• Energy Research

Suitable plant species are able to accumulate heavy metals and to produce biomass useful for non-food purposes. In this study, three endemic Mediterranean plant species, Atriplex halimus, Portulaca oleracea and Medicago lupulina were grown hydroponically to assess their potential use in phytoremediation and biomass production. The experiment was carried out in a growth chamber using half strength Hoagland's solutions separately spiked with 5 concentrations of Pb and Zn (5, 10, 25, 50, and 100 mg L(-1)), and 3 concentrations of Ni (1, 2 and 5 mg L(-1)). Shoot and root biomass were determined and analyzed for their metals contents. A. halimus and M. lupulina gave high shoot biomass with relatively low metal translocation to the above ground parts. Metals uptake was a function of both metals and plant species. It is worth noting that M. lupulina was the only tested plant able to grow in treatment Pb50 and to accumulate significant amount of metal in roots. Plant metal uptake efficiency ranked as follows: A. halimus > M. lupulina > P. oleracea. Due to its high biomass production and the relatively high roots metal contents, A. halimus and M. lupulina could be successfully used in phytoremediation, and in phytostabilization, in particular.

Food security is a complex issue whose comprehension requires multidisciplinary research exploring environmental, socio-economic, and policy aspects. World population is expected to continue increasing in the next decades. As a consequence, the global food demand is also expected to increase, exacerbating the contribution of food consumption and production patterns to environmental problems and climate change. In addition, the problem of socio-economic inequalities is also noteworthy, with a very high number of undernourished people at global level. Considering the complex nature of food security, the integration of environmental and socio-economic indicators is much needed for assessing its multiple dimensions. In this study, environmental and socio-economic indicators were assessed to explore the sustainability of food patterns and food security in Lebanon. Environmental indicators were calculated to assess the environmental costs and impacts of the Lebanese and refugee diets. All the environmental indicators calculated for the Lebanese diet resulted higher compared to the refugee diet. The overall contribution of the refugee diet to the investigated impact categories resulted in about 25%, confirming its significance in terms of direct and indirect natural resources consumption and environmental impacts. The socio-economic indicators showed that food security is a critical issue for the Lebanese population and, particularly, for the refugees living in Lebanon. In particular, 59% and 15% of Lebanese and refugee populations resulted having an adequate individual access to food. In conclusion, the outcomes of the study provide scientific information to support policy-makers and a benchmark for future studies aimed at improving food security in Lebanon.

Abstract Bio-based waste management processes, as anaerobic digestion, couple waste treatment with energy production using natural processes based on microbial metabolism. Microbial fuel cells (MFCs) combine the production of electric power to the lowering the load of waste organic and mineral nutrients. In this study, the coordinated utilization of MFCs with anaerobic digestion in a two-steps process has been investigated. A single chamber, air cathode, membraneless MFCs with graphite plates as electrodes, fed with the organic fraction of municipal waste, was run for 4 weeks. The energy obtained was characterized by a maximum current density of 42.3 mA/m2 kg, a power density of 1.98 mW/m2 kg, and a columbic efficiency ηC ∼5%. pH of the slurry was maintained at 6.8 ± 0.9 along the experiment. MFC spent substrate was then used in a batch experiment for biohydrogen and biomethane production through AD. The biohydrogen increased by 276%, as compared to that produced from the same fresh untreated Organic Fraction of Municipal Solid Waste. A decrease in methane production of 66% was however observed. The analysis of MFC spent substrate revealed the prevalence of Lactobacillaceae, Bacillaceae, Clostridia and Pseudomonadaceae, with Pseudomonas aeruginosa colonizing the cathode.

