Abstract

Agricultural waste poses significant environmental, economic, and social challenges resulting from the production and processing of various agricultural commodities. The accumulation of agricultural waste has adverse effects on the environment, including soil and water pollution, greenhouse gas emissions, and biodiversity loss. Additionally, it leads to economic losses and health risks, necessitating attention from policymakers, researchers, and farmers. This study addressed these concerns by exploring the feasibility of converting vegetable waste into charcoal briquettes. The research objectives are twofold: (1) to determine the levels of moisture content, volatile matter, and ash content in vegetable waste charcoal briquettes, and (2) to compare these levels with those of commercial charcoal briquettes. The study was conducted at the Malaybalay City Public Market, known for its diverse selection of locally grown fresh fruits and vegetables. The collected vegetable waste was securely transported in trash bags/sacks for carbonization. Subsequently, the carbonized vegetable waste briquettes were assessed based on moisture content, volatile matter, and ash content levels. Based on the results, briquettes made from vegetable waste and cassava starch are a promising and sustainable alternative to traditional charcoal briquettes, offering advantages such as increased combustion efficiency, reduced emissions, and prolonged burning duration. Moreover, the t-test results revealed that there is a significant difference in ash content and volatile matter levels of vegetable waste and commercial briquettes. This means that vegetable waste briquettes have the potential for more effective burning than commercial briquettes. However, the t-test revealed that the level of moisture content of the vegetable waste and commercial briquettes are not significantly different from one another. This means that the moisture content of commercial briquettes and briquettes made from vegetable waste is not significantly different from each other. Therefore, briquettes produced from vegetable waste are a promising alternative to traditional charcoal briquettes. Lastly, it is recommended to examine the impact of various binders on the properties of vegetable briquettes, as well as the potential utilization of different types of agricultural waste as feedstock for briquette production.

1. Introduction

Agricultural waste is a growing concern as it has significant environmental, economic, and social impacts; a significant environmental concern that arises from the agricultural industry, resulting from the production and processing of various agricultural commodities. Agricultural waste refers to the residues generated from the production, processing, and consumption of agricultural products. ¹ These wastes include crop residues, manure, animal, agro-industrial, and food waste. The accumulation of agricultural waste has led to several negative impacts on the environment, such as soil and water pollution, greenhouse gas emissions, and loss of biodiversity ^{2 3}. Agricultural waste can lead to economic losses and health risks and requires attention from policymakers, researchers, and farmers ⁴. Finding ways to reduce the generation of agricultural waste and utilize it sustainably could lead to environmental, economic, and social benefits.

In the Philippines, agriculture is one of the most important sectors contributing to the country's economic growth and providing livelihood to a significant portion of the population. However, this sector also generates a significant amount of vegetable waste, which poses various environmental and health hazards. The agriculture sector in the Philippines produces a large amount of organic and inorganic waste. The Philippines produces about 35 million tons of vegetable waste annually, revealing that the management of agricultural waste in the country needs to be improved, and there needs to be more awareness among farmers and local government units about the proper disposal and utilization of these wastes. ^{5 6} The vegetable waste problem in the Philippines is a complex issue affecting the environment and the economy.

Malaybalay City, Philippines, is the capital of the province of Bukidnon, located in the Northern Mindanao region of the Philippines. The city's economy is heavily reliant on agriculture. As a result, a considerable amount of vegetable waste is generated annually. The Malaybalay City Environment and Natural Resources Office (CENRO) and the Department of Agriculture (DOA) 2020 have reported that vegetable waste significantly contributes to the city's economic dependence on agriculture. This includes generating around 20 tons of vegetable waste per day, mainly from the processing of vegetables. This waste is mainly generated in landfills or burned, resulting in the emission of greenhouse gasses. This accumulation of agricultural waste poses several environmental and health hazards, including air and water pollution, soil degradation, and the proliferation of disease vectors ^{7 8}.

One of the major limitations of vegetable waste is the management in the country as well as the lack of appropriate technologies and infrastructure to handle and dispose of waste properly. ⁹ Many rural areas need access to proper waste management facilities, such as landfills or composting facilities, leading to illegal dumping and burning of agricultural waste ¹⁰. Furthermore, existing waste management facilities in urban areas often need to be increased to handle the volume of vegetable waste generated by the large agricultural sector in the Philippines ¹¹. There is a need for more comprehensive laws and regulations that will provide clear guidelines and standards for waste management. ¹² The gaps and limitations of agricultural waste management in the Philippines are identified as a need for appropriate technologies and infrastructure, inadequate policies and regulations, and a lack of knowledge and awareness among farmers and local communities. To address this problem, the government, private sector, and local communities must implement sustainable waste management practices and promote renewable energy sources.

