Pepper Stem Research Articles

Genetic resistance and silicon in the control of stem rot in Capsicum spp.

Pepper stem rot is a disease caused by Sclerotium delphinii, a necrotrophic pathogen and a natural soil inhabitant. Identifying genotypes of Capsicum resistant to the pathogen and applying silicon (Si) can be effective management measures. The objective of the study was to identify sources of resistance in 24 accessions of Capsicum spp. against S. delphinii, and to evaluate the potential of sodium silicate (Si) to induce resistance. Two experiments were conducted: In Experiment I, the resistance reaction of Capsicum in a greenhouse was evaluated. The experiment was conducted in two periods of the year (July and November 2019). In Experiment II, the effect of Si on Capsicum resistance was evaluated. The experimental design used in Experiment I employed randomized blocks in a factorial design of 2 (isolates) x 24 (accessions), with five replications. For Experiment II, six accessions were selected with contrasting resistance responses observed in Experiment I, in a factorial design of 1 (isolate) x 6 (accessions) x 4 (doses: 0.0, 0.025, 0.05, and 0.1 mL per vase). Accessions BGH 71 and BAGC 134 showed greater resistance to the pathogen. Accession BAGC 134 demonstrated high resistance stability in both periods and against the two isolates tested. Si doses had no significant effect on the resistance reaction. Therefore, the genotypes BGH 71 and BAGC 134 have the potential to be used in breeding programs for Capsicum for resistance to S. delphinii for control of stem rot.

Lysine 2-hydroxyisobutyrylation proteomics analyses reveal the regulatory mechanism of CaMYB61-CaAFR1 module in regulating stem development in Capsicum annuum L.

Plant stems constitute the most abundant renewable resource on earth. The function of lysine (K)-2-hydroxyisobutyrylation (Khib), a novel post-translational modification (PTM), has not yet been elucidated in plant stem development. Here, by assessing typical pepper genotypes with straight stem (SS) and prostrate stem (PS), we report the first large-scale proteomics analysis for protein Khib to date. Khib-modifications influenced central metabolic processes involved in stem development, such as glycolysis/gluconeogenesis and protein translation. The high Khib level regulated gene expression and protein accumulation associated with cell wall formation in the pepper stem. Specially, we found that CaMYB61 knockdown lines that exhibited prostrate stem phenotypes had high Khib levels. Most histone deacetylases (HDACs, e.g., switch-independent 3 associated polypeptide function related 1, AFR1) potentially function as the "erasing enzymes" involved in reversing Khib level. CaMYB61 positively regulated CaAFR1 expression to erase Khib and promote cellulose and hemicellulose accumulation in the stem. Therefore, we propose a bidirectional regulation hypothesis of "Khib modifications" and "Khib erasing" in stem development, and reveal a novel epigenetic regulatory network in which the CaMYB61-CaAFR1 molecular module participating in the regulation of Khib levels and biosynthesis of cellulose and hemicellulose for the first time.

Single and binary adsorption of paracetamol and diclofenac onto biochar produced from pepper stem: Which adsorption properties change in the binary system?

The importance of combating the contamination of water resources with emerging pollutants must be kept all the more in view by scientists, since such pollutants are harmful and pose challenges for traditional water treatment methods. The current study was designed to scrutinize the adsorption properties of a low-cost biochar for two pharmaceuticals in both single and binary systems. The work was focused on understanding how paracetamol (PARA) and diclofenac (DIC) co-adsorb, and it can serve as a beacon for similar studies, especially in modeling the adsorption processes of such systems. Using a low-cost biochar from pepper stem (PS) with a high surface area = 727.5 m2/g as adsorbent, experiments were carried out in both the single and binary systems to investigate the adsorption behavior of the mentioned pharmaceuticals. Results showed that, in the single system, the PS biochar demonstrates a slightly greater adsorption capability for both PARA and DIC, with a capacity of 354.66 and 256.10 mg/g, respectively, compared to its capacity for each pharmaceutical in the presence of the other in the solution. Interestingly, the effect of the presence of one of the pharmaceuticals on the thermodynamic parameters (ΔGº, ΔSº, and ΔHº) of the other was ignorable, and interactions such as hydrogen bonding, π-π, n-π, and anion-π interactions were at work for the adsorption processes, with different extends in each pharmaceutical-biochar case. On the other hand, the presence of one of the pharmaceuticals was effective on the kinetics of the adsorption process of the other and caused a decrease in its adsorption rate, especially in the initial stage of the process. Overall, in addition to the suitability of pepper stem biochar for PARA and DIC, results showed that the presence of one pharmaceutical is not influential on all the adsorption properties of the other, and the results can be exploited for studding similar systems.

