2.1. Bottlenecks
Nowadays, sustainability and its conciliation with the waste
management system are hot topics. However, despite the various
technologies available for waste valorization, a large number of
issues remain unaddressed (Stehlík, 2009).
The environmental aspect including the emissions of pollutants
and greenhouse gases, is of particular interest. Waste streams often
consist of diverse types of materials, originating from a number of
different sources. These raw materials may contain elements such
as chlorine, sulfur and heavy metals that could affect the quality of
the products formed in the waste treatment process (e.g. syngas,
bottom ash, fly ash, digestate, vitrified slag). Consequently, special
abatement technologies need to be used to reduce the content of
pollutants in the products generated and/or in the emissions to air,
water and soil. Evidently, these stringent measures come at a price.
Another bottleneck is the economic feasibility of ELFM which
depends strongly on the development of innovative technologies
with high WtE efficiencies (Van Passel et al., in this issue). These
new technologies need to prove their economic viability prior to
full-scale implementation. Energy efficiency is an important system
indicator used for comparison with conventional, well-established
technologies. A lack of data (both experimental and theoretical)
often hampers such a comparative study.
An urgent need exists to gain modeling expertise in the field of
waste valorization processes. A validated system model facilitates
system design and optimization, in addition to reducing the need
for experimental work. Numerical experiments can be used to
predict operating conditions when scaling up or down and as such
to define optimal operating windows. Furthermore, the suitability
of various feedstock can be assessed.
A basic prerequisite for waste treatment processes is the
adequate characterization of materials contained in the available
waste streams. Characterization data give an indication of the
suitability of a specific waste stream for the different valorization
options. Furthermore, these data are of crucial importance in
determining the technical and economic feasibility of available
valorization processes. Unfortunately only limited data are
currently available describing the characteristics of wastes from
landfills.
The existing environmental legislation mainly focuses on
disposal of waste on landfills and on conventional waste treatment
techniques, hereby acting as a barrier to the introduction of innovative
waste valorization technologies. The ongoing shift towards
more sustainability through valorization of waste as both energy
and materials should contribute to improve and adapt the existing
policy