US-12623937-B2 - Bioelectrochemical bioreactor

US12623937B2US 12623937 B2US12623937 B2US 12623937B2US-12623937-B2

Abstract

The present invention relates to a method for converting one or more influent streams comprising organic compounds present in an aqueous liquid stream such as wastewater and optionally inorganic carbon compounds into an effluent stream comprising short chain organic molecules in a bioreactor comprising electrodes, said method comprising: • the electrochemical oxidation of said organic compounds, thereby forming inorganic carbon compounds; and; • the electrochemical of said inorganic compound such as ammonium, ammonia and sulfides present in an aqueous liquid stream entering the bioreactor. • the bio-electrochemical reduction of said inorganic carbon compounds, thereby forming short chained organic molecules (such as methane); characterized in that said bioreactor is an anaerobic bioreactor comprising a biofilm growing on the cathodes and optionally the anodes as well as microorganism in suspension.

Inventors

Carlos Antonio Saldias Dinamarca
Rune Bakke

Assignees

Universitetet i Sørøst-Norge

Dates

Publication Date: 20260512
Application Date: 20210518
Priority Date: 20200518

Claims (12)

1 . A method for converting one or more influent streams into an effluent stream comprising short chain organic C1 to C6 hydrocarbons or derivatives thereof in a single anaerobic bioreactor comprising electrodes; wherein the one or more influent streams comprise a wastewater stream comprising organic compounds and a gaseous or aqueous syngas stream comprising inorganic carbon compounds consisting primarily of hydrogen and carbon monoxide, and optionally one or both of carbon dioxide and methane; wherein the wastewater stream and the syngas stream are introduced separately or are pre-combined prior to introduction into the single anaerobic bioreactor; and wherein said single anaerobic bioreactor comprises biofilms growing on cathodes and optionally on anodes, as well as microorganisms in suspension; said method comprising: electrochemical oxidation of said organic compounds, thereby forming inorganic carbon compounds; and bio-electrochemical reduction of said inorganic carbon compounds, thereby forming short chained organic C1 to C6 hydrocarbons or derivatives thereof; wherein said method further comprises solubilizing the syngas and/or pre-fermenting the syngas with homoacetogenic bacteria prior to said syngas entering into said single anaerobic bioreactor.
2 . Method according to claim 1 wherein said single anaerobic bioreactor does not comprise a membrane to divide the single anaerobic bioreactor into multiple chambers.
3 . Method according to claim 1 further comprising: bio-electrochemical oxidation of organic compounds using biological reactions with the microorganisms present in a biofilm on the anode; electrochemical oxidation of inorganic compounds, including electrochemical oxidation of hydrogen sulfide and/or ammonium; and/or bio-electrochemical oxidation of inorganic compounds, including bio-electrochemical oxidation of hydrogen sulfide and/or ammonium.
4 . Method according to claim 1 , wherein said effluent stream of said single anaerobic bioreactor is biogas comprising methane.
5 . Method according to claim 1 , wherein the single anaerobic bioreactor is operated at an absolute pressure between 1.0 and 3.0 bar.
6 . Method according to claim 1 , wherein the electrodes comprise said anodes and cathodes arranged in a surface area to volume ratio of at least 5 m 2 /m 3 .
7 . Method according to claim 1 , wherein the electrodes comprise anodes and cathodes which are alternatingly stacked vertically or horizontally within said single anaerobic bioreactor.
8 . Method according to claim 1 , wherein said single anaerobic bioreactor is an Up-flow Anaerobic Bed reactor.
9 . Method according to claim 8 , wherein the Up-flow Anaerobic Bed reactor is an Up-flow Anaerobic Sludge Bed (UASB) reactor.
10 . Method according to claim 1 , wherein the voltage applied to the electrodes for the electrochemical oxidation and bio-electrochemical reduction ranges between 250 mV and 1200 mV vs. standard hydrogen electrode (SHE) at the cathode.
11 . Method according to claim 1 , wherein the suspension in the single anaerobic bioreactor has a redox potential between −250 and −450 mV.
