Environmental Engineering Reference
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is comparatively less dependent on specific technical developments, less
dependent on scale of production, has a greater feedstock flexibility and
potential, and can be integrated into the natural gas distribution network
(A
˚
hman 2010). Apart from renewable electricity, the regulated and
unregulated emissions of biomethane, together with its carbon footprint,
are lower than for all other biofuels. In contrast to electric vehicles, the
natural gas vehicle (NGV) market is fully mature and ready to deliver given
the proper incentives, inclusive of long-distance road transport within the
next few years, through implementation of liquefied natural gas (LNG) and
dual-fuel technology. The climate benefit of using biogas in combined heat
and power (CHP) schemes replacing coal may be theoretically better than
replacing fossil transport fuels, but full utilization of the produced heat is
highly unlikely, especially during the summer. Also, the argument must be
made as to why would we waste a high-quality energy carrier such as biogas
on electricity production, when the oil dependency of our transport systems
needs to be solved today, not in a distant, uncertain future? It is argued that
the large-scale use of biomethane has been wrongfully overlooked in studies
focusing on long-term and large-scale options for the transport sector
(A
˚
hman 2010).
18.1.1 Hydrogen and the future gas engine
Hydrogen has for decades been hailed as the answer to all of the problems of
the current oil-dependent transport industry. However, the technical
challenges have so far been too steep to overcome. Recent developments
with respect to fuel cell technology and hydrogen production may change
this. Major vehicle manufacturers such as BMW and Toyota are planning to
launch fuel cell powered vehicles before 2020. Reverse fuel cell technology
may make it possible to produce hydrogen from surplus wind electricity at
higher yields compared with traditional electrolyzers.
It is very likely that fuel cells and e-mobility will be important players in
future transport systems in order to meet the challenges of energy efficiency,
increased renewability and climate change mitigation. However, the
challenge of transforming transport needs to start right away; the
technology of NGVs is commercially available today for all types of
vehicles and all types of distances. The needs of the heavy-duty vehicle
(HDV) market will be fulfilled in the short-term through fuel-efficient
methane diesel engines and space-efficient on-board storage of liquefied
methane. In addition, mid-term engine developments such as exhaust gas
recirculation (which improves low-load performance), high-energy ignition
systems (which increase the dilution limit) and better detection and control
of the calorific gas quality will make it possible to attain diesel engine
efficiency in future NGVs. The relative efficiency gain of hybridizing the
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