Biogas Plant Biomass Recirculation for Degradation Efficiency
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Solution Overview
Problem
Current biogas production processes face inefficiencies due to limited degradation of organic matter, nutrient recovery challenges, and high energy consumption, particularly in using continuous systems and noble organic substrates, which also fail to effectively recycle bacterial biomass and fibrous fractions.
Innovation Solution
The process involves anaerobic digestion of organic substrates followed by separation and recirculation of fibrous and bacterial biomass fractions, using microfiltration to increase bacterial density and extend hydraulic residence time, along with the use of filtered digestate for biogas purification and nitrogen recovery, eliminating the need for chemical additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If continuous stirred tank reactor (CSTR) is used for biogas production, then the system operates continuously with fixed temperature control, but the bacterial biomass is continuously removed with digestate leading to low degradation efficiency
Solution Approach 1:
The continuous reactor is segmented into multiple zones with different retention times. The first zone operates as a continuous stirred tank for initial degradation, while subsequent zones function as plug flow reactors that retain bacterial biomass longer, allowing progressive degradation without continuous biomass removal.
Solution Approach 2:
The system extracts and separates bacterial biomass from the digestate stream using solid-liquid separation equipment. The recovered biomass is then recirculated back to the reactor, preventing its loss with the effluent and maintaining high active biomass concentration for continued degradation.
2Duration of action of stationary object
If huge fermentation volumes are used to extend hydraulic residence time, then bacteria multiplication can replace subtracted biomass, but the plant complexity and cost increase significantly
Solution Approach 1:
The system implements a feedback loop where bacterial biomass is continuously monitored in the digestate stream, separated when present above threshold levels, and recirculated back to the reactor. This closed-loop control maintains optimal biomass concentration without requiring excessive reactor volume.
Solution Approach 2:
Instead of discarding all digestate effluent, the system recovers valuable bacterial biomass through solid-liquid separation and returns it to the reactor. This selective recovery maintains high biomass concentration while allowing continuous operation with compact reactor volumes.
3Quantity of substance
If noble organic substrates like agricultural foodstuffs are used, then biogas production is sustained, but the degradation efficiency of organic matter remains limited
Solution Approach 1:
The system maintains continuous action of bacterial biomass on organic substrates through biomass recirculation. By keeping high concentrations of active bacteria in the reactor and preventing their washout, the degradation process operates continuously at high efficiency, converting more organic matter to biogas per unit time.
4Quantity of substance
If nutrients recovery from digestate is implemented using state of the art processes, then nitrogen and phosphorous can be recovered, but the engineering plant complexity and power consumption increase significantly
Solution Approach 1:
The solid-liquid separation equipment serves dual functions: it separates bacterial biomass for recirculation to maintain reactor performance, and simultaneously concentrates nutrients (nitrogen and phosphorous) in the separated solid fraction for potential recovery or agricultural use. This multi-functionality eliminates the need for separate nutrient recovery equipment.
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 approach enhances biogas production efficiency, increases nutrient recovery, and reduces energy consumption by recycling bacterial and fibrous fractions, achieving higher methane content in biogas and producing usable fertilizers, while simplifying plant engineering and reducing costs.
Implementation Method 1
Fermentation of organic substrates operated by suitable consortiums of anaerobic bacteria (bacterial biomass) allows to produce power from agricultural and industrial products and by-products. In particular, starting from the organic substrate, the bacterial biomass produces a mixture of gases (called biogas), through a sequence of known reactions including hydrolysis, acetogenesis and methanogenesis.
Implementation Method 2
through a sequence of known reactions including hydrolysis, acetogenesis and methanogenesis
Implementation Method 3
a third phase of separation of the bacterial biomass present in the digested liquid fraction through microfiltration
Data Source
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AI summary
The present invention relates to an improved process for biogas production from organic substrates, preferably zootechnical sewages, with an improved degradation efficiency, and to a plant for the actuation of said process. In a preferred embodiment, the present invention allows the purification of produced biogas and the recovery of nutrients from the digestate.