Bioprocess Design

Functional Redundancy in the Anaerobic Digestion Microbiome

Researcher: Dr. Simon Mills

Project: Anaerobic digesters are often subject to perturbations e.g. shock organic loading rates (OLRs), resulting in dysbiosis in the anaerobic digestion (AD) microbiome. Process recovery after a perturbation may take time, as low abundance microbes, more suited to the prevalent conditions, establish. However, it may be possible to alleviate this effect by increasing functional redundancy in the AD microbiome. The concept of functional redundancy states that in multi-species assemblages many coexisting but taxonomically distinct microorganisms can have the same metabolic functions. Therefore, if functional redundancy could be increased in the AD microbiome, the impact of perturbations could be lessened due to the greater diversity of microorganisms which can perform the necessary functions for stable bioreactor performance. The aim of this work is to use a series of minor perturbations to increase functional redundancy and make the microbial communities in anaerobic digesters more resistant and resilient to shock OLRs.

Relevance and impact: Shock organic loads often cause volatile fatty acids (VFAs) accumulation and process failure in anaerobic digestion. Process failure occurs when high VFA concentrations inhibit methanogenesis. Increased functional redundancy in the AD microbiome could lead to better resistance to shock loads as a more diverse community is more likely to contain members which are capable of functioning at variable environmental conditions. Therefore, understanding ecological concepts such as functional redundancy can inform operational decisions and management strategies for anaerobic digestion. 

Groundwater treatment to drinking water: autotrophic denitrification assisted by electrochemical H₂ production and disinfection

Researcher: Dr. Eleftheria Ntagia

Project: Groundwater polluted with nitrates and fecal bacteria is an extensive problem in countries that lack adequate sanitation facilities, such as Sub Saharan African (SSA) countries or countries where the economy is based on cattle farming, such as Ireland. Polluted groundwater that is used as drinking water is the main cause for water-borne diseases outbreaks, such as diarrhoea and cholera. This research will focus on the integration of two technologies, pyrite-based autotrophic denitrification and electrochemical disinfection to tackle both pollutants in a single, potentially more sustainable and cost-effective system. 

Relevance and impact: Pyrite is a ubiquitous, low-cost mineral, that is frequently found as a waste product of mining activities. Pyrite-based autotrophic denitrification is therefore a cost-efficient solution, fit for groundwater that is poor in organic compounds. Pyrite is used as the electron donor in this case, and a circum-neutral pH is maintained, resulting in minimization of chemical inputs for this process. In electrochemical chlorination, Cl─ naturally contained in groundwater, is anodically oxidized to Cl₂, or further HOCl and ClO─ based on the pH of the solution. Additionally in this case chemical inputs are minimized as the disinfectant is produced on site, and chemicals are recovered, being the cathodic production of H₂. The reactions in the electrochemical cell are driven solely by electricity, which can be provided by renewable energy, e.g. a solar panel. The combination of the two processes can thus ensure a small footprint and cost effective drinking water treatment application that is location and electrical grid independent.

Dark fermentation of seaweed biomass for hydrogen production

Researcher: Mr. James Larwrence

Project: Dark fermentation is a vital part of the whole anaerobic digestion process (AD) and ultimately ends with VFA and hydrogen production produced by anaerobic fermentative bacteria. One such biomass that has be seen to be effective in production of biofuels i.e. biohytane, during AD is macroalgae (seaweed). Interest in this area has been constantly growing due to the increase of energy demand as well as the potential shown by macroalgae in wastewater treatment and biofuel production. Biohythane consists of a blend methane 70–90% v/v and 10-30% v/v hydrogen. Research has shown that this biofuel exhibits major potential in terms of application in the automotive industry. By harnessing this potential this research will aim to apply the same principles in hopes of decarbonising and fuelling maritime ferries. Biohythane is produced in a two-stage fermentation process. The first stage involves hydrogen production being controlled by a diverse population of hydrolytic and acidogenic bacteria whereas the second stage sees methanogenic archaea control methane generation.

Relevance and impact: Availability of fossils fuels is a major problem that the transportation sector faces. Increased pollution, fossil fuel availability and other adverse effects are just some of the reasons that have prompted a need to find additional resources for fuel. This alongside the fact the transportation sector is growing into one of the biggest energy consumers in today’s world has led it to be incredibly difficult to decarbonize. Another factor which has made decarbonization extremely difficult is down to the use of high-powered vehicles. For this reason, alternative sources of energy must be investigated with anaerobic digestion of macroalgae offering a viable opportunity for production of biofuels. 

