Development of rice and coffee husk briquettes as sustainable fuel sources for domestic cooking applications in Uganda

In this project, groundnut shells and bagasse briquettes from agricultural wastes were developed with cassava and wheat starch binders using low pressure and high pressure techniques. In the low pressure technique, briquettes were produced after carbonization of groundnut shells and bagasse. The resulting bio-char was mixed with 30, 50, 70 and 90 g of cassava and wheat flour starch binder for each 1000 g of groundnut shells and bagasse bio-char. Groundnut shell briquettes were also developed under high pressure (230 MPa) using groundnut shells (1000 g) without a binder, groundnut shells (1000 g) with cassava flour starch binder (250 g) and groundnut shells with wheat flour starch binder (250 g). Thermophysical properties of the briquettes were determined using thermo-gravimetric analysis. A Bomb calorimeter was used to determine the higher heating values of the briquettes. Thermal characteristics were determined by observing the flame temperature during combustion. The mechanical integrity of the briquettes was determined using the drop test method. The higher heating values for groundnut shell and bagasse briquettes developed using low pressure techniques were between 21 and 23 MJ/kg for both cassava and wheat starch binders. The results were all above the 16 MJ/kg average recorded for noncarbonized groundnut shell briquettes developed under high pressure.

Characterization of briquettes developed from rice and coffee husks for domestic cooking applications in Uganda

The goal of this project was to develop briquettes from coffee and rice husks agricultural wastes as sustainable fuel sources for domestic cooking applications. Clay and cassava starch were used as binders. Physical properties of the coffee husks and rice husks as well as the developed briquettes were determined using Thermogravimetric analysis. Higher heating value (HHV) results were determined using bomb calorimetry. Drop test method was used to determine the mechanical and storage integrity of the developed briquettes. The results showed that the type of binder used in the development of the briquettes significantly affected both their physical properties and calorific values. Average higher heating values for briquettes developed with cassava starch binder ranged from 21.9 to 23.0 MJ/kg for coffee husks and 15.9-16.6 MJ/kg for rice husks. For coffee and rice husk briquettes developed with clay binder, average higher heating values ranged from 13.0 to 19.5 MJ/kg and 9.5-13.8 MJ/kg, respectively. Generally, cassava starch binder imparted higher drop strengths (over 95%) onto the briquettes than clay binder material. The characteristics were influenced by the physical properties of the raw biomass material as well as the high SiO2 ash in the clay binder.

Emissions and emission factors for Dichrostachys cinerea, Morus Lactea, Piliostigma thonningii, Combretum molle, and Albizia grandibracteata firewood species and their charcoals

Firewood and charcoal are the most dominant sources of fuel for domestic cooking applications in sub-Saharan Africa. In this project, performance and emission characteristics of firewood and charcoal from five commonly used species, namely, Dichrostachys cinerea, Morus Lactea, Piliostigma thonningii, Combretum molle, and Albizia grandibracteata were obtained. The water boiling test and emissions monitoring system for CO, CO2, and PM2.5 were used to determine fuel and energy consumption, thermal efficiency and emissions, and emissions’ factors. The results showed that firewood combustion required higher energy consumption compared to charcoal combustion. High-power thermal efficiency was the highest (> 45%) for all charcoal derived from the firewood species. During hot-start, cold-start, and simmering operations, it was observed that thermal efficiencies were generally higher for charcoal fuels (>80%) compared to the firewood (< 40%) from where they were pyrolyzed. Firewood has a much lower indoor CO emissions footprint when compared to using charcoal. Nonetheless, CO emission levels for both firewood and charcoal exceed the Environmental Protection Agency (EPA) guidelines of 35 ppm (1-h average). CO2 emission factors are the most dominant and highest contributors to greenhouse gas emissions from household use of firewood and charcoal. Overall, this work re-affirms the need for proper ventilation when firewood and charcoal are used in combustion.

State-of-the-art review on flame retardancy and thermal stability of agricultural residue fiber-reinforced polylactic acid

Bio-composites containing natural fibers and biopolymers are an ideal choice for developing substantially biodegradable materials for different applications. Polylactic acid is a biopolymer produced from renewable resources and has drawn numerous interest in packaging, electrical, and automotive application in recent years. However, its potential application in both electrical and automotive industries is limited by its flame retardancy and thermal properties. One way to offset this challenge has been to incorporate natural or synthetic flame retardants in polylactic acid (PLA). The aim of this article is to review the trends in research and development of composites based on agricultural fibers and PLA biopolymers over the past decade. This article highlights recent advances in the fields of flame retardancy and thermal stability of agricultural fiber-reinforced PLA. Typical fiber-reinforced PLA processing techniques are mentioned. Over 75% of the studies reported that incorporation of agricultural fibers resulted in enhanced flame retardancy and thermal stability of fiber-reinforced PLA. These properties are further enhanced with surface modifications on the agricultural fibers prior to use as reinforcement in fiber-reinforced PLA. From this review it is clear that flame retardancy and thermal stability depends on the type and pre-treatment method of the agricultural fibers used in developing fiber-reinforced PLA.