• Energy Research

The paper deals with the benefits coming from the application of a proper process temperature (55 degrees C) instead of a 'reduced' thermophilic range (47 degrees C), that is often applied in European anaerobic co-digestion plants. The experimental work has pointed out that biogas production improve from 0.45 to 0.62 m(3)/kg VS operating at proper thermophilic conditions. Moreover, also methane content was higher: from 52% to 61%. A general improvement in digester behaviour was clear also considering the stability parameters comparison (pH, ammonia, VFA content). The second part of the study takes into account the economic aspects related to the capital cost of anaerobic digestion treatment with a 1 MW co-generation unit fro heat and power production (CHP). Moreover, the economic balance was also carried out considering the anaerobic supernatants treatment for nitrogen removal. The simulation showed how a pay-back-time of 2.5 yr and between 3 and 5 yr respectively could be determined when the two options of anaerobic digestion only and together with the application of a nitrogen removal process were considered.

The paper deals with the benefits coming from the application of a proper process temperature (55 degrees C) instead of a 'reduced' thermophilic range (47 degrees C), that is often applied in European anaerobic co-digestion plants. The experimental work has pointed out that biogas production improve from 0.45 to 0.62 m(3)/kg VS operating at proper thermophilic conditions. Moreover, also methane content was higher: from 52% to 61%. A general improvement in digester behaviour was clear also considering the stability parameters comparison (pH, ammonia, VFA content). The second part of the study takes into account the economic aspects related to the capital cost of anaerobic digestion treatment with a 1 MW co-generation unit fro heat and power production (CHP). Moreover, the economic balance was also carried out considering the anaerobic supernatants treatment for nitrogen removal. The simulation showed how a pay-back-time of 2.5 yr and between 3 and 5 yr respectively could be determined when the two options of anaerobic digestion only and together with the application of a nitrogen removal process were considered.

Abstract The paper presents the results of a pilot- and full-scale experimental campaign on the anaerobic co-digestion of waste activated sludge and biowaste both in mesophilic and thermophilic conditions. The study demonstrated the possibility to increase the specific biogas production from 0.34 to 0.49 m 3 /kgTVS and the gas production rate from 0.53 to 0.78 m 3 per m 3 of reactor per day changing the reactor temperature from the mesophilic (37 °C) to the thermophilic (55 °C) range. The experimental work was carried out at pilot-scale, and the results match the full-scale behaviour. Ammonia nitrogen recycled from the anaerobic digestion section to the wastewater treatment plant accounted for about 4% of the total nitrogen loading. Digestate characteristics in terms of biological stability and heavy metals content suggested the opportunity of a short time post-aerobic stabilisation, leading to a high quality compost product.

Abstract The paper presents the results of a pilot- and full-scale experimental campaign on the anaerobic co-digestion of waste activated sludge and biowaste both in mesophilic and thermophilic conditions. The study demonstrated the possibility to increase the specific biogas production from 0.34 to 0.49 m 3 /kgTVS and the gas production rate from 0.53 to 0.78 m 3 per m 3 of reactor per day changing the reactor temperature from the mesophilic (37 °C) to the thermophilic (55 °C) range. The experimental work was carried out at pilot-scale, and the results match the full-scale behaviour. Ammonia nitrogen recycled from the anaerobic digestion section to the wastewater treatment plant accounted for about 4% of the total nitrogen loading. Digestate characteristics in terms of biological stability and heavy metals content suggested the opportunity of a short time post-aerobic stabilisation, leading to a high quality compost product.

The aim of this study was to compare the environmental performance and sustainability of different management options for livestock waste in Cyprus. The two most common practices in the country, i.e. the use of anaerobic lagoons and conventional biogas plants, were compared with the innovative scheme developed in the LiveWaste project (LIFE12 ENV/CY/000544), which aims not only to produce bioenergy, but also to treat the digestate for nutrient recovery and water reuse. The Life Cycle Assessment (LCA) methodology was combined with the Analytic Hierarchy Process (AHP) to compare the performance of these alternatives. Four relevant indicators were selected for each dimension of sustainability (environmental, social and economic). The results of the evaluations showed that anaerobic lagoons are not an appropriate option for the sustainable management of livestock waste due to environmental (e.g. climate change, acidification and eutrophication) and social impacts (e.g. noise exposure, visual impact and risk perception for human health). The most important strengths and weaknesses of anaerobic treatment with and without digestate treatment were identified. Compared to conventional anaerobic digestion where digestate is directly applied as an organic fertiliser, the technology proposed in the project entails higher technological complexity due to nitrogen removal and phosphorus recovery. The rise in chemical and electricity requirements increased the impacts on some indicators, such as climate change and operational cost (emissions of greenhouse gases and operation costs were around 50% higher), while reduced impacts in others due to proper nutrient management, as acidification and eutrophication impacts (which were 10 and almost two times lower, respectively). For the specific Cypriot conditions, where the overapplication of nutrients leads to pollution of water bodies, the innovative treatment scheme with higher technological development presents an interesting approach. Nevertheless, the treatment of the digestate should be analysed taking into account the specific characteristics of each scenario.

