A review of anaerobic digestion of paper and paper board waste

Paper and paper board (PPB) products represent one the largest fractions of municipal solid waste. PPB are mainly composed of lignin, cellulose, and hemicellulose (lignocellulose). Previous research has shown that the anaerobic digestion (AD) of unprocessed lignocellulosic materials is limited by the occurrence of lignin. Additionally, it is well known that removal of lignin improves AD of unprocessed lignocellulosic materials. Unlike unprocessed lignocellulosic materials, PPB are subjected to a series of mechanical and chemical processes during their fabrication, which may have an effect on the AD of PPB. This review aims to (1) summarize the AD of PPB with respect to the compositional and structural changes caused by the papermaking process; (2) evaluate the results of technologies that have been applied to increase the degradability of PPB; and (3) discuss the current and future challenges that involve the AD of PPB. The data analyzed in this review revealed that lignin content only explains 56% of variation in PPB methane yields. Consequently, other properties affected by paper-making processes most likely also influence their AD. Codigestion and pretreatment are potential alternatives to improve AD of PPB. However, to achieve further improvement, research is needed to identify and quantify the non-compositional properties that dictate degradability, and to develop pretreatment processes that can target the rate/yield limiting properties precisely.