12 . Method according to claim 1 , wherein the method further comprises the step of adding a nutrient solution to the influent.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a U.S. national stage entry under 35 U.S.C. § 371 of PCT International Patent Application No. PCT/EP2021/063085, filed May 18, 2021, which claims priority to European Patent Application No. 20175145.0, filed May 18, 2020, the contents of each of which are incorporated herein by reference in their entirety. FIELD OF THE INVENTION The present invention relates to the field of organic slurries and wastewater treatment systems. More specifically, the present invention relates to the conversion of one or more influent streams comprising organic compounds present in an aqueous liquid stream and optionally inorganic carbon compounds, into one or more effluent stream(s) comprising short chain organic molecules in a bioreactor comprising electrodes, said method comprising both the bio-electrochemical reduction of inorganic carbon compounds to form short chained organic molecules and the electrochemical and/or the bio-electrochemical oxidation of organic and/or inorganic compounds. BACKGROUND OF THE INVENTION Global society is moving out from a dependent fossil fuel base economy towards more renewable, non-fossil based fuels. Carbon base materials, chemicals and transportation fuels are for the most part made from fossil resources and there is no sufficiently efficient industrial technology for non-fossil based production immediately available. There is also an urgent need to reduce greenhouse emissions associated with fossil fuel consumption. The demand for alternatives such as renewable methane gas is expected to have a steady growth as more liquefied biomethane is used in both land bases and maritime heavy transport. The amount of available organic waste alone will not suffice the growing market which targets the use of fuels from recyclable organic sources. In Europe biogas is today mainly used for heating, electricity generation and transport fuel. The share of biogas used as transport fuels is higher in Scandinavian countries because local public (communal) transportation is increasingly done by vehicles that run on upgraded biogas. Several land based heavy transport companies and truck producers have also engaged in the use and production of machines running of liquefied biogas. The composition of biogas may vary with typical between 30-50% CO2, 70-50% methane and 350-10000 ppm H2S. In order for the biogas to be used it needs to be further upgraded (e.g. removing CO2 and H2S) using technologies such as amine scrubbers. These upgrading processes are generally energy intensive and use chemicals such as amines and alkali solutions that in turn need to be removed in downstream processes. European legislation strongly discourages both the transport and deposition of sludge's in open fields. This has been the preferred solution of e.g. biogas plants where after the process of anaerobic digestion the remaining sludge is driven away to farmland to be used as a fertilizer. However new research and public awareness have given light to the dangers of spreading microplastics and other chemicals in the fields because much of it ends up in waterbodies due to runoff. Another negative aspect of this relates to the use of fossil fuel for transporting the sludge over great distances, as such increasing the environmental burden. This creates a necessity to treat sludge of organic nature onsite. Recently, gasification or pyrolysis of organic sludge has become more common. During the gasification or pyrolysis organic sludge is converted into energy rich gasses, syngas, that comprises mainly of CO2, H2 and CO. Syngas can be transformed to other chemicals in a process known as syngas fermentation, which is a biological mediated process where CO2, CO, H2 gasses are converted to acids (e.g. acetic acid) and solvent (e.g. ethanol). This process is performed by a very metabolically diverse group of bacteria. This biological mediated process is however dominated by thermodynamic constrains. The concentration of acids and solvents reach a maximal concentration below the desired magnitude to make the volumetric production economically feasible. In view of the above, there is a clear need to resolve at least some of the problems that currently restrict the use of biogas. SUMMARY OF THE INVENTION The inventors have now uncovered a process that allows for biogas upgrading as an electrochemical step that is integrated with anaerobic digestion for biogas production. For instance, with the methods and apparatuses described herein the methane content in biogas can be upgraded, e.g. to 80.0% or more, in particular to 85.0% or more, in particular to 90.0% or more, in particular 92.0% or more, more in particular 94.0% or more and more in particular 96.0% or more. The present invention provides in a method for converting one or more influent streams comprising organic compounds present in an aqueous liquid stream and optionally inorganic carbon compounds, preferably C-1 inorganic carbon comp