MRF 1: Sorting from comingled recyclables with low mechanical intensity

Process Description

According to the collection system applied, a number of recyclate fractions are comingled inside a bin. The design of the MRF aims to separate the recyclable waste in a number of fractions (in order to increase after sales price): printed paper, cardboard, mixed paper, PET, PVC, PE, PS/PP, PE film, ferrous metals, aluminium and mixed glass; it usually includes:

• A Reception Hall where trucks unload the materials on reinforced floor.
• A front loader that pushes the materials into a hopper that feeds the bag opener (the bag opener will not be necessary if citizens are advised to simply empty their packaging waste in the dedicated bin instead of putting it in bags before discarding it).
• A chain conveyor leads materials to the hand-picking line which is a slowly moving conveyor in front of the hand-picking personnel. Personnel stand on a metal platform of about 5 m above the floor level. Each person collects a specific material type and drops it off to a silo to their side (paper, glass, plastic and aluminium). Silos are emptied with the use of a forklift vehicle (electrically operated) or with the use of the front loader in case pressing into bales is required (it is usual for paper and plastics). The front loader feeds the hopper of a press that in the same time produces bales, whereas materials are strained together with the use of lags.
• A magnet, placed at the end of the handpicking line to recover ferrous metals.
• Area for storage purposes.
• Area for the necessary manoeuvres of the vehicles.

The entire plant is housed in a building with reinforced floor and metal roof. Lighting and electrical installations are required as well as a fresh water supply system for cleaning purposes.

Process Mass Flow Diagram

Process Photo

Process Operational Data

Area

Sufficient space for the activities occurring at a Material Recover Facility is crucial. Site acreage should be large enough to accommodate the physical structure, pre-processing materials and post-processing products storage and orderly vehicle movement. In addition a buffer space with trees and shrubs will help improve aesthetics and decrease noise.

The amount and location (indoors, outdoors) of space allocated to product storage is influenced, in great degree, by the markets. The market specifications will influence whether or not the products may be stored outdoors pending shipment, while the market demand of recovered materials will determine the storage capacity of the facility. Although each facility must be sized for materials storage in accordance with individual site-specific criteria, it is prudent to provide sufficient storage capacity to hold processed materials for one week up to one month (EPA, 1991; Tchobanoglous, 2002). The sitting requirements, according to data from existing facilities in United States, vary greatly ranging from 5m²/TPD (tonnes per day) to 40m²/TPD depending on the capacity and degree of mechanization for materials separation (Dubanowitz, 2000), while Golder Associates Ltd (2009) reports 0.30 m² per tonne of waste per year.

Energy

Energy usage of Material Recovery facilities includes mainly:

• Electricity used for the operation of motors (conveyers, balers, magnets, optical separators etc.), ranging from 15 to 20 kWh per tonne of feedstock depending on the degree of mechanization (EPA, 1991)
• Diesel used for heating and vehicle (front loaders and forklifts) movement, estimated at 7.7 kWh per tonne of feedstock (EPA, 1991).

According to data from two Greek facilities in Greece, specific electricity consumption is 15-19 kWh per tonne of feedstock, while fuel consumption is up to 10.5 kWh per tonne (HERRCO,2011).

Water

Material Recovery facilities use water only for buildings and equipment cleaning and for personnel needs. According to EPA water usage ranging from 0.05 to 0.2 m³ per tonne of feedstock (EPA, 1991) depending on the capacity.

Process Environmental Indices

Air Emissions

The main environmental issue related to air quality arising from the operation of Material Recovery Facilities is dust emissions from tipping operations, storage and loading operations. Operations are usually conducted indoors where ventilation and localized dust suppression measures are taken as required for stationary sources. Dust emissions data from this type of facilities are largely unavailable, but it is estimated that are not significant.

Wastewater

The Material Recovery Facilities for separately collected materials are constructed on a concrete pad that prevents seepage of any waste pollutants into the soils. Moreover, these facilities typically handle pre-cleaned, dry and solid components of the waste stream, which often is prewashed by the waste generator of food and other organic residues. Thus, the only wastewater generated is from cleaning processes and personnel and it is estimated that it is equal to water consumed.

Residual

The solid wastes of Material Recovery Facilities include mainly residual non-recyclable wastes which are removed from the source separated recyclate with handpicking. Residual of Material Recovery Facilities is Municipal Solid Waste and it is disposed to landfill. According to data from existing facilities residual ranges from 0.2 tonnes per tonne of feedstock to 0.3 tonnes per tonne of feedstock (Tchobanoglous, 2002; WRAP, 2006), depending on the degree of mechanization and sorting equipment efficiency.