Environmental Engineering Reference
In-Depth Information
production, biorefineries based on lignocellulosic feedstocks can rely on bigger biomass per
hectare yields, since the whole crop is available as feedstock.
Therefore, lignocellulosic raw materials are the most suitable biomass source for
providing a large and constant feedstock supply to biorefineries, on condition that sustainable
practices and managements are followed. Over the next 10 to 15 years, it is expected that
lower cost residue and waste sources of lignocellulosic biomass will provide the first influx of
next-generation feedstocks, with cellulosic energy crops expected to begin supplying
feedstocks for bioenergy production towards the end of this time frame, then expanding
substantially in the years beyond (Worldwatch Institute, 2006).
2.2. Criteria for Biorefinery System
In addition to the definition, biorefinery systems should also follow some requisites
which act as guidelines for the future deployment of biorefinery concepts. The criteria which
a biomass or bioenergy system has to follow to be named biorefinery are the following:
1. Biomass Refining:
a biorefinery, similarly to the upgrading of crude oil that occurs in oil
refinery, is based on feedstock upgrading processes, where raw materials are
continuously upgraded and refined. This means that a biorefinery should separate all the
biomass feedstock components in order to be individually exploited, leading through a
chain of several processes to a high concentration of pure chemical molecules (e.g.
ethanol) or a high concentration of molecules having similar functions (e.g. the mixture
of C alkanes in FT-fuels).
2. Combustion of residues:
a feedstock can not be directly combusted without any
previous treatment, since the aim of a biorefinery is to increase the value of the different
biomass components as material and energy source. Therefore, the most desirable option
is to send combustion for heat and electricity production only the residues and leftovers
of the several technological treatments and conversion processes.
3. Value chemicals/materials:
a biorefinery should produce at least one value
chemical/material product, besides the low-grade and high-volume animal feed and
fertilizers, according to the specifications of the first criterion.
4. Fuel-Energy products:
as a direct consequence of the second criteria, a biorefinery
should produce at least one energy product besides heat and electricity. Therefore, the
production of at least one biofuel (liquid, solid or gaseous) is required.
5.
Fossil fuel replacement:
the products of a biorefinery must be able to replace fossil fuel
based products coming from oil refinery, both chemicals and energy carriers. Concerning
the chemicals, this objective can be met by producing the same chemical molecule from
biomass instead of from fossils (e.g. phenols), or producing a molecule having a different
structure but an equivalent function (e.g. succinic acid from biomass vs. maleic anhydride
from fossils) or new biobased products able to replace petroleum based products (e.g.
synthetic biodegradable plastics from starch). Concerning the fuels, a biorefinery must
replace conventional fossil fuels (mainly gasoline, diesel, heavy oil, coal and natural gas)
with the production of biofuels coming from biomass upgrading, both liquid (e.g.
bioethanol, biodiesel, FT-fuels), gaseous (e.g. synthetic natural gas, hydrogen) and solid
(e.g. lignin, charcoal, residues).
