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Compostable bags — BMP: 8 studies, weighted mean 119 m³ CH₄/t VS

Compostable bags for biowaste are thin biopolymer films; in BMP tests they degrade partially, and the result depends on the temperature and the bag composition.

rating: neutralCH₄ ≈ 52 % (estimate)

Published Updated 3 min readFeedstockData Editorial Team

Photo Tek monde / Wikimedia Commons, licence CC BY-SA 4.0, source file; changes: cropping

Weighted mean
119m³ CH₄/t VS
Range
36–205m³ CH₄/t VS
Records
8studies
Publications
2sources
Temperatures
35 °C, 37 °C, 55 °Cof the test

Methane in biogas

Medium methane content · ≈ 5.2 kWh/m³ of biogas

estimate from the substrate type The collected studies contain no measurement. The interval follows from the approximate composition (carbohydrate-dominated (no protein or fat characteristics)) and the yields of compound groups according to FNR.

How we calculate it and what the zones mean

Rating for biogas plants

neutral — editorial rating for biogas plantsNo clear advantages — worth charging a fee for accepting it

Potential per tonne of fresh matter: moderate, but limited by the poor degradability of the organic matter (116 m³ CH₄/t); no particular threats to stability. Handling costs: physical contaminants (packaging, plastics), slow degradation.

Why? Rating factors

Potential per tonne +1

  • +1potential 116 m³ CH₄/t fresh matter (BMP 119 × DM 98.8 % × VS 99.1 %); low degradability of VS (BMP 119 m³ CH₄/t VS) — points capped

Process stability 0

  • 0no factors

Handling and costs −1.5

  • −1physical contaminants (packaging, plastics) — depackaging and separation
  • −0.5slow degradation — long retention time

Total points: −0.5 · thresholds: ≥ 2.5 very good, ≥ 1 good, below — neutral; negative with cumulative process risk.

Editorial rating per the methodology · confidence of the rating: medium · excluding market prices

Add to the co-digestion calculator CSV data

BMP curves from 8 studies

Weighted mean Individual records

BMP curves: Compostable bagsCumulative methane production over time for 8 records and the weighted mean of 119 m³ CH₄/t VS. 8 of the curves are model curves (first-order kinetics).0501001502002500510152025303540time [d]m³ CH₄/t VSCalabro’ et al. (2020) · 1: 42 m³ CH₄/t VS (model curve)Calabro’ et al. (2020) · 2: 67 m³ CH₄/t VS (model curve)Calabro’ et al. (2020) · 3: 111 m³ CH₄/t VS (model curve)Calabro’ et al. (2020) · 4: 144 m³ CH₄/t VS (model curve)Calabro’ et al. (2020) · 5: 152 m³ CH₄/t VS (model curve)Calabro’ et al. (2020) · 6: 186 m³ CH₄/t VS (model curve)Álvarez-Méndez et al. (2023) · 1: 36 m³ CH₄/t VS (model curve)Álvarez-Méndez et al. (2023) · 2: 205 m³ CH₄/t VS (model curve)mean119

Dashed lines are a model curve (first-order kinetics, B(t) = B₀·(1 − e−kt)); the end point comes from the publication. All curves are model curves.

Cumulative methane production over the test [m³ CH₄/t VS]. The thick line is the weighted mean of all records (119); dots mark the end values given in the publications. Point at the chart to read values; click a legend item to hide or show a record.

Records and sources

Download CSV
SourceBMP
m³ CH₄/t VS		TemperatureSampleCurve
Calabro’ et al. (2020) · 1 DOI4235 °C · mesophilicraw comp. bagsend point (model curve)
Calabro’ et al. (2020) · 2 DOI6755 °C · thermophilicRaw comp. bagsend point (model curve)
Calabro’ et al. (2020) · 3 DOI11135 °C · mesophilicRaw comp. bagsend point (model curve)
Calabro’ et al. (2020) · 4 DOI14435 °C · mesophilicraw comp. bagsend point (model curve)
Calabro’ et al. (2020) · 5 DOI15235 °C · mesophilicRaw comp. bagsend point (model curve)
Calabro’ et al. (2020) · 6 DOI18655 °C · thermophilicRaw comp. bagsend point (model curve)
Álvarez-Méndez et al. (2023) · 1 DOI3637 °C · mesophilicFruit selection bag FB2 (PLA/PBAT bag)end point (model curve)
Álvarez-Méndez et al. (2023) · 2 DOI20537 °C · mesophilicTrash bag TB1 (PLA/PBAT bag)end point (model curve)
Weighted mean119arithmetic mean 118, SD 64

Typical composition

Dry matter (DM)
98.8% (range 97.7–99.9)
Volatile solids (VS)
99.1 % DM (range 98.7–99.5)

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: MY-D); dry matter: 2 determinations, volatile solids: 2 determinations. Samples were tested dried/air-dry – the DM refers to the material in the test, not to fresh material.

Sources: Calabro’ et al. (2020).

The composition of the raw material varies between batches — for plant calculations use an analysis of your own sample. The calculator inserts typical values automatically.

Process properties

  • slowly degrading
  • physical contaminants
  • editorial classification

Advantages

  • Methane potential in the Substraty.pl BMP dataset: weighted mean 118.8 m³ CH₄/t VS (SD 64.5; 8 records, 2 sources).
  • Thin film has a large contact surface.

