Comments regarding EPA’s Proposed Approval on Rule 4352 from Earth 

Justice

1. NOx Limit of 165 ppm @ 12% O2 for MSW-fired facilities 

Comment: New Jersey Department of Environmental Protection (NJDEP) has set NOx 

emissions limits for MSW-fired boilers at 150 ppmv at 7% O2 (approximately 142 

ppmv at 12% CO2).

Response: 

The District conducted research on the establishment of the 150 ppmv @ 7% O2 

NOx emission limit from the NJDEP. Based on that research, it was determined that 

there are five facilities with MSW-fired boilers operating in New Jersey. The five 

NJDEP facilities vary in MSW stoker/boiler equipment and permit conditions from 

the Valley’s MSW facility. These equipment differences allow the facilities under 

NJDEP jurisdiction to meet a slightly lower NOx limit than the facility in the San 

Joaquin Valley. Four of the five NJDEP facilities have different types of grates 

(reciprocating, horizontal, and roller grate) than the stoker grate/boiler 

configurations of the Covanta Stanislaus facility. These units also utilize a staged 

combustion design with ammonia injection to achieve lower NOx emissions limits. 

Additionally, NJDEP does not enforce a visible emissions limit on these units. 

Therefore, when NOx emissions start to get close to reaching the 150 ppmv limit, 

the facilities can simply inject more ammonia to control the NOx without the 

implications of violating an opacity limit. Therefore, due to these differences, the 

MSW facilities cannot simply be compared to each other. 

The fifth NJDEP facility has the same Martin grate system and stoker grate/boiler 

configuration as the Covanta Stanislaus facility. However, to meet the lower NOx 

limit, this facility has changed their design to operate using staged combustion 

which injects overfire-air flow in different areas of the boiler than the Covanta 

Stanislaus facility. This, in turn, cools the combustion gas in the boiler and directly 

conflicts with two of Covanta Stanislaus’ Title V permit conditions issued under the 

District’s New Source Review regulations and ARB’s T-BACT guidelines for 

reduction of toxic organic air emissions, e.g., dioxins: 

“11. A furnace roof temperature of 1,100 degrees F shall be stabilized, as measured 

by multiple thermocouples, to ensure that a minimum temperature of 1,800 degrees F 

is established above the grate prior to the ignition of MSW. 

12. During any period of time that MSW is burning on the grates, the combustion 

gas retention time shall be maintained at a minimum of one second, the combustion 

zone temperature shall be maintained at a minimum of 1,800 degrees F, and the 

furnace roof temperature shall be maintained at an average (4 hour arithmetic block) 

of 1,100 degrees F, except during periods of start-up, shutdown, and malfunction, as 

defined in 40 CFR 60.58b(a).” 
When using staged combustion, the operator cannot guarantee the four hour 

temperature required by condition 12 and thus compliance with these two permit 

conditions, which are federally enforceable through the facility’s Title V permit. 

These two conditions in particular were included as a part of the Health Risk 

Assessment required by ARB and the Department of Health Services, now the Office 

of Environmental Health Hazard Assessment (OEHHA) and approved by the 

Stanislaus County APCD, now the SJVAPCD, and the County's Health Officer, in order 

for the ATC to be issued in 1986 for this Stanislaus facility. ARB determined the 

requirements for completing the HRA, as well as requiring T-BACT from its BACT 

document released at that time for MSW-fired facilities. AB2588 testing in 1988-

1989 and the first Title V Permit for Stanislaus led the District to complete its own 

HRA following CAPCOA guidelines and using the actual tested emissions from 

Stanislaus' annual stack tests. The current Covanta Stanislaus Title V Permit still has 

the same original HRA permit conditions for metals and trace organics emissions 

(i.e, dioxins, PCB's and PAH's) in g/s as well as the operating conditions, mentioned 

above, regarding furnace temperature and residence time. It also has the newer 

MACT operating conditions, including adding activated carbon for mercury control, 

which can also help to keep dioxins to the very low levels that Stanislaus achieves 

every year. Therefore, these conditions are critical to address the facility’s potential 

toxics issue and removing or adjusting these permit conditions would not only 

increase the toxic risk for the facility but also affect those in the vicinity of the 

facility. 

Since the NJDEP facilities do not have either of these limits placed on their facilities, 

they can use staged combustion to help meet a lower NOx limit. Due to the TBACT/HRA limits, it may not be feasible to require a change in permit conditions to 

allow the Covanta facility to use staged combustion to meet a lower NOx limit. Even 

if they were able to increase their toxic exposure to the surrounding community, 

based on estimates that were put together in August 2011 for a staged combustion 

system at Covanta Stanislaus that could reduce NOx emissions from 165 ppm down 

to 150 ppm, it would cost $2.31 million for engineering, procurement, fabrication, 

installation, and start-up costs. The following table outlines the cost estimates. 

