A sustainable approach to managing city park waste through biochar as a renewable energy source

An abundant natural resource known as lignocellulosic biomass is seen to be a promising and sustainable alternative to renewable energy. A carbon-rich, porous substance called biochar is created when biomass is thermally decomposed during pyrolysis procedures in order to make biofuels. Biochar can be made in big industrial facilities or on a local scale. In order to limit the usage of fossil fuels and find a solution for managing urban park garbage, this project will examine the potential of biochar made from waste from city parks as a renewable energy source. A 25-gram natural zeolite catalyst was used to produce biochar at temperatures between 100 and 500 °C with sample weights of 50, 100, 150, and 200 grams. Calorimetric analysis, FTIR analysis, SEM analysis, XRF analysis, ultimate analysis, and proximate analysis are used to characterize the product. The results showed that the zeolite process produced the maximum calorific value of biochar at 6009.8 cal/gram, the highest yield of biochar at 200 °C, and the weight of 50 grams of biomass without a catalyst at 96%. Aliphatic OH and CH groups associated with phenols, alcohols, and carboxylic acids can be seen using FTIR analysis. Large holes can be seen in leaf litter biochar according to SEM examination. For biochar products, the XRF examination of the metal elements Al, Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Co, Zn, Rb, Sr, Na, Mg, Sr, and Pb is within the permitted limits. Leaf waste can be converted into a non-toxic renewable energy source because biochar has a low sulfur concentration of 4.0%. The findings of this study are anticipated to fill in some gaps left by earlier studies, particularly with regard to the use of garbage from municipal parks and the advancement of renewable energy sources..


Introduction
Sustainable waste management in municipal parks is an important problem since it offers advantages beyond composting and landfill disposal.Waste management will be unsuccessful if there is too much waste, whether it is in the incorrect location, too far from locations where garbage can be sold, or not sufficiently recycled.Waste management solutions are selected in areas where there is less emphasis on economic concerns based on how easily they are accepted by the environment [1].Reducing waste at the source will be the most important level for controlling waste issues [2].It makes perfect sense to blame this predicament on careless rubbish management in the public park.Waste management in city parks should be a problem, especially in light of managing technology and the many green spaces present in every city.Processing waste into energy is an alternative to burning or burying it because waste may contain energy.Therefore, recycling waste into energy products at the place of generation is seen as a realistic solution to the problem of city park waste within the context of sustainable city park trash management.Pyrolysis is an effective technology for converting waste from public parks into energy 1257 (2023) 012012 IOP Publishing doi:10.1088/1755-1315/1257/1/012012 2 products since it can produce a variety of goods without affecting the environment.Pyrolysis technology has the potential to reduce emissions by a factor of 20 when compared to incinerator combustion [3].By converting garbage into energy products, pyrolysis technology has a number of benefits, particularly in reducing the quantity of waste produced in urban areas.The products, which also include charcoal and bio-oil, have benefits.In general, the pyrolysis of wood biomass yields more biochar than bio-oil and gas, with the amount of biochar produced from the pyrolysis of waste from city parks expected to be larger than that of other pyrolysis products.
Biochar is a pyrolyzed substance that is dark black in color and possesses refractory qualities.It enhances the soil's nutritional content and aids in carbon sequestration [4].Applying biochar to the soil can minimize emissions of nitrous oxide and methane, as well as chemical leakage into groundwater.Additionally, it might strengthen the structure of the soil.Functional and aromatic oxygen-containing groups are present in biochar.Biochar's physicochemical characteristics enable it to be utilized for a long period, safely store carbon in the environment, and enhance soil health [5].Biochar, an organic solid and carbon residue created by pyrolysis, is mostly composed of carbon (85%), oxygen, and hydrogen [6].Compared to fossil fuels, which have lower energy content, biochar has approximately 32 MJ/kg of LHV inorganic ash.Biochar can be used as fertilizer to lower the amount of carbon in the atmosphere because it contains a variety of plant nutrients [7].The composition of biochar is influenced by the raw materials used to create it [8].Studies on the production of biochar from garbage in urban parks with sustainable management are still in the early stages, particularly when it comes to tackling technical and environmental issues.Previous studies have concentrated more on different biomass types and pyrolysis procedures with varied operating parameters.This study, however, focuses on research relevant to waste management solutions for urban parks by turning rubbish sources into biochar and evaluating the advantages of biochar as a sustainable energy source.

