Factors influencing sorption of trace elements in contaminated waters onto ground nut shells

Biosorbent materials such as nut shells has been considered a promising alternative to the classic methods to remove potentially toxic elements from contaminated waters, improving water quality for other uses. The present study evaluated the sorption capacity of almond, hazelnut, pistachio and walnut shells for the single and simultaneous removal of As, Cd, Co, Hg, Ni, Pb and Zn from contaminated waters. The influence of key parameters such as sorbent dose, ionic strength (ultrapure water vs. mineral water), element competition (mono-vs. multi-element spiked solution) and initial element concentration (maximum allowed value in wastewater discharges and ten times lower) was assessed. Hazelnut shells stood out as the material with higher potential to remove Cd, Co, Hg, Ni, Pb and Zn in the tested conditions, achieving up to 99% of removal (Cd and Pb). Arsenic was not removed by none of the studied materials and the removal of Cr was only obtained in a simple matrix and in mono-element solution (41% of removal). An increase of matrix complexity negatively affected the sorption capacity of all the biosorbents in the removal of all the elements tested. The same behavior was obtained when the elements were simultaneously present in solution, with Pb, Cd and Hg being highly influenced by the presence of other elements. The increase in sorbent dose from 1 to 5 g/L allowed to at least duplicate the removal of Cd, Co, Ni and Zn by all the biosorbents. When decreasing the initial element concentration ten times the maximum allowed value in wastewater discharges, a significant increase of elements removal was attained, more pronounced for Hg and Pb. The possibility to change initial conditions towards high efficiencies validate the high potential of those biosorbents to be used in water remediation, with special focus on hazelnut shells, although other sorbents such as walnut or almond shells can be considered efficient with appropriate initial conditions and depending on the target elements to be removed.

Biodiesel production using microbial lipids derived from food waste discarded by catering services

Biodiesel production using microbial oil derived from food waste discarded by the hospilatity sector could provide a sustainable replacement for diesel fuel. Discarded potato peels were used in solid-state fermentations of Aspergillus awamori for the production of glucoamylase (30 U/g) and protease (50 U/g). Hospitality food waste hydrolysis led to 98% (w/w) starch to glucose conversion yields. Crude hydrolyzates were used in shake flask fermentations with the oleaginous yeast Rhodosporidium toruloides Y-27012 leading to 32.9 g/L total dry weight (TDW) with 36.4% (w/w) intracellular lipid content. Fed-bath bioreactor cultures resulted in TDW of 53.9 g/L and lipid concentration of 26.7 g/L. Principal component analysis showed a fatty acid profile similar to soybean oil and solid food waste oil. Microbial oil was transesterified into biodiesel with satisfactory performance considering the European standard EN 14214. This work demonstrated that valorization of food waste for biodiesel production is feasible.

Survival of foodborne pathogens on stainless steel soiled with different food residues

Insufficient and ineffective cleaning practices can cause food residues to remain in kitchen and can facilitate bacterial attachment and persistence by protective films. The present study investigated the survival of five major foodborne pathogens on stainless steel coupons, in the presence of cooked rice, whole eggs, and soymilk. Foodborne pathogens showed different survival rates by desiccation and disinfection depending on food residues. Overall, the pathogens showed stronger survival than the control at 0.13-3.97 log CFU/coupon with 5% residues, and at 0.75-5.29 log CFU/coupon with 50% residues. Staphylococcus aureus was not affected by the food residue with showing the least difference in concentration, while Escherichia coli O157:H7 showed the most significant increase by food residue. The cells with cooked rice were observed using FE-SEM, and demonstrated bacterial binding or embedment. All results suggest that food safety can be practically ensured by food residue types and appropriate cleaning and disinfectants.

Technical emptiability of dairy product packaging and its environmental implications in Austria

BACKGROUND

Food waste is a major ecological concern around the globe. While the main function of packaging is to contain and protect food, it may also lead to food waste if residues remain in a package after emptying. Such residues could be attributed to wasteful behavior of consumers, but also to properties of packaging (e.g., geometry, surface tension) and food (e.g., surface tension, viscosity).

METHODS

In this study, the technical emptiability (ability of packaging to be emptied entirely) of 36 dairy products is analyzed. Firstly, the amount of food residues in packaging after emptying at room and refrigerator temperature was weighed and set in relation to the original filling quantity. Secondly, streamlined life cycle assessments (LCAs) based on the Product Environmental Footprint guidance with a functional unit of "one kg of consumed dairy product at room or refrigerator temperature in the home of the consumer" are conducted. Finally, technical emptiability was included in the streamlined LCA and attributed to the primary packaging in order to evaluate its environmental impact.

RESULTS

Technical emptiability for both temperatures combined was found to be between 0.25% (±0.11) and 5.79% (±0.43) for the analyzed dairy products. While there were differences in emptiability results of the same product and different temperatures, no significant trend (p = 0.94) between emptiability and temperature could be observed. Liquid yogurt, cream, and buttermilk in beverage cartons and plastic bottles yielded the highest amounts, while milk in beverage cartons and glass bottles yielded the lowest amounts regarding food residues. Looking at global warming potential, poor technical emptiability of cream in a beverage carton leads to even higher environmental impacts than the production and waste management of its packaging.

DISCUSSION

The streamlined LCA results show that food residues can contribute substantially to the footprint of packaging and can have similar or even higher environmental impacts than packaging production and waste management. Yet, emptiability is remarkably under-researched to this day. Future studies should further develop the methods presented in this paper, while LCA analysts should include technical emptiability when assessing the sustainability of packaging, particularly for those containing resource-intensive goods.

Biomethanation macrodynamics of vegetable residues pretreated by low-frequency microwave irradiation

The effects of microwave irradiation on the digestibility and biogas production of cauliflower (Brassica oleracea var. botrytis) and cabbage (Brassica oleracea var. capitata) leaves were investigated using biochemical methane potential (BMP) assays. Cow dung was utilised as inoculum. Different microwave powers (87.5, 175 and 350W) were applied in a first set of runs for 15min. The second set consisted of 20, 25 and 30min irradiation at 350W. Based on ANOVA analysis (α=0.05), biogas production was significantly higher for the irradiated substrates compared to controls. The peak biogas production was 700ml for 36days HRT for 350W/25min. Peak COD, SCOD, volatile and total solids removals were 54.84%, 39.08%, 34.60% and 71.96%, respectively. Phosphate and total nitrogen increased significantly. Cumulative biogas production data fitted the modified Gompertz equation well. The highest biogas yield was 0.271L/g VS_removed at a 350W microwave irradiation for 30min.