The Agronomy And Economics of Arundo Donax: the Importance of Energy Crops – PART 2

importance of energy crops


Arundo donax (or giant reed) is a perennial energy crop with such outstanding qualities which are gaining increasing importance nowadays: low cost production, low input, high yields and fast growth rate, just to mention a few. As global warming brings along uncountable (and often unpredictable) changes in agriculture and economics, it is time we realized the importance of energy crops (like giant reed) and considered investing into their cultivation on an industrial scale. 

Studies focusing on the agronomy and economics of giant reed can be divided into three fields: yield, harvest and economic as well as environmental impact assessment. In this article below, the researches considering economic and environmental impact are summarised, based on a systematic literature review

Economic and environmental importance of energy crops

The energy and economic possibilities in 15 annual and perennial species (including giant reed) produced under temperate and tropical regions was studied by Fazio and Barbanti. What they found was that the complementary use of crop residues boosted net energy and energy efficiency. In their scenario giant reed was deemed to be the best lignocellulosic crop. 

A similar research was made by assessing economic and ecologic characteristics of four lignocellulosic herbaceous plants (switchgrass, silver reed, giant reed and hybrid pennisetum) planted in contaminated lands of China. Although all ecotypes were found to have huge ecological values, giant reed was treated as optimal in economic value. With around 8 100 00 hectares of contaminated lands in China alone (and altogehter some 22 million hectares in our world), realizing the importance of energy crops with phytoremeditational potentials is vital – if not urgent.

As for the Mediterranean, Fernando et al. made an excellent review on the environmental, economic and socioeconomic aspects of giant reed, mischantus and switchgrass produced on Mediterranean marginal lands. Perennials, like Arundo donax, were found to be more environmentally friendly than annual crops as input necessities are lower and permanence period is longer. In 2017, a whole study based on a simulation model was published, in which the response of giant reed in the marginal areas of an agricultural district of southern Italy (Destra Sele) and expected farm incomes under climate change (2021–2050) were evaluated. It has been confirmed that growing giant reed on marginal farmlands (unsuitable for food crops) can support the resilience of farming communities, with giant reed chip production being twice as much profitable than chopped biomass: 636 euros versus 339 euros per hectare. 

Arundo donax as biofuel

Mehmood et al.made a detailed overview on biomass production potentials on marginal lands for nine species, including giant reed, and concluded that this crop was suitable for production in the Mediterranean region and had impressive bioenergy feedstock indices. Nassi O Di Nasso et al. also reviewed literature written on economic and environmental characteristics of giant reed production in Italy. The authors concluded that giant reed has high production levels, low nutrient requirements, a positive energy balance together with the lowest greenhouse gas emissions and the lowest cost/ton of dry biomass or per unit of energy. 

Ascenso et. al evaluated multiple biomass-feedstock in the optimisation of power and fuel supply chains for sustainable mobility by using a linear programming framework. In their study, first and second generation bioethanol and bioelectricity supply chains were assessed considering corn, stover, giant reed, miscanthus, poplar and wood residues as possible biomass feedstock.  

As for bioethanol,the potential process yield of Arundo donax is 265 kg of ethanol per dry metric ton of raw material, which can be put into the following formula:

4 tons of Arundo = 1 ton of cellulose ethanol

1 tonne of Arundo = 330 liters of cellulose ethanol

In a study carried out by Accardi et. al a simplified process for the production of second generation bioethanol from giant reed was economically evaluated, by using a simulation software. The results of this research propose that giant reed production for biofuel has high economic potential, and it has the possibility to create a competitor for oil and other fossil fuels. 

When talking about biogas, giant reed has noteworthy results as well:

  • Arundo donax: total production on 1 ha = 16,000 m3 / ha,100 metric tons of silage / ha x 160 m3 of biogas / metric ton)
  • Corn: total production on 1 ha = 11,000 m3/ ha, 50 metric tons of silage / ha x 220 m3 of biogas / metric ton)
  • Triticale: total production on 1 ha = 4,800 m3/ ha, 30 metric tons of silage / ha x 160 m3 of biogas / metric ton

Giant reed enables 150% more biogas production than corn, and with 50% lower input considering price. The explanation is simple: corn is a plant one has to take care of every year with high input: buying and planting seeds every year and treating it with pesticides as it is highly sensitive. On the contrary, Arundo donax – once established – do not require chemicals nor weed controlling, it has no pests typical for this species, and as it is a perennial, soil preparation is only needed once. 

The importance of energy crops in soil carbon sequestration

Pindozzi et al. analysed land use changes and the importance of energy crops in hilly Italian areas and found that perennial crop production in these areas would be favourable in all economic dimensions. In the Campania region, giant reed production above 750 metres could yield about 12.6 t/ha and could also immensely reduce soil erosion, as about 10 million tons of CO2would be saved per year by planting perennials, like Arundo donax. Read more about soil carbon sequestration of giant reed here! 

Clearly, results differ by location and the method used, but most studies showed that giant reed could be an economic and environmentally wise choice in marginal and less favoured areas – and, altogether, in the years of climate change. 

Click here to read part one on the importance of energy crops!

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