title: Site-Specific Management of Miscanthus Genotypes for Combustion and Anaerobic Digestion: A Comparison of Energy Yields.
abstract: In Europe, the perennial C4grass miscanthus is currently mainly cultivated for energy generation via combustion. In recent years, anaerobic digestion has been identified as a promising alternative utilization pathway. Anaerobic digestion produces a higher-value intermediate (biogas), which can be upgraded to biomethane, stored in the existing natural gas infrastructure and further utilized as a transport fuel or in combined heat and power plants. However, the upgrading of the solid biomass into gaseous fuel leads to conversion-related energy losses, the level of which depends on the cultivation parameters genotype, location, and harvest date. Thus, site-specific crop management needs to be adapted to the intended utilization pathway. The objectives of this paper are to quantify (i) the impact of genotype, location and harvest date on energy yields of anaerobic digestion and combustion and (ii) the conversion losses of upgrading solid biomass into biogas. For this purpose, five miscanthus genotypes (OPM 3, 6, 9, 11, 14), three cultivation locations (Adana, Moscow, Stuttgart), and up to six harvest dates (August-March) were assessed. Anaerobic digestion yielded, on average, 35% less energy than combustion. Genotype, location, and harvest date all had significant impacts on the energy yield. For both, this is determined by dry matter yield and ash content and additionally by substrate-specific methane yield for anaerobic digestion and moisture content for combustion. Averaged over all locations and genotypes, an early harvest in August led to 25% and a late harvest to 45% conversion losses. However, each utilization option has its own optimal harvest date, determined by biomass yield, biomass quality, and cutting tolerance. By applying an autumn green harvest for anaerobic digestion and a delayed harvest for combustion, the conversion-related energy loss was reduced to an average of 18%. This clearly shows that the delayed harvest required to maintain biomass quality for combustion is accompanied by high energy losses through yield reduction over winter. The pre-winter harvest applied in the biogas utilization pathway avoids these yield losses and largely compensates for the conversion-related energy losses of anaerobic digestion.
authors.affiliation: Department Biobased Products and Energy Crops, Institute of Crop Science, University of Hohenheim Stuttgart, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kiesel
authors.affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University Aberystwyth, UK.
authors.forename: Christopher
authors.initials: C
authors.lastname: Nunn
authors.affiliation: Department Biobased Products and Energy Crops, Institute of Crop Science, University of Hohenheim Stuttgart, Germany.
authors.forename: Yasir
authors.initials: Y
authors.lastname: Iqbal
authors.affiliation: Department of Plant Breeding, Wageningen University Wageningen, Netherlands.
authors.forename: Tim
authors.initials: T
authors.lastname: Van der Weijde
authors.affiliation: Department Biobased Products and Energy Crops, Institute of Crop Science, University of Hohenheim Stuttgart, Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Wagner
authors.affiliation: Faculty of Agriculture and Natural Sciences, Konya Food and Agriculture University Konya, Turkey.
authors.forename: Mensure
authors.initials: M
authors.lastname: Özgüven
authors.affiliation: Russian State Agrarian University-Moscow Timiryazev Agricultural Academy Moscow, Russia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Tarakanov
authors.affiliation: Department Biobased Products and Energy Crops, Institute of Crop Science, University of Hohenheim Stuttgart, Germany.
authors.forename: Olena
authors.initials: O
authors.lastname: Kalinina
authors.affiliation: Department of Plant Breeding, Wageningen University Wageningen, Netherlands.
authors.forename: Luisa M
authors.initials: LM
authors.lastname: Trindade
authors.affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University Aberystwyth, UK.
authors.forename: John
authors.initials: J
authors.lastname: Clifton-Brown
authors.affiliation: Department Biobased Products and Energy Crops, Institute of Crop Science, University of Hohenheim Stuttgart, Germany.
authors.forename: Iris
authors.initials: I
authors.lastname: Lewandowski
keywords: biogas; biomass; energy yield; harvest time; moisture content; substrate-specific methane yield; yield