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Anaerobic mono-digestion of lucerne, grass and forbs - Influence of species and cutting frequency

Wahid, R; Feng, L; Cong, WF; Ward, A; Møller, HB and Eriksen, J (2018) Anaerobic mono-digestion of lucerne, grass and forbs - Influence of species and cutting frequency. Biomass and Bioenergy, 109, pp. 199-208.

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Online at: https://www.sciencedirect.com/science/article/pii/S0961953417304506?via%3Dihub

Summary

In the present study, biogas potentials of multispecies swards including grass, lucerne, caraway, ribwort plantain and chicory from two- and four-cut regimes (Mix-2 and Mix-4) for mono-digestion applying batch and continuous modes under lab-scale conditions were investigated. The gas yields in terms of volatile solids (VS)loaded from Mix-2 and Mix-4 were compared with pure stand lucerne from the four cuts regime (Lu-4). The batch test results indicate that methane yield on a VS basis was highest from Mix-4 (295 L kg−1), followed by Mix-2 (281 L kg−1) and Lu-4 (255 L kg−1). The results were confirmed with continuous experiments, during which the reactor digesting Mix-4 was stable throughout the experiment with low ammonia and volatile fatty acid (VFA)concentration. Meanwhile, mono-digestion of Lu-4 led to elevated VFA levels, even at a comparatively low organic loading rate of 1.76 g L−1 d−1 but it was not possible to ascertain whether this was due to organic overload alone or if high ammonia levels during Lu-4 digestion were contributing to the reduced performance. It was found that four cuts per year was suitable for a lab-scale mono-digestion system as the substrate was less fibrous and has lower dry matter content, which minimize blockage during feeding and digestate unloading. Micronutrient concentrations, including cobalt, nickel and molybdenum decreased over time during the continuous experiments and were critically lower than the optimum concentration required by methanogens, particularly in Mix-4, but the gas yields of the reactor treating this substrate showed no decrease over time.


EPrint Type:Journal paper
Subjects: Crop husbandry > Crop combinations and interactions
Soil > Nutrient turnover
Research affiliation: Denmark > Organic RDD 2 > MultiPlant
DOI:10.1016/j.biombioe.2017.12.029
Deposited By: Eriksen, Senior scientist Jørgen
ID Code:32974
Deposited On:14 May 2018 12:50
Last Modified:14 May 2018 12:50
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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