ITEM SOURCE COST 

Staged Combustion Retrofit

Direct Capital Costs 

Total Purchased Equip Cost

(PEC) 

Covanta $1,400,000 

Direct Installation Costs 25% PEC Covanta $350,000 

Total Direct Capital Costs $1,750,000 

Indirect Capital Costs 

Facilities 5% PEC OAQPS $70,000 

Engineering 10% PEC OAQPS $140,000 

Process Contingency 5% PEC OAQPS $70,000 

Total Indirect Capital Costs $280,000 

Project Contingency 20% PEC OAQPS $280,000 
Total Capital Costs (TCC) Direct Capital + Indirect Capital + 

Project Contingency 

OAQPS $2,310,000 

Annualized Capital Costs (10 

years @ 10%) 0.1627*TCC District Standard $375,837 

Direct Annual Costs 

Operating & Maintenance Costs (conservative estimate) Covanta $60,000 

Total Direct Annual Costs $60,000 

Indirect Annual Costs 

Capital Recovery 

0.1627 x PEC 

OAQPS/District $227,780 (10% int. rate, 10 yr period) 

Total Indirect Annual Costs $227,780 

Total Annual Costs Annualized capital +Direct 

Annual+Indirect Annual $663,617

The 165 ppm limit from each of the two boilers equates to a current Title V limit of 

1130 lbs per day of NOx. It is assumed that the concentration reduction of NOx from 

165 to 142 ppm would also equal a reduction of 158 lbs/day. However, there is a 

permit condition limiting the annual emissions from these units to 172.2 tons/year. 

It is estimated that the staged combustion and 142 ppm limit would reduce 24.0 

tons of NOx/year (i.e 172.2 – (172.2*(142/165)) = 24.00). 

Therefore, if Covanta were to be able to modify their Title V permits and increase 

their toxic risk, the cost effectiveness to install staged combustion would be still 

$27,650/ton, which is not considered cost effective. 

 

Additionally, based on recent source tests, conducted by an ARB certified laboratory 

utilizing EPA approved methodologies; the facility has provided information 

demonstrating that the actual conditions of the Covanta Stanislaus facility operates 

where the ratio of percent excess air (O2) and percent CO2 are approximately 1-to1. For example, the results of the source tests showed that measured ppm values @ 

7% O2 were only 1-2 ppm higher than those measured values @ 12% CO2. (i.e. 129 

ppm NOx @ 7% O2 was also measured as 128 ppmv NOx @ 12% CO2)1 Therefore, 

using the operating conditions found at the Covanta Stanislaus facility, the 150 

ppmv NOx @ 7% O2 should only be approximately 148 ppmv NOx @ 12% CO2 and 

not 142 ppmv @ 12% CO2. Thus the revised emissions reductions can be calculated 

as: 172.2 – (172.2*(148/165)) = 17.74 tons NOx reduced. And the corresponding 

cost-effectiveness would be: $37,404/ton

 

 

1 Although the source test shows that these units are capable of meeting limits lower than their 

permitted limit of 165 ppmv @ 12% CO2, as discussed below, the Continuous Emissions Monitor 

(CEMS) data has demonstrated that these units cannot maintain a NOx emission limit of 150 ppmv 

and commonly exceed that threshold multiple times throughout the year. 
2. Inject ammonia or add nozzles to meet a lower limit 

Comment: The District needs to provide a technical analysis demonstrating ammonia 

injection and adding more nozzles are a viable reason for rejecting a lower limit. 

Response: 

In addition to staged combustion, the NJDEP facilities have stated they will 

potentially incorporate more nozzles and ammonia injection to ensure they comply 

with the new NOx limit. While it may be technologically feasible to install more 

ammonia injection nozzles, more nozzles do not guarantee a lower NOx emission 

rate. The orientation of the nozzles in the combustion gas stream has a much 

greater impact on the resulting NOx emissions than just the number of nozzles in 

the system and the facility’s nozzles have already been optimized. This is based on 

the temperature window where SNCR works to reduce NOx effectively, i.e., not 

creating more NOx by combusting the NH3 or allowing more un-reacted NH3 to slip 

into the flue gas stream below the temperature window. Also, the amount of 

ammonia injected into the flue gas is closely controlled by Covanta to maximize NOx 

reductions and to prevent excessive ammonia slip. Any increase in ammonia 

injection would result in negligible NOx reductions and would exit the system and 

cause a detached plume; thereby, violating numerous other permit conditions for 

Covanta Stanislaus, such as its Title V limits on visible emissions, ammonia slip, and 

condensable particulate matter. Further optimization of the ammonia injection 

system does not appear to be a viable alternative for the purposes of achieving 

additional NOx reductions and may only meet NOx emission levels at the expense of 

unavoidable ammonia slip. 

