Material and methods
Experimental trial has been conducted using the winter cut of Giant Reed and Miscanthus crops, harvested on the 9th of
December, fine-cut and put in mini-silos of 1.5 l of volume for a silage phase of 44 days. In this preliminary experiment, It has been decided to evaluate a biomass with a reduced moisture content. Methane production has been analyzed by the AMPTS II gasometer. Three replicates in batches of 400 ml were performed for each treatment. The trial had a control treatment performed with 400 g of inoculum, degased pigs slurry from a biogas plant. Giant Reed and Miscanthus treatments were performed with an inoculum/crop volatile solid ratio equal to 2.
BMP has been expressed in ml per g of solid volatile by subtracting the intrinsic biogas potential of the inoculum. Experiments were conducted for a total of 39 days, till the methane production was considered not relevant.
Results
The methane production for this winter cut was, as expected, not particularly high, with cumulative values of 132.2 ml CH4 VSg-1 for Giant reed and of 128.6 ml CH
4
VSg-1 for Miscanthus, which are lower than the average maize yield (345 ml CH 4
VSg-1; Ragaglini et al., 2014). Thus, Giant reed and Miscanthus can be considered
having the same BMP. It could be observed a second peak of Giant reed, which could be related with fermentative processes during digestion.
The suitability of Giant reed and Miscanthus silages for biogas
production: a preliminary comparison
Francesco Candoni*, Francesco Danuso, Mario Baldini, Fabrizio Ginaldi
*Dipartimento di Scienze Agrarie e Ambientali, Università degli Studi di Udine,
corresponding author: [email protected] research founded by University of Udine
XLIII° Convegno della Società Italiana di Agronomia – Pisa, 17-19 settembre 2014
XLIII° Convegno della Società Italiana di Agronomia – Pisa, 17-19 settembre 2014
Introduction
The recent policies enacted by EU foresee an increased interest for cultivation of energy crops, mainly in marginal areas. Giant reed (Arundo donax L.) and Miscanthus (Miscanthus sinensis x giganteus) are two of the most promising energy crops (Ragaglini et al., 2014). Perennial grasses have already been recognized as high-yielding crops that can minimize environmental impacts, because of the reduced input requirements. Biochemical Methane Potential (BMP) has been widely used to assess methane yields of organic matter when degraded in anaerobic conditions, including plant biomass (Raposo et al., 2012). The aim of this study was to start a comparison of silage biomass of Giant reed and Miscanthus, with the purpose to evaluate their suitability for biogas production, in a northeast area of Italy.
Tab 1. Experimental treatments
Fig. 1. BMP of Giant Reed and Miscanthus (3 replicates)
References: Ragaglini et al., (2014). Suitability of giant reed (Arundo donax L.) for anaerobic digestion: Effect of harvest time and frequency on the biomethane yield potential. Bioresour. Technol., 152, 107-115 Raposo et al., (2012). Anaerobic digestion of solid organic substrates in batch mode Renew Sust Energ Rev, 16(1), 861-877.
Conclusion
The low values of BMP could be explained by the delayed harvest in December, suitable for burning but usually not suggested
for biogas production. Considering that in field conditions, Giant reed mean yields are around 30 t ha
-1, while for Miscanthus
only 20 t ha
-1(Ragaglini et al., 2014), the spread of yields between two crops with a similar BMP reduces the suitability of
Miscanthus for biogas production. Only in the end of the research plan it will be possible provide a more detailed assessment,
involving summer cuts with higher moisture and digestibility of VS content.
Miscanthus
Giant reed
AMPTS II
Acknowledgments: Daniele Goi for the use of AMPTS II, Francesco da Borso for scientific advices , Fabio Zuliani and Valentina Cabbai for technical support
Treatments Material Crop
(g) Inoculum(g) Water(g) VS crop(%) VS inoculum(%) Ratio
Control Inoculum 0 400 0 0 4.5 0
A Giant reed 21 376 9 39.9 4.5 2
M Miscanthus 19 381 0 46.1 4.5 2
Crop pH start pH 44days TS start TS 44days
Giant Reed 5.49 4.53 44.6 % 43.1%
Miscanthus 6.51 5.91 53% 49.2%
