Investigation of Factors Affecting the Dilute Acid Pretreatment of Napier Grass Using a Full Factorial Statistical Approach

Abstract

Recent concerns over economic and environmental issues associated with fossil-based fuels and products usage have sparked interest in renewable alternatives. Lignocellulosic biomass such as Napier grass (Pennisetum purpureum) can be green processed to generate an additional revenue stream (i.e., juice) and solid fiber stream. Fibers can be converted into biofuels and biobased products, but requires pretreatment to unlock structural sugars. Dilute acid pretreatment has been widely studied due to low cost and its effectiveness in disrupting the biomass structure, however limited research is available on how the factors of acid concentration, time, temperature and solid:liquid ratio and their interactions affect sugar release. To investigate this, two full factorial experimental designs were used. Compositional analysis of the feedstock indicated no significant changes occurred over three separate harvests except for ash content. Statistical analysis indicated that temperature, acid concentration and their interaction had the most impact on sugar release. Solid:liquid ratio had a highly linear relationship to sugar release (i.e., lower solids loading rate yielded higher sugars) and had a significant interaction with temperature. Knowledge about these factors is critical to the optimization, scale up and design of bioprocessing facilities.