Wood to RNG

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2 years 8 months ago #184 by emoreside
Wood to RNG was created by emoreside
Hi there,

A few questions for my wood to RNG process:

1) A catalyst is consumed during the process. How will this affect my results? I see placeholders in the Alt Fuel Prod sheet, cell A76. How do I use these?

2) The process has a biocarbon (solid fuel) co-product. I don't see this as an option in the co-prods sheet. I've tried setting a value under the placeholder cell A114, but I don't see an effect.

3) In the input sheet, AX94 says "calculated" - why?

4) In the results sheet, "gas leaks and flares" is set to zero, and is linked to the same category for the "wood residue to wood" pathway, which is also set to zero. How would this change? Should it be taken into account?

5) Are fugitive emissions inherently taken into account for an RNG process? Do I have to set a value somewhere?

Thank you!

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2 years 8 months ago #186 by rdo
Replied by rdo on topic Wood to RNG
1. To make use of a placeholder chemical you will have to partially define it. Row 76 on Alt Fuel Prod corresponds to row 146, where the inputs are. You can choose the region of the electricity - generic is wherever the model is being run - in column B. In columns C through G you can choose how much of each input is used in producing one unit (usually kg) of your chemical. Columns H, I, and K are calculated automatically, you don't need to touch them. Column J is non-energy emissions, for example of the process of producing your chemical has some offgassing unrelated to the energy emissions you would put the grams of CO2 equivalent in.

2. The process of using a placeholder coproduct is much the same as adding a placeholder chemical. In this case row 114 corresponds with row 157. For this you will need to enter the type of allocation in column B, displacement is preferred for modelling but some regulatory schemes may dictate what to use. The fuel density in columns C and D. And the energy that is displaced in columns E through I. This energy would be the quantity and type of energy that would be used to produce whatever product your coproduct is displacing. If you do not have this information then you will have to rely on energy or mass allocation.

3. The model assumes that any natural gas put into the local pipelines can come out anywhere those pipelines run. Thus the pipeline distance for natural gas is always based on regional calculations instead of user input.

4. From a modelling perspective, that would not change from being zero and the equation exists purely for consistency purposes. The equation exists so it is a traceable zero rather than an untraceable zero.

5. There are some losses in distribution and dispensing that are automatically accounted for, if those are not set to zero. If there are additional fugitive emissions that would have to be added on the Equip Emis Factors sheet in BV81.

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2 years 8 months ago #188 by emoreside
Replied by emoreside on topic Wood to RNG
Is it typical to include a catalyst that is only replaced every 2 - 3 years? Or is the effect negligible in this case?

Many thanks!

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2 years 8 months ago #190 by rdo
Replied by rdo on topic Wood to RNG
The appropriate way to model that would be to amortize it over the 2-3 year lifecycle. If you apply 1kg every three years in a 200 million litre per year plant than you are applying 1/(200000000*3) = 1.7E-9 kg/L.
Now, my example will be negligible for most chemicals and fuels, but that is best practice.

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2 years 8 months ago #191 by emoreside
Replied by emoreside on topic Wood to RNG
If my placeholder co-product is displacing coal, do I have to indicate this in both sheets: 'co-prods' H157 AND 'input' AI286?

Thanks!

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2 years 8 months ago #194 by rdo
Replied by rdo on topic Wood to RNG
Nope.
Input!AI286 refers specifically to displacing coal-generated electricity with excess electricity from your process. If AI273 is zero, then AI286 to AI296 do not matter.

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2 years 8 months ago #199 by emoreside
Replied by emoreside on topic Wood to RNG
My co-product is biocarbon which will replace coal. I know the energy density of biocarbon and the mass of coal which is displaced by one unit of biocarbon.

My confusion:
- coprods!A114 is under the heading "emissions displaced by electricity production". I am not producing electricity. Would my biocoal co-product belong here?
- can I interpret coprods!H157 to mean the amount of coal that the biocoal displaces?

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2 years 8 months ago #201 by rdo
Replied by rdo on topic Wood to RNG
It seems like you basically have it but our labelling might need improvement.

Your interpretation of H157 is correct. That should be how many kilograms of coal is displaced by 1kg of your biochar.

114 is the correct place for your biocoal. From row 90 to row 116 are all intended to be chemical coproducts and are calculated as such. They are distinct from the electricity inputs in rows 84 to 89. I'll mark this as a spot to improve legibility in the next major update.

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2 years 8 months ago #202 by emoreside
Replied by emoreside on topic Wood to RNG
Thank you! That's helpful!

Some more process questions:

1) AltFuelProd!A145 mentions a catlayst. Is catalyst disposal taken into account when the catalyst is at the end of its lifetime? Should it be?

2) Should human emissions be a factor (i.e. employees travelling to and from plant, etc.)

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2 years 8 months ago #205 by rdo
Replied by rdo on topic Wood to RNG
1. Yes it should take disposal into account. However this is generally going to be negligible for most of the used chemicals because they either get consumed and don't need disposal or they last a long time so you're looking at relatively low amounts to dispose.

2. Generally no, the system boundaries will be drawn around the plant. So keeping it heated or cooled so people can work there is counted, but their commute to the plant is not.

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2 years 8 months ago #206 by emoreside
Replied by emoreside on topic Wood to RNG
Hi again. Thanks for your help so far!

Again re. my placeholder biocoal coproduct, I've tried comparing two methods:
a) coprod!B157 = Energy; coprod!C157 = 32 MJ/kg
b) coprod!B157 = Displacement; coprod!H157 = 1.4 kg coal/kg biocoal

(1.4 comes from HHV_biocoal/HHV_coal)

Each of these yield very different results in the resultant 'emissions dislaced - coproducts'.

Can you comment on why?

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2 years 8 months ago #207 by doconnor
Replied by doconnor on topic Wood to RNG
It is almost always the case where the different allocation approaches change the results. There are also advantages and disadvantages of the different approaches for co-products.

Energy allocation has the advantage in that is is simple to apply, you only need to know the energy content of the product and co-products and the co-products get their share of the emissions based on their energy content.

There are some unintended implications though. Two plants producing the same co-product could get different emission benefits. The more efficient plant with lower emissions in total will allocate few emissions to the co-product, so not all of the improvements in energy efficiency would be reflected in the CI of the main product.

If you are comparing a bio co-product to a fossil product then energy allocation won't reflect the biogenic nature of the co-product. If the main product and the co-product are used in different regulatory schemes the biogenic benefits may not be captured at all.

The displacement approach addresses most of these issues but it is not always possible to determine exactly what is being displaced. So more detailed knowledge of the system and how that system interacts with other systems is necessary. These interactions may also vary in different locations. This complexity is often cited for the reason many regulators choose to use energy or mass allocation rather than displacement, even though they are not the ISO preferred approaches.

Regards
Don O'Connor

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