Sample preparation
Before being put through characterization testing in the lab, the samples were randomly chosen from various locations of the park in Bandung, stirred, and stored for around 2 kg in plastic to preserve their natural moisture content.After being ground up in a blender, samples of organic waste were sieved using a 20-mesh screener.The samples were dried for 24 hours at 105 o C in an oven until the moisture content was less than 10% of the total weight.After that, these were utilized as pyrolysis sample materials.

Pyrolysis process
Samples that had been prepared in the previous stage were then put into a fixed bed-type pyrolysis reactor equipped.The process took place at a temperature of 100-500 o C, and the sample weight used was 50-200 grams.The process takes place without a catalyst and uses a zeolite catalyst.The reduced sample is weighed every 1 hour, the biochar product is then characterized and the total yield is calculated.Characteristic analysis of bio-char consisting of proximate and ultimate following ASTM standards.The FTIR measurement was analyzed using an FTIR analyzer over 400-4,000 cm1.The Geological Engineering Laboratory of ITB Bandung also conducted surface area testing using SEM-type JEOL JSM-6340 F and XRF (Rigaku Supermini 200, Europe) studies.The calorific values were calculated using a Bomb Calorimeter (Parr 1261, Volt: 230V 50/60Hz), in accordance with ASTM.The yield of biochar generated during this pyrolysis procedure can be calculated using the formula below:

Results and Discussion
3.1 Biochar yield in pyrolysis process based on temperature.
Figure 1 shows the impact of temperature on the yield of residual solid, samples.The highest yields were produced by the uncatalyzed method (96%), followed by the catalysed process (90%).This shows that the impact of a catalyst on the production of biochar is negligible to nonexistent.The increase in biochar yield for all processes was obtained between 100°C and 400°C, and it decreased at 500°C.The yields of biochar decreased as temperatures increased in both catalyzed and uncatalyzed procedures.This is due to the fact that at higher temperatures, a bigger amount of a substance decomposes into liquid products and some into gases.Puspitasari et al. [9] claim that the limited generation of biochar at high temperatures was caused by a spontaneous increase in reactor pressure, which caused the biomass to have the propensity to condense into non-condensable gas.According to Stegen and Kaparaju [10], the heating level had a greater effect on the production of biochar because of the cellulose content.The rate of polymerization declines as the temperature drops below 325 K, which indicates that cellulose starts to react destructively.Anhydrocellulose, which is created when cellulose breaks down and becomes more stable, yields more biochar at lower temperatures (575 K) [11].

