Economic Issues of Biomass Energy Conversion - Biomass Gasification, Pyrolysis and Torrefaction - page 35

thermal conversion plant, whether it is a combustion, gasification, pyrolysis,
or torrefaction plant. Fermentation-based plants like ethanol plant would,
however, have different configuration as the feedstock is cereal instead of
lignocellulose biomass.
The cost of biomass conversion depends on its several major processing
steps like:
1. Biomass collection
2. Preprocessing
3. Biomass conversion (torrefaction, pyrolysis, gasification, or combustion)
4. Gas cleaning/product treatment
5. Product utilization (energy or chemical production).
Once the availability of biomass is assured (see Section 2.2 ), the project
moves to the next step of financial analysis. The cost of delivered fuel is
also known from the availability analysis. The financial analysis involves
assessment of capital and operation and maintenance (O&M) cost of the
above components of a biomass plant. The following section briefly dis-
cusses the considerations for determination of O&M cost of the first three
components of a biomass plant.
2.3.1 Biomass Collection System
Unlike fossil fuel, biomass is not necessarily collected from a single concen-
trated source. It is a relatively light and bulky material with low heat content
on a volume basis. So, a biomass plant involves handling of large volumes
and at times transportation over long distances. Therefore, logistical network
from forest to the plant should be well planned during project development.
The flow of biomass from collection point to product (solid, liquid, or gas),
from production to end use should carefully identify all steps of conversion
and losses. Systematic collection of data is important while ensuring that
consistent units are used throughout the process chain.
Biomass collection and handling for gasification, pyrolysis, or torrefac-
tion plants is very similar to that for a biomass steam power plant, for
which a good amount of experience and cost base is available. Based on
existing data, a reasonable cost estimate for new plant equipment, required
for collection and feeding the biomass into the conversion unit can be
arrived at.
2.3.2 Preprocessing
Biomass rarely comes in a form ready to be fed into the reactor. It is often
mixed with metals and debris, which are to be separated (see Chapter 12)
before use. The moisture content of the biomass delivered is sometimes well