Pengaruh Tanaman Sela terhadap Pertumbuhan Tanaman Cabai Rawit (Capsicum frutescens L.)

Cayenne pepper is a food ingredient that is liked by almost all people, including the people of Jeneponto. However, cayenne pepper production in 2021 will decline, one of the contributing factors is plant-disturbing organisms. The system that can be utilized is the organic farming system, one of the organic farming systems currently being developed is the companion planting system which is considered capable of increasing crop productivity. The aim of this study was to analyze the growth and yield of cayenne pepper (Capsicum frutescens L) with the sweet corn (Zea Mays L) companion planting system. The study was designed according to a completely randomized design with three treatments and three replications. The first treatment was cayenne pepper as a control (A), cayenne pepper and sweet corn or companion planting (B), and sweet corn as a control (C). The research was carried out for 56 WAP for cayenne pepper and for sweet corn it was carried out for 70 WAP. The observed variables were plant growth (plant height, cayenne pepper stem diameter, number of fruit, and fresh weight). From the results of the study it can be concluded that the use of companion planting systems can be utilized as a cropping system in the growth and increase in the production of cayenne pepper plants.

The adsorption of naproxen on adsorbents obtained from pepper stalk extract by green synthesis

Abstract This study presented the adsorption of naproxen on adsorbents filled with Cu, Fe, and Cu/Fe nanoparticles (NPs) obtained by the green synthesis method from pepper stem waste. The resulting adsorbents were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, and thermal gravimetric-differential thermal analysis. The amount of naproxen not adsorbed in the solution was determined from the cyclic voltammetry method, which is one of the electrochemical methods. The equation of the calibration curve used in the conversion of current to concentration and the R 2 value were y = 2.6165 x − 288.22 y=2.6165x-288.22 and 0.999, respectively. While the adsorption with the BS-extract was 3.3%, it was 46.142% for Cu-NP, 92 mg/g, and 57.622% for Fe-NP. With 116.0 mg/g Cu/Fe-NP, 82.406% and 165.0 mg/g capacity were reached. In the isotherm calculations, since the R 2 values for each adsorbent were in the range of 0.998–0.997, it was determined that the Freundlich and Halsey isotherms were compatible. Accordingly, under these conditions, Naproxen adsorption was multilayered and the adsorbent surface had a heterogeneous structure. Graphs drawn from the kinetic data showed that the adsorption obeyed the second-order kinetics. The R 2 value of the kinetic curves was 1 for all adsorbents. Thermodynamic data were determined by Van’t Hoff curves with R 2 values in the range of 0.998–0.996. The enthalpy value for Cu/Fe-NP was calculated to be 31.854 kJ/mol, the entropy value was 0.1993 kJ/mol-K, and the free energy was −27.5374 kJ/mol. These values were 34.605 kJ/mol, 0.272 kJ/mol-K, and −46.451 kJ/mol for Fe-NP, respectively; and 19.79 kJ/mol, 0.247 kJ/mol-K, and −54.3226 kJ/mol for Cu-NP. While all NPs (except Cu-NP) had a high recovery percentage in three cycles, this decreased to 80% at pH 10. For Cu-NP, the recovery percentage decreased at pH 8.5 and 7, but surprisingly it increased at pH 10. As a result, it can be inferred that NPs play a good role in adsorbent development, and Fe and Cu NP-doped BS adsorbents have a better effect on naproxen adsorption and have been evaluated as adsorbents suitable for use several times.

