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Converting Organic Waste to Energy

Anaerobic digestion is defined as a series or collection of processes by which microorganisms break down biodegradable material in the absence of oxygen. This is part of a process used by CleanCap to convert organic waste into biogases.

Agricultural, Farming & Husbandry Masses Utilized for Biogas Production:

Food industries have done a particularly excellent job of reducing organic waste and implementing technologies to create biogases. The first step of converting biomass to biogas is through the breakdown of organic materials in a digester.

The origin of the substrates include:

  • Pig, cattle, fish & foul slurry
  • Energy crops such as grain & grasses
  • Produce waste from vegetables, fruits & nuts

The main components required to create biogases are:

  • Carbohydrates
  • Proteins
  • Fats
  • Cellulose & Hemicelluloses

These masses are broken down into the following three scenarios and associated digestion processes.

High Solids

(Dry Stackable Substrate)
High dry solids are designed to process materials that have a solid content of between 25 to 40% and process slurries without the addition of other liquids such as water. Traditionally these dry digestion systems are continuous vertical plug flow digesters or batch tunnel horizontal digesters. Vertical plug flow digesters are cylindrical upright tanks that are continuously fed feedstock. The feedstock comes in through the top of the digester and utilizes gravity to flow downward during the digestion process. With batch tunnel digesters, the feedstock is deposited into a chamber with a gas-tight door. With either of these digesters the mixing is done inside the digester.

High Solids

(Wet-Pumpable Substrate)
High wet solids are designed to process thick slurry. The thick slurry requires a higher energy input to move the input during processing. This thick material is often associated with abrasion problems, but their advantage is a lower land requirement due to lower volumes associated with moisture. High solid digesters require regular correction of performance calculations as larger fractions of the feedstock mass are potentially converted into biogas. These calculations include gas production, retention time, kinetics, dilution, etc.

Low Solids

(Wet-Pumpable Substrate)
Low wet solids transport material through the digestion system using standard pumps that require a low energy input but a large area of land due to increased volumes required with their digestion models larger liquid-to-feedstock ratio. The benefits beyond low energy consumption that come from digestion in a liquid environment includes a more thoroughly circulated material and improved contact between the bacteria and its feedstock. This permits the bacteria to readily access feedstock and increase the rate of gas production.

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Digestion & System
Configuration

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Biogas & Environmental Conditions

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Industrial
Wastewater