Production and Characterization of Coffee Husk Fuel Briquettes as an Alternative Energy Source

Biomass energy accounts for more than 92 percent of overall energy consumption in Ethiopia. As a result, Ethiopia is one of the world’s most biomass-dependent countries. The high reliance on wood fuels and agricultural residues for fuel harms society’s social, economic, and environmental well-being. This study aims to create and test the quality of fuel briquettes made from the coffee husk. Also built and produced are a carboniser/charcoal kiln, a manually operated molder system, and a briquette stove for burning the manufactured briquette. The carboniser converts 15 kg of raw coffee husk into 6 kg of carbonised char in 25 minutes, and the manually operated briquette molder can press 30 kg per hour. The efficiency of converting raw coffee husk into carbonised char content was 40.12%. In the geological survey of Ethiopia, the geochemical laboratory directorate received triplicate samples of the fuel briquette charcoal for analysis. Moisture content, fixed carbon content, ash content, sulfur content, and calorific value were determined using a bomb calorimeter and a ceramic lining furnace. Physical properties of fuel briquettes ranged from 10.03% moisture content, 970 kg/m3 density, 81% fixed carbon, 5.15% ash content, 0% sulfur, and 30.54 Kcal/kg higher heating value, according to laboratory results. The results of the study revealed that the coffee husk fuel briquettes produced have more positive characteristics. Fuel briquettes were cost-effective and environmentally friendly and reduced deforestation compared to firewood. This study clearly shows that briquettes made from coffee husk could be used as an alternative energy source when this kind of waste is well managed.

Influence of Post- and Pre-Acid Treatment during Hydrothermal Carbonization of Sewage Sludge on P-Transformation and the Characteristics of Hydrochar

Phosphorus (P) recovery from alternative P-rich residues is essential to meet the growing demands of food production globally. Despite sewage sludge being a potential source for P, its direct application on agricultural land is controversial because of the obvious concerns related to heavy metals and organic pollutants. Further, most of the available P recovery and sludge management technologies are cost-intensive as they require mandatory dewatering of sewage sludge. In this regard, hydrothermal carbonization (HTC) has gained great attention as a promising process to effectively treat the wet sewage sludge without it having to be dewatered, and it simultaneously enables the recovery of P. This study was conducted to analyse and compare the influence of acid (H2SO4) addition during and after HTC of sewage sludge on P leaching and the characteristics of hydrochar. The obtained results suggested that despite using the same amount of H2SO4, P leaching from solid to liquid phase was significantly higher when acid was used after the HTC of sewage sludge in comparison with acid utilization during the HTC process. After HTC, the reduction in acid-buffering capacity of sewage sludge and increase in solubility of phosphate precipitating metal ions had a greater influence on the mobilization of P from solid to liquid phase. In contrast, utilization of H2SO4 in different process conditions did not have a great influence on proximate analysis results and calorific value of consequently produced hydrochar.

Toward Automatic Detection of Gastric Lesion for Upper Gastrointestinal Endoscopy with Neural Network

In this paper, we compared the performance of several neural networks in the classification of early gastric cancer (EGC) images and proposed a method of converting the output value of the network into a calorific value to locate the lesion. The algorithm was improved using transfer learning and fine-tuning principles. The test set accuracy rate reached 0.72, sensitivity reached 0.67, specificity reached 0.77, and precision rate reached 0.78. The experimental results show the potential to meet clinical demands for automatic detection of gastric lesion.

Investigation of Pressed Solid Biofuel Produced from Multi-Crop Biomass

The paper presents the preparation and use of pressed solid biofuel of multi-crop plants (fibrous hemp (Cannabis sativa L.), maize (Zea mays L.) and faba bean (Vicia faba L.)) as mono, binary and trinomial crops. The results of the investigation show that three main chemical elements (carbon, oxygen and hydrogen) accounted for 93.1 to 94.9% of the biomass pellet content. The moisture content varied from 3.9 to 8.8%, ash content from 4.5 to 6.8% and calorific value from 16.8 to 17.1 MJ·kg−1. It was found that the density (DM) of all variants of pellets was very similar; the faba bean biomass pellets had the highest density of 1195.8 kg·m−3 DM. The initial ash deformation temperature (DT) of burning biomass pellets was detected, which varied from 976 to 1322 °C. High potassium (K), calcium (Ca) and phosphorus (P) concentrations were found in all types of biomass ash. The quantities of heavy metals in pellet ash were not large and did not exceed the permissible values according to Lithuanian legislation. These chemical properties of multi-crop biomass ash allow them to be used in agriculture for plant fertilization.

Climate impact of an optimised gas treatment on old landfills

It is a well-established fact that the quality and quantity of landfill gas (LFG) start declining after a landfill is closed to further waste intake. Conventional gas treatment and utilisation systems such as flares and gas-driven engines require a certain quality of LFG: specifically, a sufficient methane concentration. Various measures are utilised to maintain the necessary quality of LFG, including a turn-down of gas extraction rates and a shutdown of low-quality gas wells, resulting in a decline of LFG production. This, however, does not have to be the case. The low calorific value (LCV) LFG capture and treatment technology developed by e-flox and referred to in this article as ‘LCV LFG System’ can significantly increase the collection rate and the amount of treated methane in an old landfill. This article introduces such new treatment measures, describes gas capture calculation methodologies and presents actual results based on a medium-sized landfill in Germany. The study demonstrates, among other things, that the LCV LFG system can reduce the CO2 avoidance costs to roughly 10 €/tCO2eq. We present this new technology as a quick and straightforward measure of dealing with the climate issues related to methane emissions of old landfills.

