PROJECT DESCRIPTION
BACKGROUND
Spain accounts for 14% of the EUs livestock, producing around 76 million tonnes of manure every year. About 70% of this manure is used as fertiliser. However, mismanagement of manure can lead to soil and water pollution (eutrophication) as well as the generation of greenhouse gas emissions.
The plastic industry is another significant source of waste and pollution. Between 2009 and 2010, production of plastic increased by6% to 265 million tonnes globally. Europe alone consumed 57 million tonnes (21.5%) of plastic, of which some 10.4 tonnes were unrecoverable waste. Independent processes of separation, pre-treatment and valorisation have already been developed on an industrial scale for specific wastes. However, an evaluation of the environmental, energy and economic advantages of the integration of these processes has yet to be performed.
OBJECTIVES
The LIFE REVA-WASTE project aimed to demonstrate the sustainable management of a broad spectrum of waste (industrial waste, waste treatment plant waste and agrofood waste) in an integrated plant. This objective was to be achieved through the development and practical application of a mixed plant concept, which would support a new waste management strategy, based on separation, pre-treatment, recycling and valorisation.
In order to maximise the benefits of an integrated plant for all the above-mentioned categories of waste, two different processes would be integrated. The first would be an anaerobic digestion system, for the transformation of easily biodegradable organic waste into biogas, and the second would be a low-temperature pyrolysis (chemical) treatment, for the valorisation of the non-recyclable plastic waste fraction. Biogas, together with pyrolysis gases, would be used as fuel in an adapted cogeneration engine. As an added value, and in order to close the cycle with minimum environmental impact, the digestate generated in the anaerobic reactor would be used as a slow-release fertiliser, while the solid fraction obtained in the pyrolysis process was intended to be transformed into carbon pellets and the liquid fraction used in second generation biofuels.
RESULTS
The REVA-WASTE project demonstrated the management of a broad spectrum of wastes, although not in an integrated plant as planned. The biogas produced during the anaerobic digestion line, together with the gases from the pyrolysis process, are used as fuels in an adapted alternative co-generation engine. Moreover, the digestate generated in the anaerobic reactor is being used as fertiliser, the solid fraction obtained in the pyrolysis process is being transformed into carbon pellets, and the liquid fraction obtained during the pyrolysis gas distillation process is being re-used as second-generation biofuel. Although the process itself has been validated, the concept of integrated mixed plant has not been fulfilled, as some of its elements (co-generation engine and struvite crystalliser) finally were not integrated.
Nevertheless, the project designed and developed a prototype for allowing a sustainable management of a broad spectrum of wastes in an integrated plant. Energy savings of more than 98% and 68% for heating and cooling operations respectively, are in theory achievable. Moreover, the problems relating to waste management through energy recovery of residual streams treated in the pyrolysis line have been overcome. Tests carried out in the project showed that it is possible to fully evaluate biomass and mix-plastic residues with yields of solid (carbon pellets), liquid (bio-hydrocarbons) and synthetic gas phase of around 9%, 5% and 86% respectively. Organic waste from the anaerobic digestion line can also be fully valorised as twoproducts: biogas and digestate. The biogas can be evaluated together with the gaseous products of the pyrolysis and the digestate can be agronomically enhanced in the form of struvite, allowing for the recovery of up to 90-95% of the nitrogen and phosphorus contained in the starting residues (depending on operating conditions).
The REVAWASTE management strategy is based on the separation, pre-treatment, recovery and recycling of waste in line with the Waste Framework Directive. It reduces the adverse impacts of waste generation and management, by minimising the rejected amount arriving at landfill and by reducing the overall impacts of resource use and improving the effectiveness of such use by optimising the energy consumption of treatment systems.
The mixed plant is currently being operated by the project partner INFINITVE. The model will be a reference for other waste management companies and all the implemented lines are transferable. The replication of the REVAWASTE model would lead to the creation of local employment: at least two operators per plant plus personnel responsible for the logistics of waste are needed. General public resistance to waste treatment plants being located locally, however, remains an obstacle, but one way to overcome this barrier is to locate the treatment plant in the vicinity of another waste treatment centre. This option simplifies administrative requirements and lowers costs.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).
