A black-and-white diagram showing how the anaerobic digestion process works. The diagram shows a biodigester. To the left of this image are the words "bio waste and organic waste" with an arrow pointing down that indicates that this waste goes into the biodigester. To the right are the words "biofertilizer and sludge" with an arrow pointing away from the biodigester, showing that biofertilizer and sludge come out. On top of the biodigester is the word "biogas," and indicates that biogas is the output of the anaerobic digestion process

Understanding Pretreatment in Anaerobic Digestion

| | Industrial Processing News

Anaerobic digestion is a critical process for treating organic waste and sludge. Through anaerobic digestion, biogas production is possible, which can be processed into renewable fuel/natural gas or even combusted to generate energy in the form of heat and electricity.

However, if organic waste and sludge aren’t pretreated, problems can occur during this critical process.

Why Pretreatment is Necessary

Shred Food Waste

Various existing pretreatment methods exist, but mechanical pretreatment is one of the most effective methods. Mechanical pretreatment involves disintegrating and/or grinding solid particles down, which releases cell compounds and improves surface area for anaerobic digestion. A pretreatment solution (which may include materials like stones, straw, wood, and plastic) is also often used to improve processing.

There are many benefits of mechanically pretreating waste before anaerobic digestion, starting with improved sludge treatability and a minimized risk of larger solids causing clogs or other operational problems further down the line. Likewise, it has been found that pretreatment, in general, can speed up biodegradation by providing better contact between substrate and anaerobic bacteria. This, in turn, can cut down on treatment costs while increasing the rate of methane production.


  • Improves Sludge Treatability
  • Minimizes Clogged & Damaged Downstream Equipment
  • Increases Biodegradation Process & Methane Production
  • Reduce Treatment Costs

Our Recommended Products & Solutions

Industrial shredders and grinders are used for the mechanical pretreatment or preconditioning of organic waste and sludge.

JWC Environmental manufactures high-quality industrial grinders and shredders for many applications, including anaerobic digestion.

Our recommended products for mechanical pretreatment include the 3-SHRED, 3-SHRED-2, 4-SHRED-2, 3-HYDRO In-line, and 4-HYDRO In-line.



Our 3-SHRED and 3-SHRED-2 industrial shredders are ideal for cutting problem solids down to size. These models feature two rows of high-torque sharp steel cutters that rotate slowly to cut through debris and aid in pretreatment/preconditioning, ensuring that larger particles don’t cause issues downstream. These models have motors ranging from 5 to 10 horsepower (depending on your needs) and cutting chamber lengths between 8 and 24 inches.

The 3-SHRED and 3-SHRED-2 also feature automated monitoring controls and hardened steel cutters to maximize longevity. Various cutter configurations are available, as are custom hoppers and stands to meet your exact processing and pretreatment needs.



If you need a more powerful industrial waste shredder for waste pretreatment, the 4-SHRED-2 has you covered. This slow-speed, high-torque model is specifically designed to handle some of the most challenging jobs and features strong shafts and severe duty seals for high-impact solids loading.

Each 4-SHRED-2 comes with a powerful 15- to 40-horsepower motor (depending on your needs) with cutting chamber lengths ranging from 18 to 32 inches. This model is also versatile in its configurations, so you can fully customize the shredder to meet your processing and preconditioning needs.

3-HYDRO In-line

3-HYDRO In-line grinder Industrial

The 3-HYDRO In-line is a dual-shafted, slow-speed, high-torque grinder that easily cuts through even the toughest of solids (including wood and rock that may be used in pretreatment solutions). It has a 5-horsepower motor and flow rate ranging from 450 to 2,450 GPM.

This industrial grinder also features a compact footprint, making it easier to integrate into an existing system, and a built-in smart controller with load sensing that optimizes its performance while protecting against jams.

4-HYDRO In-line

4-HYDRO In-line Industrial grinder

The 4-HYDRO In-line model offers all the same features as the 3-HYDRO In-line (including a small footprint that can be installed into 12 to 20-inch diameter pipelines) but features more power with its 10-HP motor and higher flow rates (2,700 to 6,860 GPM).

This grinder is ideal for preconditioning challenging solids in high-flow applications, maximizing surface area, and improving overall process efficiency.

Learn More About Our Pretreatment Solutions

JWC Environmental has been a trusted manufacturer of industrial grinding and shredding equipment since our inception in 1973. Today, we hold more than 70 different patents for product innovation and are a five-time recipient of the Water Environment Federation’s Innovative Technology Award.

Explore our case studies to learn more about how our products have impacted anaerobic digestion and biogas plants, or contact us today to schedule a consultation with a JWC Environmental product specialist. Our team is ready to help you find the best solution!

Contact a Representative

Find out more today about how JWC can fulfill your grinding, screening, shredding or processing needs.