Environmental Engineering Reference
In-Depth Information
1.5 Waste Biomass and Its Application for Energy and Fuels
The use of waste biomass is seen as a potential source of energy and fuel based on
carbon debt. However for production, collection and transportation of this waste
(often containing water) is required and at what economic cost? What types of
conversion technologies are available at what scales and investment costs?
1.6 Biomass to Liquids (BTL)
BTL is a thermal based process to making biofuels from biomass including
agricultural waste. Up till now the conversion of biomass to biofuels has gen-
erally focused on particular components of the biomass such as carbohydrates
(for bioethanol) and fatty acids (for biodiesel) being used. In the BTL process
the whole plant (if required) can be utilised in a multi-stage (thermal) process,
which has been conventionally used in the fossil based industries. Initially the
biomass undergoes a gasification process producing synthesis gas which is then
converted via a Fischer-Tropsch (FT) process to hydrocarbons, which can be fur-
ther processed using hydrocracking [5]. However such technology requires large
amounts of the thermal exchange capacity. This in turn would require higher cap-
ital investments. Due to the types of investments required it could be expected
that operation of such a facility may be operated in a more centralised location
operating at larger scale, thus reducing the possibilities for opportunities for local
communities.
1.7 Biogas
The production of biogas utilises a wide variety of raw materials with many using
waste streams from other industries. A general description of the process is given in
Fig. 1.
The raw materials can range from manures, waste from food production (and
supermarkets) to rest streams from farming. The quality of the biogas should be
improved to remove impurities such as water and hydrogen sulphide to allow it to
be used as a methane source in traditional pipeline supplies and other installations.
Biogas in this state may be used as traditional fossil methane (natural gas) that can
be used as a source of energy (for heat and electricity) as well as transportation
fuel. In general production is less dependant on specific crops for the process and
thus biogas installations are being developed where organic waste is generated and
offers the possibility for small scale production close to waste sites, so land use for
its production is less controversial. A similar situation can be regarded for biomass
incineration (not to be confused with incineration of municipal waste) which uses
organic rest streams from agriculture (for example straws) and manures (such as
chicken droppings). However, here only energy can be produced.
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