Phosphorus recovery from organic wastes aiming at its valorisation as a fertilizer

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Struvite quality assessment during electrodialytic extraction

Publication . Oliveira, V.; Kirkelund, Gunvor M.; Labrincha, J.; Ferreira, Célia

Struvite recovered from anaerobically digested sludge can be conducted by a two – step process. The first step consists of electrodialytic extraction of phosphorus and heavy metals from the waste. The second step comprises the chemical precipitation of phosphorus as struvite. This work studied if the quality of phosphorus recovered as struvite is affected by the reduction of energy on the electrodialytic extraction step. Four electrodialytic experiments were carried out to assess the effect of the energy reduction through stirring time. This was followed by four struvite-precipitation experiments. The efficacy of the electrodialytic extraction of heavy metals is not affected by reducing the stirring from continuous mode to just 25% of the time. XRD analysis confirmed that the precipitates were constituted by pure struvite, while no significant accumulation of heavy metals was found in produced struvite. The struvite meets the requirements for use as phosphorus-based fertiliser.

2020Book part

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Phosphorus flows in the Portuguese agriculture and livestock sectors

Publication . Rocha, Joana; Oliveira, V.; Ferreira, Célia

Phosphorus plays a vital role as a limiting nutrient for plant growth, but the majority of minable phosphate rock reserves are located in just a small handful of countries: South Africa, Jordan and Morocco. Therefore, Portugal is totally dependent on imports, with phosphate rock being added to the European Union list of critical raw materials it is essential to increase its sustainable use. Thus, the main objective of this work was to compute substance flow analysis of phosphorus in the agriculture and livestock production sectors in Portugal. The data was gathered from several statistical sources and computed into phosphorus contents employing mass conservation law. Phosphorus flows were computed and quantified using STAN software. As result, we identified phosphorus flows, losses, and sinks. We can conclude that, both in agriculture and livestock production sectors, it is possible to decrease losses and increase phosphorus efficiency use by applying best management practices.

2020Book part

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Improving the energy efficiency of an electrodialytic process to extract phosphorus from municipal solid waste digestate through different strategies

Publication . Oliveira, Verónica; Kirklund, G.; Horta, Carmo; Labrincha, João; Ferreira, Célia; Kirkelund, Gunvor M.

This work assesses the possibility of energy optimisation during the electrodialytic extraction of phosphorus from the municipal solid waste digestate. Strategies tested for energy optimisation consisted in (i) using a dualstage extraction approach; (ii) replacement of continuous stirring by pulse stirring and; (iii) utilisation of pulse electric current as an alternative to a constant current. Experiments were carried out using different stirring profiles (continuous stirring, pulsed stirring, manual stirring and no stirring) and different profiles for generating the electric field (continuous current and pulsed current). Dual-stage approach decreased the energy consumption by 30%. Energy was mainly used in the stirring operation (80%). Applying this strategy caused a faster acidification of the waste suspension and reduced the time required for the extraction. As for the second strategy, use of pulse stirring, it is possible to save energy by operating the stirrer 25% of the time, without compromising the phosphorus extraction values, which are close to 90%. Corresponding energy savings reached 70%. The third strategy tested, use of pulse current, had as side-effect a significant decrease of the phosphorus extracted, so the implementation of pulse current is not recommended. Overall, the energy efficiency of the electrodialytic extraction of phosphorus can be improved by 80% through the use of the dual-stage approach and the use of stirring for 25% of the time. There is also a potential in further reducing the energy use by further improving the stirring system.

2019-06Journal article

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Synthesis of PPy-ZnO composite used as photocatalyst for the degradation of diclofenac under simulated solar irradiation

Publication . Silvestri, Siara; Ferreira, Célia; Oliveira, Verónica; Varejão, Jorge M. T. B.; Labrincha, João; Tobaldi, David Maria

2019-04Journal article

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Effects of struvite recovered from wastes on crop cultivation

Publication . Oliveira, V.; Horta, C.; Rocha, Joana; Ferreira, Célia

Struvite recovered from wastes has been considered a promising second generation fertiliser. The main objective of this work is to evaluate the effects of struvite fertilisation on i) rye (Secale cereale L.) cultivation (through a 45-d pot experiment), in terms of macronutrients, micronutrients and heavy metals and ii) on soil fertility (through a 30-d incubation experiment) in terms of available phosphorus and exchangeable bases (Ca2+, Mg2+ and K+). Struvite-fertilisation increased the soil available phosphorus resulting in improvement of the soil fertility class from low to medium class. In terms of exchangeable bases, the soil fertility class did not change. Furthermore, the struvite-fertilisation led to the highest concentration of total phosphorus in the plant. No relevant effects were found regarding the concentrations of Ca, Mg and K in the plant as well as the micronutrients. The levels of heavy metals on crop did not increase after soils fertilisation with struvite.

2020Book part

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