How to maximise DAF solids recovery for your rendering plant: A valuable byproduct
Maximising solids recovery not only helps you meet environmental compliance standards but also plays a significant role in the economic viability of your operations.
In this practical and comprehensive guide, we will provide valuable insights, industry benchmarks, formulas, and actionable tips to help you optimize DAF solids recovery for rendering. Additionally, we will explore the economics of tallow, pricing dynamics of DAF solids recapture, and how they relate to the grading of rendered tallow.
Why Solids Recovery Matters in DAF Systems
Efficient solids recovery in DAF systems is crucial for several reasons. First and foremost, it helps you comply with regulatory requirements by ensuring that the effluent discharged into the environment meets the specified standards.
In addition, higher solids recovery rates lead to improved process efficiency, reduced costs, and enhanced product quality.
By effectively removing suspended solids from the wastewater, you minimise waste generation and optimise the rendering process, ultimately contributing to a more sustainable and economically viable operation.
How to optimise DAF system operation
Regular maintenance and inspection: Conducting routine maintenance and inspections are critical to ensure optimal DAF system performance. This includes checking for any mechanical issues, worn-out components, or clogged pipelines that may hinder solids recovery.
Calibration and adjustment of key parameters: Proper calibration and adjustment of the DAF system parameters can significantly improve solids recovery. These parameters include the air-to-solids ratio, coagulant dosage, and flotation time. Experimenting with different settings and monitoring the results can help you identify the optimal values for your specific operation.
pH and temperature control: Maintaining the appropriate pH level and temperature range enhances the effectiveness of the DAF process. Generally, maintaining a pH level between 6.0 and 7.0 and a temperature range of 40-50°C is recommended. Regularly monitor and adjust these parameters to ensure optimal conditions for solids flotation.
Influent flow rate control: Monitoring and controlling the influent flow rate is crucial to prevent overloading the DAF system. Excessive flow rates can reduce solids recovery efficiency and compromise the overall performance of the system. Implement flow control measures to maintain a consistent and manageable flow rate within the DAF system's design limits.
What Are the Industry Benchmarks for Solids Recovery?
While the specific solids recovery benchmarks may vary depending on site conditions, achieving an average solids recovery rate of 80-90% is considered achievable in well-operated DAF systems.
To track solids recovery, you can regularly measure Total Suspended Solids (TSS) levels in both the influent and effluent streams.
Establishing baseline performance metrics and setting targets can help you identify areas for improvement and track your progress over time.
By continuously striving to improve your solids recovery rates, you can optimize the rendering process and enhance the overall efficiency of your operation.
Tallow Grading and Associated Price Impact
Tallow, the rendered fat obtained from the rendering process, holds significant economic value in various industries.
The grading of rendered tallow directly influences its market price, with higher grades commanding premium prices. Maximizing solids recovery in the DAF system is key to improving tallow quality, which in turn leads to higher-grade products and increased profitability.
Tallow is typically graded based on specific parameters, such as Free Fatty Acid (FFA) content, color, and impurity levels.
It’s important to note that like all commodity markets, the tallow market fluctuates depending on market conditions.
Credit: MLA
As of January 2023, the price for FFA <1% tallow averaged $2,547 per tonne, which was up $450/tonne since November 2021 however $143/tonne below the December 2022 price. (AUD)
Let's explore the commonly used tallow grade names and their associated values:
Prime Tallow (FFA below 2%)
Prime tallow is the highest quality grade, characterized by low FFA content (typically below 2%) and a light color. It is considered the most desirable grade for various applications, including food production and cosmetics.
Prime tallow commands a premium price, often ranging from $1200 - $1500 per tonne.
Choice Tallow (FFA 2-3%)
Choice tallow is a slightly lower grade compared to prime tallow. It may have a slightly higher FFA content (around 2-3%) and a slightly darker color. Despite the minor differences, choice tallow is still widely used in many industries, such as animal feed and soap manufacturing.
The price range for choice tallow is generally between $1000 - $1200 per tonne.
Standard Tallow (FFA 3-5%)
Standard tallow represents a more commercially available grade with a higher FFA content (around 3-5%) and a darker color. It is commonly used in industrial applications, such as biofuel production and lubricant manufacturing.
The price for standard tallow is typically in the range of $800 - $1000 per tonne.
Lower-grade Tallow (FFA above 5%)
Lower-grade tallow includes varieties with higher FFA content (above 5%) and a darker color. These grades are less desirable for most applications but may still find uses in specific industries or processes that can accommodate the higher impurity levels.
The price for lower-grade tallow usually ranges from $600 - $800 per tonne.
When to Consider Advanced DAF Technologies
While conventional DAF systems are effective in most cases, there may be situations where advanced DAF technologies can offer improved solids recovery rates. These advanced technologies include dissolved air nanobubble flotation and electrocoagulation flotation.
Dissolved air nanobubble flotation: This technology involves generating smaller air bubbles, known as nanobubbles, to enhance the flotation process. The smaller size of these bubbles increases the surface area available for attaching to solids, resulting in improved solids removal efficiency. Consider implementing this technology if your conventional DAF system consistently falls short of desired solids recovery targets.
Electrocoagulation flotation: Electrocoagulation involves the application of an electrical current to the wastewater, causing the coagulation and flocculation of suspended solids. The resulting flocs are then removed through the flotation process. This technology can be effective in cases where conventional coagulation methods are insufficient for solids removal.
When considering advanced DAF technologies, it's important to evaluate their capital and operating costs, as well as their compatibility with your specific rendering process. Conduct thorough research, seek expert advice, and consider pilot testing before implementing any new technology to ensure optimal results and cost-effectiveness.
Daily tests for DAF operators to assess quality
To determine the quality of DAF solids on a daily basis, DAF system operators can perform simple tests to assess certain key parameters. Here are two tests that operators can easily conduct and suggested benchmarks to evaluate the quality of the solids:
Total Suspended Solids (TSS) Test
Procedure: Collect a representative sample of the DAF solids and filter it through a pre-weighed filter paper. Dry the filter paper with the retained solids in an oven at a specified temperature (e.g., 105°C) until a constant weight is achieved. Calculate the weight of the dried solids as a percentage of the initial sample weight.
Benchmark: A TSS benchmark of 85-95% can be considered as an indicator of effective solids recovery. This means that the DAF system is efficiently removing a high percentage of suspended solids from the wastewater stream.
Free Fatty Acid (FFA) Content Test
Procedure: Extract a sample of the DAF solids and perform an acid-base titration to determine the FFA content. This involves adding a standardized base solution to the sample, which neutralizes the free fatty acids. The volume of base solution required to neutralize the sample indicates the FFA content.
Benchmark: A lower FFA content is generally desired in the DAF solids to ensure higher-quality tallow. While specific benchmarks may vary depending on the rendering plant's requirements, aiming for an FFA content below 5% is a common target to produce tallow suitable for various applications.
Maximizing solids recovery in DAF systems is crucial for Australian meat processing and rendering sites to achieve environmental compliance and economic viability.
By implementing the practical tips and strategies outlined in this comprehensive guide, you can optimize your DAF system's performance, enhance tallow quality, and capitalize on the economic opportunities associated with higher-grade products. Continuous monitoring, regular maintenance, and a proactive approach to process optimization are essential for long-term success in solids recovery.
Remember, by maximizing solids recovery, you not only contribute to a sustainable and environmentally responsible operation but also improve the profitability and competitiveness of your rendering business.