• Energy Research

Soil is an important natural resource for agriculture and deserves special attention to possible problems that may arise. Heavy metal contamination of the soil can cause serious problems for the ecosystem in general, with consequent impact on water resources, soil quality, crop yield and human health due to the potential for heavy metal bioaccumulation in the different trophic levels of the food chain. Remediation of heavy metal contamination in soils can be done by using crops that have potential of growth and biomass production in marginal soils. The main objective of this work was to compare the growth and biomass production of Kenaf (cultivar H328, developed by IBFC in China) in soils contaminated by zinc (Zn), copper (Cu), chromium (Cr) and lead (Pb) in two different climate types (Tropical climate and Mediterranean climate). The study was performed in a pot essay and the plants were tested in clay soils. The soils were artificially contaminated, and the concentrations chosen were based on the limits established by the Decree Law 276 of 2009 (Portuguese regulation that establishes the regime for the use of sewage sludge in agricultural soils) - Zn: 450 mg/kg; Cr: 300 mg/kg; Pb: 450 mg/kg and Cu: 200 mg/kg. Results indicate that the growth in Mediterranean climate contaminated soils was more affected than in tropical climate. On average, the yields in Mozambique were 4900 g/m2, and in Portugal, merely 107 g/m2. Characterization of biomass indicate that kenaf can phytoextract zinc, copper, chromium, and not so much lead. Proceedings of the 28th European Biomass Conference and Exhibition, 6-9 July 2020, Virtual, pp. 205-208

The increasing demand for biomass for the production of bioenergy is generating land-use conflicts which might be avoided through the establishment of dedicated energy crops on marginal land, e.g. heavy-metal contaminated land. Yet, heavy metals contaminated soils might induce the reduction of crop yields and the quality of agricultural products, desertification, and the loss of ecosystem services. Therefore, assessment of bioenergy from marginal land should take into account constraining factors, such as productivity and biomass quality. Hence, the aim of this work was to study the effects of soils contaminated with heavy metals (Chromium, Copper, Lead and Zinc) on growth and productivity of kenaf. The study was performed in a pot essay and the plants were tested in sandy soils and clay soils. The soils were artificially contaminated, and the concentrations chosen were based on the limits established by the Decree Law 276 of 2009 (Portuguese regulation that establishes the regime for the use of sewage sludge in agricultural soils) - Zn: 450 mg/kg; Cr: 300 mg/kg; Pb: 450 mg/kg and Cu: 200 mg/kg. Results indicate that all the contaminated soils affected the growth and yields of kenaf. Highest yield reduction was observed in sandy contaminated soils than in clay contaminated soils, although this trend was not statistically significant. Copper was the metal that affected most yields and growth of kenaf in clay soils. In sandy soils, it was chromium that affected most, yields and growth of kenaf. Overall, yield reduction due to heavy metals contamination was above 50%, which may hinder its economical exploitation. Biomass is being characterized to evaluate the phytoremediation ability of this cultivar to the heavy metals studied. Proceedings of the 27th European Biomass Conference and Exhibition, 27-30 May 2019, Lisbon, Portugal, pp. 186-188

Abstract Side by side biomass productivities, harvesting time (autumn vs. winter) and frequency (annual vs. biennial) of three perennial grasses were compared under northern and southern Mediterranean climates. Miscanthus ( Miscanthus × giganteus Greef et Deu.) was compared to giant reed ( Arundo donax L.) in Catania (37°24′N, 15°03′E), and to switchgrass ( Panicum virgatum L.) in Bologna (44°55'N, 11°45′E). Generally, giant reed produced about 50% higher biomass than miscanthus in Catania. Miscanthus almost halved biomass productivity in the driest year, while giant reed reduced biomass yield by only 30% under the same conditions. In Bologna, miscanthus and switchgrass produced similar amounts of cumulative biomass over 6 years. Switchgrass kept more stable annual yields than miscanthus, which, however, evidenced a higher potential under favorable climate conditions. Autumn harvest significantly reduced biomass productivity and quality (moisture content, ashes, cellulose and hemicellulose), particularly under South Mediterranean climate. In Catania, autumn biomass was 50% (giant reed) to 85% (miscanthus) lower than winter biomass, while in Bologna, autumn cut reduced switchgrass yield by 20%. Biennial harvesting resulted in almost 40% lower cumulative biomass yield than annual cut, after 6 years.

