BMP testingFruit, vegetables and their residuessingle study (2 samples)

Sapodilla fruit and peels — BMP: 2 studies, weighted mean 286 m³ CH₄/t VS

Sapodilla (Manilkara zapota) is a tropical fruit; the dataset covers peels and whole spoiled fruit from one study, i.e. a waste with a high sugar content.

CH₄ ≈ 52 % (estimate)

Published 5 June 2022Updated 29 October 20263 min readFeedstockData Editorial Team

Photo Kristof Zyskowski & Yulia Bereshpolova / Wikimedia Commons, licence CC BY 2.0, source file; changes: cropping

Weighted mean: 286m³ CH₄/t VS
Range: 244–327m³ CH₄/t VS
Records: 2single study (2 samples)
Publications: 1source
Temperatures: 35 °Cof the test

Methane in biogas

≈51–54% CH₄

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

not rated — editorial rating for biogas plants

Not rated: no dry matter or volatile solids in the data. We calculate the rating when the dry matter and volatile solids of the material are known.

Editorial rating per the methodology

Add to the co-digestion calculator CSV data

BMP curves from 2 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 (286); 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

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Source	BMP m³ CH₄/t VS	Temperature	Sample	Curve
Gunaseelan (2004) · 1 DOI	244	35 °C · mesophilic	Achras sapota peels	end point (model curve)
Gunaseelan (2004) · 2 DOI	327	35 °C · mesophilic	Achras sapota - whole rotten fruit	end point (model curve)
Weighted mean	286	arithmetic mean 286, SD 59

Typical composition

Volatile solids (VS): 95.8 % DM (range 95.7–95.9)

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: MY-D); dry matter: 0 determinations, volatile solids: 2 determinations. No DM in the sources – the calculator has to ask for a value.

Sources: Gunaseelan (2004).

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

Low confidence: the description is based on general characteristics of the substrate group, not on studies of this material. Treat it as a hint to be verified.

No published process studies

The literature we use does not describe the advantages or drawbacks of digesting this substrate beyond the BMP test results. Below are process characteristics assigned on the basis of the type of material — an editorial classification, not a study result.

easily degradable: sugars, starch, glycerol → fast hydrolysis and acidification (VFA), needs buffering
acidic: low pH of the substrate (silages, stillage, whey, fruit)
dilutes the feed (low DM): low dry matter, dilutes the feed
seasonal: seasonal availability — requires storage
poor in trace elements: poor in trace elements — mono-digestion requires supplementation
carbon-rich: high C/N → nitrogen deficiency; combine well with nitrogen-rich substrates
low in nitrogen: high C/N → nitrogen deficiency; combine well with nitrogen-rich substrates

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

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

What it is and where it comes from

Sapodilla (Manilkara zapota, Achras sapota in older studies) is a fruit tree native to Central America, also grown in India and South-East Asia. The fruit has sweet, grainy pulp and a thin, rough skin. The dataset contains several records from one study: peels and whole spoiled fruit, which corresponds to the waste arising in trade and processing in producing countries.

Properties relevant to digestion

Ripe pulp contains a lot of simple sugars, so it ferments quickly and can cause a sudden rise in the concentration of organic acids. The peel is richer in fibre and tannins, which slow hydrolysis. The plant produces latex (chewing gum was obtained from the tree), and unripe fruit is astringent because of tannins. Spoiled fruit has a variable composition, because some of the sugars have already been consumed by microorganisms during spoilage.

How to read the spread of results

The records come from one study and one temperature, so there are no data on variability between laboratories. The difference between peels and whole fruit results from their different composition. The result is influenced by cultivar, degree of ripeness and spoilage, the share of peel in the sample, chopping, moisture content and inoculum. For spoiled waste, how long the material lay before the test is also important, because it had already undergone partial aerobic decomposition.

In biogas plant practice

In Poland, sapodilla does not occur as a waste of significant scale. In tropical countries, discarded fruit can be treated like other fruit waste: chopped, mixed with a substrate of higher dry matter content and dosed gradually while monitoring pH. For reliable planning, a BMP test of the actual material is necessary. Literature values serve as an indication only. It is also worth remembering that spoiled fruit that lay for a long time before delivery has already partly used up its sugars, and its composition depends strongly on storage time and conditions. For this reason, records from one study are not sufficient to predict the result for a batch from another source, and when assessing profitability one must take into account the seasonality of supply, the costs of transporting wet material, and the presence of seeds and latex.

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.

Full methodology and correction policy

Bibliography

Gunaseelan, V. (2004). Biochemical methane potential of fruits and vegetable solid waste feedstocks. Biomass and Bioenergy 26(4), 389–399. DOI: 10.1016/j.biombioe.2003.08.006 DOI

All sources of the site: bibliography.