Characteristics of Biochar 3.2.1 Proximate and ultimate analysis of Biochar
Tables 1 and 2 display the findings of the biochar's proximate and final analyses.The water content in Table 1 is 4.8%, which is consistent with the findings of the study by Fadillah et al. [12].The biomass's moisture content has a significant impact on the fuel's performance and energy content.The calorific value decreases as the water content rises.8 to 12% is a good range for humidity [13].Waste from municipal parks still falls under the category (15%) for the thermal conversion procedure [14].According to Table 1, biochar produced with a 65% catalyst has an ash content that is 23.5% lower than biochar produced without the use of a catalyst.This difference is caused by the zeolite catalyst, which was mixed with the biochar and increased its ash content.Contrary to the volatile content, it can be shown that uncatalyzed biochar has a volatile content that is 3.6% higher than 2.7% catalysed biochar.biochar, but the total carbon content is greater in the catalyzed biochar.The ash content has a bad correlation with the heating value because silica, in particular, is a mineral that lowers the heating value [15].According to Fang and Jia [16], a high ash percentage in biomass fuel is very undesirable since it decreases the calorific value produced.Due to the high ash concentration, both catalysed and uncatalyzed biochar still need to be treated before being used as fuel.The fixed carbon value of biochar was 24.4% without a catalyst, whereas it was 26% with one.The high fixed carbon value of catalysed biochar is apparently due to the catalyst being mixed with the raw materials burned during the pyrolysis process.Compared to rice husk (60.10%), biochar has a lower fixed carbon concentration (17,18).Table 2 presents the results of the final analysis, both before and after pyrolysis.Some elements, such as carbon from 40 to 60%, oxygen from 0.96 to 11.8%, and sulphur from 0.31 to 0.43%, appear to have risen.Contrarily, nitrogen and hydrogen decreased from 56% to 23%.It is thought that the sickness was caused by the heating process used to make some of the components evaporate.According to Yin [19], the elements C and H in biomass will bind to form fixed carbon and volatile organic matter, which have a significant impact on the energy content of biomass [20].The relationship between C, H, O, and S elements and heating value (HHV), which connects HHV values to constituents C, H, O, and S, is explained by Sheng and Azevedo [21], Ozyuguran and Yaman [22], and Xing et al. [23].Despite the fact that the O elemental relationship was not particularly strong, the O content had no effect on the drop in HHV.Vieira et al. [17] claim that in order to speed up the combustion reaction, a higher oxygen content in the sample is necessary; nevertheless, this does not increase the energy value of the biochar, only its value as a fuel.So biochar has the potential to become a very eco-friendly renewable energy source.

X-Ray Fluorescence (XRF) Analysis
X-Ray The fluorescence analysis of biochar in Table 3 reveals that some substances that are regarded as harmful to the environment can still be included without endangering the environmental safety of the resulting products.Additionally, Wapinski et al. [24] state that P, Mg, Zn, Cu, Ca, Sr, and Ba are the main components in the creation of fertile soil, indicating that biochar can replace these minerals to boost soil fertility in addition to acting as an energy source.According to the EBC standard (Europan Biochar Certificate) (2012) [25], the heavy metals Pb, Cu, Hg, Cr, and Ni, as well as Cd and Zn, are allowed in biochar.According to Table 3, the use of the metal elements Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Co, Zn, Rb, Sr, and Pb in biochar products does not pose a threat to the environment and can even be utilized as a component to increase soil fertility.Biochar has a lot of potential as a technique of reducing atmospheric CO2 levels and raising stable soil carbon stocks, as well as improving soil carbon sequestration.Along with sequestering carbon from the soil, biochar can also serve as a fertilizer and a soil enhancer [24].In biochar, mg, and k are the two main minerals that are frequently found.It is recommended to utilize biochar as a biological fertilizer because of its mineral composition, which includes K and P. there are several substances A number of inorganic substances have been found to be effective for enhancing soil nutrients for use in agriculture, including phosphorus, potassium, calcium, dissolved silicon, and iron [26].Metal mineral occurrence in biochar is significantly influenced by the type of raw material utilized and the conditions during heating.Khiari et al. [27] state that the minerals Ca, K, Mg, P, and Si are present in hemp wood biochar.Across all samples, these components are equally distributed.While this was going on, an XRF study of the plantain fiber showed that indium and potassium, with 35.001% and 25.05% of each, were the most common elements.

