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

Litchi peel and seed — BMP: 2 studies, weighted mean 89 m³ CH₄/t VS

Lychee (Litchi chinensis) as a substrate means the peel and seeds from fruit processing; records from a single study show the difference between the husk and the hard seed.

CH₄ ≈ 52 % (estimate)

Published 18 December 2023Updated 29 October 20263 min readFeedstockData Editorial Team

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

Weighted mean: 89m³ CH₄/t VS
Range: 71–107m³ CH₄/t VS
Records: 2single study (2 samples)
Publications: 1source
Temperatures: —of the test

Methane in biogas

≈51–53% 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 (protein from total nitrogen (N 1.2 % DM × 6.25)) 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 (89); 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
Zhao et al. (2016) · 1 DOI	71	—	Litchi (Litchi chinensis) – Seed	end point (model curve)
Zhao et al. (2016) · 2 DOI	107	—	Litchi (Litchi chinensis) – Peel	end point (model curve)
Weighted mean	89	arithmetic mean 89, SD 26

Typical composition

Volatile solids (VS): 97.1 % DM (range 96.2–98)
Nitrogen: 1.2 % DM
C/N ratio: 44

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: BCBPD); dry matter: 0 determinations, volatile solids: 2 determinations. C/N was calculated as the ratio of C and N content (% DM) from the same source. No DM in the sources – the calculator has to ask for a value.

Sources: Zhao et al. (2016).

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

fibrous
slowly degrading
seasonal
variable composition
dilutes the feed (low DM)
editorial classification

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.

Advantages

Methane yield in the compendium: median 89 (range 71-107) m³ CH₄/t VS, 2 records from 1 study (weighted mean 89).
In the tests by Labatut et al., some of the substrate mixtures with slurry showed synergy; co-digestion is a reasonable way of using weaker substrates (Labatut et al. (2011))

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

combines well
substrates: easily degradable — e.g. Maize silage (whole crop), Food waste, Sorghum, whole crop, Whey, Beet leaves and tops
In BMP studies, easily degradable substrates increased the yield of the mixture with slurry (synergy in some mixtures).^[1]

Dosing

No source limits on the dose for this substrate.

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

Lychee (Litchi chinensis) is a fruit tree grown mainly in China and other countries of South-East Asia, as well as in the subtropical regions of Africa and the Americas. The soft, jelly-like flesh is edible, whereas the peel (the outer husk) and the large, dark seed become waste. In Poland the fruit appears in imported trade, so the waste arises mainly in households and catering outlets. The dataset contains several records from one study: peels and seeds.

Properties relevant to digestion

Lychee peel is woody and contains polyphenols, including tannins, which can inhibit some microorganisms but are tolerated at a moderate dose. The seed is rich in starch and other storage carbohydrates, but it is surrounded by a hard seed coat that limits access for enzymes. Grinding or crushing increases the contact surface and speeds up decomposition. The material contains little protein, so it does not contribute large amounts of ammonia, and its C/N ratio is high.

How to read the spread of results

The records describe different parts of the fruit, so the difference between them results from composition, not measurement uncertainty. Because they come from a single study, it is not known how the values would change in other laboratories, with a different inoculum or temperature (no temperature is stated in the dataset). The result is affected by the variety, the ripeness of the fruit, the degree to which the seeds are comminuted, the method of drying the sample and the duration of the test, because hard fractions may not reach a plateau within a typical period.

In biogas plant practice

Lychee is not a planned substrate. Peels and seeds may appear as a minor addition to a stream of fruit waste. If they go into the digester, they should be shredded and the dose kept low, so that the polyphenols do not reduce microbial activity. In projects based on such waste, a dedicated BMP test is essential, because the composition depends on the ratio of peel to seeds in the particular batch. Food waste of plant origin is waste within the meaning of the Waste Act, so the installation must hold the appropriate permit.

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

Zhao, C.; Yan, H.; Liu, Y.; Huang, Y.; Zhang, R.; Chen, C.; Liu, G. (2016). Bio-energy conversion performance, biodegradability, and kinetic analysis of different fruit residues during discontinuous anaerobic digestion. Waste Management 52, 295–301. DOI: 10.1016/j.wasman.2016.03.028 DOI

All sources of the site: bibliography.