Anaerobic Digester Coupled with Aerobic Composter for Waste Treatment

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Solution Overview

Problem

Existing methane digestion processes face challenges with inhibition by lack of digestible carbon, impossibility of rejecting raw digestates into the environment, and high energy expenditures due to thermal needs, particularly in handling volatile organic solids and solid wastes.

Innovation Solution

A process that couples anaerobic digestion with aerobic composting in a closed vessel, allowing for the addition of raw compost and composting percolates into the digester, enabling co-composting of digestates with ligneous matters to produce a stable biofertilizer and capturing heat from the composting silo for use in the digester, while also utilizing thermal pretreatment and energy recovery from biogas.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If anaerobic digestion is used to treat organic wastes, then biogas is produced, but digestate requires further treatment and carbon availability becomes limiting

Engineering Contradiction:

Improvebiogas productionVSAvoiddigestate disposal

Core Design Contradiction:

PowerVSLoss of substance

Solution Approach 1:

The patent recovers digestate from anaerobic digestion and uses it as substrate for composting, transforming a waste product into a valuable resource. The composting process converts digestate into stable compost and humic percolates, which are then recycled back to the digester, eliminating disposal issues while maintaining carbon availability for continued biogas production.

Inventive Principle:

Principle #34Discarding and recovering

2Productivity

If thermal energy is provided to the digester to maintain optimal temperature, then methane productivity increases, but energy costs increase

Engineering Contradiction:

Improvemethane productivityVSAvoidenergy expenditure

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The system generates its own thermal energy requirements through the composting process. The exothermic composting reactions produce heat that is captured and transferred to the digester, allowing the system to maintain optimal digestion temperatures without external energy input. The composting unit essentially serves as a heat generator for the anaerobic digestion process.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent converts the potentially harmful effect of excess heat from composting into a beneficial resource. The heat that would otherwise be wasted is captured through heat exchangers and transferred to the digester, transforming an energy loss into a valuable thermal input that maintains optimal digestion conditions.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If composting is used to treat digestate, then stable compost is produced, but heat must be managed and carbon must be supplied

Engineering Contradiction:

Improvecompost stabilityVSAvoidcomposting temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The system implements a feedback loop where humic percolates extracted from the composting process are recycled back to the digester as carbon source. This feedback mechanism ensures continuous carbon availability for both processes, while the stabilized compost from composting is used as amendment, creating a self-regulating system that maintains optimal conditions for both anaerobic digestion and composting.

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This integrated approach enhances methane productivity, reduces energy costs, and produces a stable biofertilizer, addressing the limitations of existing processes by optimizing carbon availability and thermal management, and enabling continuous operation with diverse organic waste inputs.

Implementation Method 1

a process for anaerobic digestion of a first part of said wastes, which takes place in at least one digestion chamber

Methodology Applied

Scientific EffectAnaerobic digestion: Anaerobic Digestion

Implementation Method 2

a process for aerobic composting of a second part of said wastes which takes place in at least one composting chamber

Methodology Applied

Scientific EffectAerobic composting: Composting

Implementation Method 3

at least one chamber of said digestion chambers is heated using a heat-transfer liquid; said aerobic composting chamber is cooled by a heat-transfer liquid; and the heat recovered on said aerobic composting chamber is used to heat at least one of the digestion chambers

Methodology Applied

Scientific EffectHeat transfer: Heat Exchanger

Implementation Method 4

a burner configured to burn the energy fraction of the biogas (which mainly includes methane) produced by said anaerobic digestion chamber

Methodology Applied

Scientific EffectCombustion: Combustion

Data Source

PatentUS20230271866A1Method and device for treating organic waste, including the anaerobic digestion thereof and the composting of the digestates

Publication Date: 2023.08.31 JUA

AI summary

The invention relates to a continuous process for treating organic waste taking place in a plant, said process for treating organic waste comprising a process of anaerobic digestion of a first part of said waste, which takes place in at least one digestion chamber, and a process of aerobic composting of a second part of said waste, which takes place in at least one composting chamber, the process for treating organic waste comprising the steps of:—collecting digestate and biogas at the end of said anaerobic digestion process,—collecting compost and humic percolate at the end of said aerobic composting process,—feeding at least part of said digestate