Progress towards the standardization of test parameters and protocols for evaluating densified fuel products

Densification technologies used in managing biomass and coal fines to produce fuel briquettes or pellets are gaining rapid acceptance and application due to the widespread uptake of renewable energy. This has resulted in the mushrooming of many standard and non-standard evaluation tests for densified solid fuels in this industry. These tests are sometimes inconsistently applied especially if the available options for evaluation, underlying assumptions and principles of the test methods chosen are misunderstood. A critical review of the fuel briquettes evaluation tests to understand their relevance, strengths and limitations is necessary to advance public and research knowledge. This study investigated current methods of standardization to identify best practices, inconsistencies, trends and gaps in the application of fuel briquettes testing protocols. Procedures for evaluating combustion or thermal properties include calorific value, burn rate, open air combustion test and water boiling test; ignition time; after-glow test; specific fuel combustion or thermal efficiency were discussed. Physical and chemical property evaluations involved densities and related ratios, proximate and ultimate analyses. Equally important are mechanical parameters frequently informed by tensile/compressive strength, impact resistance, friability and water resistance. As renewable densified fuels gain more global popularity, it is critical to have a uniform standard of evaluating their quality.