Effect of Biopesticides against Stem Borer (Lophobarispiperis) and Thrips sp. on Pepper (Piper)

One of the pepper crop production obstacles is the presence of pests. The research was designed in a randomized block with three treatments, namely (1) botanical pesticides, (2) biological pesticides and (3) control (water), and nine replications. The treatment application is carried out once a month, done immediately after observing the intensity of the pest attack. The results showed that the attack of pepper stem borer was low (below 10%), so the effect of the treatment could not be seen significantly. The Thrips attack was high enough, it was seen that there was the ability of botanical pesticides to reduce the intensity of the attack. Meanwhile, the biological pesticide had not yet shown its ability to reduce the intensity of Thrips sp.

Activated carbon synthesis and methylene blue adsorption from pepper stem using microwave assisted impregnation method: Isotherm and kinetics

BackgroundAdsorption is a potent technique used to separate hazardous compounds due to its practical, affordable, and ecologically benign uses. Activated carbons are often employed for better results in adsorption processes. Agricultural by-products and wastes have recently been used in the development of large-pored adsorbents. These adsorbents are gaining popularity as an alternative to commercial activated carbons. MethodsThis study integrated the known carbonization method with a microwave device, and waste pepper stalks (locally known as isot) activated with phosphoric acid were carbonized at 650 °C for 30 min. The activated carbon (BSAC) obtained was utilized in the adsorption of dyestuff (methylene blue MtB). The adsorption was investigated according to pH, concentration, and kinetic model. ResultsThe monolayer adsorption capacity (qmax) was 178.4121 mg g−1 based on Langmuir isotherm, which was the most appropriate match. Response surface methodology (RSM) was used to examine the removal of MtB. The central composite method was used in RSM. In experimental design, solution initial concentration (75–150 ppm), adsorption time (120–240 min) and activated carbon amount (50–100 mg) were selected and adsorption capacity (qe) was chosen as response parameter. The adsorption capacity was 75.0072 mg g−1 under optimum conditions (88 ppm solution initial concentration, 191 min, adsorption time and 95 mg activated carbon). ConclusionThe activated carbon obtained from pepper (isot) stems with microwave impregnation process integrated into the traditional method are a cheap and environmentally friendly adsorbent for MtB removal.

Thermogravimetric analysis-based proximate analysis of agro-byproducts and prediction of calorific value

Domestic agro-byproduct potential in Korea is estimated to be approximately 4,018 × 103 tons of oil equivalent per year. Majority of agro-byproducts are unused and discarded. These unused agro-byproducts can potentially be converted into solid fuel for value addition. The energy potentials of solid fuels are generally characterized by proximate analysis and measuring calorific value; however, owing to the use of coal and coke, both the analyses could be expensive and time-consuming. Proximate analysis via thermogravimetric analysis is a relatively low cost and less time-consuming method than proximate analysis by ISO method (ISO 18134-1:2015, ISO 18123:2015, ISO 18122:2015). Thermogravimetric analysis-based proximate analysis of four agro-byproducts (pepper stem, perilla stem, corn stalk, and kenaf) was conducted. Additionally, the calorific values obtained from several equations based on the proximate analysis results were compared to that of the calorific value measured using calorimeter. The maximum difference between proximate analysis using thermogravimetric analysis and ISO method was 4.73%p, which was attributed to change in moisture content. It is recommended to measure the moisture content of biomass for 120–150 min (at 105 °C) and ash content for 80–120 min (at 815 °C). Three of the equations indicated a difference of less than 1.5 MJ kg−1 between the TGA-derived and the measured calorific value. For this study, It was determined that both proximate analysis and prediction calorific value can be conducted by thermogravimetric analysis.