Drawbacks and risks

  • Commercial PBAT and PLA/PBAT bags degrade poorly anaerobically under mesophilic conditions, and none of those tested met EN 13432 in the anaerobic test (Álvarez-Méndez et al. 2023).
  • Film can wrap around agitators.

Co-digestion — what to combine it with, what to watch out for

Dosing

No source-based threshold; treat as a contaminant and remove.

Introduce gradually, starting with a small dose and monitoring the process (e.g. FOS/TAC, pH, gas composition).

Practical requirements

  • Shred: shredding increases the surface available for degradation and speeds it up, but does not necessarily raise the final gas yield (FNR 2010, Ch. 3 “Triturado”).

Sources of the process data

  1. Benn, Zitomer (2018). Pretreatment and anaerobic co-digestion of selected PHB and PLA bioplastics. Front. Environ. Sci.
  2. Alvarez-Mendez et al. (2023). Anaerobic digestion of commercial PLA and PBAT biodegradable plastic bags. Heliyon
  3. Narancic et al. (2018). Biodegradable plastic blends create new possibilities for end-of-life management of plastics but they are not a panacea for plastic pollution. Environ. Sci. Technol.
  4. FNR (2010). Guía sobre el Biogás – Desde la producción hasta el uso (hiszp. wydanie „Leitfaden Biogas”, GIZ 2013)

The co-digestion calculator will assess a specific mixture containing this substrate.

What it is and where it comes from

Compostable bags are used to collect biowaste in homes and catering outlets. They are made from blends of biodegradable polymers, usually starch with aliphatic polyesters, sometimes with PLA and fillers. In municipal biowaste they enter the installation together with the contents. Their share by mass is small, but they affect the operation of screens and separation systems.

Properties relevant to digestion

The starch part of the bag degrades relatively quickly, whereas aliphatic polyesters hydrolyse more slowly, especially at lower temperatures. A thin film has a large specific surface area, which favours contact with enzymes, but shreds of film may wrap around agitators and form layers. The dry matter of the bags often contains a significant inorganic fraction, so the result expressed per VS depends on the formulation. The bags do not bring in high concentrations of nitrogen or sulphur.

How to read the spread of results

The spread is typical of a multi-component material. The set contains tests under mesophilic and thermophilic conditions, with different numbers of replicates. The result is affected by the manufacturer and composition of the bag, film thickness, particle size (whole pieces or ground), test duration, inoculum activity and the way VS is calculated. Low values may mean that the test was too short for slowly degrading polyesters, and not that the bag is resistant to digestion.

In biogas plant practice

The bags usually reach installations as part of separately collected municipal waste. Shredding them, or removing them at the sorting plant if the installation uses mechanical preparation, is recommended. It should not be assumed that a bag will degrade fully in one mesophilic digestion cycle, and residues may end up in the digestate. Biowaste regulations and the installation's permits decide whether such bags may be accepted together with biowaste.

Operators note that in practice the problem is not so much the BMP result of the bags themselves as their mechanical behaviour: the formation of fibrous coils and the clogging of pumps and separators. For this reason the decision on accepting bags concerns the technological layout of the installation more than the methane potential.

Methodology in brief

BMP is the amount of methane obtained from volatile solids (VS) in a batch test, given in m³ CH₄ per tonne of VS (numerically the same as NmL CH₄/g VS in the publications) and converted to normal conditions (0 °C, 101.325 kPa). The weighted mean gives each publication a total weight of 1, split equally between its results for the substrate — a paper testing twenty varieties does not outweigh a paper with a single sample. In inter-laboratory programmes the unit is the laboratory (total weight 1), and within it the weight of a test grows with the number of bottles (replicates). Results after pretreatment (e.g. thermal, chemical, enzymatic) are shown separately and are not included in the mean.

Solid lines are curves measured in the tests. Where a publication gives only the final result, we draw a first-order kinetic model, B(t) = B₀·(1 − e−kt): only the end point comes from the publication, and the shape of the curve serves purely as visualisation — do not read the production on a particular day from it. For this substrate k = 0.091 d−1 was assumed (no kinetic data for the group – the median of all available rate constants k (93 values) was used).

The statistics describe the spread of published results — a descriptive compilation, not a meta-analysis or a guarantee of plant yield.

Full methodology and correction policy

Bibliography

  1. Calabro’, P.; Folino, A.; Fazzino, F.; Komilis, D. (2020). Preliminary evaluation of the anaerobic biodegradability of three biobased materials used for the production of disposable plastics. Journal of Hazardous Materials 390, 121653. DOI: 10.1016/j.jhazmat.2019.121653 DOI
  2. Álvarez-Méndez, S.J.; Ramos-Suárez, J.L.; Ritter, A.; Mata González, J.; Camacho Pérez, Á. (2023). Anaerobic digestion of commercial PLA and PBAT biodegradable plastic bags: Potential biogas production and 1H NMR and ATR-FTIR assessed biodegradation. Heliyon 9(6), e16691. DOI: 10.1016/j.heliyon.2023.e16691 DOI

All sources of the site: bibliography.

Other substrates in the group “Bioplastics and compostable packaging”