Anaerobic digestion of food waste is aimed both at the reduction of the volume of waste and the production of methane. Carbonaceous additives such as activated carbons were widely studied as enhancer of methane production. In this paper a low-cost alternative additive, the biochar, was proposed to assess its use for improving both the operational stability and the energetic output of anaerobic digestion. The main objective of the present work is to assess and quantify the increase of CH4 yields induced by the biochar addition and to identify all the main mechanisms responsible of this improvement. The risk related to the Polycyclic Aromatic Hydrocarbons release from biochar in the anaerobic digestion media was discussed as well. To this aim, biochar obtained from steam assisted slow pyrolysis of Populus nigra L. up to 600 °C was used. Anaerobic digestion of food waste mixture was carried out in a batch reactor in mesophilic conditions (37 °C). Four tests were conducted by adding 0, 1, 4 and 10 wt% of biochar on wet food waste mixture basis. Results showed that more CH4 is produced even in the first hours of the anaerobic digestion test when 10 wt% of biochar was added to the food waste mixture (about 65 wt% more at 96 h), thus denoting a reduction of the lag phase. A total increase of CH4 yield of 14 and 42% when 4 and 10 wt% of biochar was added to the food waste mixture. In conclusion, analyses of both the liquid phase during the tests and biochar sampled at the end of anaerobic digestion process revealed that biochar favored the decomposition of acetic acid, adsorbed some inhibitors such as butyric acid, and provided a suitable habitat for microbial colonization.

To investigate the effects of moist olive husks (MOH-residues) on soil respiration, microbial biomass, and enzymatic (o-diphenoloxidase, beta-glucosidase, dehydrogenase and alkaline phosphatase) activities, a silty clay soil was incubated with 0 (control), 8 x 10(3) (D), 16 x 10(3) (2D) and 80 x 10(3) (10D) kg ha-1 of MOH-residues on a dry weight basis. Soil respiration and microbial biomass data indicated that the addition of MOH-residues strongly increased microbial activity proportionally to the amounts added. Data of qCO2 suggested that the respiration to biomass ratio of the microbial population was strongly modified by MOH-residues additions during the first 90 days of incubation. The qCO2 data suggested a low efficiency in energy yields from C oxidation during the first 2 months of soil incubation. qFDA seemed to be relatively unaffected for treatments D and 2D as compared to the control, but was significantly lowered by the application of 10D, showing the lowest hydrolytic activity of microbial biomass in this treatment up to 360 days of incubation. o-Diphenoloxidase activity was delayed, and this delay was extended with the addition of larger quantities of MOH-residues. Alkaline phosphatase, beta-glucosidase and dehydrogenase activities were in line with the findings on microbial biomass changes and activities. The biological and biochemical data suggest that the addition of a large quantity of MOH-residues (80 x 10(3) kg ha-1) strongly modifies the soil characteristics affecting the r- and K-strategist populations, and that these changes last for at least the 360 days of incubation. The data also suggest that application rates exceeding 16 x 10(3) kg ha-1 are not recommended until the agro-chemical and -physical functions of the soil are further studied.

The influence of temperature and heating rate on the yield and properties of biochar derived from pyrolysis of solid olive mill waste (pomace) was investigated. Three pyrolysis temperatures (430 +/- 10 degrees C, 480 +/- 10 degrees C and 530 +/- 10 degrees C) and 3 heating rates (25 degrees C min(-1), 35 degrees C min(-1) and 45 degrees C min(-1)) were studied. The biochar production was carried out using a vertical downdraft gasifier. Increasing the pyrolysis temperature, and/or the heating rate, the biochar yield lowered, the C content and biochar aromaticity increased and the surface functional groups were reduced. The highest biochar yield was obtained by low pyrolysis temperature (430 +/- 10 degrees C) and low heating rate (25 degrees C min(-1)). This biochar is characterized by a high heating value (31 MJ/kg) that makes it a possible fuel candidate and, in the meantime, due to its high concentration in C (70.2%-84.1%), low electrical conductivity (0.28 dS m(-1)-0.47 dS m(-1)) and the lack of phytotoxicity it is suitable for amendment in agricultural soils and for long term carbon sequestration.

The effect of four triazinyl-sulfonylurea herbicides (cinosulfuron, prosulfuron, thifensulfuron methyl, triasulfuron) on soil microbial biomass, soil respiration, metabolic activity, metabolic quotient, and some enzymatic activities (acid and alkaline phosphatase, β-glucosidase, arylsulphatase, and fluorescein diacetate hydrolysis) were monitored under controlled conditions over 30 days. The herbicides were applied at the normal field dose (FD) and at ten-fold (10 FD) the field dose, in order to mimic a long term toxic effect. The measured soil microbial parameters showed that the FD had slight effects on soil microflora, while at 10 FD the tested herbicides exerted a stronger detrimental effect on soil microbial biomass and its biochemical activities.