The Québec Residual Materials Management Policy, introduced in 2011, aims to ban by 2022 the disposal and incineration of organic materials, such as sludge from sewage treatment plants and source-sorted organic fraction of municipal solid waste (SS-OFMSW). This Policy is part of the Government’s commitment to build a green economy and reduce Québec’s greenhouse gas emissions in order to contribute to Québec’s objectives in the fight against climate change. For the valorisation of municipal sludge and SS-OFMSW, various processes can be used, including composting and biomethanisation.
The biomethanisation process allows the conversion of organic residues into biomethane and the recycling of nutrients that are concentrated in the remaining digestate. The latter contains the undigested resilient organic matter, water and micro- and macronutrients, such as nitrogen and phosphorus.
In order to facilitate the achievement of the measures enacted in the Québec Residual Materials Management Policy by municipalities and industries, the Ministère de l’Environnement et de la Lutte contre les changements climatiques (MELCC) offers the Organic Material Biomethanisation and Composting Program, which provides financial support to municipal and private sectors for the installation of infrastructure to treat organic waste through one of these two processes. As a result, biomethanisation projects are rapidly developing in the province (e.g. Québec City, Saint-Hyacinthe). However, the continued development of this technology is currently hampered in several regions of Québec and elsewhere in the world, because the resulting digestates can often not (or only sparingly) be applied on agricultural land in their crude form. This problem is triggered by strict fertilization limits in the context of environmental regulations, practical reasons (large volumes) and economic constraints (high transport and storage costs). Therefore, one of the biggest challenges for biomethanisation facilities is finding a cost-effective and sustainable strategy for the treatment and valorization of the nutrient-rich digestates.
In recent years, several technologies for the recovery of nutrients as concentrated bio-fertilizers from digestates have been developed, some of which have already been applied at full scale. However, finding the optimal location and the combination and sequence of unit processes to treat a particular waste flow and the optimal operating conditions for the overall treatment train that maximize the recovery of resources at minimum cost and environmental footprint are key concerns. Given the large spatiotemporal variation of the composition of residual materials and the large spatial variation of agricultural land for distribution of the end-products, selecting the optimal treatment scenario and associated bio-based end-products is not obvious. A holistic spatiotemporal approach to biomethanisation project planning and digestate valorization is needed to reduce the overall costs and greenhouse gas emissions throughout the value chain, while respecting the provisions of local normative frameworks and social constraints, such as traffic nuisance. Such an approach must take into account transport distances, the nature of the organic waste in the area, the current treatment scenario and the alternative sustainable resource recovery scenario, the proximity to markets for recycling of recovered fertilizer products, the potential use of biogas and the fossil fuel that it replaces.
The general objective of this project is to develop a user-friendly decision-support software tool that allows setting up optimal organic waste valorization chains for the Québec province. The tool will provide capabillties for planning the optimal location of new composting or biomethanisation projects, for developing optimal valorisation chains (including waste collection and end-product distribution), and for the optimal choice of process technologies and their operational parameters. The software tool will integrate three key components: 1) a multidimensional spatiotemporal database system including georeferenced and non-georeferenced data, 2) a model-based decision module for simulation and optimization, and 3) a user-friendly interface to facilitate knowledge transfer and interpretation.