For my studies I'm wanting and attempting to make a landfill greenhouse gas emissions (GHG) model that predicts the amount of greenhouse gas equivalent emissions ($GHG_{eq}$ [tonnes/year]) by analysing a series of landfill core drill samples and extrapolating the data to predict how much GHGs would be produced if the samples can be representative of the landfill as a whole and allowed to naturally degrade. Note that this comes with the assumption of minimal heterogeneity which I know is not the best assumption for most landfills but I'm hoping to get a LOT of data (it's better than nothing).

As the most notorious GHG from landfill is methane, I'm going to simplify this question to just predicting the amount of methane which would be produced from the (combustible) material in landfill assuming it would just sit there forever.

Note that I have cross-posted my question from the chemistry stack exchange.

The Data:

I have this data which is the average of 3 landfill drill core samples and shows the type of waste which has been calculated from sorting and weighing different types of material found in landfill (Table 1) and the chemical composition and high heating value (HHV)/calorific value of the material (Table 2) which I've had tested in an independent lab. For Table 1, an assumed "type" of plastic, rubber, wood (etc.) is made with a constant chemical composition to simplify the model (although I do recognise that there are many different types of plastics and woods etc.).

Data for average of 3 landfill drill core samples

The Method (?):

I've seen the generic methanogenesis combustion reaction as:

$\ce{CO_2 + 4H_2 -> CH_4 + 2H_2O}$

I've also seen an elemental formula for hydrocarbon combustion along the lines of:

$\ce{C_xH_y + $(x + \frac{y}{4})$O_2 -> xCO_2 = $\frac{y}{2}$H_2O + $Heat + Light$}$

I know how to calculate the conversion rate going from any GHG such as $\ce{CO_2}$ or $\ce{CH_4}$ to $GHG_{eq}$ but it's this first step - the predicting of the GHGs themselves with what formula - which I'm lost at.

The Questions:

  1. How can I calculate $\ce{CH_4}$ from landfill samples with the attached data and which reaction should be used?
  2. (Bonus) What other considerations should be accounted for with any of the other data? (e.g. the Sulfur going into $\ce{SO_2}$ emissions (etc.)).
  • $\begingroup$ Hopefully nothing is combusting in the landfill. Doesn't the methane come from anaerobic decomposition of the organic materials? $\endgroup$
    – Mark
    Nov 4, 2022 at 0:43
  • $\begingroup$ The equations given so far are combustion reaction equations. One of the products from the reaction is methane. It's just semantics. I'm trying to quantify the methane product which is combusted (past tense relative to the time of reaction). $\endgroup$
    – Hendrix13
    Nov 6, 2022 at 15:03
  • $\begingroup$ Closing this question because it was crossposted and has an accepted answer on Chemistry: How can combusted methane from landfill samples be quantified? $\endgroup$
    – hichris123
    Nov 12, 2022 at 22:25