Preventing Contamination in Recyclables: A Guide to Cleaner Bales for MRFs

Top Causes of Contamination in Recyclables and How to Prevent Them

Contamination is one of the biggest challenges Material Recovery Facilities (MRFs) face. When contamination levels are high, bale quality drops, resulting in price deductions, rejected shipments, and increased reprocessing costs. Reducing contamination is essential to maintaining strong buyer relationships and improving profitability. In this article, we’ll break down the common contaminants in plastic, fiber, and metal streams, highlight key prevention strategies, and discuss operational upgrades that can help MRFs improve bale quality.

Why Contamination Is a Persistent Problem

Contamination occurs when non-recyclable or incorrect materials enter the recycling stream, lowering the quality of sorted materials. In some cases, contaminated bales are so compromised that they are sent to landfills—turning what should have been a revenue stream into an expense. Contamination can stem from several sources, including:

• Improper sorting at the source: Consumers and businesses often place non-recyclable items in recycling bins, either due to confusion or “wishcycling” (placing items in recycling bins in the hope they are recyclable).

• Inefficient sorting systems: Aging or outdated equipment may fail to properly separate materials, allowing contaminants to mix into sorted streams.

• Human error: Manual sorting can introduce inconsistencies, particularly when staff are not adequately trained or are fatigued from repetitive tasks.

Common Contaminants in MRFs and Their Impact

1. Plastic Streams

• Contaminants: Non-recyclable plastics (e.g., plastic bags, styrofoam), food residue, and mixed resins (e.g., #3–#7 plastics in a #1 PET stream).

• Impact: Contaminated PET or HDPE bales are often rejected by buyers, particularly if food contamination or incompatible resins are present.

• Prevention Tip: Use optical sorters with near-infrared (NIR) technology to detect and separate different resin types. Educate communities on keeping recyclables clean and avoiding “wishcycling.”

2. Fiber (Paper and Cardboard) Streams

• Contaminants: Greasy pizza boxes, wet cardboard, glass shards, and plastic liners from food packaging.

• Impact: Contaminants weaken the structural integrity of fibers, reducing the value of the bale and making it unsuitable for paper mills.

• Prevention Tip: Implement “clean stream” campaigns that focus on public education, encouraging consumers to avoid recycling soiled paper products.

3. Metal Streams

• Contaminants: Paint cans with leftover chemicals, aerosol cans, and mixed metals (e.g., aluminum mixed with ferrous metals).

• Impact: Hazardous materials like leftover paint or gas can create safety risks and damage equipment. Mixed metals lower the purity level of the bale, reducing its market value.

• Prevention Tip: Install magnetic separators and eddy current systems to separate ferrous and non-ferrous metals. Provide clear guidelines for acceptable and non-acceptable metal items.

Strategies to Prevent Contamination in MRF Operations

1. Employee Training and Quality Control Programs

Training staff to identify and remove contaminants during manual sorting can drastically improve bale quality. Regular refresher courses and incentive programs can also increase sorting accuracy.

• Best Practice: Implement “shift audits” where supervisors randomly inspect sorted streams and provide real-time feedback to staff. Facilities that implement these audits report up to a 15% reduction in contamination rates.

2. Community Engagement and Education

Many MRFs receive highly contaminated streams due to improper consumer recycling habits. Public outreach and education can significantly reduce contamination at the source.

• Pro Tip: Partner with municipalities to launch “recycling do’s and don’ts” campaigns that include visual guides for acceptable items. Some MRFs also host facility tours to show residents the impact of contamination firsthand.

3. Upgrading Sorting Technology

Investing in advanced sorting equipment can improve detection and removal of contaminants.

• Optical Sorters: Near-infrared (NIR) sensors can distinguish between different types of plastics and separate non-recyclable items more accurately.

• Robotic Sorters: AI-powered robotic arms can identify and remove contaminants with precision, increasing sorting consistency.

• Air Classification Systems: These systems use air currents to separate lightweight contaminants (like plastic films) from heavier recyclables.

4. Implementing Contamination Audits

Regular contamination audits can help MRFs identify patterns and adjust their processes.

• Example: A Midwest MRF reduced its contamination rate by 20% after conducting monthly audits that revealed the primary contaminants in its PET stream were plastic bags and bottle caps. They responded by improving pre-sorting processes and adding additional education signage for inbound waste haulers.

5. Partnering with Waste Haulers for Pre-Screening

MRFs can work directly with waste haulers to implement pre-screening processes before materials reach the sorting line.

• Pro Tip: Incentivize haulers with financial bonuses for delivering clean loads or penalize them for excessive contamination. Some MRFs have reported significant reductions in contamination by using these accountability measures.

Case Study: A Northeast MRF’s Contamination Reduction Success

A large MRF in the Northeast faced recurring rejections from buyers due to contamination in its mixed paper bales. After implementing an outreach program for haulers, investing in optical sorters, and conducting weekly team training, they reduced their contamination rate from 18% to 8% within 12 months. This resulted in higher payouts from buyers and fewer load rejections, improving annual revenue by $200,000.

Conclusion

Contamination in recyclables can severely impact an MRF’s profitability, but it’s a challenge that can be managed with the right strategies. By implementing employee training, improving public education, upgrading sorting technology, and fostering partnerships with haulers, MRFs can reduce contamination rates, improve bale quality, and secure better buyer relationships. Midas Peak helps MRFs develop tailored strategies for contamination prevention and connects them with cutting-edge sorting technology and buyer networks. Contact us to learn more about how we can support your operations.