July 2019

Triangle NoTES


July 2019


Recently I was looking into Tier II reports in the public domain to see how the “doughnut hole” nitrogen correction affected the reported NMOC results. Although that impact is still a big concern, especially for the landfill operators, the thing that flagged for me was something I had thought had been put to rest years ago. The illegal shipment of landfill gas samples back to the laboratory became very evident in the review of the reports. One report in particular documented the violation so well I am sure the US DOT could issue the citations from it if they were so inclined and there was not a statute of limitations which had been exceeded.


As a result I am mentioning it in this newsletter and also sending a copy to each state agency for which I can find a contact email. This is so the review of any proposed protocols would not give some indirect approval of the illegal shipment.


According to the US DOT regulations for shipping non-pressurized gas samples, which are classified as flammable, the container must be less than five liters in volume. Pure landfill gas is classified as flammable according to the formula specified in the US DOT regulations. The only way to bypass the flammability issue is to dilute the sample to where the concentration of methane falls below the limit using the previous formula. If the sample is not classified as flammable it can be shipped in any sized container by any means. If the sample is classified as flammable the shipping limitations must be met and the proper documentation has to be provided for the shipment, which is time consuming and expensive.


We have always partially filled the canister with helium prior to shipment so the return of the samples would not normally be classified as flammable. This allows us to use many different sizes of canisters without a problem. We also rely on the use of a 4.5L canister in case there was any issue with sampling that would negate our helium pre-charge. If this happened we could still have the sample legally shipped back to us as a flammable shipment. I only remember one case where this occurred and it was a significant problem. There had been some samples taken from a compressor station and they had accidentally been taken from the wrong port and were filled to 60 psi before anyone knew. To ship legally all we had to do was to measure the final pressure and then release it down to atmospheric before shipping as a flammable shipment.


Now, to look at what caught my eye with the other report. There was listed a specific number of sites from which samples were to be taken, which is a maximum of 50 for a landfill. These were going to be composited in the field which is not uncommon, but the number of samples for analysis was uncommon. There were only ten data points, which meant there were five samples composited into one container. As the requirement for a valid composite sample is a minimum of 1L, this could have barely been legal if there had been a 5L canister used. Unfortunately the report documented there was 5 inches Hg of vacuum left in the Summa canister used. This indicates a common 6L Summa canister was used, which exceeds the volume requirement specified by the US DOT. Some people have tried to claim they are legally shipping the sample because there are only five liters of sample in the canister at ambient pressure. The problem is that a gas expands to fill the size of any container so there are six liters of gas at a lower pressure in the canister. The US DOT understands this so that is not a valid defense for the violation.

The report also documented that the canisters were shipped via cargo aircraft with the dates and even tracking numbers. Even though it is just as illegal to ship flammable gases over the highways the critical nature of an aircraft's integrity seems to add to the enforcement concerns over such a shipment.


In any case, these are considered serious violations by the US DOT, which is why I have worked with them to ensure that we prepare the canisters for our clients correctly to prevent as many potential issues as possible. I do not know how probable it is for anyone to be caught illegally shipping flammable gases, but I have heard that is is very expensive when someone is caught. I am told they consider each canister a separate violation and people have been fined tens of thousands of dollars. I think any fine such as that would ruin someone's day if not their continued employment potential.


The other defense I have heard used for such a shipment was that they were required to sample and ship in that manner based upon some aspect of the permit, approved protocol, or regulatory requirement. This would not have been an issue if the original shipping requirements had been left in the methods as that should have clarified the regulatory position.


With this in mind I would like to point out some of the red flags in a protocol.


Compositing more than four sample locations into one canister is a big warning flag. Four composites can be done with 4.5 L canisters and shipping as flammable. This can also be done with 8L canisters which are pre-charged with helium and are shipped as non-flammable. Anything over four composites would be a very unusual sized canister with a pre-charge. A 6L Summa canister will get three samples composited but with a minimal vacuum left after sampling the 1L fractions.


No matter what volume of sample to be taken at atmospheric pressure, if the container is over 5L in volume there can be no legal shipment unless the canister is correctly pre-charged. If the container is 5L or less it can be legally shipped as a flammable gas shipment. If the canister is properly pre-charged any size can be used and shipped normally.


Also, unless someone from the US DOT gives instructions on shipping a larger volume without the correct pre-charge and will provide the appropriate documentation, do not listen to them. Any advice given which is contrary to the specific regulations and basic science can cause problems for the shipper. The adviser is protected because it is the responsibility of the shipper to ensure all of the regulations are followed accordingly.