Briquetting compresses biomass or other materials into denser and more convenient forms, such as cylindrical or square blocks, using a mechanical press or extruder. Briquetting has gained significant attention recently as a promising strategy to reduce greenhouse gas emissions, promote sustainable development, and create new business opportunities in the bioenergy and circular economy sectors. Briquettes can be made from biomass feedstocks, such as agricultural residues, forestry residues, municipal solid waste, and energy ¹³. Biomass briquettes can be used for various purposes, such as replacing traditional solid fuels for cooking, heating, and industrial processes or as feedstock for power generation or biofuel production ^{14, 15}.

In this context, Malaybalay City in the Philippines noted for its extensive agricultural resources, has the potential to use vegetable waste as a raw material for briquettes. ¹⁶ Considering Chinese pechay (Brassica rapa subsp. Pekinensis), Cabbage (Brassica oleracea var. capitata), and Carrot (Daucus carota) peelings are typical waste in the City's public market, and they were used in the study as the primary source of vegetable waste. Customers and retailers frequently throw away these vegetables due to flaws, spoilage, or an excess supply. As a result, they are classified as agricultural waste, which includes by-products, residues, and wastes created during agricultural production, processing, and distribution.

With that said, the vegetable waste from Malaybalay City has the potential to be used as feedstock, a raw material for making briquettes which can provide an alternative source of fuel and help to reduce environmental pollution. Further, this study aimed to investigate the possibility of using agricultural waste as raw material for briquettes.

2. Methodology

This study utilized a quantitative research design, which involved collecting and analyzing numerical data to test a hypothesis and answer research questions. The study's primary objective was to investigate the feasibility of converting vegetable waste into coal briquettes as a fuel source. To achieve this objective, the study employed the quantitative method, which involved procedures for testing hypotheses and generating knowledge.

The data were analyzed using means, standard deviation, and independent samples t-tests.

Vegetable waste, such as Chinese pechay (B. rapa subsp. Pekinensis), cabbage (B. oleracea var. capitata), and carrot (D. carota) peelings were manually collected from numerous vegetable vendors in the Malaybalay City Public Market before being transported by vehicle to Maramag, Bukidnon. Only non-rotten vegetable waste was carefully selected for collection, while rotten vegetables were eliminated. Once the briquettes had been made, they were transported to Davao Analytical Laboratories, Inc., where they underwent lab tests for criteria including moisture content, volatile matter, and ash content. The Davao Analytical Laboratories, Inc. is a reputable testing laboratory with expertise in analyzing fuels and other materials. The outcomes of the tests performed by this lab offered a more thorough evaluation of the quality and usability of the briquettes.

3. Results and Discussion

When the chemical characteristics of briquettes created from vegetable waste and those manufactured from commercial trash are compared, it is clear that there are substantial variances between the two types. The briquette made from vegetable waste has been shown to have a much greater ash content, which is one of the key differences. This increased ash concentration shows that the briquette has a larger presence of inorganic components and contaminants, which has the ability to alter its combustion properties as well as its overall energy efficiency.

Table 2 displays the results of a t-test to compare the ash content of commercial briquettes to that of briquettes made from vegetable waste. The amount of inorganic material that is left over after a substance has been burned is referred to as its ash content. Briquettes made from vegetable waste have an average ash level of 23.17% (SD 0.80%), while commercial briquettes have an ash percentage of 3.83% (SD 1.40%). According to the results of a t-test that was carried out at a significance level of 0.05, there is a statistically significant difference in the amounts of ash that are contained in the two different kinds of briquettes. This suggests that briquettes made from vegetable waste typically have a higher ash content than those made from other types of waste, making them more suited for use in some kinds of combustion processes.

Moreover, using briquettes generated from vegetable waste could be more environmentally beneficial than commercial briquettes because vegetable trash is a renewable resource, and vegetable waste briquettes could have lower carbon emissions than commercial briquettes. It is similar to a study of ¹⁷, which stated that higher ash content is associated with increased combustion efficiency, decreased emissions, and enhanced heat transfer. Also, vegetable waste may include a higher proportion of organic matter, which, when burned as briquettes, results in a greater quantity of ash ¹⁸.

