optimising methane yield from anaerobic digestion of manure: effects of dairy systems and of...

8/10/2019 Optimising methane yield from anaerobic digestion of manure: Effects of dairy systems and of glycerine supplem

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Optimising methane yield from anaerobic digestion

of manure: Effects of dairy systems and

of glycerine supplementation

Th. Amon a,*, B. Amon a, V. Kryvoruchko a, V. Bodiroza a,

E. Potsch b, W. Zollitsch c

aUniversity of Natural Resources and Applied Life Sciences, Department of Sustainable Agricultural Systems,

Division of Agricultural Engineering, Peter-Jordan-Strasse 82, 1190 Wien; AustriabFederal Research Institute for Agriculture in Alpine Regions, A-8952 Irdning, Austria

cDivision of Livestock Sciences, Department of Sustainable Agricultural Systems, Austria

Abstract. Biogas production is a very promising option to generate renewable energy. Currently,

specific parameters on the anaerobic digestibility of animal manures are unavailable which restrictsthe exploitation of the promising potentials. Manures received from contrasting dairy systems were

anaerobically digested. The resulting methane yield ranged between 125 and 166 Nl CH4(kg VS)1

depending on the milk yield and diet of the dairy cow. A 6% supplementation of glycerine to pig

manure and maize silage resulted in a significant increase in CH4 production from 569 to 679 Nl

CH4 (kg VS)1. D 2006 Elsevier B.V. All rights reserved.

Keywords:Anaerobic digestion; Biogas; Animal manure; Glycerine

1. Introduction

Biogas production from agricultural biomass offers environmental benefits and is an

additional source of income for farmers. Renewable energy is produced. Methane

emissions during manure storage are reduced and the fertiliser quality of the digestate is

high. Biogas plants require a targeted nutrient supply to achieve optimum biogas yields.

The research project aim was twofold: to find a relationship between dairy cattle diet,

manure composition and methane yields; and to optimise anaerobic digestion of pig

0531-5131/D 2006 Elsevier B.V. All rights reserved.

doi:10.1016/j.ics.2006.03.007

* Corresponding author. Tel.: +43 1 47 654 3502; fax: +43 1 47 654 3527.

E-mail address: [email protected](Th. Amon).

International Congress Series 1293 (2006) 217220

www.ics-elsevier.com
http://dx.doi.org/10.1016/j.ics.2006.03.007mailto:[email protected]://dx.doi.org/10.1016/j.ics.2006.03.007mailto:[email protected]


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manure with maize silage and glycerine supplementation. With RME production steadily

increasing so is the amount of glycerine generated as a by-product. Thus, it is crucial to

find recycling strategies for glycerine.

2. Materials and method

In part 1 of the research project, experiments were carried out to quantify the specific

CH4yield of dairy cow manures. The Federal Research Institute for Agriculture in Alpine

Regions conducted feeding trials with dairy cows at contrasting milk yields, and collected

their manures. Manures for the digestion experiments had a feces to urine ratio of 2:1

(basis fresh matter). The milk yield ranged from 11.2 to 29.2 l milk per cow and day.

Animal diets differed in their concentrate level and in forage composition. Low yielding

cows were fed only roughage. With increasing milk yield, the concentrate supplementation

increased to 11.0 kg DM per cow and day and the roughage intake decreased ( Table 1).

In part 2 of the project, glycerine was added in increasing amounts to a mixture of

maize silage, pig manure and rapeseed meal. The pig manure was received by a

conventional fully slatted floor system. Feces and urine were collected together as slurry.

Manure was directly taken from the slurry store. Pig manure characteristics were: 4.22%

DM and 4.22 XP, 2.27 XL, 10.72 XF, 45.67 NFE, 21.36 total N (all data given as g per kg

dry matter). For more details refer to [1].

Substance and energy turnover during anaerobic digestion were measured in three

replicates in 1 l eudiometer batch experiments at 38 to 40 8C, conducted according to DIN

38 414 [2]. Biogas quality (CH4

, H2

S, NH3

) was analysed 10 times during the 6-week

digestion period. Substrates were analysed prior to digestion for pH, dry matter (DM),

crude protein (XP), crude fibre (XF), cellulose (Cel), hemi-cellulose (Hem), lignin (ADL),

crude fat (XL), starch (XS), sugar and ash (XA) with standard analysing procedures. For a

more detailed methodology description refer to [3].

Statistical data analysis was carried out with the software package SPSS, version 11.5.

Each treatment was measured in three replicates. In the first step, mean, standard deviation

and frequency distributions of the data were determined. Variance analysis methods were

applied to find significant differences in the means. The following tests and procedures

Table 1Dairy cow feeding and performance and the resulting manure characteristics

Production system Composition of dairy cow manure [g (kg DM)1]

Treatment Concentrate Hay Grass

silage

Maize

silage

Milk

yield

pH DMa XP XF XL ADL GE [MJ]

Intake [kg DM (cow day)1]

Dairy_1 0.0 5.4 6.4 5.8 11.2 6.95 143.7 162.6 265.9 46.4 162.1 15.8

Dairy_2 0.0 5.2 10.4 0.0 11.2 6.79 128.8 154.3 265.8 34.5 128.2 17.3

Dairy_3 4.6 4.0 4.8 5.2 17.6 6.60 135.0 156.6 310.1 23.8 124.7 14.6

Dairy_4 5.8 5.0 10.0 0.0 16.0 6.60 159.6 150.6 279.5 29.1 183.3 19.3

Dairy_5 11.0 3.2 3.8 3.6 29.2 6.70 148.5 180.2 273.3 28.5 190.4 15.6Dairy_6 10.0 3.0 6.2 0.0 29.2 6.66 157.3 296.5 248.5 30.3 121.7 16.8

DM=dry matter; XP=crude protein; XF=crude fibre; XL=crude fat; ADL=lignin; GE=gross energy.a [g (kg FM) 1].

