Biomass and methane yield of giant reed (Arundo donaxL.) as affected by single and double annual harvest

Abstract

The replacement of silage maize with giant reed as energy crop has been proposed as a mean for reducing the need of irrigation water as well as monetary and environmental costs of cultivation. Little is known about giant reed response to within‐season harvesting, and its effect on the methane production in anaerobic digestion. The effect of three harvest schedules on yield, biomass composition and methane production of giant reed was evaluated at one site of the Po Valley, northern Italy, for three consecutive years. In a completely randomized block design with four replicates the treatments applied annually were: (i) double harvest 1: first cut at the end of June + second cut at the beginning of October (DH1); (ii) double harvest 2: first cut at the end of July + second cut at the beginning of October (DH2); (iii) single harvest at the beginning of October (SH). The crop stand was established in the year 2015 and treatments were repeatedly applied in the years 2016, 2017 and 2018. The SH treatment determined the highest average annual dry matter (DM) yield (59.0 Mg DM ha−1). The DM yield for treatments with double harvest was significantly lower, that is, −30% for DH1 and −15% for DH2. In terms of specific methane yield there was little advantage in harvesting biomass twice during the growing season. The average specific methane yield varied substantially between years (i.e. from 144 to 233 ml CH4 g−1 VS), and in every year the values tended to decrease with the ageing of harvested biomass. Methane yield per hectare, however, was driven by DM yield, thus SH also determined the highest average value (9110 m3 CH4‐STP ha−1). In conclusion, the single annual harvest at the end of the growing season is an ideal strategy for maximizing methane production from giant reed.

Potassium Hydroxyde Pre-Treatment Enhances Methane Yield from Giant Reed (Arundo donax L.)

“…These SMY values are in line with the CH 4 yield obtained from other substrates commonly used in AD such as, for example, cattle slurry, wheat straw, vegetable waste, garden waste [3,36] or from Brassica napus which recently was reported to yield up to 259 mL CH 4 g −1 VS when irrigated with abattoir wastewater [37]. In this study, untreated giant reed (GR) reached 192 mL CH 4 g −1 VS, which is consistent with what was reported by other authors for this crop [17,38] and is comparable with the SMY of miscanthus, which varied between 166 and 202 mL CH 4 g −1 VS, depending on the genotype [18].…”

Arundo donax L. Biomass Production in a Polluted Area: Effects of Two Harvest Timings on Heavy Metals Uptake

“…Giant reed biomass has found wide applications in energy production; it can be used in combustion, gasification and pyrolysis and to produce biogas [1]. In fact, when harvested in autumn its biomass can be used in anaerobic digestion in substitution/partial integration with the traditional energy crops [48][49][50], and the biomass harvested in winter can be used for the combustion process, due to its high heating value of about 18.7 MJ kg −1 [1].…”

Model-Based Assessment of Giant Reed (Arundo donax L.) Energy Yield in the Form of Diverse Biofuels in Marginal Areas of Italy

“…The Bologna province (BO, Emilia Romagna region) contains an overall ML area of 880 km 2 . The climate in the region is temperate sub-continental, characterized by relatively high temperatures and evenly distributed precipitation throughout the year [25]. Average annual air temperature is about 13 • C, fluctuating from 0 to 5 • C in winter months, to peaks over 30 • C in the period June-August.…”

“…Furthermore, the very deep root system allows the crop to adsorb soil pollutants, favoring soil phytoremediation and aggregation [10]. Thanks to the advantageous balance between biomass yield, fiber composition and amount and cost of agronomic inputs needed to grow the crop under unstressed conditions, giant reed, as a second-generation energy source, demonstrated to provide higher energy yield per hectare compared to conventional crops also in Mediterranean and Italian environments [17,24,25]. Corno et al [24] reported that giant reed produces on average 11,000 L ha −1 of bioethanol, which is approximately 1.25 times more than the yield obtainable from miscanthus, 1.8 times more than sugar cane and sugar beet, and 3.7 times more than corn and sweet sorghum.…”

“…As regards biogas production, giant reed is characterized by a lower anaerobic bio-gasification potential compared to conventional crops (i.e., corn, sorghum and rye) because of the absence of aboveground storage organs containing high-energy compounds such as starch [24]. Nevertheless, the high biomass productivity allows to obtain higher biomethane production per hectare compared to other energy crops, especially when a single annual harvest at the end of the growing season is adopted [25]. Although the crop biomass does not require any fermentation pretreatment when it is harvested within a range of dry matter content between 30 and 38% [27], a recent study showed that a thermo-chemical pre-treatment with KOH at 120 • C was able to increase the methane yield by about 20%, while reducing the anaerobic digestion duration by about 10 days [28].…”