Biogas recovery from a state-of-the-art Italian landfill.

The Fossetto landfill has operated in the municipality of Monsummano Terme (Tuscany, Italy) since 1988, being considered a state-of-the-art landfill for 35 years. Initially, Fossetto acted as a conventional sanitary landfill for mixed municipal solid waste. With changes in regulations and technology, the Fossetto landfill was gradually equipped with a biogas recovery and valorisation system, a mechanical-biological treatment (MBT) plant in 2003 and a reverse osmosis leachate treatment plant, so the concentrated leachate has been recirculated back into the landfill body since 2006. Long-term biogas monitoring, enables the calculation of the efficiency of biogas recovery using a rather simplified methodology, which was assessed as being approximately 40% over the prior ten-years period. This value was lower than expected, confirming the results of previous studies and indicating the need of attributes. Applying the USEPA LandGEM model showed that the adoption of MBT substantially reduced biogas generation yields and rates by up to approximately 90% which was facilitated by the adoption of landfill leachate recirculation transforming the conventional landfill into a bioreactor. Detailed fugitive emission monitoring has allowed the evaluation of the impact of the cover type (final or temporary) and the emissions hotspots. From these results, possible remedial actions have been suggested including the more frequent monitoring of the fugitive emissions using simple and cost-effective methods (e.g., UAVs). Approximately 50% of fugitive emissions can be attributed to emissions hotspots, which reduce biogas recovery and the efficiency of temporary covers.

Evaluation of Electrospun Self-Supporting Paper-Like Fibrous Membranes as Oil Sorbents.

Presently, adsorption/absorption is one of the most efficient and cost-effective methods to clean oil spill up. In this work, self-supporting paper-like fibrous membranes were prepared via electrospinning and carbonisation at different temperatures (500, 650 or 800 °C) by using polyacrylonitrile/polymethylmethacrylate blends with a different mass ratio of the two polymers (1:0, 6:1 or 2:1). After morphological and microstructural characterisation, the as-produced membranes were evaluated as sorbents by immersion in vegetable (sunflower seed or olive) and mineral (motor) oil or in 1:4 (v:v) oil/water mixture. Nitrogen-rich membrane carbonised at the lowest temperature behaves differently from the others, whose sorption capacity by immersion in oil, despite the great number of sorbent and oil properties involved, is mainly controlled by the fraction of micropores. The encapsulation of water nanodroplets by the oil occurring during the immersion in oil/water mixture causes the oil-from-water separation ability to show an opposite behaviour compared to the sorption capacity. Overall, among the investigated membranes, the support produced with 2:1 mass ratio of the polymers and carbonisation at 650 °C exhibits the best performance both in terms of sorption capacity (73.5, 54.8 and 12.5 g g-1 for olive, sunflower seed and motor oil, respectively) and oil-from-water separation ability (74, 69 and 16 for olive, sunflower seed and motor oil, respectively).

Organic matter removal and ammonia recovery by optimised treatments of swine wastewater.

The organic matter and nitrogen contents of swine wastewater (SW) can be reduced and, at the same time, a fertiliser as ammonium salt can be recovered by wastewater treatments. One of the most promising technique is air stripping (AS). However, the operational parameters (pH, temperature and air flow rate) of AS must be optimised, in order to maximise the ammonia recovery and reduce the requirement of chemicals and energy. In this study 27 batch tests at laboratory scale were carried out on real SW, varying (individually or simultaneously) the pH (not adjusted, 8 and 10), temperature (ambient, 40 and 60 °C) and flow rate (0, 1 and 5 Lair LSW-1 min-1) of AS; the changes in soluble COD (sCOD) and total ammonia nitrogen (TAN) concentrations were evaluated in response to the parameters adjustments. For the tests including AS, the ammonium sulphate recovered was also measured. In general (about 50% of the tests), more than 80% of TAN was removed. Most of these tests were carried out with pH and temperature control and AS at the highest flow rate; the highest efficiency was found for a combination of chemical, thermal and aeration treatments. For a few tests with the same process control, an increase (up to 50%) or a very limited (less than 10%) decrease of sCOD were detected; therefore, these treatments can be adopted prior of anaerobic digestion of SW. A high flow rate, which increases the removal efficiency of both sCOD and TAN, should be adopted, when AS is used as pre-treatment of activated sludge or lagooning plants. Very high amounts (over 80% of the theoretical yield) of ammonium sulphate were recovered by AS at the maximum air flow rate (5 Lair LSW-1 min-1), which would provide a nitrogen fertiliser at a sustainable cost.

Anaerobic digestion of orange peel in a semi-continuous pilot plant: An environmentally sound way of citrus waste management in agro-ecosystems.

The management of residues of citrus processing involves economic and environmental problems. In particular, the uncontrolled disposal of citrus processing waste near production sites can have heavy impacts on air, soil, surface water bodies and groundwater. Anaerobic digestion has been proposed as a viable alternative for citrus waste valorisation, if some problems, linked to the biochemical processes, are overcome. Although many experimental tests have studied the inhibitory effects of the high essential oil content of orange peel on biomethanisation processes, fewer experiences have been carried out in continuous or semi-continuous pilot digesters, more similar to the full-scale biogas plants, using real orange peel. This study has evaluated the methane production through anaerobic digestion of industrial orange peel using a pilot plant (84L) with semi-continuous feeding at increasing Organic Loading Rates (OLR) and essential oil (EO) supply rates (EOsr) until the complete process inhibition. Under mesophilic conditions, the highest daily specific methane yield was achieved at OLR of 1.0gTVSL-1 d-1 and EOsr of 47.6mgL-1d-1. Partial inhibition of the anaerobic digestion was detected at OLR and EOsr of 1.98gTVSL-1d-1 and 88.1mgL-1 d-1, respectively and the process irreversibly stopped when OLR and EOsr reached 2.5gTVS L-1 d-1 and 111.2mgL-1 d-1, respectively. Under thermophilic conditions, the cumulative methane production (0.12LgTVS-1) was about 25% of that under mesophilic conditions (0.46LgTVS-1). The thermophilic digestion was completely inhibited at lower OLR (1.98gTVSL-1 d-1) and EOsr (88.1mgL-1 d-1) compared to mesophilic conditions. This study confirmed the suitability of anaerobic digestion of orange peel for biomethane production (provided that the right management of the process is set), in view of an environmentally sound way of agricultural residues management in agro-ecosystems.