Th. Amon et al. / International Congress Series 1293 (2006) 217220218


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were used: ANOVA and the one factorial post hoc tests bStudentNewmanKeulsQ and

bScheffeQ. Homogeneity of variances was analysed with the Levene test statistic. Normal

distribution was checked by the rule 0.9bmeanb1.1 and 3sbmean.

3. Results and discussion

3.1. Methane production from dairy cattle manure

Table 1andFig. 1give the nutrient composition of the contrasting dairy cow manures

and the methane yield in norm litre per kg of volatile solids. The dairy cows of the

treatments: dairy_1 and dairy_2 had a low milk yield, dairy_3 and dairy_4 had a medium

milk yield, and dairy_5 and dairy_6 had a high milk yield. In each level of intensity,

manures with contrasting crude protein levels were produced. The manures with the higher

crude protein levels (dairy_1, 3, and 6) gave higher CH4 yields. Lignin in the manure

Fig. 1. Specific methane yield and standard deviation of contrasting dairycow manures (different letters indicate

significant differences atp b0.05; for treatment descriptions see Table 1).

Table 2

CH4 yield from pig manure, maize silage and rapeseed meal and influence of glycerine supplementation

Treatment Specific biogas yield Specific CH4 yield

[Nl (kg VS)-1] S.D. [Nl (kg VS)-1] S.D.

100% glycerine 1295 42.30 750 81.85

100% pig manure 412 n.m. 216 n.m.

94% pig manure,

6% glycerine

1114 27.82 617 37.04

Basic mixture (BM)a 569 35.12 335 20.64

BM + 15% glycerine 615 71.72 400 44.8

BM + 8% glycerine 591 20.56 365 12.71

BM + 6% glycerine 679 28.20 439 18.22

BM + 3% glycerine 634 17.68 411 11.46BM+ 6% glycerine+ 10%

rapeseed meal

701 8.19 432 5.05

a Basic mixture (BM)=31% maize silage, 15% maize corns, 54% pig manure (basis: fresh matter).

Th. Amon et al. / International Congress Series 1293 (2006) 217220 219


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reduced the specific CH4yield. The higher the concentrate level and milk yield, the greater

was the reduction in CH4 yield through an increase in lignin content. Manures of the

treatments dairy_3 and dairy_6 produced the highest specific CH4

yield. The cows of the

treatment dairy_6 were fed a protein-dominated diet which resulted in an increase in N

excretion. The diet of the treatment dairy_5 was well balanced in energy and protein

content. Feed conversion increased and nutrient excretion decreased. The manure of the

treatment dairy_5 showed the lowest specific methane yield.

3.2. Anaerobic digestion of pig manure and maize silage and effect of glycerine

supplementation

Increasing amounts of glycerine were added to pig manure, maize silage and rapeseed

meal and the resulting CH4yield was measured (Table 2). The basic mixture produced 335

Nl CH4 (kg VS)1

. Supplementation of glycerine always resulted in an increase in CH4production. A bco-fermentation effectQwas observed. The CH4yield of the basic mixture

supplemented with glycerine was higher than the combined CH4yields of both substrates

if digested separately. The co-fermentation effect was especially high with glycerine

additions of 36%.

4. Conclusions

Anaerobic digestibility of dairy cow manures is determined by the animals diet and

performance. Methane yields from dairy cow manure should not only be estimated with

one single default factor, but ratio composition and milk yield should be considered. This

is essential when estimating methane yields from agricultural biogas plants and when

setting up emission factors for inventory preparation.

Glycerine was found to increase the CH4 yield from anaerobic digestion of protein

dominated substrates (in our experiments: maize silage, rapeseed meal and pig manure).

For a stable digestion process, the amount of glycerine should not exceed 6%.

Acknowledgements

The work was funded by the Austrian Federal Ministry of Agriculture, Forestry,

Environment and Water Management, by Pioneer Saaten Ltd. Parndorf, by RaiffeisenWare Austria AG, by the Sudsteirische Energie und Eiweierzeugung Reg.Gen.m.b.H

Mureck SEEG, and within the scope of the Austrian Program on Technologies for

Sustainable Development, bEnergy systems of tomorrowQ. This program is an initiative of

the Austrian Federal Ministry of Transport, Innovation and Technology (BMVIT).

References

[1] V. Kryvoruchko, et al., Influence of nutrient composition on methane production from animal manures and

co-digestion with maize and glycerine, International Scientific Conference bBioecotechnologies and Biofuel

in AgroindustryQ, National Agrarian University of Ukraine, Kyiv, Ukraine, 2004 (June 34), pp. 143148.

[2] DIN 38 414, Bestimmung des Faulverhaltens bSchlamm und SedimenteQ, Beuth Verlag, Berlin, 1985.

[3] T. Amon et al., Biogas production from maize and dairy cattle manureinfluence of biomass composition on

the methane yield. Agriculture, Ecosystems & Environment (in press).

Th. Amon et al. / International Congress Series 1293 (2006) 217220220

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