The aim of this study was to compare the environmental performance and sustainability of different management options for livestock waste in Cyprus. The two most common practices in the country, i.e. the use of anaerobic lagoons and conventional biogas plants, were compared with the innovative scheme developed in the LiveWaste project (LIFE12 ENV/CY/000544), which aims not only to produce bioenergy, but also to treat the digestate for nutrient recovery and water reuse. The Life Cycle Assessment (LCA) methodology was combined with the Analytic Hierarchy Process (AHP) to compare the performance of these alternatives. Four relevant indicators were selected for each dimension of sustainability (environmental, social and economic). The results of the evaluations showed that anaerobic lagoons are not an appropriate option for the sustainable management of livestock waste due to environmental (e.g. climate change, acidification and eutrophication) and social impacts (e.g. noise exposure, visual impact and risk perception for human health). The most important strengths and weaknesses of anaerobic treatment with and without digestate treatment were identified. Compared to conventional anaerobic digestion where digestate is directly applied as an organic fertiliser, the technology proposed in the project entails higher technological complexity due to nitrogen removal and phosphorus recovery. The rise in chemical and electricity requirements increased the impacts on some indicators, such as climate change and operational cost (emissions of greenhouse gases and operation costs were around 50% higher), while reduced impacts in others due to proper nutrient management, as acidification and eutrophication impacts (which were 10 and almost two times lower, respectively). For the specific Cypriot conditions, where the overapplication of nutrients leads to pollution of water bodies, the innovative treatment scheme with higher technological development presents an interesting approach. Nevertheless, the treatment of the digestate should be analysed taking into account the specific characteristics of each scenario.

Italy is among the top biowaste-generating countries in Europe, and has a well-structured waste management framework with quite a number of centralized composting facilities. In recent years, there has also been huge interest from local communities in decentralized composting. Although decentralized community composting is common in some countries, there is still a lack of information on the operative environment together with its potential logistical, environmental, economic, and social impacts. Considering the national Italian legislation on community composting as well as successfully implemented projects at EU level, Italy can set a model especially for Mediterranean countries that intend to build decentralized composting programs. Therefore, in the context of this review paper, a brief overview of the composting process was presented together with main applications in centralized and especially in decentralized composting, while the main focus was kept on the operative and legislative information gathered from Italian community composting. There is a huge difference in the number of composting plants between the regions, and the lack of centralized facilities in the central and southern regions can be supported by decentralized solutions. Decentralizing waste treatment facilities and thus creating local solutions to urban waste management strategies will help to achieve the resource recovery and valorization targets in line with the circular economy.

Italy is among the top biowaste-generating countries in Europe, and has a well-structured waste management framework with quite a number of centralized composting facilities. In recent years, there has also been huge interest from local communities in decentralized composting. Although decentralized community composting is common in some countries, there is still a lack of information on the operative environment together with its potential logistical, environmental, economic, and social impacts. Considering the national Italian legislation on community composting as well as successfully implemented projects at EU level, Italy can set a model especially for Mediterranean countries that intend to build decentralized composting programs. Therefore, in the context of this review paper, a brief overview of the composting process was presented together with main applications in centralized and especially in decentralized composting, while the main focus was kept on the operative and legislative information gathered from Italian community composting. There is a huge difference in the number of composting plants between the regions, and the lack of centralized facilities in the central and southern regions can be supported by decentralized solutions. Decentralizing waste treatment facilities and thus creating local solutions to urban waste management strategies will help to achieve the resource recovery and valorization targets in line with the circular economy.