Abstract Advanced biofuel production requires feedstock with specific composition in terms of quantity and quality. Decisions about the harvest time of perennial energy grasses have important implications for bioconversion process as well as for the life-span of the plant stand. Four-year data from long term-field trials were used to identify the optimal crop-specific harvest date (autumn vs. winter), in relation to advanced biofuel production. Three different perennial energy grasses (i.e., switchgrass, giant reed and miscanthus) were grown at Bologna and Catania (Italy), under northern and southern Mediterranean climate, respectively, adopting a low input management. In addition to the biomass yield and composition, the net energy value (NEV) from agricultural activities, and the energy return on investment (EROI) at the biorefinery gate was also evaluated. At Bologna, switchgrass biomass yield and quality (hemicellulose, cellulose and acid detergent lignin – ADL) were significantly enhanced when harvested in winter. At Catania, giant reed productivity, cellulose and ADL content were unaffected by harvest date, while hemicellulose and ash content decreased in winter. Biomass composition of miscanthus was more stable in Catania than Bologna, however, yield and components resulted significantly higher in Bologna than Catania, due mainly to the more even precipitation distribution throughout the vegetative crop development. The NEV was positive for all energy crops, treatments and locations, with the highest value for miscanthus grown at Bologna. The EROI of lignocellulosic bioethanol ranged from 4.16 for switchgrass in the autumn harvest at Bologna to 4.37 for miscanthus grown at Catania, which showed also the highest theoretical bioethanol production (169.2 kg h−1) at a feeding rate of 300 kg h−1 of raw material. Nonetheless, miscanthus grown at Bologna attained the highest bioethanol yield (12,254 L ha−1). This study proved that investigated perennial grasses are worth to be grown as lignocellulosic feedstock under low input for at least one decade, upon which Mediterranean region biorefineries may gain fourfold the energy invested.

Several crops species can be cultivated for energy production, being an auspicious option for the partial substitution of fossil fuels. In addition to energy production, some crops have also the ability to remove contaminants from the soil, potentiating soil remediation. Due to limitations in the availability of arable land, the hypothesis of introducing such crops on marginal soils, such as heavy metals contaminated soils, should be explored. In this context, this work aims to assess the effects of soils contaminated with zinc or lead on the productivity and quality of biomass of four oil crops Thlaspi arvense L., Brassica carinata A. Braun and Camelina sativa L. Crantz, spring and winter varieties, in the phytoremediation of soils artificially contaminated with Zn (450/900 mg.kg-1) or Pb (450/900 mg.kg-1). This work was carried out in pots, under controlled conditions, with the duration of one vegetative cycle. B. carinata was the most productive crop (600 g/m2), followed by T. arvense (350 g/m2). Both camelina’s showed lower yields (average 110 g/m2). B. carinata and C. sativa (both winter and spring varieties) can be considered tolerant to the heavy metals in study (tolerance index, yields in contaminated soils/yields in control soils, higher than 0.75) contrasting with the low tolerance displayed by T. arvense (tolerance index lower than 0.50). All oil crops exhibited high phytoextraction potential for zinc, but B. carinata showed the greatest accumulation index (metal content in the biomass from contaminated pots/metal content in the biomass from control pots), while the remaining oil crops, showed lower accumulation index. B. carinata and the spring variety of C. sativa showed the highest zinc accumulation in the leaves, while the winter variety of C. sativa, in the stems, and T. arvense, in the roots fraction. Contrasting, all these crops showed low phytoextraction potential for Pb, and the highest accumulation was observed in the roots fraction. Nevertheless, the metals content in the siliquae fraction of all oil crops tested was minor. Proceedings of the 28th European Biomass Conference and Exhibition, 6-9 July 2020, Virtual, pp. 30-33

