Growing global demand and utilization of fossil fuels has elevated wealth creation, increased adverse impacts of climate change from greenhouse gases (GHGs) emissions, and endangered public health. In most developing countries, biomass wastes, which include but are not limited to agricultural residues, are produced in large quantities annually. They are either inefficiently used or disposed of indiscriminately, which threatens the environment. It is possible to convert these wastes, through densification, into high-density and energy-efficient briquettes. Densification of biomass into briquettes presents a renewable energy option as an alternative to fossil fuels. This paper reviews biomass briquetting with reference to biomass resources, feedstock pre-processing, briquetting process parameters, briquetting technology, and briquettes quality evaluation parameters. The review also includes the economic aspect of briquetting relating to costs and feasibility.

The objective of this research was to investigate the quality of hybrid briquettes developed from corncobs (CC) and oil palm trunk bark (OPTB) under a low-pressure densification technique. The materials were combined in varying ratios of CC to OPTB (100:0, 75:25, 50:50, 25:75, 0:100) and wastepaper pulp (10% by weight) was added to each mixture as a binder. The briquettes were produced using a manually operated 20-tonne hydraulic piston press at 28 °C temperature and ≤7 MPa compaction pressure. The mechanical strength of the briquettes was determined by the drop test and compression test methods, while a bomb calorimeter was used to determine the calorific values. The results showed that the physical properties of hybrid briquettes ranged from 9.24–10.00% moisture content, 0.38–0.40 g/cm³ density, and 87.60%–92.00% water resistance. Mechanical strength showed a 98.28%–99.08% shatter index and 18.47–21.75 MPa compressive strength, while calorific values ranged from 16.54–16.91 MJ/kg. The hybrid briquettes fared better than the CC briquettes. The significance of this study lies in the production of briquettes with suitable physical, mechanical and thermal properties by utilizing OPTB which have hitherto not been used, mixed with corncobs. This could bring substantial environmental and socio-economic benefits to rural communities of the developing countries.

Carbon Quantum Dots (CQDs) have exceptionally solid and tuneable fluorescence properties which empower their application in vast fields. The hydrothermal approach is regarded as direct and efficient, through polymerization and carbonization reactions, and has been widely applied to prepare various materials due to the high reactivity of the reactants, easy control of the solution, little harm to the environment and low energy consumption under hydrothermal condition. The attracting feature of this route is that neither any strong acid nor post-synthetic surface passivation is necessary. As of now, a lot of important progress in the hydrothermal synthesis of carbon quantum dots such as materials use as precursors and influence of hydrothermal synthesis parameters. Hydrothermal synthesis is one of the most commonly used methods for preparation of nanomaterials. It is basically a solution reaction-based approach. In this review, the main focus is to review the hydrothermal route for carbon quantum dots using different source of materials and their fundamental characterizations, followed by the influence of hydrothermal synthesis conditions to carbon quantum dots.

This study was carried out to evaluate the physical and thermal characteristics of briquettes made from a mixture of paper pulp and Mesua ferrea leaves. Paper pulp/ground Mesua ferrea leaves mixtures prepared were of 80–20%, 60–40%, 50–50% ratio and 100–0% mixture which served as a reference briquette. The mixtures were densified at a room temperature of 28 °C under three different compression pressures; 5.1, 10.2, and 15.3 MPa. The characteristics of the briquette samples were assessed in terms of moisture content, density, shatter index and calorific value. The findings revealed the following range of values for all samples; moisture content (5.55–12.33%), density (0.24–0.37 g/cm³), shatter index (79.18–99.9%), and calorific values (15.77–18.99 MJ/kg). Specifically, 100–0% briquettes yielded the highest moisture content and the lowest calorific value as expected. In contrast, the 50–50% briquettes yielded the lowest moisture content, highest calorific value and lowest shatter index. The quality of these briquettes was found to be comparable to biomass briquettes produced from other agricultural waste. The novel contribution of this study was the use of garden waste to develop briquettes with appropriate physical and thermal qualities that could serve as alternate fuel sources for local applications.

In Nasarawa state, over 70% of the population are involved in subsistence farming. Varied agricultural resources are produced in millions of tons annually. Large quantity of residues is generated that are either left to rot on farmlands or disposed of by burning in open air. In many rural areas, the residues are also used in their raw form for cooking purposes which is inefficient. The disposal and use of the residues cause pollution in the environment which affects human health. Residues can provide a source of clean and renewable energy in the form of solid biofuel called briquettes through densification. Briquetting is a densification technology that converts residues with a low heating value per unit volume into high density and energy concentrated fuels. This paper offers a perspective on the potentials of agricultural residues in Nasarawa state to produce briquettes as an alternative clean and sustainable domestic cooking fuel. The paper concludes that briquettes could be economically and environmentally friendly alternative to fuelwood. The use of biomass briquettes would reduce dependence on fuelwood, environmental pollution and the amount of time spent on cooking. Adopting the briquetting technology will enhance access to clean and affordable energy in line with the 7th goal of the United Nation’s Sustainable Development Goals.

This study evaluated the technical and economic viability of a household scale composite briquette project. The objectives were to assess the quality of briquettes, estimate the cost of production, and determine the feasibility of the project. Briquettes were made from a blend of corncobs and the bark of oil palm trunk using a manual press. Production cost was estimated from the market price of commodities and specific economic indicators were used for feasibility analysis. Sensitivity analysis was performed on some essential input parameters that may affect the profitability of the project. Economic analysis revealed that the unit production cost of the briquettes was USD 0.16 per kg. The net present value was USD 6755.91 from the sale of briquettes at USD 0.26 per kg. An accounting profit is possible once briquette sales are above the break-even point of 7329.8 kg. Households could save about 25% from their per-capita expenditure on fuelwood when briquettes are utilized. Overall, the household briquette project is technically and economically viable in Nigeria. The significance of this study lies in the provision of a piece of baseline information to encourage local bio-energy development and serve as a guide for stakeholders in Nigeria with a potential interest in investing in briquette technology.