The vegetable waste briquette showed the same moisture content results as commercial briquettes and exhibited a slightly reduced moisture content, suggesting a possible increase in its energy content and enhanced combustion efficiency compared to the commercial briquette. The higher moisture content of the commercial briquette necessitates additional energy for drying, thus making the vegetable waste briquette a more desirable option for energy utilization and overall effectiveness during combustion processes.

Table 4 displays the results of a t-test that compared the amount of moisture found in briquettes made from vegetable waste to that found in commercially produced briquettes. Briquettes made from vegetable waste have an average moisture content of 30.20% (standard deviation = 1.13), but the average moisture content of commercial briquettes is 32.67% (standard deviation = 3.0).

According to the results of a t-test performed at a significance level of 0.05, the amount of moisture content contained inside the two different types of briquettes is not statistically significant (the p-value is more than 0.254). This indicates that the moisture content of commercial and briquettes made from vegetable waste is similar. It can be explained based on another study which stated that briquettes compressed and air-dried at the same time duration and placed in a well-ventilated area would have the same moisture content ^{19 20}. Because of this, the amount of moisture that is contained in briquettes made from vegetable waste is not noticeably different from the amount of moisture that is contained in commercial briquettes.

The briquette made from vegetable waste has a greater volatile matter concentration than other briquettes, suggesting that it may be ignited more efficiently and release more flammable gases, possibly contributing to a more effective combustion process. Additionally, tests by ²¹ and ²² indicate comparable findings. In these studies, the researchers examined their biomass briquettes' ash level, moisture content, and volatile matter. Evidence suggests that vegetable waste briquettes, compared to commercial briquettes, tend to have a greater ash level and a higher volatile matter content.

The results of the t-test for the volatile matter content of vegetable waste briquettes and commercial briquettes are presented in Table 6. Volatile matter refers to the vaporizable portion that affects the efficiency of combustion. The mean volatile matter content of vegetable waste briquettes is 27.4% (SD 3.81576), whereas the mean volatile matter content of commercial briquettes is 19.3333% (SD 3.86954). The t-test reveals a statistically significant difference at the 0.05 level (p-value 0.031), indicating that vegetable waste briquettes contain substantially more volatile matter than commercial briquettes.

Briquettes made from vegetable waste contain more volatile matter than commercial briquettes, which may indicate that they have the potential for more effective burning. This is supported by another study which found that a more excellent volatile matter content led to an increase in the calorific value, the efficiency of combustion, and the amount of time it took to burn ^{23 24}.

4. Conclusion

Considering the findings of the study as answers to the stated problems, these conclusions were drawn from the study:

Briquettes produced from vegetable waste are a promising alternative to traditional charcoal briquettes with higher ash content, low moisture content, and higher volatile matter levels. This proves vegetable waste briquettes contribute to increased combustion efficiency.

Moreover, vegetable waste briquettes are significantly different from commercial briquettes in terms of ash content and volatile matter levels. This implies that they have a longer burning duration than conventional charcoal briquettes and are more efficient. However, there is no significant difference in the moisture content levels of vegetable waste and commercial briquettes. This suggests that both vegetable waste and commercial briquettes are not significantly different from each other and have good moisture content levels.

5. Recommendations

This study recommends using binding materials other than cassava starch to enhance the quality and properties of briquettes, leading to improved efficiency, performance, and sustainability. The investigation should focus on exploring the physical properties of vegetable waste charcoal briquettes, including density, calorific value, and combustion characteristics. A comparison of these properties with commercially available charcoal briquettes would help evaluate the viability of vegetable waste as a raw material.

Furthermore, future research should examine the impact of other binding materials on the properties of vegetable briquettes and the potential utilization of different types of agricultural waste as feedstock for briquette production.

To ensure the overall quality, strength, combustion performance, and shelf life of vegetable waste briquettes, it is recommended that they undergo an adequate curing period. This would significantly enhance their characteristics and suitability for various applications.

Acknowledgment

The authors would like to express their sincere and heartfelt gratitude to all those who played a pivotal role in the success of this study. We are deeply indebted to Mr. Jhovel Roy D. Calo, our esteemed research adviser, for his invaluable assistance and expertise, which were instrumental in ensuring the triumph of this paper. Additionally, we extend our utmost appreciation to Mr. Ian Jay P. Saldo for his unwavering dedication, countless sleepless nights of revising, and numerous consultations, all of which had a profound impact on the significant improvement of this paper. Undoubtedly, the collective efforts and unwavering commitment of all individuals involved contributed equally to the advancement of this study.

References