Numerical Simulation of the Influence of CO2 on the Combustion Characteristics and NOX of Biogas

The existence of inert gases such as N2 and CO2 in biogas will reduce the proportion of combustible components in syngas and affect the combustion and NOX formation characteristics. In this study, ANSYS CHEMKIN-PRO software combined with GRI-MECH 3.0 mechanism was used to numerically simulate the effects of different CO2 concentrations (CO2 volume ratio in biogas is 0–41.6%) on flame combustion temperature, flame propagation speed and nitrogen oxide formation of complex biogas with low calorific value. The results showed that when the combustion reaches the chemical equilibrium, the flame combustion temperature and flame propagation speed decrease with the increase of CO2 concentration, and the flame propagation speed decreases even more slowly. Meanwhile, the molar fraction of NO at chemical equilibrium decreases with the increase of CO2 concentration and the decrease is decreasing, which indicates that the effect of CO2 concentration in biogas on NO is simpler. While the molar fraction of NO2 does not change regularly with the change of CO2 concentration, the effect of CO2 concentration in biogas on NO2 is complicated. The highest molar fraction of NO2 was found at chemical equilibrium when the CO2 concentration was 33.6%, when the target was a typical low calorific value biogas.

Selected Parameters of Oat Straw as an Alternative Energy Raw Material

Straw is treated as agricultural waste, and it is available in almost every region of Poland. A total of 30 million tons of straw is produced per year, of which there is a surplus of approximately 13.5 million tons of undeveloped straw. For energy purposes, straw from cereals or rapeseed is most often used. When analyzing scientific publications, it was noticed that, in Poland, large amounts of oat straw are produced, and there is no alternative use for it. Hence, we conducted research to determine the energy value of oat straw. Raw material was obtained from an individual farm from 2018 to 2020. Selected energy parameters for straw burned alone (100%) or co-fired with coal were analyzed in the following weight proportions: 70/30, 80/20, and 90/10 coal/oat straw. It was shown that changing weather conditions, in particular years, had a modifying effect on some of the energy parameters of straw. The calorific value of straw was lower than that of coal, but its impact on environmental pollution turned out to be significantly lower. The difference in combustion heat between coal and straw was 11.74 MJ·kg−1. Investigations into pollutant concentrations were performed for cubes of compressed straw and hard coal. Mixtures of these fuels were not studied in this part of the work. The combustion of straw resulted in a reduction of harmful NO, NOX, and SO2 pollutants and an increase in CO compared to coal combustion. As for hydrogen content—it was the highest in carbon and the lowest in straw. In the case of analytical moisture, an inverse relationship was observed. In the case of both coal and straw, the ash content varied throughout the years of research. As the boiler power increased from 5 to 25 kW, the consumption of burned raw material increased significantly. The results indicate that the surplus of oat straw can be rationally used to obtain thermal energy, including co-combustion with coal. This will allow one to avoid burning straw in the fields, which causes great harm to the natural environment.

Potential Bio-Fuel from Refinery Waste through Anaerobic Digestion

In this study we report biofuel potential in waste cake obtained from oil refinery. The sample was analyzed for its calorific value using auto bomb calorimeter (LECO AC-500), proximate analysis using Thermogravimetric analyzer (LECO 701) and elemental analysis using CHNS analyzer (LECO Tru-Spec). The elemental analysis of dry waste cake vs wet cake depicted the percentage composition of carbon (49.8%, 40.8%), hydrogen (7.9%, 6.0%), nitrogen (2.8%, 1.9%), Sulphur (1.9%, 0.5%) and oxygen content (37.6%, 40.4%). As for as the thermal degradation behavior of dry and wet cake in TGA is concerned, higher moisture contents (68.50%) found in wet cake and lower in dry cake (40.1%). Whereas the volatile matter in dry cake (30.9%) and low volatile in wet cake (14.3%). Similarly, %age of ash become high in dry cake (17.3%) and low in wet cake (5.11%). The results reflected that higher heating value of dry waste cake is higher (22.5 MJ/kg) than wet waste cake (20.5 MJ/kg) and commonly used sugarcane bagasse (17.88 MJ/kg).

Experimental study of an internal combustion engine fueled by a low-calorific value producer gas

This paper describes an experimental study of the operation of an internal combustion engine of fueled by a low-calorific value gas. The main operating parameters of low-power ICE were determined. Efficiency was also evaluated when the ICE was converted to operate on producer gas. In the experiment, it was shown that the engine reached a stable operating mode under load and data on the temperature and exhaust gases composition were obtained. According to our estimates, in the steady-state operation of the internal combustion engine with a load, the efficiency factor was about 22 %. When using the model gas, the from generator output power, was about 30-40 % of the nominal value, under variable load conditions. However, it was found that in steady-state operation, the power of the internal combustion engine was 40-55% of the nominal value.