Anaerobic Digestion of Lignocellulosic Substrates: Benefits of Pre-Treatments

Abstract

This paper offers a review of the most actual pre-treatment technologies applied to lignocellulosic biomasses to produce methane. By reviewing the recent literature findings, we aim to explain the rationale behind the pre-treatment selection, how the substrate composition influences the choice, and the effect of each treatment on the lignocellulose fraction. The well-known anaerobic digestion is still a hot topic as proved by the number of scientific published papers. To increase competitiveness in the energy production market, the methane production has to be maximized; lignocellulosic biomass feedstock needs a pre-treatment step to be better exploited. The increased biomass conversion efficiency will positively influence the cost-benefit ratio. Lignocellulosic biomass duly pre-processed has proven to be a valid feedstock option in modern anaerobic digestion plants. The strengths of the biogas as an energy carrier are explained outlining the current role of anaerobic digestion among the available processes to recover energy from biomasses. The pre-treatments presented here are grouped in three traditional main categories (physical, chemical, and biological), even if the most recent and successful applications are a combination of more processes, and a sharp separation is not always applicable. There is no one best treatment technology, but the choice is dependent on biomass characteristics, process parameters, and plant size. Therefore, the trend is toward the application of combined technologies to maximize biogas production while reducing inhibition effects.