11.2.1.1 Bark and Wood Residues from the Pulp and Paper Sector

In 2007, forest mills in the United States of America (USA) produced about

86.7 million dry tons of primary mill residues [17], which were composed mainly of bark, sawdust, wood chips and shavings. Of this amount, over 35 million dry tons of wood residues were used as combustibles and could have been used as feedstock for bioreflneries. Wood pyrolysis has been shown to generate high-value products, such as bio-char (promising activated carbon) and bio-oil. Ensyn and DynaMotive are two companies running commercial-scale pilot plants, which convert wood residue via fast pyrolysis. There are many incentives to develop in situ bioreflneries (close to pulp and paper plants) in order to avoid significant issues related to transportation and storage.

11.2.1.2 Black Liquor

Black-liquor pyrolysis has been the subject of several studies, but the main efforts have been invested towards gasification. This has been motivated by the fact that black-liquor pyrolysis generates too much solid char [18], which would need to be burned to release the inorganics. The advantage of gasification is that it includes the char combustion process. Thus far, pyrolysis has been mostly considered in the scientific literature as a precursor step to gasification. Consequently, it will not be considered as a potential feedstock for pyrolysis aiming at biorefineries.