BMP testingFruit, vegetables and their residues
Pumpkin — BMP: 7 studies, weighted mean 341 m³ CH₄/t VS
Pumpkin and its waste (flesh, spoiled fruit, processing residues) is a watery substrate rich in sugars and starch, readily fermentable and requiring size reduction of seeds and skin.
rating: neutralCH₄ ≈ 52 % (estimate)
Photo George Chernilevsky / Wikimedia Commons, public domain, source file; changes: cropping
- Weighted mean
- 341m³ CH₄/t VS
- Range
- 199–478m³ CH₄/t VS
- Records
- 7studies
- Publications
- 3sources
- Temperatures
- 38 °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.
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 (28 m³ CH₄/t); process risk: acidification. No additional handling requirements.
Why? Rating factors
Potential per tonne +1
- +1potential 28 m³ CH₄/t fresh matter (BMP 341 × DM 10.8 % × VS 76.8 %)
Process stability −1
- −1acidification: rapid degradation / acidic pH, risk of VFA accumulation, needs buffering
Handling and costs 0
- 0no factors
Total points: 0 · thresholds: ≥ 2.5 very good, ≥ 1 good, below — neutral; negative with cumulative process risk.
Add to the co-digestion calculator CSV data
BMP curves from 7 studies
Weighted mean Individual records
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 (341); 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| Source | BMP m³ CH₄/t VS | Temperature | Sample | Curve |
|---|---|---|---|---|
| Dubrovskis i Plume (2017) · 1 | 391 | 38 °C · mesophilic | Pumpkin biomass, bioreactor R3 | end point (model curve) |
| Dubrovskis i Plume (2017) · 2 | 397 | 38 °C · mesophilic | Pumpkin biomass, bioreactor R4 | end point (model curve) |
| Dubrovskis i Plume (2017) · 3 | 421 | 38 °C · mesophilic | Pumpkin biomass, bioreactor R5 | end point (model curve) |
| Dubrovskis i Plume (2017) · 4 | 478 | 38 °C · mesophilic | Pumpkin biomass, bioreactor R2 | end point (model curve) |
| Kolbl et al. (2014) · 1 DOI | 366 | 38 °C · mesophilic | Muscate Pumpkin | end point (model curve) |
| Kolbl et al. (2014) · 2 DOI | 436 | 38 °C · mesophilic | Rotten Pumpkin | end point (model curve) |
| Czubaszek et al. (2022) DOI | 199 | — | Pumpkin residue | end point (model curve) |
| Weighted mean | 341 | arithmetic mean 384, SD 89 | ||
Typical composition
- Dry matter (DM)
- 10.8% (range 9.5–12.1)
- Volatile solids (VS)
- 76.8 % DM (range 69.5–84)
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.
Sources: Kolbl et al. (2014).
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
Advantages
- Methane yield in the compendium: median 397 (range 199-478) m³ CH₄/t VS, 7 records from 3 studies (weighted mean 341).
- Waste of pumpkin, courgette and apples was studied in one compilation as biogas substrates (Dubrovskis et al.) (Dubrovskis et al. (2017))
Co-digestion — what to combine it with, what to watch out for
- combines well
substrates: nitrogen-rich — e.g. Pig slurry, Poultry manure, Waste activated sludge (secondary sludge), Chlorella vulgaris, Nannochloropsis salina
A nitrogen-rich co-substrate balances the low C/N of fruit and vegetable waste (Bouallagui et al. 2009).[1]
- combines well
substrates: high alkalinity (buffer) — e.g. Cattle manure, Pig slurry, Cattle slurry, Duck slurry, Rumen and digestive tract content
Co-digestion of easily degradable substrates with dairy slurry increased the methane yield relative to slurry alone.[2]
Dosing
No source limits on the dose for this substrate.
Introduce gradually, starting with a small dose and monitoring the process (e.g. FOS/TAC, pH, gas composition).
Sources of the process data
- Improvement of fruit and vegetable waste anaerobic digestion performance and stability with co-substrates addition
- Biochemical methane potential and biodegradability of complex organic substrates
- Biogas from wastes of pumpkin, marrow and apple
- Addressing case specific biogas plant tasks: Industry oriented methane yields derived from 5L Automatic Methane Potential Test Systems in batch or semi-continuous tests using realistic inocula, substrate particle sizes and organic loading
- Methane Production Potential from Apple Pomace, Cabbage Leaves, Pumpkin Residue and Walnut Husks
- Effects of size and thermophilic pre-hydrolysis of banana peel during anaerobic digestion, and biomethanation potential of key tropical fruit wastes
- Effect of particle size on biogas generation from biomass residues
The co-digestion calculator will assess a specific mixture containing this substrate.
