Environmental Engineering Reference
In-Depth Information
combine 5 million tonnes of the UK's food waste with 40 million tonnes of
animal slurry would allow the generation of 3 541 300MWh of electricity:
enough to supply 913 000 households and to save 1.8million tonnes of CO
2
equivalent GHGs from grid-based electricity production.
This type of scheme is certainly in line with the recent EC communication
on biowaste management (COM(2010)235) (European Commission, 2010)
which highlights how AD can offer a means of realising a wide range of
environmental benefits in a cost-effective manner as well as producing
renewable energy. Optimisation of biogas yield in this case means taking
into account the whole biomass resource available for AD and paying due
attention to the capacity of the land base for receiving digestates.
6.8
Future trends
The rapid expansion of AD into new applications and feedstock types has
presented many challenges. We are only just beginning to meet these by a
better understanding of the process microbiology rather than by empirical,
and often ad hoc, testing and guidelines. Improvements in process
performance, volumetric biogas productivity and process stability are
more likely to be achieved through understanding and manipulating the
microbial catalyst and its environment than invention of some revolutionary
new process. Although good engineering design will always pay dividends, it
needs to be focused on translating advances in fundamental knowledge and
applied science into workable solutions. We have to overcome the idea that
an anaerobic digester is a rudimentary low-technology waste treatment and
disposal system, and replace it with one of a process capable of delivering
the multiple benefits of low-cost second-generation renewable energy
production, a sustainable route to nutrient recycling and a means of
abating GHG emissions.
Speece (1996) recalls 20 years (1960-1980) of lost opportunity in AD
because we did not face the challenges but simply accepted that the process
did not work with some substrates. We now have new tools such as gene
sequencing and improved analytical methods that can provide us with the
opportunity to explore the structure and function of the anaerobic
community in more detail. It is unlikely that this will lead to 'revolutionary'
new processes in the short term, but in the longer term as a more complete
picture is built up it will help identify practical interventions to maximise the
efficiency of the biochemical pathways and syntrophies in the process. We
are only at the beginning in terms of the types of substrate being used: there
is still the challenge of marine biomass, so we had better start learning about
what drives halotolerant and halophilic methanogenic communities! There
are large quantities of feedstock material with a relatively high proportion of
poorly degradable carbon: the availability of this needs to be increased by
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