PRODUCTION AND PHYSIO-CHEMICAL CHARACTERIZATION OF BIOCHAR OBTAINED FROM COFFEE PROCESSING WASTES AND CROP RESIDUES OF COFFEE PLANTATION

Biochar is a pyrogenous organic material obtained mostly from various plant based waste biomass through pyrolysis process. The production of biochar from various plant based waste biomass is a part of the modern agenda to recycle bio-wastes and its application in agriculture is reported to improve the soil health in several ways. The other potential benefit of biochar include pollution remediation due to its high cation exchange capacity and specific surface area. In the present study, production and physico-chemical characterization of biochars obtained from coffee processing waste biomass (cherry husk and parchment husk) and crop residues from coffee plantation (diseased uprooted coffee stem and pepper stem waste) were attempted following standard methodologies. The statistical analysis of the data on biochar yield and physico-chemical parameters (moisture, pH, fixed carbon level, ash and volatile matter) of the biochar produced in the present study indicated that among the four waste biomass studied, significantly (p=0.05) highest biochar yield (40.53%) and fixed carbon level (54.53%) were recorded in cherry husk waste biomass. While, biochar obtained from pepper stem waste showed significantly (p=0.05) highest pH level (10.85%) and lowest moisture level (3.59%). Significantly (p=0.05) highest volatile matter (66.3%) and ash (18.13%) contents were observed in the biochars obtained from pepper stem waste and cherry husk, respectively. These data indicated that biochar yield and physico-chemical parameters of the biochar primarily depends on the chemical nature of waste biomass or crop residues. Therefore, screening of biochar obtained from various waste biomass or crop residues is pre-requisite for assessing its agronomical and environmental potentials. The results of the present study has provided baseline information of biochars obtained from various coffee processing waste biomass as well as crop residues from coffee plantation.

Analysis of the Relationship between Sweet Pepper Stem Growth and Labor Load

Analysis of the Relationship between Sweet Pepper Stem Growth and Labor Load

Systematic Analysis of the Grafting-Related Glucanase-Encoding GH9 Family Genes in Pepper, Tomato and Tobacco.

Grafting is an important agricultural practice to control soil-borne diseases, alleviate continuous cropping problems and improve stress tolerance in vegetable industry, but it is relatively less applied in pepper production. A recent study has revealed the key roles of β-1, 4-glucanase in graft survival. We speculated that the GH9 family gene encoding glucanase may be involved in the obstacles of pepper grafting. Therefore, we performed a systematic analysis of the GH9 family in pepper, tomato and tobacco. A total of 25, 24 and 42 GH9 genes were identified from these three species. Compared with the orthologues of other solanaceous crops, the deduced pepper GH9B3 protein lacks a conserved motif (Motif 5). Promoter cis-element analysis revealed that a wound-responsive element exists in the promoter of tobacco NbGH9B3, but it is absent in the GH9B3 promoter of most solanaceous crops. The auxin-responsive related element is absent in CaGH9B3 promoter, but it presents in the promoter of tobacco, tomato, potato and petunia GH9B3. Tissue and induction expression profiles indicated that GH9 family genes are functionally differentiated. Nine GH9 genes, including CaGH9B3, were detected expressing in pepper stem. The expression patterns of NbGH9B3 and CaGH9B3 in grafting were different in our test condition, with obvious induction in tobacco but repression in pepper. Furthermore, weighted correlation network analysis (WGCNA) revealed 58 transcription factor genes highly co-expressed with NbGH9B3. Eight WRKY binding sites were detected in the promoter of NbGH9B3, and several NbWRKYs were highly co-expressed with NbGH9B3. In conclusion, the missing of Motif 5 in CaGH9B3, and lacking of wound- and auxin-responsive elements in the gene promoter are the potential causes of grafting-related problems in pepper. WRKY family transcription factors could be important regulator of NbGH9B3 in tobacco grafting. Our analysis points out the putative regulators of NbGH9B3, which would be helpful to the functional validation and the study of signal pathways related to grafting in the future.

