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AbstractPulp mill sludge is a challenging by-product in wastewater treatment plants (WWTP), due to high moisture content, and poor dewatering characteristics. Solar drying was identified as an appropriate pre-treatment to reduce sludge moisture and enhance its energy efficiency for combustion purposes. Brazil is the world’s second-largest pulp producer, and its high intensity of annual solar irradiation makes it a prime candidate for the application of solar sludge drying technology. This study evaluates the main characteristics of primary sludge (PS) from pulp mills at 65% and 95% moisture content. An active passive solar dryer, followed by ASPEN Plus software simulation was used to evaluate drying properties and combustion potential. CO2 emission impact was explored, and the environmental effects of primary sludge combustion after solar drying were estimated. As indicated by the findings, the sludge commenced with a solids concentration of 21%, eventually reaching 95.5%, thereby enhancing its suitability for combustion. From the simulation, a heat rate expenditure in sludge combustion reported 24672 kW and 16295 kW for a solids content of 65% and 95%, respectively. Therefore, employing solar drying before the sludge incineration is crucial for minimizing energy consumption during combustion. Additionally, solar energy being cost-free, offers an opportunity to alleviate environmental harm.

AbstractPulp mill sludge is a challenging by-product in wastewater treatment plants (WWTP), due to high moisture content, and poor dewatering characteristics. Solar drying was identified as an appropriate pre-treatment to reduce sludge moisture and enhance its energy efficiency for combustion purposes. Brazil is the world’s second-largest pulp producer, and its high intensity of annual solar irradiation makes it a prime candidate for the application of solar sludge drying technology. This study evaluates the main characteristics of primary sludge (PS) from pulp mills at 65% and 95% moisture content. An active passive solar dryer, followed by ASPEN Plus software simulation was used to evaluate drying properties and combustion potential. CO2 emission impact was explored, and the environmental effects of primary sludge combustion after solar drying were estimated. As indicated by the findings, the sludge commenced with a solids concentration of 21%, eventually reaching 95.5%, thereby enhancing its suitability for combustion. From the simulation, a heat rate expenditure in sludge combustion reported 24672 kW and 16295 kW for a solids content of 65% and 95%, respectively. Therefore, employing solar drying before the sludge incineration is crucial for minimizing energy consumption during combustion. Additionally, solar energy being cost-free, offers an opportunity to alleviate environmental harm.

Low-lying coastal areas and archipelago countries are particularly threatened by the impacts of climate change. Concurrently, many island states still rely on extensive use of imported fossil fuels, above all diesel for electricity generation, in addition to hydrocarbon-based fuels to supply aviation and marine transportation. Land area is usually scarce and conventional renewable energy solutions cannot be deployed in a sufficient way. This research highlights the possibility of floating offshore technologies being able to fulfil the task of replacing fossil fuels with renewable energy solutions in challenging topographical areas. On the case of the Maldives, floating offshore solar photovoltaics, wave power and offshore wind are modelled on a full hourly resolution in two different scenarios to deal with the need of transportation fuels: By importing the necessary, carbon neutral synthetic e-fuels from the world market, or by setting up local production capacities for e-fuels. Presented results show that a fully renewable energy system is technically feasible in 2030 with a relative cost per final energy of 120.3 €/MWh and 132.1 €/MWh, respectively, for the two scenarios in comparison to 105.7 €/MWh of the reference scenario in 2017. By 2050, cost per final energy can be reduced to 77.6 €/MWh and 92.6 €/MWh, respectively. It is concluded that floating solar photovoltaics and wave energy converters will play an important role in defossilisation of islands and countries with restricted land area.

Low-lying coastal areas and archipelago countries are particularly threatened by the impacts of climate change. Concurrently, many island states still rely on extensive use of imported fossil fuels, above all diesel for electricity generation, in addition to hydrocarbon-based fuels to supply aviation and marine transportation. Land area is usually scarce and conventional renewable energy solutions cannot be deployed in a sufficient way. This research highlights the possibility of floating offshore technologies being able to fulfil the task of replacing fossil fuels with renewable energy solutions in challenging topographical areas. On the case of the Maldives, floating offshore solar photovoltaics, wave power and offshore wind are modelled on a full hourly resolution in two different scenarios to deal with the need of transportation fuels: By importing the necessary, carbon neutral synthetic e-fuels from the world market, or by setting up local production capacities for e-fuels. Presented results show that a fully renewable energy system is technically feasible in 2030 with a relative cost per final energy of 120.3 €/MWh and 132.1 €/MWh, respectively, for the two scenarios in comparison to 105.7 €/MWh of the reference scenario in 2017. By 2050, cost per final energy can be reduced to 77.6 €/MWh and 92.6 €/MWh, respectively. It is concluded that floating solar photovoltaics and wave energy converters will play an important role in defossilisation of islands and countries with restricted land area.