Biomass in biogas production: Pretreatment and codigestion

Globally, there is increasing awareness that the implementation of 'waste to energy' technology is one of the best means to achieve sustainable energy development. The most popular approach is the conversion of organic-rich compounds into clean and renewable products by anaerobic digestion (AD). Biogas can be produced from agricultural residues, municipal/industrial biowastes, and sustainable biomass, especially materials that are locally available. However, in many cases, the methane yields obtained from the conventional AD process are regarded as having limited profitability. This paper summarizes the recent knowledge regarding the different strategies that are used to enhance AD efficiency and the methods to strengthen the existing incentives to overcome today's barriers to biogas production. Special attention was given to several approaches used to improve the biodegradability of organic matter and the methane potential of feedstocks, mainly codigestion and pretreatment of single/mixed substrates. The statistical analyses indicated enormous variability among biogas systems, thus, there is a need for unification of the methods applied for process control and the parameters used for the discussion of results. A synchronized methodology is also needed to understand the environmental advantages and drawbacks of selected utilization pathways in biogas production. Currently, the underestimated potential of AD is of growing interest, and pretreatment/codigestion can directly increase the effectiveness of this technology and lead to its optimization. Nonetheless, a proper evaluation of the environmental (e.g., sustainable biomass) and social (e.g., bioaerosol nuisance) aspects is also needed.