Environmental Engineering Reference
In-Depth Information
way of an independent certificate trading company or body, such as is in
Holland (www.vertogas,nl) and Switzerland (Kornmann and Wellinger
2009).
From a technical viewpoint, biomethane grid injection is established and
uncomplicated. Issues remaining to be addressed are related to feed-in
regulations and economy. It is important to deliver a gas quality within
specification to customers. Most grid injection so far has been in low-
pressure distribution lines, close to the customer. If it is necessary to meet a
higher heating value specification, as is the case with H-gas quality in certain
parts of the European gas grid and the Danish gas used in Sweden, it is
sometimes necessary to add propane. This, of course, incurs an extra cost.
Renewable ethane or propane can be synthesized from biomass-based
glycerol in a catalyzed process in a financially feasible manner and cleaned
of CO
2
together with the biogas in the upgrading unit of the biogas plant
(Brandin et al. 2008). In most of Europe, the mixing of gases with different
gas specifications is already done at large scale. Here, it would be better to
inject biomethane before the mixing points into high-pressure transmission
lines. This solution would also circumvent the potential problem of lower
customer demand during the summer, effectively lowering the maximum
amount of biomethane allowed to be injected into that particular
distribution area.
The investment costs associated with upgrading and subsequent grid
injection, together with the necessity of adding propane or high pressuriza-
tion work, can be economically prohibitive for individual biogas plant
owners. However, from a societal point of view, the benefits of increasing
the availability and utilization of domestic gas production are obvious, and
it has been suggested that upgrading and injection of biomethane should be
an integral part of grid infrastructure management, the costs thus being
shared by all gas customers (EP ITRE 2008a, 2008b, 2008c; European
Commission 2009; SEI 2009).
18.2.2 Distribution solutions far from the natural gas transport
network
Far away from the national natural gas transport network, other
biomethane distribution solutions come into play; for example, by road in
mobile storage units, either in compressed or liquefied state, or by laying
down local gas lines. A report issued by the Swedish Gas Association shows
the relation between transport distance and transported volumes for the
different upgrading and distribution alternatives available on the market
(Benjaminsson and Nilsson 2009). The results are summarized in Fig. 18.1.
For short to medium distances and larger volumes, local gas grids provide
the best alternative. Considering road transport, compressed vehicle
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