Production of biohydrogen and biochemicals from dairy effluent

Researcher: Dr Paolo Dessi

Project: Dairy effluents are characterized by high organic loads representing, at the same time, a serious hazard for the environment and a huge opportunity for bioenergy and biochemical production. The high lactose content makes dairy effluents, particularly cheese whey, a promising substrate for hydrogen production through dark fermentation. Besides hydrogen, dark fermentation generates side-stream products, mainly CO2 and volatile fatty acids (VFAs), requiring a down-stream treatment prior to discharge in the environment. Due to their solubility, recovery of short chain volatile fatty acids is difficult and expensive. However, it was recently demonstrated that long chain VFAs and their respective alcohols can be generated from short chain VFAs and CO2 via microbial electrosynthesis. Combining dark fermentation with electrosynthesis is thus a promising biorefinery approach for treatment of dairy effluents, yielding biohydrogen and long chain VFAs and/or alcohols.

Relevance and impact: The integrated process pursues the double aim of production of green energy and reduction of carbon emissions. Produced hydrogen can be used directly as vehicle fuel or converted into electricity in fuel cells. Long chain fatty acids and alcohols are chemical commodities with high market value, due to their various applications in the energy and chemical industry sector.

 Bioelectrochemical systems using open-source derived electronics

Researcher: Mr Carlos Sanchez Fernandez

Project: Our hypothesis is that culturing under controlled electrode potential conditions enrich for different exoelectrogen communities for enhanced direct electron exchange. This can be applied to improve microbial fuel cell (MFC) performance by improving the start-up process and improve the efficiency of the electron transfer. This reduces the use of high cost materials. However, controlling this electrode potential is nowadays performed by using commercial potentiostats limited to research environments. For this reason, open source potentiostats will be develop. This will facilitate to apply the technology to a diverse range of problems and allow interoperability with other circuits like the energy harvesters used in successfull MFCs. This project aims to combine open-source potentiostats and energy harvesting for MFC conditions to deploy improved sewage treatment solutions for the abundant septic tanks in Ireland.

Relevance and impact: Bioelectrochemical systems play with two powerful forces: electricity and biology. The versatility of electricity to direct chemical transformations joined to the catalytic potential of microorganisms allows to easily develop new add-on units to solve the pollution problems, like those facing septic tanks in Ireland. Moreover, the cheaper access and experimental flexibility attained with open sourced electronics and reactor designs allow new creative solutions and more comparable results accross universities and continents. This will allow to develop new technologies to fight environmental challenges, and help to make one step more towards energy autonomy and circular economy.

 Syngas bioconversion to solvents by Clostridium, co-cultures and anaerobic sludges

Researcher: Ms Yaxue He

Project: Carbon monoxide (CO), one of the main compounds in syngas, can be biotransformed to solvents by Clostridium sp., which are widely studied bacteria mediating solventogenesis using syngas. This research will focus on solvent fermentation by Clostridium sp., improvement of solvent production and decrease of waste byproduct formation, sulfate removal by a co-culture with sulfate-reducing bacteria (SRB), improvement of the strain tolerance towards butanol, the mechanism and route of solvent production as well as continuous fermentation and solvent extraction technology.

Relevance and impact: Solventgenesis from carbon monoxide rich gas or syngas is an attractive alternative compared with traditional solvent fermentation methods which are economically unfavorable and need very large infrastructure. Solvent production by co-cultures or sludge could tolerate higher CO concentration than pure culture of Clostridium sp.

Automated control and opimization of heterogeneous anaerobic digestion processes

Reseacher: Mr Peyman Sadrimajd

Project: Anaerobic digestion (AD) is the biochemical conversion of biomass to methane and carbon dioxide. In sectors such as agriculture or industrial wastewater treatment, it is desired to have plants with maximum efficiency and minimum maintenance requirements. The goal of a bioprocess control system is to maximize yields (product volume and quality) while considering safety, equipment limitations, and economical factors. An ideal control system satisfies these goals in an automatic manner without human interventions. Conventional control systems operate plants in sub-optimal conditions and cannot handle disturbances and shocks in the influent because of nonlinearities in the complex and partly unknown AD process. The focus of this project is on generalizable machine learning techniques capable of handling nonlinearities and optimal control at the same time.

Relevance and impact: The integrated process simulation and control framework will lead to automated and optimal control systems. The same architecture can be used in different bioprocesses such as anaerobic digestion, bioelectrochemical systems, resource recovery, and other bioprocesses. The resulting technology will increase substrate utilisation and reduce operational risks, which will eventually result in higher economic output and lower environmental footprint.