Flexible Intermediate Bulk Containers (FIBCs)—often called big bags, bulk bags, or jumbo bags—are widely used to move powders and granules in logistics, agriculture, chemicals, and construction. Most FIBCs use a flexible woven fabric that is typically polypropylene (PP), which makes them a strong candidate for recycling when you manage contamination and feeding correctly.[1]
This guide focuses on what buyers and plant managers need to spec: feedstock sorting rules, the right size-reduction approach for woven tapes, washing and drying decisions, and pelletizing details that keep output consistent.
Start with the product and the standard (what a FIBC is)
If you’re sourcing mixed big bags, it helps to separate “bag design” concerns from “recycling line” concerns.
- FIBCA defines a FIBC as an intermediate bulk container with a body made of a flexible woven material (typically polypropylene).[1]
- ISO publishes a packaging standard for FIBCs for non-dangerous goods (materials, construction, design requirements, type testing, certification, and marking).[2]
For recyclers, the key takeaway is simple: most big bags are PP-based, but construction details (coated vs uncoated, liners, stitching, loops, printing) drive how you set up shredding, washing, drying, and filtration.
What makes big bag recycling harder than film
Woven PP behaves differently than film:
– Tape wrapping: long woven tapes can wrap shafts and rotors and stop production.
– Low bulk density after shredding: “fluffy raffia” feeds poorly into extruders unless you densify it.
– Powder carryover: cement, fertilizer, minerals, and other residues drive washing load and wear.
– Thread and seam contamination: stitching threads, labels, and handles show up in melt filtration.
A practical sorting map (what to separate before you buy equipment)
| Stream | Typical source | Main risk | What to do |
| Clean post-industrial PP big bags | In-plant packaging scrap | Low contamination; high throughput expectations | Prioritize anti-wrap size reduction and stable feeding into extrusion |
| Dusty post-consumer big bags | Construction, agriculture, minerals | Sand/stone/metal and heavy dust load | Plan multi-stage washing + strong separation + wear protection |
| Coated / laminated bags and liners | Moisture or dust containment bags | Mixed layers and melt quality variation | Decide whether to separate liners and define your target product grade |
| Food-contact / regulated applications | Food ingredients | Customer specs on resin origin and cleanliness | Keep segregated and follow your buyer’s quality and compliance requirements |
The industrial process: from big bags to PP pellets
1) Size reduction that won’t wrap and jam
Big bags should not go straight to a granulator. Start with a low-speed shredder designed for tough, stringy materials.
What to verify in your RFQ:
– Anti-wrap / anti-tangle rotor features
– Stable feeding (ram, swing arm, or other positive feed)
– Output size target (matched to your washing and extrusion setup)
For reference: a single-shaft option is here: single-shaft shredder with drawer.
2) Washing and separation (match it to the contamination)
Once shredded, woven PP flakes (raffia) usually need friction washing plus separation steps that remove heavy contamination. Dirty big bags can carry sand, stone, metal, and fine powders, and those will destroy knives, clog screens, and lower pellet quality if they make it to the extruder.
If your main feedstock is post-consumer and dirty, start from a full woven bag washing configuration: PE film and fabric recycling equipment.
3) Drying and densifying raffia for consistent extrusion feeding
Woven material traps water in the weave. If you feed wet raffia into an extruder, you’ll see unstable melt pressure and poor pellet surface quality.
Many lines use a two-stage approach:
– Mechanical dewatering (centrifugal) to remove free water
– Squeezing/compacting to push moisture down further and increase bulk density
If you need a dedicated squeeze step, see: plastic film squeezing machine.
4) Extrusion, melt filtration, and pelletizing
For big bags, melt filtration is the place where line design shows up in output quality:
– Stitching threads, labels, and fine contamination load the screen pack.
– Vacuum degassing helps control residual moisture and volatiles.
– A continuous screen changer keeps production running when contamination varies.
For light, low-density raffia flakes, a compactor-feeding pelletizing line is often used to stabilize feeding: cutter-compactor recycling granulating line.
