3.2 EPA Regulatory Framework:
RICE NESHAP and NSPS
The RICE NESHAP requirements from
the EPA have received a lot of
attention in the last few years largely
because of the impact these
requirements have on existing non-
emergency diesel and natural gas
generators. These requirements have
meant that many existing non-
emergency diesel generators have had
to add oxidation catalysts and other
equipment to their engines. In keeping
with the overall focus of this article on
new emergency diesel generators, we
will review RICE NESHAP and NSPS
from this standpoint.
A facility is deemed by the EPA to be
an “area” source if it has the potential
to emit < 10 tons/year of any single
hazardous air pollutant or < 25
tons/year of any combination of
hazardous air pollutants annually. A
“major” source has emissions greater
than the “area” source levels. Typically
major sources have more stringent
requirements.
The EPA has classified over 70 area
source categories – examples would
be a stationary reciprocating internal
combustion engine (RICE), or a boiler.
Each of these categories has special
NESHAP
(National
Emissions
Standards for Hazardous Air Pollutants)
requirements and an associated
timeline.
While NESHAP can impact new and
existing RICE, NSPS only applies to
new installations. Like RICE NESHAP,
NSPS typically specifies performance
standards that are defined within the
EPA “Tier” levels discussed later in this
article.
For the Critical Power Engineer, RICE
NESHAP and NSPS are typically not a
major issue for new emergency diesel
gensets > 500HP. Since 2008 all major
manufacturers have produced engines
which meet RICE NESHAP and NSPS
requirements for new emergency
diesel engines. To meet RICE NESHAP
and NSPS requirements for new diesel
emergency engines, the engine must
be certified to at least Tier 3 or, if it is
greater than 752HP, it must be certified
to at least Tier 2. Most of the resulting
obligations from RICE NESHAP apply
to the facility operators not the Critical
Power Engineer designing the facility.
For example site operators should use
Ultra Low Sulfur Diesel (ULSD) fuel.
This is not a big constraint since ULSD
has been in wide use since 2007. The
facility operator must also record
emergency operation with reference to
a non-resettable hour meter and make
this information available to the EPA if
requested. There are other relatively
straightforward record keeping and
maintenance obligations for facility
operators to maintain compliance with
RICE NESHAP.
3.3 EPA Regulatory Framework
Tier 2,3,4
There has been a lot of press coverage
on Tier 4 and its subsets Tier 4i
(interim) and Tier 4f (final). The Tier 4
standards have had a huge impact on
engine
manufacturers
because
significant emissions reductions have
been required to meet these
standards. It is not uncommon for a
large T4 stationary engine to cost 40%
more than a similar power Tier 2 or Tier
3 engine because of the extensive
emissions after-treatment equipment
that may be required. In addition large
stationary T4 gensets often require
significantly more space allocation than
Tier 2 or Tier 3 units.
The concept of EPA “Tiers” started in
the early 1990’s. The current level for
new stationary non- emergency diesel
engines exceeding 560HP is Tier 4
interim (T4i) and by Jan2015 Tier final
(T4f) will be in place for large stationary
gensets. Under Tier 4 a large engine is
considered to be one which exceeds
752 HP whereas under RICE NESHAP
it is 500 HP. In general, EPA T4
standards target on-highway, off- road
mobile sources and stationary non-
emergency engine driven generators.
EPA T4 is not required for emergency
gensets, but some engine vendors are
advocating use of T4 engines to ensure
there are no operating restrictions
beyond the current 100 hour
maintenance and testing limit currently
in place. If a new engine is not T4 it
must have a permanent label
indicating that it is for emergency use
only. It is important to note that, in
addition to significant extra cost and
space requirements, there can be
some significant disadvantages to
using T4 certified engines for
emergency applications. For example
under current EPA rules a certified T4
emergency engine used in a data
center must shutdown if the urea (also
known as Diesel Exhaust Fluid or DEF)
is unavailable. This is not a desirable
situation for an emergency generator
running during a long utility outage.
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Figure 3
Possible EPA Impacts for Diesel Engines Used for Emergency Standby