Covanta Stanislaus provided CEMS data that would support this conclusion. If the 

limit was lowered to 150 ppm at 7% O2, the facility would have had multiple NOx 

exceedances for both of their units, only to be countered by adding excess NH3 such 

that a visible ammonium chloride plume would have been created. Therefore, the 

facility would need to be retrofitted in such a way as to incorporate more nozzles 

and would require reconditioning the boiler and changing the current equipment 

arrangement and operation, while accounting for these additional construction and 

operating costs when determining cost effectiveness of this new system. 

In addition to meeting the 165 ppm @ 12% CO2 MACT limit since 1988, Covanta 

Stanislaus has also been fully offset for NOx emissions for that 24 year duration, 

based on the District’s offset regulations under its New Source Review regulation. 

Whereas, NJDEP does not require offsets and the facilities had been only tasked to 

meet a MACT limit of 205 ppm at 7% O2 until this recent regulation, thus giving 

more of an emission reduction benefit than would be the case for the Valley. 

 
3. ACT reference range 

Comment: The TSD cites the 1994 ACT, in which NOx emissions from units with SNCR 

controls range from 35 to 167 ppmv at 12% CO2. This calls into question the 165 to 

210 ppmv at 12% CO2 range from the District’s 2011 Staff Report, and places the 

District’s NOx emissions limit of 165 ppmv at 12% CO2 at the highest end of the range. 

Response: As discussed above, there are many factors to consider when setting an 

emission limit for municipal solid waste combustion units. The NOx emission range 

identified in the ACT represents MSW facilities using a wide variety of emission 

control techniques such as: Selective Catalytic Reduction (SCR) Systems, Selective 

Non-Catalytic Reduction – Urea (SNCR-Urea) systems, and SNCR-Ammonia systems. 

The units equipped with SCR systems are those that can meet the lower emission 

limits identified by the ACT. However, the District is unaware of any MSW units 

equipped with SNCR that can achieve anywhere close to the lower range of 

emissions. In fact, the units operating in New Jersey are examples of units achieving 

some of the lowest NOx levels for these types of units. Therefore, although the 165 

ppm @ 12% CO2 NOx limit is on the higher end, the limit falls within ACT 

recommendations and is representative of the type of control Covanta Stanislaus 

has in place. The 165 ppm @ 12% CO2 limit is a Maximum Achievable Control 

Technology (MACT) limit and provides a small buffer to allow Covanta Stanislaus to 

meet it without violating other permit conditions. It would not be cost effective to 

require SCR to achieve a lower NOx limit, as demonstrated in the Staff Report. 

4. Start up and shut down 

Comment: The rule allows a normal startup period of up to 96 hours, a curing startup 

period of up to 192 hours, and a shutdown period of up to twelve hours, during which 

Rule 4352’s NOx and CO emissions limits do not apply. Other air districts in the state 

have set more stringent limits on startup. 

Response: 

District staff researched the rules in Placer, Yolo-Solano and SacMetro Air Districts 

mentioned by Earth Justice. The District contacted SacMetro, Yolo-Solano and 

Placer and determined that their rules only apply to biomass facilities and currently 

have one and two facilities, respectively, subject to these rules. District Rule 4352, 

however, applies to all solid fuel-fired boilers burning biomass, coal/coke or MSW, 

not just biomass facilities. The District has confirmed with all the facilities operating 

within the Valley that the current start-up and shutdown periods are necessary. 

Firstly, Shutdown and start-up periods are not frequent occurrences. Scheduled 

start-up/shutdowns only take place 2 – 4 times per year for maintenance and 

repairs. During this time, the operator needs the option to allow the boiler to get 

down to a low enough temperature to allow for “cold repairs”. This would then 

require a longer start-up time afterwards to get back up to the operating 

temperature. Also, when starting up, the units are not operating with a full load 
which in turn releases fewer emissions during that timeframe as opposed to normal 

operation. 

However, operators currently limit their start-up and shutdown times as much as 

possible. During the recent rule amendment, Valley operators specifically asked to 

add the “hot standby condition” definition to allow for a shutdown and start-up 

period to not require shutdown to refer to when the unit reaches ambient 

temperature, which can vary significantly and may not always be reasonable or 

efficient to let the equipment reach that temperature. This allows operators to 

perform maintenance and repairs on a boiler that has cooled sufficiently for the 

work but has not cooled to ambient temperature. This practice then minimizes 

shutdown and start-up times whenever possible to avoid unnecessary down time 

resulting in reduced productivity and reduced profit.