Why general-purpose film equipment often fails on big bags
Many plants try to run big bags on equipment sized for film and see avoidable downtime:
1. Tape wrapping: woven tapes wind on shafts and stop the rotor.
2. Filtration overload: stitching threads and residual dust fill screens quickly.
3. Feeding instability: fluffy raffia does not feed consistently without densification or force feeding.
Buyer checklist: what to specify when you request quotes
| Item to specify | What to include | Why it matters |
| Feedstock profile | Bag type(s), coated/uncoated, liners, contamination type | Drives washing load, wear parts, and filtration design |
| Target output | Pellet grade/use (raffia tape, injection molding, etc.) | Sets filtration and quality targets |
| Throughput | Peak-day input and available run window | Avoids under-sizing and stockpiles |
| Dryness targets | Moisture target before extrusion and how you’ll measure it | Wet feed causes melt instability and low pellet quality |
| Filtration plan | Screen changer type, melt filtration level, contamination variability | Controls uptime and reject rate |
| Wear and spares | Knife material, screw/barrel materials, spare parts kit | Reduces downtime from wear and contamination events |
FAQ (real buyer questions)
1) Are big bags (FIBCs) usually polypropylene, and does that mean they’re recyclable?
Most FIBCs use a flexible woven fabric that is typically polypropylene, which is one reason recyclers target them for PP pellet production.[1] “Recyclable,” however, depends on your acceptance spec and your process. If the stream is clean and segregated, you can often go straight to size reduction, drying, and pelletizing. If it’s post-consumer and dusty, you’ll need stronger separation, more washing, and heavier melt filtration. Before you buy equipment, define the feedstock profile (coated vs uncoated, liners, dust type) and the pellet grade your buyer needs.
2) Do coated bags, liners, and stitching threads change the process?
Yes. Coated bags and liners can introduce mixed layers and more variation in melt flow, while stitching threads and webbing handles show up in melt filtration. The practical approach is to build sorting rules that match your target product grade. If you sell pellets into higher-spec markets, you may need tighter sorting (remove liners, separate certain bag types) and stronger filtration. If you’re selling into lower-spec applications, you may accept more variation but you still need stable running equipment. Ask your pellet buyer what they reject most often and design sorting and filtration around that.
3) What shredder setup prevents “tape wrapping” downtime?
Look for low-speed, high-torque shredding with features that reduce wrapping and keep material moving into the cutting zone. Positive feeding (ram or swing-arm style feeding) helps prevent big bags from riding on the rotor and stalling throughput. In the RFQ, specify that the supplier must demonstrate performance on woven PP big bags (not only on film) and provide references or trial output. Also define the output size range you need for washing and drying. If the supplier only quotes nameplate capacity without addressing wrapping behavior, treat the quote as incomplete.
4) When is washing required, and how do I avoid overpaying for it?
Washing requirements depend on what the bags carried. If bags are dusty (cement, fertilizer, minerals), washing is often necessary to protect extrusion and hit pellet quality targets. For clean post-industrial big bags, a lighter cleaning setup may be enough. The mistake is sizing washing on “average” contamination: you need to plan for the dirtiest lots you will accept, or tighten your inbound spec and reject those lots at the gate. A simple buyer rule is to define contamination limits (by weight or by inspection), then size washing and separation for that limit and verify with a trial.
5) What dryness level is needed before pelletizing woven PP raffia?
Woven PP can hold water in the weave, so “surface dry” is not always dry enough. If you feed wet raffia, you’ll see unstable melt pressure and poor pellet appearance. Ask the supplier how they measure dryness (moisture meter method and sampling plan) and what drying stages are included (centrifugal dewatering, squeeze/compaction, hot air assist). Your target depends on your extruder and the grade you sell, but the key is consistency: stable dryness across shifts is usually more important than chasing an aggressive number that isn’t repeatable.
6) What should I ask about melt filtration for big bag pelletizing?
Ask how the line handles stitching threads, fine dust, and contamination variability without constant shutdowns. Continuous screen changing is common when input quality varies because it lets you change screens without stopping the extruder. Also ask whether the system includes vacuum degassing and how they control melt pressure and temperature stability. Finally, match the filtration plan to your target market: higher-spec pellets usually require tighter filtration, which increases screen-change frequency if your sorting and washing aren’t strong. Your best ROI often comes from upstream sorting and washing that reduces filtration load.
Next step
If you want a recommendation based on your big bag stream (clean post-industrial vs dirty post-consumer), start here:
– Line options for woven bags and fabrics: PE film and fabric recycling equipment
– Request a quote: contact Energycle