What it is and where it comes from
Pumpkin (Cucurbita) is grown for preserves, as an ornamental pumpkin and as a food. Waste arises on farms, in sorting plants and in processing plants, and after the autumn season also as unsold fruit and decorations. The compilation contains several records from several studies: pumpkin fruit waste tested in several reactors, butternut squash and spoiled pumpkin, and also pumpkin residues from a Polish study, under mesophilic conditions (in one study the temperature was not stated).
Properties relevant to digestion
Pumpkin flesh contains a lot of water, sugars and starch and little protein and fibre, so it is readily and quickly fermentable. The skin is harder and more fibrous, and the seeds contain fat and protein, which changes the character of digestion. Large, hard parts must be size-reduced, because otherwise they degrade slowly. Like other fruit and vegetables, pumpkin at a large dose can cause rapid acidification, particularly in mono-digestion, and the low nitrogen level argues for co-digestion with slurry. Spoiled fruit is more microbiologically active and may contain moulds.
How to read the spread of results
The records concern different materials: fruit waste, butternut squash, spoiled pumpkin and processing residues. The species and variety (giant, butternut, common pumpkin), the degree of ripeness and spoilage, the presence of skin and seeds and size reduction all matter. The series from reactors of a single study are replicates or variants of the same experiment, so they are not independent. There are also differences in the inoculum, the substrate-to-inoculum ratio and test length.
In biogas plant practice
Pumpkin is a seasonal and local substrate, suitable as a supplement to the mix in the autumn period. It requires washing or separation of soil, size reduction (including seeds and skin) and careful dosing with control of pH and volatile fatty acids. Ensiling in a mixture with drier material is suitable for storage. As agricultural or food waste it is subject to requirements arising from the installation's permit. The yield of a specific batch is confirmed by a BMP test. It is worth remembering that ornamental pumpkins after the season may contain contaminants such as paints, waxes or decorative elements. Such batches should be carefully inspected and cleaned before they reach the shredder, so as not to introduce foreign substances into the digester.
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 = 0.245 d−1 was assumed (median of rate constants k reported in the sources and/or fitted to the mean measured curves).
The statistics describe the spread of published results — a descriptive compilation, not a meta-analysis or a guarantee of plant yield.
Bibliography
- Dubrovskis, V.; Plume, I. (2017). Biogas from wastes of pumpkin, marrow and apple. Agronomy Research 15(1), 69–78. https://agronomy.emu.ee/wp-content/uploads/2017/03/Vol15Nr1_Dubrovskis.pdf source
- Kolbl, S.; Paloczi, A.; Panjan, J.; Stres, B. (2014). Addressing case specific biogas plant tasks: Industry oriented methane yields derived from 5L Automatic Methane Potential Test Systems in batch or semi-continuous tests using realistic inocula, substrate particle sizes and organic loading. Bioresource Technology 153, 180–188. DOI: 10.1016/j.biortech.2013.12.010 DOI
- Czubaszek, R.; Wysocka-Czubaszek, A.; Tyborowski, R. (2022). Methane Production Potential from Apple Pomace, Cabbage Leaves, Pumpkin Residue and Walnut Husks. Applied Sciences 12(12), 6128. DOI: 10.3390/app12126128 DOI
All sources of the site: bibliography.
Other substrates in the group “Fruit, vegetables and their residues”
Durian shells — BMP: 2 studies, weighted mean 93 m³ CH₄/t VS
93 m³ CH₄/t VS weighted mean from 2 studies
≈52 %
Rambutan seeds — BMP: 3 studies, weighted mean 449 m³ CH₄/t VS
449 m³ CH₄/t VS weighted mean from 3 studies
good — editorial rating for biogas plants≈52 %
Radish — BMP: 3 studies, weighted mean 286 m³ CH₄/t VS
286 m³ CH₄/t VS weighted mean from 3 studies
≈56 %
Mango peels — BMP: 13 studies, weighted mean 448 m³ CH₄/t VS
448 m³ CH₄/t VS weighted mean from 13 studies
≈52 %