Wayne Stollings

Triangle Environmental Services, Inc.


Wstollings@aol.com


P.O. Box 13294 122 US Hwy 70 E

Research Triangle Park, NC 27709 Hillsborough, NC 27278


(919) 361-2890 (800) 367-4862 Fax: (919) 361-3474

Triangle NoTES


February 2019


To continue with the discussion on the 'Ultimate Analysis' of landfill gas with some of the feedback and what we have determined in the interim.


First, it is understood that some of the elements would not be included in the calculations. The trace sulfur and chlorine, for example. There would also not be an inclusion for the hydrogen and oxygen from the organic compounds reported in the Method 25-C analysis. While there can be even more analyses to determine these components, to a greater degree it seems to be a strong potential for the diminishing return on expenditures.


To better determine what the results would resemble for a landfill gas report, I did a couple of groups of calculations based on a set of three samples which showed consistent results over all of the analysis.


On the wet basis, the mid-range sample had 35.15% CO2, 47.36% CH4 , 12.31% N2, 2.14% O2,, and 0.07% NMOC which left a calculated 2.98% H2O to bring everything to 100%. This translated to a weight basis of 55.76% CO2, 27.38% CH4 , 12.43% N2, 2.14% O2,, 1.93% H2O and 0.03% NMOC using the molecular weight of the components.


Converting this to the elemental components and using the atomic weight of the individual atoms for a weight calculation created a difference just from rounding error. The MW of CH4 is different from the accepted weight of four hydrogen atoms and one carbon atom due solely to rounding. The difference is 0.01 lower for the MW of CH4. With the amount of CH4 in the sample, the difference total is 0.02% higher using the atomic weight of the atoms.


Converting the results to a elemental level and taking the analytical variation between the three analyses of each sample the results are 35.74 +0.01% C, 44.72 +0.02% O, 12.43 +0.01% N, and a constant 7.11% H, which does include water vapor. Some of the references I have found for the solid fuel reports include the water content in the elemental percentage, while others list the water separately from the elemental percentage. The difference seemed to be related to the determination of BTU value based on the elemental percentages. Since the BTU value can more easily be determined by the molecular components in the gas samples and the elemental approach would be mainly for gas density, the water being included in the elemental percentage seem more reasonable to me.


If we do not include the Method 25-C results and use only the Method 3-C as seems to have been indicated in the Subpart D reference to fixed gas analysis, the results become 35.71% C, 44.75% O, 12.43% N, and 7.12% H. This loss of NMOC as carbon does not seem to be very significant when compared to the rounding and analytical uncertainty variations and especially when the costs are included. It does, however, help to offset the other elements not included due to even higher analytical costs.



The percentage breakdown of the molecular components by volume and by weight both including and excluding the NMOC carbon portion:


CO2

CH4

N2

O2

NMOC

H2O - by

subtraction

35.15%

47.36%

12.31%

2.14%

0.07%

2.98%

By vol

55.76%

27.38%

12.43%

2.47%

0.03%

1.93%

By wt

35.15%

47.36%

12.31%

2.14%

NA

3.04%

By vol -NMOC

55.75%

27.38%

12.43%

2.47%

NA

1.98%

By wt -NMOC


The percentage breakdown of the atomic components:


C

O

N

H


35.74%

44.72%

12.43%

7.11%

Incl NMOC carbon

+0.01%

+0.02%

+0.01%

+0.00%

Analytical variation

35.71%

44.75%

12.43%

7.11%

-NMOC carbon

Note: The MW of CH4 is 16.04 as opposed to 16.05 when the rounded atomic weights are used. This makes a 0.02% increase in the atomic versus molecular weight comparison.


Now the information I received in feedback on projects which had used Method 3-C for a mass or density calculation can be discussed. There were two projects discussed and one was more of a biogas than landfill gas location.


The first project was one in which the correction for moisture resulted in a total in excess of 100% for the three samples involved. The solution was to normalize the reported concentrations to 100%, which seemed like a good choice at the time. In our recent discussion I pointed out this meant the measured concentrations were adjusted by an assumed moisture content and then normalized to 100% thereby leaving the moisture at the assumed level and adjusting the measured components accordingly. Fortunately, leaving the measured components at the wet basis and assuming the adjustment for moisture would take that to 100% made an insignificant change to the calculations which had been previously used.


The second project was one in which the correction for moisture was fairly accurate given the totals were near 100% with a close over-and-under range. For this project the components were averaged over the three runs and those averages were used in the final calculations. This also included the average of the three analyses of NMOC as carbon in the totals. The average total did not exceed 100% but was very close so normalization was not considered. This is almost the same process which would be used in totaling the components as wet basis and then considering the moisture as being the remaining percentage. The averaging of the three runs would be a very good addition to the calculations as well.




