Science and Engineering Connect

Study on the Potential of Co-pelletizing Fuel from Municipal Wastewater Treatment System Sludge, Tea Ground, and Coffee Ground

Kantima Kaewtapan — 2024-12-27

Background and Objectives: To utilize sludge from wastewater treatment system and the high calorific value characteristics of tea and coffee grounds to their maximum benefits, the present research used these materials to produce co-pellet fuel. The appropriate ratio for fuel production and the characteristics of the co-pellet fuel were then investigated.

Methodology: Experiments were conducted at different ratios of municipal wastewater treatment sludge, tea ground and coffee ground of 1:1:1, 1:2:1, 2:1:1, 3:1:1, 3:1:2 and 3:2:1. The resulting samples were assessed for their fuel characteristics according to the standards set by the American Society for Testing and Materials (ASTM).

Main Results: The sludge from the wastewater treatment system was noted to be unsuitable for fuel production. On the other hand, co-pellet fuel could be produced by mixing the sludge with tea ground and coffee ground at a ratio of 1:1:2. The resulting mixture had a moisture content of 20%, an ash content of 5.96 ± 0.97% and a heating value of 4,796 ± 49 kcal/kg. Additionally, when a 1:2:3 ratio was used, the co-pellet fuel exhibited the longest combustion time, lasting 385 seconds.

Conclusions: The co-pellet fuel prepared at a ratio of municipal wastewater treatment sludge, tea ground and coffee ground of 1:1:2 could be effectively pelletized. Its ash content and heating value meet the standards outlined in the guidelines for processing waste materials into fuel pellets and briquettes established by the Department of Industrial Works. Additionally, they comply with the Industrial Product Standard for Compressed Biomass Fuel Pellets, as specified by the Thai Industrial Standard (TIS) 2772-2560.

Practical Application: Co-pellet fuel produced from the sludge of municipal wastewater treatment system in combination with tea grounds and coffee grounds can serve as an alternative energy source for households and has the potential to be transferred to industrial applications.

Utilization of Cassava Pulp from Starch Production Process and from Biogas System to Produce Value-Created Micro- and Nano-Cellulose

Chittaphone Banditvong — 2024-12-27

Background and Objective: Cassava pulp (CP) is a solid waste byproduct from the starch extraction process in the cassava industry, presenting significant environmental challenges such as foul odor and water contamination. In Thailand, the cassava industry has adopted the circularity concept to practice resource minimization, waste reduction, and value creation. Strategies have been developed to utilize CP for energy generation and low-value applications such as animal feed. Additionally, CP can be converted into biogas through anaerobic digestion. Another promising approach is the production of high-value products such as micro- and nano-cellulose. Micro-cellulose consists of micro-sized fibers isolated from plants, and can serve as a reinforcing material in the textile and pulp industries. Nano-cellulose, on the other hand, exhibits such properties as biodegradability and high surface area. These properties make micro-cellulose and nano-cellulose ideal for use as reinforcing polymers, food packaging, and pharmaceuticals. The present study aimed to produce micro- and nano-cellulose from cassava pulp obtained from (i) a starch production process and (ii) a biogas system (CP and CP_biogas, respectively) using acid hydrolysis.

Methodology: The study focused on the extraction of micro-cellulose and nano-cellulose from CP and CP_biogas. Starch was removed from cassava pulp using enzymatic treatment (α-amylase). Lignocellulosic fiber was then isolated using 0.7% (w/v) NaClO₂ and alkaline with 17.5% (w/v) NaOH to obtain micro-cellulose. Subsequently, the micro-cellulose was hydrolyzed with H₂SO₄ to produce nano-cellulose. The two-factor Central Composite Design (CCD) was utilized to optimize the design of the experiment. The two factors were H₂SO₄ concentration, ranging from 46-74% w/w and reaction time ranging from 48-132 min. In total, 11 experimental conditions were scheduled. The micro-cellulose and nano-cellulose obtained were characterized to determine their crystallinity indices using X-ray diffraction, their particle size using dynamic light scattering, and their morphology using scanning electron microscopy.

Main results: The study revealed that after the removal of starch by α-amylase, 87.5% of the starch was extracted from CP, while CP_biogas had all its starch removed. Following bleaching and alkaline treatment, a fibrous fraction with cellulose contents of 91% and 88% (CP and CP_biogasrespectively) was obtained. The micro-cellulose extracted from CP and CP_biogas had average particle sizes of 104.9 µm and 106 µm and crystallinity indices of 68% and 70%, respectively. The optimal hydrolysis conditions for nano-cellulose extraction from CP and CP_biogas were 60% H₂SO₄ and 132-min reaction time. Nano-cellulose particles smaller than 100 nm comprised 10% and 12% of the total nano-cellulose yields from CP and CP_biogas, respectively, with an increase in crystallinity index to 71% and 76%. Statistical analysis reveals that increasing the reaction time could result in a higher yield of nano-cellulose.

Conclusions: Micro-cellulose and nano-cellulose derived from CP and CP_biogas in exhibit promising characteristics, including crystallinity indices of 71% and 76% for nano-cellulose obtained from CP and CP_biogas, respectively. Such characteristics demonstrate significant potential for innovative industrial applications in the paper, composite, and textile industries. In comparison, commercial nano-cellulose typically has a crystallinity index exceeding 80%; the nano-cellulose obtained in this study demonstrates crystallinity indices slightly below commercial standards. Utilizing solid wastes such as CP (CP and CP_biogas) to produce micro-cellulose and nano-cellulose addresses waste management challenges, while creating economic value from a previously underutilized byproduct.

Practical Application: The presented approach aligns with the principles of circular economy, where waste materials are repurposed into valuable resources, enhancing resource efficiency and sustainability. The study highlights the significant potential of converting CP waste into high-value cellulose products, contributing to the advancement of sustainable industrial practices and the development of innovative materials.

Outcomes and Impacts of Research on Waste Management in Thailand in the Fiscal Years 2020-2021

Areeya Obidiegwu — 2024-12-27

Background and Objectives: Investment in research and development (R&D) is a critical function of government in driving multifaceted national development. Given the constraints of public budgets, R&D expenditure should be efficiently utilized to maximize societal welfare. This study aimed to evaluate the outputs and outcomes of a waste management research program (Zero Waste) to determine its economic and environmental impacts on the society.

Methodology: Research impact pathway, project inputs, outputs, outcomes, and impacts of the whole research program were evaluated. An in-depth research impact analysis of the 5 case studies were also conducted, analyzing the economic surplus generated from the utilization of the research.

Results: The research program received funding from the National Research Council of Thailand during the fiscal years 2020-2021, with a total allocation of 153.11 million Baht. The program efficiently allocated resources to achieve its objectives, which align with the national environmental strategies. However, only a subset of research projects demonstrated potential for generating significant impacts, with constraints in the utilization of research outputs, indicating a low level of sustainability in research investment. All selected research projects yielded positive net present values that justified the research investment, with the highest net benefit of THB 22.7 million. Research projects across different sub-fields produced varying proportions of economic and environmental impacts, reflecting the degree of public good characteristics of the research outputs.

Recommendations: Program Management Units (PMUs), especially those involving the environmental research domain, should focus on measures that enhance research utilization and knowledge transfer. This is particularly important for research projects generating high environmental impacts with greater positive externalities than research with relatively higher economic impacts, which tend to have higher adoption rates. To improve the utilization of these research findings in public policy domains, concrete mechanisms are necessary to create clear linkages with end-users, such as policymakers or relevant government agencies.