University of Vaasa - Vaasan yliopisto

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on the other hand state that a large-scale wood chipper produces wood chips at the
manipulating site in the desired quality and quantity, which are then delivered justin-time
to the plant. A storage facility for solid roundwood and wood chips serves as
a buffer.
Börjesson and Berglund (2007) assess that 5 to 10%, or even up to 20%, of the total
amount of biogas produced at biogas plants is generated during the storage of
digestates. Uncontrolled losses of methane may account for approximately 0.5 to 1%
of the total methane flow at the plant. Therefore, it is of special importance to collect
the biogas produced during storage, or to cleanse excess gas in a compost filter
(Börjesson & Berglund 2006).
Logistics in general
Logistics is considered to have major impacts on the bio-energy plants’ profitability,
while scale effects are very significant. Main logistic variables are for example
specific vehicle transport costs, vehicles capacity or distribution density (Caputo et
al. 2005). Other operational issues of high relevance is finding effective storage and
feeding mechanisms for the biomass (Perry & Rosillo-Calle 2008). Power generated
from biomass is regarded to be more expensive than power from fossil fuels partly
due to high logistic costs in the biomass supply chain. The low calorific value and
low bulk density of biomass in comparison to coal and oil necessitates a larger
number of lorry movements (Caputo et al. 2005). Thus, gasification is found to be
more beneficial than combustion under adverse logistic conditions, marked by high
biomass specific transport costs, low vehicles capacity and biomass distribution
density, particularly in case of ample plant capacity (Caputo et al. 2005).
Ayoub et al. (2007) highlight the important competency of managing biomass
logistics and power plant positioning by optimising the transport routes through
network optimisation techniques. Sustainability of biomass exploitation is ensured by
determining which biomass is feasible for collection in what quantities, the collection
points and, hence, their geographical position. Puy et al. (2008) and Madlener and
Bachhiesl (2007) also confirm that supply logistics play an important role and often
constitute the restricting factor when establishing bio-energy systems.
System design
The biomass chain may be disassembled into biomass cultivation and harvesting,
loading, transportation, handling and warehousing, processing of the feedstock,
disposal or recycling of residues such as ashes and digestate, and production of
ancillary inputs (agrochemicals, transport fuels, equipment) (Rentizelas,
Tatsiopoulos & Tolis 2009; Elghali et al. 2007). Introducing domestic biomass
supply systems require considerable logistical mobilisation as well as infrastructure
for waste recovery and the use of multi-biomass feedstock (Perry & Rosillo-Calle
2008). On the other hand, multi-biomass supply chains also entail potential for cost
reduction since they allow spreading capital costs and dropping warehousing