From what has been used in the field already and what I have seen in these calculations of the single test run, there is little impact from the uncertainty of the analysis or the trace compounds which are not included. The conversion to the elemental level adds a slight positive bias due to the rounding issues, which could be considered as an offset to the lost elements. Whether that offset is sufficient or too much will be something a regulatory entity will have to determine if this process is to be used to determine the fuel density. The addition of the NMOC from the Method 25-C does not seem to be critical nor significant, but it is an easy addition which arguably makes the total calculations more accurate. Given the alternative here would be for the unreported percentage carbon from NMOC to be replaced by moisture, the density of water is greater than that of carbon if that were used. If even an ordinary hydrocarbon, such as hexane, were chosen to be used in place of the NMOC only the dry basis density would change as the moisture density would be greater than the hydrocarbons.


How does this all shake out? Just from the cost to benefit comparison it would be like this:


Method 3-C measured concentrations wet basis with only moisture assumed to make the difference to 100% total weight. The lowest cost approach and seems to give ~99+% of the density of the gas .


Methods 3-C and 25-C measured concentrations wet basis with only moisture assumed to make the difference to 100% total weight and converting the NMOC to at least hexane for a slightly better assumption. Higher cost and maybe only the perception of greater accuracy. This approach still seems to give ~99+% of the density of the gas if only just slightly higher.


Methods 3-C, 25-C, and 16 for Total Reduced Sulfurs wet basis with only moisture assumed to make the difference to 100%. Much higher cost and maybe only the perception of greater accuracy. This approach still seems to give ~99+% of the density of the gas.


Any other analytical methods will increase the costs, but really have little impact on the gas density given the insignificant percentages involved. Even the cumulative effect does not seem to be noticeable given the calculation for the NMOC compared to the water variation.


The change to density for the dry basis will be the largest changes, as the moisture density would offset much of these minor additions for gas density on the wet basis.



Wayne Stollings

Triangle Environmental Services, Inc.



Wstollings@aol.com

P.O. Box 13294 122 US Hwy 70 E

Research Triangle Park, NC 27709 Hillsborough, NC 27278

(919) 361-2890 (800) 367-4862 Fax: (919) 361-3474

January 2019

Triangle NoTES


January 2019


I have again had requests for an 'ultimate analysis' of landfill gas referencing ASTM Methods for coal and coke. Of course, the methods for solids cannot be applied to gases, but there are some possible ways to get close to the concept.


The ultimate analysis of coal and coke using methods in the ASTM D3176 series would report the elemental constituents, which can also be done with some of the gas methods. The problem is there are small gaps which have not been determined to be insignificant by any regulatory agency to my knowledge.


To give a starting basis for comparison, 40 CFR Subpart D 60.46 for fossil fuel fired steam generators, references ASTM D3176 for solid fuels and three series for natural gas fuels. The D1137 series has been withdrawn by ASTM, which leaves the D1945 and D1946 series for this comparison. These ASTM methods are similar to the fixed gas analysis of Method 3-C and NMOC analysis of Method 25-C which are my options of choice in this case.


Method 3-C gives the concentrations of O2, N2, CO2, and CH4,, which can be converted to the elemental composition of O, N, C, and H with some possible variations. The Method 3-C results are converted to a dry basis based on an assumption of moisture content. This adjustment can cause the total of the compounds to vary slightly above or below 100 percent. The carbon from organic compounds is also not reported. This may be a concern although they generally total in the hundreds or low thousands of ppm rather than percentage levels.


The carbon from the organics can be determined accurately by Method 25-C and added, but only if there are no adjustments performed to take the results to an air free basis, the same moisture determination is used for both the Methods 3-C and 25-C, and there are no additional dilutions to the sample. This will be combining two different methods and will result in a total concentration in excess of 100% more often than just the reported Method 3-C concentrations.


Alternatively, both the Method 3-C and 25-C analyses could be reported on a wet basis. Thus, a measured moisture content could be applied rather than the assumption of saturation at the barometric pressure and temperature, but this would change if the conditions were different at the analyzer. There could be instances of condensation in the sample even though dry helium is used to dilute the sample. This could result in totals of all compounds again exceeding 100%.


Another approach could be to report both of the analyses on the wet basis and once the total concentration of both was determined the difference could be assumed to be water vapor and the calculations done accordingly. All of these options will have some potential for minor loss of some of the more trace elements such as sulfur, chlorine, fluorine, or silicon, but these are generally in the low ppm ranges at most and should not have a significant impact on the total density of the gas.


