin-based biochar, namely, slow pyrolysis and fast pyrolysis. The effects of feedstock composition (cellulose, hemicellulose, lignin) and pyrolysis conditions such as temperature and heating rate on the quality of biochar are compared. The relationship between the feedstocks composition, temperature, heating rate of pyrolysis and the quality of biochar are also discussed. Future work would further correlate the effects of feedstock composition and process parameters on the quality of biochar such as surface area and functionality.

A review on sustainability and quality of biochar production from oil palm biomass in Malaysia using thermal conversion technology

Oil palm empty fruit bunch (EFB), mesocarp fiber (MF), palm kernel shell (PKS), oil palm trunk (OPT) and oil palm frond (OPF) are the common solid lignocellulosic biomass generated from oil palm industries. A palm oil plantation was estimated to generate 36.5 ton of dry biomass in each hectare every year which suggesting the abundancy of these wastes. Feedstock feasibility and common properties as a carbon-rich material, have initiated an interest to utilize these biomass for biochar production. This paper provides a review on the developed thermal conversion technologies to synthesize biochar from oil palm biomass and includes the respective product quality such as carbon contents, yield and other physicochemical properties. The sustainability of oil palm biomass as the feedstock for biochar production in Malaysia were also described by providing the overview on biomass availability, biomass industry value chain and respective characteristics. Determining appropriate type of biomass and applying effective type of thermal conversion technologies produce biochar with good physicochemical qualities. This review observed that lignin in biomass contributes significantly to biochar production and slow pyrolysis technique is a promising technology to yield a good quality of biochar.

Wood and bark lignin contents of trees from deciduous forests of eastern India

Abstract Lignin is a polyphenolic compound found in plant tissues, especially wood and bark. The lignin content determines the quality of wood biochar in agroecological uses, and is used in the production of synthetic resins and adhesives. Despite its importance in plant physiology and its agricultural and industrial utility, there exists a wide gap of knowledge of lignin contents of tropical hardwood trees of South Asia, except for a few species. We present here the first estimation of lignin content in wood and bark of 48 species from tropical deciduous forests of India. We show that some species are characterized by greater wood lignin (WL) compared with bark lignin (BL) content, contrary to the generalization held for hardwood trees, and suggest a plausible correspondence between the WL to BL ratio and timber quality.

The design of furnace for biochar production by using vacuum pump and temperature manual control

Temperature control is very prominent to be done in producing biochar, because the quality of biochar depends on combustion temperature and the amount of oxygen existing when the combustion process is happening. In this research, the designing of furnace for biochar production by using vacuum pump and temperature manual control had been done. The fuel used was LPG gas. The furnace was designed by having two parts which are cylinder tube for biochar production and tube feet as the holder of the kiln. The calibration of the furnace for biochar production was done to find out the temperature and the pressure that can be generated and its effect toward produced biochar. The calibration was done by using vacuum pump to vacuum the combustion chamber and temperature manual control as temperature indicator. There were two steps for this furnace calibration, first, the leakage test and second, combustion test of biochar production. The leakage test was done by using bubble test method. The result showed that there were still some leakages happened, but they were fixed with glue on the leak parts. As the final result of the leakage calibration, the vacuum condition obtained was -25 cmHg. And as the result of biochar combustion as long as one and two hour, the temperature reached 2800C and 2500C.

Integration of two-stage thermochemical treatment and chemical leaching for extraction of advanced biochar and high value critical raw materials from sewage sludge

The proposed study aims at assessing the reliability of a new sludge conversion technology, based on integrating thermochemical treatment, with a chemical leaching stage for producing high quality biochar and valuable liquid with high concentration of phosphorus and other critical elements. The concept is based on the fact that sludge ash usually contains about 25% of CaO, 20% of P2O5, and about 25-30% of SiO2. With the removal of these elements, ash content is drastically reduced. The study is thus composed of two phases: (1) assessment of sludge thermochemical conversion routes, and (2) chemical leaching produced biochar. In the first phase, three thermochemical routes are investigated: HTC of fresh sludge at 80% moisture, slow pyrolysis of dry sludge, slow pyrolysis of HTC solid (hydrochar). In the second phase, the solid obtained by slow pyrolysis (biochar) is upgraded through leaching treatment to extract inorganic valuable elements: P, Mg, K. The first phase of the study demonstrated that processing dry sludge in slow pyrolysis at 450°C allows to obtain a low volatile carbonaceous product with characteristics similar to a thermal coal. Second phase demonstrated that, after acid leaching process using HNO3, ash content in biochar decreased from 41.63% to 16.67%. This method also demonstrated to be a valid solution to extract more than 90% of P, K, and Mg contained in the solid, making these elements available for being recycled in agriculture and other industrial uses. At the same time, the increase of the biochar C content and calorific value makes it a valid substitute of fossil coals.