CONCLUSIONS

UNIVERSITY OF HELSINKI
FACULTY OF AGRICULTURE AND FORESTRY
Annukka Pakarinen
University of Helsinki, Department of Food
and Environmental Sciences, Helsinki
Maritta Kymäläinen
HEMP AND WHITE LUPIN FOR
MESOPHILIC BIOGASIFICATION
INTRODUCTION
Energy crops for biogasification must not
compete with food production and they
must have high biomass and biogas yields.
The contents of lignin and different
polysaccharides, like cellulose and
hemicelluloses, of the crops and their
degradability in biogasification have a key
role in the hydrolysability of the material
and thus in the biogas yield. In this work,
two annual crops cultivated in boreal
conditions, fibre hemp and white lupin,
were studied for their production of
methane and degradation of proteins (i.e.
formation of ammonia), different
carbohydrates and lignin in mesophilic
conditions to evaluate their suitability to
biogas production.
Methane
HAMK University of Applied Sciences,
Biotechnology and Food Engineering,
Hämeenlinna
Frederick Stoddard
University of Helsinki, Department of
Agricultural Sciences, Helsinki
Liisa Viikari
University of Helsinki, Department of Food
and Environmental Sciences, Helsinki
RESULTS
Ammonia
Cumulative methane production in 30 days
averaged about 345 and 200 ml/gVSfeed
for hemp and lupin, respectively.
Ammonia formation corresponded to conversion
of around 35% and 63% of the total nitrogen of
hemp and lupin, respectively.
Conversion of carbohydrates
Hemp
MATERIALS AND
METHODS
Substrates
Conversions of C6 sugars, C5 sugars and lignin
in 30 days of biogasification.
White lupin
separated into leaves, beans and stems
Hemicellulose composition in the raw materials
and after 30 days of biogasification.
Hemp
White
lupin
Chemical composition of hemp and lupin cultivated in boreal
conditions. Biomass yields 14 and 18 t DM/ha/a for hemp and
white lupin, respectively.
Biogasification
Inoculum from a sewage sludge digester.
Batch tests in 500 ml vessels at 37 °C.
Max incubation time 30 days; samples for
analyses at 1, 2, 5 and 9 days.
Total-N and NH3-N
Kjeldahl method.
analyses
by
Carbohydrate and lignin analyses
Acid hydrolysis [1] and acid methanolysis
[2] was used to depolymerize freeze dried
samples.
HPAEC-PAD was used to determine sugars
from acid hydrolysates, GC was used to
determine silylated hydrolysates after acid
methanolysis.
Lignin was analysed gravimetrically.
References:
1.
Sluiter, A., Hamnes, B., Ruiz, R., Scarlata, C., Sluiter, J., Templeton, D., Crocker, D:
Determination of structural carbohydrates and lignin in biomass. Laboratory
analytical procedure. [http://www.nrel.gov/biomass/analytical_procedures.html] 2010.
2.
Sundberg A, Sundberg K, Lillandt C, Holmbom B: Determination of hemicelluloses and
pectins in wood and pulp fibres by acid methanolysis and gas chromatography. Nord
Pulp Pap Res J 1996, 11:216–219.
Conversions of C6 sugars, C5 sugars and lignin in
30 days of biogasification.
Hemicellulose composition in the raw materials
and after 30 days of biogasification.
CONCLUSIONS
•The protein-rich white lupin produced clearly higher yield of methane compared to
cellulose-rich fiber hemp. The methane productions were 26,2 and 58,3 MWh ha-1, the
latter corresponding to typical methane yields of maize.
•The nitrogen conversion to ammonia in white lupin reached a high level (63%) which
indicates the value of digestate as fertilizer.
•C6-sugars producing methane are more easily available from lupin compared to hemp
due to lower cellulose and higher galactan content of white lupin. This was clearly
observed in higher conversion of C6-sugars in white lupin (n. 80%) than hemp (n.
50%).
•C5-sugars and pectin were clearly less efficiently converted during gasification
compared to C6-sugars - about 5% and 10% of C5-sugar conversion for hemp and white
lupin, respectively. Xylan content of hemp was over 10% and about 6% of DM in lupin.
Both substrates contained noticeable amount of pectin, about 6% of DM, abundant as
galacturonic acid.
•Lignin was not expected to be converted. A minor decrease in lignin content of lupin
measured in this study is presumably due to the protein present in Klason lignin.
Acknowledgements: Funding for the field trials was provided by the Academy of Finland's Sustainable Energy programme SusEn under the grant "Carbon-sequestering species mixtures for sustainable energy cropping", in the consortium "Bioenergy, electricity and emission trading markets (BEET)". The work was also supported by the The Graduate
School for Biomass Refining. Ms Laura Kannisto and Ms. Mervi Salonen are acknowledged for excellent technical help.

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