Fourier Transform Infrared (FTIR) Analysis
The functional groups included in biochar samples made from leaf waste are to be identified by FTIR analysis.Figure 2 displays the diffractogram of the FTIR study findings for a greater proportion of biochar products found in the 3400-3000 cm1 region.This range matches the band stretching experienced by hydrogen bonds in OH groups derived from cellulose, hydroxyphenyl glucoside linkages, or the guacil and syringyl groups of lignin [14].The single bond area, which is 2923.56-2854.13cm1, is where the second transmission was seen.Previous research has demonstrated a connection between aliphatic CH axial deformation and the functional groups of phenol, alcohol, carboxylic acid, and aldehyde.The region between 1619.91 and 1724.05cm1 showed transmission deformation, with the double bond connected to hemicelluloses' C=O stretching and the vibrations of the H-O-H deformation [14].Additionally, the transmission area of 1052.94 cm1 is connected to stretching C-O vibrations in cellulose and hemicellulose, and the areas in the ranges of 1442.49,1380.78, and 1319.07 cm1 are connected to CH deformation in cellulose and hemicellulose.Meanwhile, the areas in the ranges of 1241.93-1199.51cm1 indicate the release of C-O and lignin and xylan strain.Lower temperature biochar production results in larger yields and more functional groups, such as C=O and C-HH, which can serve as nutrient exchange sites following oxidation [31].Primary, secondary, and tertiary alcohols, enols, esters, and ethers are formed through the reactions of OH with CO [32].Research by Pratama et al. (2018), which asserts that carbonization causes the C=O group, which is the same as the carboxylic group, to vanish, supports this criterion.This is so that the oxygen functional groups on the carbon surface can be broken down by heating in the absence of oxygen.At a temperature of 400 oC, the carboxylic group (C=O) will disintegrate [33].The O-H groups convert from hydrogen bonds to monomer groups during carbonization.This is because, during the carbonization process, cellulose compounds aromatize to form polyaromatic structures, allowing the O-H groups to connect to aromatic compounds [34].The dehydration of the biomass brought on by an increase in temperature, which results in the breakdown of cellulose, lignin, and hemicellulose, is another factor contributing to the reduction in hydroxyl groups after heating [17].The spectra of the biochar samples revealed a reduction in hydroxyl groups as a result of the high temperature-induced dryness of the biomass.

Figure 2
Results of FTIR analysis of biochar

Scanning Electron Microscopy (SEM) Analysis
Figure 3 illustrates the surface shape of biochar before and after the pyrolysis process, as part of the SEM study used to examine the morphological structure of the material.There is a sizable distinction.The biochar's surface form was still quite regular and had tight pore morphologies prior to processing.The biochar's surface shape changed significantly following the pyrolysis process, and it was seen that the pore structure had enlarged and the surface had become uneven.The heating procedure that transformed the morphological form of the leaf waste into biochar was what resulted in the change in the biochar's morphological form.The same circumstances were also attained in Vieira et al.'s [17] study on rice husk pyrolysis, where it was discovered that rice husk shape changed with temperature changes rather than at constant temperatures.Several organic molecules evaporate, changing the form of the surface [35].The increased pore size in Figure 3 demonstrates how the heating process without oxygen can enlarge the pores of the biochar, allowing for the use of the material as both an adsorbent and a fuel source.The biochar surface develops an ionic charge that can be utilized in ion exchange processes due to the presence of functional groups such as phenolic, carboxylic, lactonic, carbonyl, and pyranose [35].

Summary
The application of biochar as a renewable energy source can solve the problem of waste management in city parks, especially the problem of climate change, and also increase soil fertility.Some things that are important in the context of an urban park waste management approach by converting city park waste from sources to biochar are the availability of sufficient raw materials, a study of the characteristics of garden waste, the existence of appropriate technology, and the benefits of products that can be used practically and economically by the community.The availability of raw materials in abundant quantities with characteristics that have the potential to be developed as an energy source in the form of biochar or briquettes is one solution that has been a problem of processing waste from source.Besides that, greenhouse gas emissions will be reduced because there is no transportation of waste to landfills.The problem faced in city park waste management is the design of pyrolysis technology with a capacity that is adjusted to the needs.In addition, biochar products have a higher selling price compared to compost, so to maintain the sustainability of waste management from sources to biochar, socialization regarding the use of biochar as an energy source, as well as a substitute for fertilizer, is needed so that it changes the community's paradigm towards the use of biochar from city park waste.

Conclusion
Biochar can be a solution to solve the problem of sustainable city park waste management.The high amount of yield in the process without a catalyst shows that the production of biochar can be carried out in a practical and simpler technology with relatively low temperatures.The characteristics of biochar indicate that there are no harmful minerals with a high calorific value and low sulfur content which has the potential to be used as a sustainable energy source and an effective strategy in sustainable manner in urban park waste management

Figure 3
Figure 3 SEM analysis results of biochar (a) before pyrolysis, (b) after pyrolysis

Table 3
Results of XRF analysis of biochar products without catalyst