Abstract Soil salinization is one of the major threats affecting crop production, in particular in the Mediterranean basin where over 1 Mha are salt-affected. Growing lignocellulosic crops, such as switchgrass (Panicum virgatum L.), in marginal saline soils could represent a valuable opportunity to mitigate land abandonment while producing feedstock for biofuels. However, little is still known about salt tolerance of upland and lowland switchgrass cultivars. This study addressed the morphological and physiological responses of Shawnee (upland) and Alamo (lowland) to a range of salinity levels from 0 to 14 dS m−1. Two consecutive experiments were carried out: one in petri dish to test the response to salinity at germination and early growth stages, the other in pot to evaluate the response to salinity until flowering stage (full-grown plants). Both upland and lowland cultivars were able to grow until “critical” salinity levels (14 dS m−1) but their tolerance differed depending on growth stage. Alamo showed a higher tolerance to salinity than Shawnee at very early growth stages (germination/emergence), presenting a germination rate more than double that of Shawnee (60 vs. 19%, main effect cultivar). Nevertheless, Shawnee resulted in a higher tolerance at a full-grown stage likely due to a more efficient salt exclusion capacity, as indicated by the higher residual soil electric conductivity at the end of the experiment detected in Shawnee pots. Final biomass production was anyhow considerably significantly higher in Alamo than Shawnee under any tested salinity level, which demonstrated the improved ability of lowland cultivar to produce biomass compared to Shawnee which otherwise might have invested resources into exclusion mechanisms.

A general obstacle to the development of perennial grasses is the relatively high cost of propagation and planting. The objective of the present study was to investigate new propagation and planting methods of giant reed (Arundo donax L.), miscanthus (Miscanthus x giganteus Greef et Deuter) and switchgrass (Panicum virgatum L.). Field and open-air pot trials were carried out in four different locations across Europe: hydro-seeding of switchgrass was tested in field trials at the experimental farm of the University of Bologna, Italy; stem propagation and bud activation methods of miscanthus were evaluated in field experiments in Péteri, Hungary; giant reed rhizome and stem propagations were compared in a field trial in Aliartos, Greece; finally, an open-air pot trial was carried out in Catania, Italy, using single-node stem cuttings of giant reed. Hydro-seeding emerged as a feasible and promising technique for switchgrass to ensure prompt seed emergence and weed control during plant establishment. Direct stem plantings of miscanthus were successful, and activated stem-buds were able to sprout in field conditions; however, timely stem transplant was determinant for shoot density and biomass yield. In giant reed, rhizome propagation showed a higher stem density and biomass yield than stem propagation; however, the yield gap was not significant from the second year onwards. Single-node rooting was mainly driven by air temperature. Nodes from basal stems showed higher rooting rates than median and apical ones. Growth regulator pretreatments enhanced rooting rate only at transplanting times under suboptimal air temperatures. In general, these experiments provided insights into propagation strategies aimed at enhancing the establishment phase of perennial grasses.

Uncertainty in predictions of long-term yields of perennial grasses makes business plans untenable in the short run. Long-term data across varied environments, including marginal lands, will help in preventing uncertainty while providing farmers and entrepreneurs with sound information to estimate reliable and affordable strategies on what, where, and how long to grow perennial grasses. In the present study, the long-term yields (11 to 22 years) of switchgrass (Panicum virgatum L.), miscanthus (Miscanthus × giganteus Greef et Deuter), and giant reed (Arundo donax L.) grown in northern and southern Mediterranean environments are reported. Switchgrass was grown in Greece and northern Italy, giant reed in southern and northern Italy, and miscanthus in southern Italy. Furthermore, lowland and upland switchgrass ecotypes were compared in Greece. Despite similar biomass productions (9.8 and 10.0 Mg DM ha−1 for uplands and lowlands, respectively), the upland ecotypes showed a significantly higher yield stability (CV of 24 and 32 % for uplands and lowlands, respectively) over a 17-year period. Biomass yield varied considerably across years and locations; giant reed outperformed switchgrass under northern Italy environment (21.2 and 13.6 Mg DM ha−1 for giant reed and switchgrass, respectively). Annual yield of switchgrass was 30 % higher in the north than south Mediterranean; miscanthus showed intermediate production compared to giant reed and switchgrass (average of 22 years) and a CV similar to switchgrass. In summary, these results evidence that multi-location, long-term trials are strongly needed to reduce uncertainties on crop yield variability and provide more accurate data from which optimized socio-economic and environmental predictions can be achieved.