A mathematical model to predict the heating-up of large-scale wood piles

Microbial communities in large-scale wood piles and their effects on wood quality and the environment

“…To evaluate storage impact on fuel quality parameters such as heating value, ash composition, moisture content, percentage of fine particles, slagging/fouling indices and the combustion profiles obtained from thermogravimetric analysis were analysed (Casal et al 2010). Factors that alter the energetic quality of stored wood chips have been characterised as (1) particle size and comminution method (Scholz et al 2005;Nati et al 2010;Zamorano et al 2011); (2) tree species composition (Röser et al 2011;Scholz et al 2005); (3) geometries of the piles (Ferrero et al 2011); (4) geographical location (Röser et al 2011); (5) methods for piling such as covered, compacted or ventilated (Jirjis 1995a, b); (6) time of storage (Noll et al 2010b;Ferrero et al 2009); (7) moisture content during piling (Filbakk et al 2011;Bedane et al 2011); (8) storage season (Brand et al 2011); and (9) microbial decomposition of stored wooden biomass (see Table 1). The most important factor affecting the quality of wood as a fuel is mainly attributed to moisture content of wood (Filbakk et al 2011;Bedane et al 2011;Lyons et al 1985;Jirjis 1995c).…”

“…Moreover, the published studies of microbial communities in wood chip piles and wood logs can be regarded as case studies rather than large statistical analyses. This is mainly due to their large-scale (Ferrero et al 2009), inadequate sampling strategies (Lindner et al 2011), and the multi-parametric setups (Noll et al 2010b) more likely case studies rather than large statistical analyses. Therefore, universally valid statements of the composition and function of a defined microbial community present in wood chips piles is difficult up to now.…”

“…respiration), slow oxidative reactions and physical processes, leads to exponentially increasing temperatures which can end up in self-ignition (Ferrero et al 2011). Self-ignition processes in wood chip piles was modelled and thereafter concluded that critical temperatures were only feasible when the initial heat was generated by microbial activity (Ferrero et al 2009; see also Due to increasing temperature inside wood chip piles, the presence of thermophilic microorganisms is dominating while other types are limited in such environments (Scholz et al 2005). Therefore, after a temperature change, a shift in the community composition and function is reasonable as frequently demonstrated in other environments (Conrad et al 2009;Noll et al 2010a).…”

“…After optimal temperature for respective microorganisms is exceeded, microbial activity will decrease to maintenance metabolism and outcompeted by more thermophilic microorganisms. Although few microorganisms can cope with high temperatures up to 110°C (Schönheit and Schäfer 1995), the overall microbial activity and in particular the wood decomposition activity will decrease in wood chip piles already at temperatures above 80°C (Ferrero et al 2009). …”

Heating processes during storage of Miscanthus chip piles and numerical simulations to predict self-ignition

“…The demand for solid biofuels is increasing and the resultant demand for biomass has resulted in an increase in the number of open air biomass storages and thus the possibility of their selfignition seems destined to grow in the coming years (Ferrero, Lohrer, Schmidt, Noll, & Malow, 2009). The increase in demand for biomass results in storage issues and a wider harvest window, from January to April, may be used to offset the associated storage space issues.…”