Environmental Engineering Reference
In-Depth Information
materials and compounds to the biogas cycle. The feedstock declaration and
sample taking procedures are detailed in Chapter3.
2.4
Resource availability and supply chain issues
The worldwide biogas bioresource is often defined as the theoretical,
technical, economic and ecological potential. Many bioresource studies have
been undertaken by researchers, policy makers, NGOs and interest groups.
These studies range from global, national and regional to local scale as well
as from general biomass assessments to studies only focusing on biogas
production.
The use of the existing biomass potential for biogas production is
generally limited by natural and human-made causes as well as by the
annual natural biomass regrowth. Of main relevance for a commercially
viable biogas plant is the local potential and availability of a suitable
biomass feedstock within a certain area around the plant to ensure
continuous, stable and economically sustainable operation of the plant. The
potential of biogas feedstocks is therefore influenced by their spatial
distribution and depends on the feedstock type. In the case of wastes such as
municipal solid wastes (MSW), agricultural wastes, food wastes or industrial
wastes, availability is limited by the quality and purity of the waste. In many
countries, the main challenge is therefore to introduce sustainable waste
collection and separation systems (sustainable in terms of energy balance
and ability to provide overall CO
2
savings), which would increase the
availability of organic wastes for AD (Rutz et al., 2011). Furthermore,
adequate political framework conditions are needed to make the theoretical
potential also economically attractive. Utilization of waste products as a
feedstock for biogas is generally sustainable and does not compete with
other potential utilizations or with land use (Singh et al., 2010), which is a
major concern in the case of energy crops (Fig. 2.3).
One important issue related to the use of agricultural wastes such as dung
and solid manure is related to the local availability of animal farms that
keep livestock in stables. Animal droppings on grazing pastures can rarely
be used for AD, except in developing countries. Furthermore, due to the
generally lower energy content and diluted nature of farm wastes, there are
economic limitations with respect to sustainable biomass transportation
distances. The main limitation of energy crops specifically grown for biogas
production is related to lower sustainability than biogas from residues
(Korres et al., 2010) and to land use issues related to competition with food
production. This is of concern in many regions of the world, but especially
in poor countries or those suffering from food shortages. In most European
countries, there is currently overproduction of agricultural commodities,
much of which is exported (EC, 2012), and it has been estimated that there is
Search WWH ::
Custom Search