Let’s say you have two feedstocks (A, B) to test and want to see whether pretreatment improves their methane production. Before you start, you’ll need to allow room for blanks, samples and controls (e.g. microcrystalline cellulose), and decide what to record so the results can be compared on the same basis.
We’ve put together a practical example based on a common testing scenario: comparing two feedstocks, each with and without pretreatment. Using an 18-channel AMPTS® III, we show how to organise the reactors, include controls and test each condition in triplicate.
For the underlying method and test requirements, see our BMP test protocol.
3 min read
Plan the reactor layout, including blanks, controls and samples
The four sample conditions occupy 12 reactors. The remaining six are allocated to inoculum blanks and a positive control.
| Reactors | Contents | Purpose |
|---|---|---|
| 1–3 | Inoculum blank | Measure background methane production |
| 4–6 | Inoculum + microcrystalline cellulose | Check inoculum activity and validate BMP results |
| 7–9 | Inoculum + A, untreated | Establish the baseline for feedstock A |
| 10–12 | Inoculum + A, pretreated | Evaluate the treatment’s effect on feedstock A |
| 13–15 | Inoculum + B, untreated | Establish the baseline for feedstock B |
| 16–18 | Inoculum + B, pretreated | Evaluate the treatment’s effect on feedstock B |
In this layout, 18 channels accommodate four sample conditions. Blanks, controls and samples are part of the capacity calculation from the beginning.
The example assumes the same inoculum and incubation conditions across the test. Some treatments or sample types will require additional controls or loading conditions, which would change the allocation.
Prepare samples for a fair comparison
For each feedstock, take representative portions from the same batch for the untreated and treated conditions. Keep the untreated portion under documented storage conditions while the other portion is treated.
Measure total solids and volatile solids for the materials being tested. Equal wet masses can contain very different amounts of organic matter, particularly if pretreatment adds or removes water.
Before loading the reactors, record:
| Information | What to include |
|---|---|
| Sample identity | Source, batch, sampling date and storage conditions |
| Pretreatment | Method, duration and relevant settings, such as temperature or particle size |
| Solids content | Total solids and volatile solids for each condition |
| Reactor loading | Amounts of sample and inoculum, working volume and inoculum-to-substrate ratio |
| Test conditions | Incubation temperature, mixing and the procedure being followed |
If treatment removes a fraction of the material, record whether that fraction is included in the test. This matters when interpreting the result.
Assess the effect of pretreatment on each feedstock
Start by checking the blanks, positive control and agreement between replicates against your chosen method’s acceptance criteria.
Then compare treated and untreated feedstock A, followed by the same comparison for feedstock B. Review both methane yield (mL CH₄/g) and the production profile.
A treated sample might reach the same yield sooner, produce more methane overall, or show little difference. The same pretreatment may also affect the two feedstocks differently.
Keep the basis of comparison clear when reporting the results. Methane yield per unit of volatile solids helps compare biological performance. Assessing the treatment’s overall benefit may also require a material balance, treatment costs and further testing under continuous feeding.
For more on sample preparation, controls and measurement, see our guide to avoiding common BMP test errors.
Avoid common errors in BMP tests
Cassie Welander, PhD • 13 July, 2026
Mistakes in experimental design, inoculum selection, sample preparation, mixing and data analysis can affect BMP results. Read our article to learn how to avoid the most common problems.
Reviewed by Mihaela Nistor, PhD, Senior Sales Scientist
With a background in biotechnology and nearly two decades at BPC, she helps customers plan their testing and select suitable instrument configurations. Her research contributions include more than 100 scientific articles, book chapters and conference proceedings.
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