Anaerobic Digesters– A New Life for Waste

Innovations for Sustainability

The state of things in the world of recycling begs for companies to get creative with innovative ways to operate more sustainably. Whether it’s by reducing waste, streamlining processes, consuming less fossil fuels, or finding new uses for materials that would otherwise face a landfill fate– each small step makes a difference. Together through persistence and innovation, we can move the needle in the right direction. One new, progressive technology growing in the U.S. is the use of anaerobic digesters to turn what would otherwise be considered as waste, into biogas, fertilizer, and animal bedding.

What is an Anaerobic Digester?

An anaerobic digester or bio digester is an airtight chamber in which anaerobic digestion of biosolids, food waste, manure, and other organic wastewater streams occurs. During the biological process of anaerobic digestion, bacteria break down organic matter in the absence of oxygen. The process produces commodities such as biogas, which generally contains between 50 to 70% methane and 30 to 40% carbon dioxide.

Byproducts of Anaerobic Digestion

This process is widely used as a source of renewable energy. The biogas created during anaerobic digestion can be used directly as fuel, in combined heat and power gas engines, or it can even be upgraded to natural gas-quality biomethane. Another byproduct of this process is fertilizer. The digestate produced can be used as an extremely nutrient-rich form of fertilizer for farming, and the separated solids that result from the process are often used as bedding materials for livestock.

Types of Digesters

There are many different styles of digesters that can be used, but the idea of taking something that would otherwise be considered trash, and converting it to something usable remains. There are covered anaerobic lagoon digesters which are sealed with a flexible cover, and methane recovered then piped to a combustion device. There are also plug flow digesters which feature long, narrow concrete tanks and are often used at dairy operations. Then there are complete mix digesters which utilize enclosed, heated tanks with either a hydraulic, mechanical, or gas mixing system and often incorporate the use of wastewater. And lastly there are dry digesters which are upright, silo-like tanks made from concrete or steel with rigid covers.

Benefits of Biogas

Economic Benefits:

• Creates jobs
• Turns cost items into revenue-generating opportunities
• Diversifies rural income streams/improves infrastructure
• Can operate alongside composting operations

Waste-Related Benefits

• Natural process for waste treatment
• Smaller footprint
• Extremely efficient decomposition
• Complete biogas capture
• Recycling and nutrient recovery
• Reduction of waste volume for transport or land application

Environmental Benefits

• Extreme odor reduction
• Reduced pathogen levels
• Reduced greenhouse gas emissions
• Increased crop yield

Energy Benefits

• Energy producing process
• Many biogas applications such as heat-only, electric-only, combined heat and electric, pipeline-quality biomethane, and transportation fuel
• Replacement of non-renewable fossil fuels

Ultimately, there are many benefits to this technology across the agricultural industry and beyond. iSustain is pleased to partner with companies that employ this process for creating renewable energy, while making a difference for sustainability one small change at a time.