Key Considerations for Designing an Efficient MRF / Recycling Process (Part 2)

Key Considerations for Designing an Efficient MRF / Recycling Process (Part 2)

Continuing from our previous article, we delve deeper into essential design considerations for MRFs. In Part 1, we discussed aspects such as understanding infeed materials and material preparation. If you missed it, you can catch up by following this link to the first article.

In this second part, our focus shifts towards line throughput and plant capacity requirements, underscoring their significant impact beyond equipment sizing.


  1. Equipment Sizing and Process Arrangement

Understanding Your Process Bottlenecks:

When designing a process for a specific target throughput, such as 20 tph, building a mass balance model using an average infeed is the place to start. Once the overall process arrangement appears coherent, proceed to size the equipment, at least approximately to start with. It is important to identify any equipment that may require to be “duplicated”, especially optical sorters, as their maximum capacities can be significantly less than front-end mechanical equipment like screens. Below is a screenshot from SortFlow Process showing equipment ranked by utilisation. This view enables us to identify quickly the process bottlenecks.

Key Considerations for Designing an Efficient MRF / Recycling Process (Part 2)

Input Scenarios:

Process bottlenecks are not “fixed”, they are influenced by input material. Try to establish extreme input scenarios to test with your models. This will allow you to identify and address potentially different bottlenecks than the ones identified with your average input scenario.


Waste Flow Analysis:

Operating a sorting process for over a decade is a common industry standard. However, the composition of input materials can undergo substantial changes during this timeframe, influenced by evolving consumer behaviors, regulatory shifts, and changes to the recyclates targeted. Engaging in thorough waste flow analysis provides essential foresight into the future material landscape destined for processing. Proactively grasping these shifting dynamics during the initial design stages can lead to significant cost savings, as unanticipated plant upgrades often come with hefty expenses. In essence, waste flow analytics provide a holistic, long-term perspective that facilitates forecasting of collection, operational, revenue and disposal costs.


  1. Choosing the Right (Level of) Technology


The target throughput serves as a pivotal factor not only in determining equipment size but also in guiding the selection of technology and the integration of machines within the processing system. Striking a balance between Capital Expenditure (CAPEX) and processing capacity is paramount for realising a viable Return On Investment (ROI). For instance, a Material Recovery Facility (MRF) processing 10 tons per hour cannot justify having an excessive number, such as 25 optical sorters, from an economic standpoint.


Output Strategy:

Crafting an optimal output strategy is crucial to strike a balance between Capital Expenditure (CAPEX) and operational costs associated with generating outputs. In smaller-scale operations, consolidating specific material types into mixed fractions can prove to be a cost-efficient approach. For instance, within a small Material Recovery Facility (MRF), prioritising the production of a Mixed Plastics output rich in Clear PET and Natural HDPE can be more economically viable than segregating all plastic grades and colours individually.

The adaptability of the sorting process also holds significance in output strategies. As market demands evolve, embracing flexible output generation practices becomes paramount. This adaptability not only boosts revenue potential but also future-proofs the operation against changing industry landscapes and consumer preferences.



High CAPEX must align with manageable OPEX to ensure profitability. Labour availability and operational costs add complexity to the financial equation, emphasising the need for a balanced approach between capital and operational expenses.


Thank you for following along with the second part of our series on Key Considerations for Designing an Efficient MRF / Recycling Process. In the upcoming third installment, we will delve into how anticipating the future can guide you in making informed decisions for the design of your new sorting process.


SortFlow Process is the industry’s first mass balance modelling application. It helps to streamline and improve the design of MRF and recycling processes. For more information about SortFlow and our applications, you can visit our website at or contact us at


Luc Mallinger, SortFlow Limited, April 2024