CFD Analysis and Validation of a Foreign Material Winnowing Machine for Pepper Harvester

The winnowing machine of chili pepper harvesters was developed to reduce the potential problem of low pepper stem and fruit separation. The developed winnowing machine was combined with two impellers and a center bearing to prevent a strain on the drive shaft and to ensure durability. The terminal velocity of chili pepper was measured, and an aerodynamic analysis was conducted based on this winnowing machine. A CFD (Computational Fluid Dynamics, Ansys Fluent 2020 R1) analysis was conducted for three levels of discharge port guide form (0, 3, and 5 guides) and three levels of rotating speed (1600, 1800, and 2000 RPM) of a winnowing machine designed utilizing aerodynamic analysis results. A validation test was conducted by fabricating a winnower test device. As for aerodynamic analysis conducted using measured values of terminal velocity, chili pepper fruits were collected at an outlet wind speed lower than 17.5 m/s and chili pepper branches were separated at a speed higher than 12.5 m/s. As a result of CFD analysis, the wind speed deviation at outlets of the 0-, 3-, and 5-guide depending on the rotating speed appeared to be 15.8, 1.4, and 1.0 m/s on average, respectively. The result of the CFD analysis showed values higher than wind speeds of the actual winnower test device by a minimum of 0 and a maximum of 2.4 m/s. Through the CFD analysis and the wind speed validation test of the winnower test device, optimal conditions to separate foreign materials were found to be a winnowing machine at a rotating speed of 1800 RPM with a discharge port having three guides or a winnowing machine at a rotating speed of 2000 RPM with a discharge port having five guides.

Design and experiment of flexible clamping device for pepper plug seedlings

At present, there are leakage and injury of pepper seedlings in the process of seedling transplantation. Based on the mechanical properties of pepper stem, a clamping mechanism with the function of crab pincers is designed using bionics principle. The clamping mechanism uses the CAM device to drive the gear and rack meshing. The control clamping gripper’s opening and closing stroke is 2–30 mm. The stroke of CAM gear is 1.94 mm, obviously save the clamping time. In order to achieve flexible clamping and reduce seedling injury, elastic silicone, rubber, and nylon materials were used as clamping materials. The finite element analysis was carried out to simulate the force in the clamping process, and the stress of the silicone gripper was found to be the minimum, and the stress range was 1.53 × 10−4–1.42 MPa. The results of clamping damage test and seedling picking migration test showed that the clamping damage rate of the silicone gripper was 3.28%. The clamping damage degree was the lowest, which is consistent with the theoretical analysis. The seedling leakage rate was 5.86%. The success rate of seedling picking was 94.14%, and the success rate of migration was 83.20%. It proved that flexible clamping device designed in this study had reliable working performance and good transplanting effect.

Integrated proteomic and metabolomic analyses reveal significant changes in chloroplasts and mitochondria of pepper (Capsicum annuum L.) during Sclerotium rolfsii infection.

Infection by Sclerotium rolfsii will cause serious disease and lead to significant economic losses in chili pepper. In this study, the response of pepper during S. rolfsii infection was explored by electron microscopy, physiological determination and integrated proteome and metabolome analyses. Our results showed that the stomata of pepper stems were important portals for S. rolfsii infection. The plant cell morphology was significantly changed at the time of the fungal hyphae just contacting (T1) or surrounding (T2) the pepper. The chlorophyll, carotenoid, and MDA contents and the activities of POD, SOD, and CAT were markedly upregulated at T1 and T2. Approximately 4129 proteins and 823 metabolites were clearly identified in proteome and metabolome analyses, respectively. A change in 396 proteins and 54 metabolites in pepper stem tissues was observed at T1 compared with 438 proteins and 53 metabolites at T2. The proteins and metabolites related to photosynthesis and antioxidant systems in chloroplasts and mitochondria were disproportionally affected by S. rolfsii infection, impacting carbohydrate and amino acid metabolism. This study provided new insights into the response mechanism in pepper stems during S. rolfsii infection, which can guide future work on fungal disease resistance breeding in pepper.