I suspect the only difference for this approach would be the elimination of the >100% totals seen more often using the moisture correction from the Methods 3-C and 25-C. Most of the Method 3-C results seem to hold near the 100% level as it is, but the assumed moisture, analytical variability, and slight errors in pressure and temperature measurements do allow for totals both slightly over and slightly under.


Given this is more of an enforcement issue, rather than a technical issue, all that would be required is an enforcement decision on the application.


To allow a better understanding of how this would appear, I have pulled a recent set of three samples to give as examples.


The three samples showed very similar concentrations of O2, N2, CO2, and CH4, which made the over all comparison very easy.


The totals for just the fixed gases on the dry basis were 100.0576%, 99.6764%, and 100.1880%.


The O2 was ~2.25%, the N2 was ~ 13.25%, the CO2, was ~36.1% and the CH4 was ~48.3% over the three samples.


The NMOC concentrations were ~650 ppmC over the three samples.


As this was on the dry basis, the H2 and O2 from the water vapor would not be applied, but the H2 would be more than offset by the increase in reported CH4 from that adjustment, while the increase in O2 and CO2 would do the same for the associated O2 from the water vapor.


The ASTM methods, while similar, are substantially different from the EPA methods, which arguably have higher QA/QC standards and are possibly more defensible due to their being codified in the Federal Register as a Standard Reference Method. Even then there has to be a modification to the Method 25-C calculations to eliminate the adjustment to an air free basis. This modification could conceivably only be approved by the EPA itself as a alternative method for this application.


The critical aspect would be what is going to be the legal definition of an 'Ultimate Analysis' for the landfill gases if this is to be used or even if such an approach is necessary to determine fuel density.


I have copied a portion of the two ASTM methods in question for comparison to the similar EPA methods specified for landfill gases.


ASTM D1945 - Standard Test Method for Analysis of Natural Gas by Gas Chromatography

Significance and Use

4.1 This test method is of significance for providing data for calculating physical properties of the sample, such as heating value and relative density, or for monitoring the concentrations of one or more of the components in a mixture.

1. Scope

1.1 This test method covers the determination of the chemical composition of natural gases and similar gaseous mixtures within the range of composition shown in Table 1. This test method may be abbreviated for the analysis of lean natural gases containing negligible amounts of hexanes and higher hydrocarbons, or for the determination of one or more components, as required.



ASTM D1946 – 90(2015) - Standard Practice for Analysis of Reformed Gas by Gas Chromatography

Significance and Use

4.1 The information about the chemical composition can be used to calculate physical properties of the gas, such as heating (calorific) value and relative density. Combustion characteristics, products of combustion, toxicity, and interchangeability with other fuel gases may also be inferred from the chemical composition.

1. Scope

    1. This practice covers the determination of the chemical composition of reformed gases and similar gaseous mixtures containing the following components: hydrogen, oxygen, nitrogen, carbon monoxide, carbon dioxide, methane, ethane, and ethylene.



METHOD 3C—DETERMINATION OF CARBON DIOXIDE, METHANE, NITROGEN, AND OXYGEN FROM STATIONARY SOURCES

1.0 Applicability and Principle



    1. Applicability. This method applies to the analysis of carbon dioxide (CO2), methane (CH4), nitrogen (N2), and oxygen (O2) in samples from municipal solid waste landfills and other sources when specified in an applicable subpart.


METHOD 25C—DETERMINATION OF NONMETHANE ORGANIC COMPOUNDS (NMOC) IN LANDFILL GASES

    1. Scope and Application


Analytes. Analyte CAS No. Nonmethane organic compounds (NMOC) No CAS number assigned. 1.2 Applicability. This method is applicable to the sampling and measurement of NMOC as carbon in landfill gases (LFG).


I know that gas density for landfill gas has a purpose, but I do not have any indication as to what has been done in this situation in the various applications. Any feedback on what has been used or accepted in the past would help determine what we can provide for our clients in such cases. Is the density based on the analysis of the fixed gases sufficient? This seems to be the case with the Subpart D reference, given the levels of NMOC as carbon are usually below the error range of the carbon in the fixed gas analysis. I look forward to input on what you think will be an appropriate approach.

Wayne Stollings

Triangle Environmental Services, Inc.


Wstollings@aol.com

P.O. Box 13294 122 US Hwy 70 E

Research Triangle Park, NC 27709 Hillsborough, NC 27278

(919) 361-2890 (800) 367-4862 Fax: (919) 361-3474