Life Cycle Assessment Model for Biomass Fuel Briquetting

PURPOSE: Previous Life Cycle Assessment (LCA) studies of biomass briquetting have shown wide variations in the LCA outcomes as a result of variations in LCA methodological parameters and briquetting technological parameters. An LCA model of biomass briquetting was therefore developed to enable transparent comparison of life cycle environmental impacts of briquetting with individual or blends of biomass feeds with a variety of technological options. METHODS: The model was developed according to the standard LCA procedure of ISO14044. A comparative approach was utilised, and a set of integrated excel worksheets that describe process flows of material, energy and emissions across different units of the briquetting process was used in developing the model components. RESULTS: The main model components include materials and process inventory databases derived from standard sources, main process calculations, user inputs and results sections. The model is open-access in a user accessible format (Microsoft Excel). A representative case study with mixed rice husks and corn cobs was used in validating the model. Results showed that the briquetting unit made the largest contribution, 42%, to the total life cycle operational energy of the briquetting system. For all the blends of rice husks and corn cobs explored in this study, the total life cycle energy of briquetting was in the range 0.2 to 0.3 MJ/MJ. For the same blend ratios, a total life cycle energy of briquetting in the range 0.2 to 1.7 MJ/MJ was also obtained with change in other LCA input parameters, in a sensitivity test. An increase in rice husk content of the blend increased the environmental impact of briquetting in terms of global warming potential (kg CO₂-eq), acidification potential (kg SO₂-eq), human toxicity (kg 1,4-DB-eq), ozone layer depletion (kg CFC-11-eq), and terrestrial ecotoxicity (kg 1,4-DB-eq) per MJ briquette energy content, as it was associated with a lower briquette density, which increased the energy required for handling.