Development of a novel and efficient biochar produced from pepper stem for effective ibuprofen removal

A potential biochar from pepper stems (PS-biochar) was developed via a one-stage pyrolysis process of precursor at 700 °C and employed to adsorb ibuprofen (IBP) in water media. Results showed that PS-biochar was a carbonaceous mesoporous adsorbent with well-developed porosity (SBET = 727.5 m2/g and VTotal = 0.36 cm3/g) and rich surface functional groups. Mechanism of IBP adsorption consisted mainly of π- π interaction, pore filling, and H-bonding. The Langmuir monolayer capacity (569.6 mg/g) was very high compared to values reported in similar studies. The successful PS-biochar regeneration after four cycles in the batch system confirmed the high performance of the NaOH (0.1 M) as a desorbing agent. Therefore, the prepared biochar can be considered as a cost-effective and high-performance material for water decontamination.

Pepper (<i>Capsicum annuum</i>) xylogen-like arabinogalactan protein (XYLP) 1 and XYLP2 promote synthesis of lignin during stem development to cope with stresses

Pepper stems exhibit a high level of strength and lignin deposition to support plant growth, which direct the cultivate style without binding sticks or scaffolding. However, regulation of lignin synthesis and accumulation in pepper stem has not been extensively studied. Herein, we first investigated the pepper stem developmental process and confirmed that increasing lignin accumulation occurs during stem growth. Then, we performed genome-wide identification and characterization of xylogen-like arabinogalactan protein (XYLP) family members and obtained 10, 22, and 19 XYLPs in pepper, tomato, and potato respectively. Evaluation of the phylogenetic relationship among the identified XYLPs suggested that these proteins are conserved in Solanaceae. Thereafter, we analyzed the 10 CanXYLP genes and observed that these genes exhibit differential expressing patterns at different stages of pepper stem development. Among these genes, two XYLPs, namely CanXYLP1 and CanXYLP2, exhibited an increased expression pattern and a strong correlation with lignin accumulation in pepper stem. We further found that CanXYLP1 and 2 play a role in pepper stem lignification by positively regulating the lignin synthesis pathway genes in pepper, and the CanXYLP1/2-silenced plants displayed a blocked lignification phenotype. Finally, we confirmed that CanXYLP1/2 expression is upregulated in response to some abiotic and biotic signals, suggesting that these two genes enhance the tolerance of pepper stem to unfavorable conditions. These results contribute to our understanding of the molecular mechanism controlling pepper stem lignification, and the relationship between the lignin content of pepper stem and XYLPs.

The intensity of major pests on pepper (Piper nigrum) in Tanggamus Regency - Lampung Province

As one of the black pepper production centers in Indonesia, Lampung pepper productivity is quite low compared to other central areas. Lampung produces around 500 kg/ha, quite far from the national average production which is around 796 kg/ha, or even the productivity of other regions such as Bangka-Belitung which has reached 1.2 tons/ha. One of the main problems that cause this is a fairly high pest attack. For this reason, a study was conducted on the intensity of the main pest attack on pepper plants in one of the pepper-producing areas in Lampung, namely Tanggamus Regency. The study was conducted in April-May 2021 by taking 100 plant spots (samples) randomly in the location. The intensity of pest attack is calculated by a scoring system. The results showed that there were three main pests that attacked pepper plants in Tanggamus Regency - Lampung Province, namely the pepper stem borer (Lophobaris piperis) with the intensity of around 38%; Thrips sp. with intensity of about 23% and fruit suckers (Dasynus piperis) with intensity of about 9%.

