A growing demand for green energy production arises as more and more people realize just how crucial it is to find alternatives for our current energy sources. This brings along the dilemma of energy crops: which one is the best for green energy production, what qualities and yields do they have? The article below will answer these questions for you, focusing on two energy crops: Arundo donax (or giant reed grass) and Miscanthus. Both are tall, rapidly-growing grasses, still Arundo donax holds more advantageous qualities than Miscanthus. Read further and find out why Arund donax is a better choice for green energy production.
Higher tolerance and adaptability than Miscanthus
In a study carried out to compare the tolerance of Miscanthus and Arundo Donax, both species were put under different soil moisture conditions, which conditions included flooded, mild and extremely dry soils. Although neither of the plants showed signs of stress, such as leaf curling or wilting, 3 days after flood treatment Miscanthus became chlorotic and its growth temporarily stopped.
As for rhizome survival, the rhizomes of the giant reed grass were also found more resilient to drought stress in comparison to Miscanthus. Fragments put under severe drought showed low rates of survival for both species, still the survival rate was 50% for Arundo donax and 0% for Miscanthus. It has also been proven that Arundo donax becomes drought tolerant after only one year of establishment
While it is true that Miscanthus may tolerate a wide range of environment, Arundo was found to tolerate wider ranges of pH and salinity than Miscanthus (a pH in the range of 5.0 to 8.7).
As a bonus advantage, it should be mentioned that Arundo donax can survive even in saline and metal-contaminated soils as well.
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Table 1 - Total concentration of As (Arsenic), Cd (Cadmium) and Pb (Lead) in mg/kg
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Shoot height and dried biomass of giant reed plants after 70 days of cultivation
Higher biomass yield than Miscanthus
Knowing the yield of energy crops is vital in order to choose right and opt for the plant which can provide you with the highest amount of biomass and the biggest profit possible.
It is believed that Arundo donax has a higher biomass yield than Miscanthus. With a yield of 15-41 dry tonne per hectare (fall harvest) and 21-49 dry tonne per hectare (winter harvest) Arundo donax beats Miscanthus, which reportedly has a yield of 2.4 dry tonne per hectare (during the first year) and it only increased later to 29.43 dry tonne per hectare. On wetlands Arundo achieved more than two times of average dry biomass production than Miscanthus.
As a result, the higher biomass yield that was gained from Arundo donax, the total energy output and net energy output of Arundo were also higher than those of Miscanthus.
Thanks to its fast growth rate, two harvests per year are feasible for Arundo but not recommended for Miscanthus. Harvested Arundo donax can be stored in 600-800 kg/bales which reduces logistic costs, too!
Higher bioethanol yield
As for bioethanol, Arundo donax has a potential yield of 265 kg ethanol per dry metric ton of raw material, thanks to its sugar yield, which is way higher than that of Miscanthus.
The following data is also pretty convincing: 4 tons of Arundo donax is equal to 1 ton of cellulose ethanol and 1 tonne of Arundo donax is equal to 330 liters of cellulose ethanol. With ethanol value being around 0.5 US dollars per litre (based on 10 year average of ethanol prices), and assuming that the biomass price is around 0.02 US dollars per kg ($20/tonne) this gives a good idea of the raw material potential of Arundo Donax.
Altogether, Arundo donax shows better performance than Miscanthus in production of bioethanol, and also has numerous other ways to use it.
Better effects on soil quality
Apart from its outstanding yields of biomass and bioethanol, the phytoremediation potential of Arundo donax also has to be mentioned. This natural procedure uses living plants to cleanse polluted soil and groundwater.
Planting Arundo donax is a cost-effective approach of this type of soil restoration. Due to its high metabolism rate it breaks down contamination faster than most plants. Arundo is likely to have a better ability for trace element removal due to its higher biomass yield. Moreover, the N and P phyto-uptake of Arundo are also significantly higher than that of Miscanthus.
As a byproduct the use of this plant also reduces erosion. As a result, you can make use of marginal and abandoned lands as well.
A study carried out in Pakistan exemplifies the effect of Arundo donax as a remedy to polluted groundwater. The presence of arsenic in ground waters made it dangerous to use it as drinking water, but this study showed that when grown in hydroponics cultures with arsenic concentrations up to 1000 µg l−1, the giant reed could translocate the metals absorbed into the shoot and to accumulate metals in the stalk and leaves above the root concentration, showing no toxic effects at As concentrations up to 600 µg l−1.
