Demonstration of an integrated waste-to-energy sys.. (INTER-WASTE)
Demonstration of an integrated waste-to-energy system for energy generation from biodegradable organic waste and wastewater
Start date: Jan 1, 2010,
End date: Jun 30, 2013
Finding alternatives to fossil fuels is a fundamental challenge as the world faces up to the threat from climate change. At the same time, agricultural and municipal solid biomass waste also pose an environmental challenge. Use of biomass wastes as fuel-stock for energy generation could reduce environmental impacts, while maintaining viable energy supplies. Such an approach could offer particular benefits to Cyprus, because the island's soils have low nutrient values, and treated sludge from the processing of biodegradable organic waste (BOW) could raise the landâs organic content, while reducing the need for synthetic soil improvers. Reducing the volume of BOW that goes to landfill will also cut greenhouse gas emissions, while use of BOW for energy generation will reduce dependence on external energy supplies.
The objective of the INTER-WASTE project was to demonstrate a sustainable conversion technology for energy generation, and sustainable processes for waste and wastewater handling. The aim was to do this through the construction of an innovative integrated system based on anaerobic processes with a Membrane Bioreactor System (MBR). This technology can treat urban wastewater, as well as other BOW (e.g. household organic waste, agricultural waste and manure), with the outputs being biogas and a stabilised solid product, with the simultaneous production of high-quality effluent that can be safely reused in agriculture. Finally, the processed wastewater will be used for irrigation.
The INTER-WASTE project combined two well-established technologies, Membrane Bioreactor System (MBR) and Anaerobic Digestion (AD), for the treatment of biodegradable organic waste (BOW) in an integrated energy-autonomous system following a zero waste approach. The project demonstrated that the innovative, integrated MBR-AD system is a sustainable option for the treatment of various organic waste fractions, while delivering marketable by-products. The replication potential of this innovative system, which is particularly suitable for small to medium scale applications, is promising. The viability of the system's application in two hypothetical scenarios - a village and a luxury hotel - was assessed.
The project team constructed and demonstrated an integrated MBR-AD prototype system, which successfully treats wastewater, sludge and other BOW, while delivering added value marketable products in the form of biogas, organic fertiliser and clean water effluent that can be safely used in agriculture. The composition of the organic waste fed to the MBR-AD unit was found to be a key parameter for the optimisation of the process and for delivering added-value products. This is due to the performance of the anaerobic process, so a careful selection of the appropriate waste mixture should be made. To this end, extensive physicochemical analyses were conducted on different types of waste, to determine the optimum waste composition.
The MBR-AD pilot unit tackles several problems associated with the use of a single integrated system. In particular, the AD unit can produce 12.1 m3/d biogas containing 59% methane from organic waste, with the resulting solid digestate having good quality characteristics on drying for land application as organic fertiliser; it reduces CO2 emissions as organic waste is treated and does not end-up in landfills; it produces high quality effluent (i.e. irrigation water) therefore enhancing reuse options of wastewater and thus relieving the already scarce water resources in Cyprus. After measuring and calculating the energy production and consumption of the MBR-AD system, the overall energy balance of the AD unit is positive; meaning that the system is energy-autonomous while the excess energy (i.e. electric and thermal) can be utilised for other purposes. The biogas can be utilised in a Combined Heat and Power (CHP) unit. More specifically, for every unit of energy in the biogas, the CHP produces: 0.55 units of heat (0.33 units for self-heating and 0.22 units excess heat), 0.35 units of electricity (0.035 units used in system and 0.315 units potentially for the grid), with 0.1 units lost (system losses). The majority of the electricity can be fed directly into the grid.
In the hypothetical scenarios, in a small Cypriot community of 1 000 people producing 605 kg/d of biodegradable waste and 144m3/d of wastewater, the technology delivers 124m3/d biogas covering the electricity needs of around 20 households, 150 m3/d of irrigation water (without sludge handling costs) and about 12 kg/d of dried solid digestate for organic fertiliser. In an all-inclusive 5-star hotel of 1 200 beds producing 1 349 kg/d of biodegradable waste and 240m3/d wastewater, it delivers 307m3/d biogas with a net energy production of 406 kWh/d and 581.3 kWh/d of heat and electric energy respectively, covering around 3.5% of the annual energy requirements (electricity and heating), 250 m3/d of irrigation water and about 26 kg/d of dried solid digestate.
An international conference promoted the projectâs findings to the scientific community and various competent authorities. The technology demonstrated is in line with the objectives of the 7th Environment Action Programme (EAP) and EU policies, particularly, the Waste Framework Directive, Landfill Directive, Water Framework Directive, and Renewable Energy Directive.
A number of entities in Cyprus have expressed an interest in the projectâs findings, including the Department of Environment, who are willing to modify/amend current national regulations and policies regarding waste management as a result; the Water Development Department of Cyprus; and several other public bodies and local organisations. The manufacture of the MBR-AD unit is based on commercially-available components and specifications, thus ensuring its easy replication. The project consortium is willing to provide the necessary know-how, based on expertise gained during its demonstration phase. The large-scale economic viability of the technology will depend on the exploitation of its end products, national policy conditions and regulatory frameworks for promoting environmentally-friendly management solutions, the pricing for feeding-in biogas electricity to the national grid, the potential for local heat energy, the market value of organic fertiliser, and the pricing of the MBR effluent (i.e. irrigation water). These and other parameters need to be examined to determine the economic feasibility of the systemâs replication and scale up.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).
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