Performance Testing and Evaluation of Drum-Type Stem-Separation Device for Pepper Harvester

The chili pepper harvester has shown potential problems of low pepper stem separation and a high pepper damage rate. The low pepper stem separation has required additional labor, which consists of separating the pepper and stem after pepper harvesting. To improve the stem separation and sorting function of pepper harvesters, three-shaft and four-shaft drum-type stem-separation devices were manufactured, and performance tests were conducted to assess these devices. In an attempt to reduce the damage rate, a brush was used as the teeth in the drum-type stem-separation device. In the factor test, the rotational speeds of shaft 1(A), shaft 2(B), shaft 3(C), and the conveyor for the three-shaft drum were 0.9, 2.7, 1.3, and 0.5 m/s, respectively. The rotational speed of the four-shaft drum was the same as that of the three-shaft drum except for shaft 4(D), and the rotational speed of this additional D was set to 1.3 m/s, which was the same as that of C. In the non-moving status during the non-picking operation of the pepper harvester, the average stem-separation efficiency (SSE) of the four-shaft drum increased by 1.2%, the average pepper with twig rate (PTR) decreased by 5.9%, and the average damage rate (DR) increased by 3.7% compared to the three-shaft drum. In the moving status during the picking operation of the pepper harvester, the SSE of the four-shaft drum increased by 3.6%, the PTR decreased by 9.1%, and the DR increased by 3.8% compared to the three-shaft drum, so an improvement in the pepper stem-separation capacity was observed.

Performance Optimisation of Fuel Pellets Comprising Pepper Stem and Coffee Grounds through Mixing Ratios and Torrefaction

Agricultural by-products have several disadvantages as fuel, such as low calorific values and high ash contents. To address these disadvantages, this study examined the mixing of agricultural by-products and spent coffee grounds, for use as a solid fuel, and the improvement of fuel characteristics through torrefaction. Pepper stems and spent coffee grounds were first dried to moisture contents of <15% and then combined, with mixing ratios varying from 9:1 to 6:4. Fuel pellets were produced from these mixtures using a commercial pelletiser, evaluated against various standards, and classified as grade A, B, or Bio-SRF. The optimal ratio of pepper stems to spent coffee grounds was determined to be 8:2. The pellets were torrefied to improve their fuel characteristics. Different torrefaction temperatures improved the mass yields of the pellets to between 50.87% and 88.27%. The calorific value increased from 19.9% to 26.8% at 290 °C. The optimal torrefaction temperature for coffee ground pellets was 230 °C, while for other pellets, it was 250 °C. This study provides basic information on the potential enhancement of agricultural by-products for fuel applications.

Development of surface torrefaction process to utilize agro-byproducts as an energy source

In this study, to improve the fuel characteristics of unused agro-byproducts and utilize these as an energy source after pelletizing, a thermochemical process termed as surface torrefaction was developed. After torrefaction, the amount of available energy and energy yield decreased due to mass reduction. Thus, surface torrefaction minimized the amount of input energy and energy yield. During this process, the carbonized surface of pellets and any moisture was removed from inside the pellet which is advantageous for storage and transportation. Changes in color and physiochemical characteristics were also observed. The calorific value and moisture content of the wood pellet (WP) and pepper stem pellet (PP) before surface torrefaction were 20.1 MJ kg−1 and 8% and 18.1 MJ kg−1 and 6.5%, respectively. After surface torrefaction, the WP and PP calorific values and energy yields were: 20.3–20.7 MJ kg−1 and 87.3–92.5%, and 18.5–20.1 MJ kg−1 and 86.8–95.9%, respectively. After torrefaction and surface torrefaction, the change in mass yield and fuel characteristics were compared. The optimal conditions for WP and PP treatments, considering hygroscopicity, calorific value, and energy yield, were determined as 300 °C for 4.5 min and 300 °C for 5 min, respectively at surface torrefaction.