Site-Specific Management of Miscanthus Genotypes for Combustion and Anaerobic Digestion: A Comparison of Energy Yields

Abstract

In Europe, the perennial C4 grass 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.

Miscanthus for biogas production: Influence of harvest date and ensiling on digestibility and methane hectare yield

“…For example, Baldini et al () and Mayer et al () found a SMY for miscanthus ranging between 160 Nml and 250 Nml CH 4 (g oDM) −1 . Other studies have reported a SMY of up to 309 Nml CH 4 (g oDM) −1 and that SMY generally decreases with later harvest dates (Kiesel & Lewandowski, ; Kiesel, Nunn, et al, ).…”

Breeding progress and preparedness for mass‐scale deployment of perennial lignocellulosic biomass crops switchgrass, miscanthus, willow and poplar

“…Multilocation field testing of wild and novel miscanthus hybrids selected by breeding programmes in the Netherlands and the United Kingdom was performed as part of the project Optimizing Miscanthus Biomass Production (OPTIMISC, 2012–2016). These trials showed that commercial yields and biomass qualities (Kiesel et al, ; Van der Weijde et al, ; Van der Weijde, Kiesel, et al, ) could be produced in a wide range of climates and soil conditions from the temperate maritime climate of western Wales to the continental climate of eastern Russia and the Ukraine (Kalinina et al, ). Extensive environmental measurements of soil and climate, combined with growth monitoring, are being used to understand abiotic stresses (Nunn et al, ; Van der Weijde, Huxley, et al, ) and develop genotype‐specific scenarios similar to those reported earlier in Hastings et al ().…”

Miscanthus ×giganteus biomass yield and quality in the Virginia Piedmont

“…To date, research on M. ×giganteus best management practices has largely focused on establishment and fertilization requirements needed to obtain satisfactory stands and high biomass production (Fike, Parrish, & Fike, ). Although several European studies have presented comparisons of different M. ×giganteus cultivars (Clifton‐Brown et al, ; Kiesel et al, ), limited information is available regarding suitable cultivars in the United States, and none for the Piedmont region.…”