• Technoeconomic Analysis (TEA)
    for AD and RNG Projects
    At Celignis Biomass Lab

The Importance of Technoeconomic Analyses of AD/RNG Projects

For the successful commercialisation of a developed technology, lab scale data provide a valuable starting point along the technology readiness level (TRL) spectrum. At Celignis, we conduct technical modelling and engineering design of pilot and industrial scale processes using experimental data supplemented with data from other reliable sources and standards.

The rigorous simulation provides reliable mass and energy balance data which constitutes the foundation for equipment design, sizing and specification and utility demand estimations.

The facility design information enables the estimation of the capital (CAPEX) and operating (OPEX) expenditures of the proposed production system using reliable costing models. This is followed by a thorough evaluation of the economic performance of the process. All the technical and economic hotspots in the process flow and value chain are identified and modulated to improve the robustness of the production system.

A thorough techno-economic evaluation (TEA) provides more clarity which guides decision making especially in the case of a significant financial commitment like the establishment of a commercial production facility.

Considering the low TRL of many emerging and developed bioprocess technologies, TEA stands as a valuable tool to investigate the promising potentials of these technologies in a more detailed design on a large scale before any major financial commitment is made. Our team of TEA experts are well equipped to evaluate the scale up and economic potential of various feedstock conversion technologies and product systems to provide clients and stakeholders with the vital data necessary to inform their decision making and resource allocation in respect of a technology or product of interest.

Our Technoeconomic Analysis Experts

Oscar has conducted several economic evaluations on several bioprocess technologies and product systems. During his PhD, he conducted comparative techno-economic studies on the biorefinery scenarios for production of prebiotics, biofuels and bioproducts. He has also worked with industrial partners to estimate the capital investment requirement and also assess the economic feasibility of biobased products from seaweed at a pilot scale.

Oscar has also good experience in the development of advanced and detailed conceptual process flow diagrams from the lab-scale process, highlighting scale up challenges and the process and engineering requirements for very unit operation in the process flow. With his proficient understanding of biological, chemical and physical systems, he has developed process simulations for several biorefinery scenarios using the appropriate modelling software. These simulations closely mimic the real life manifestation of the industrial process which is beneficial for R and D, mass and energy balance, equipment design and operation of the process or industrial plant. The simulation development significantly cuts down on unnecessary laboratory experiments, pilot scale runs and facilitates design by a convenient comparison of various process alternatives.

A serial innovator with extensive knowledge and experience in enzymes, microbes, and fermentation. Lalitha has a PhD in life sciences (Bioprocessing and Biotechnology) from Cochin University of Science and Technology (CUSAT), India (2015). In her PhD she discovered a novel natural butanol fermenter that does not form acetone and received a business plan award from CSIR, India (2011.) She also developed strategies to co-produce solvents and organic acids and was a visiting researcher in the University of Naples for three months under a Marie-Curie fellowship grant. As part of her individual Marie-Curie fellowship at Celignis, she studied the integration of AD with microalgae to produce high value feed and bioactives from the digestate.

With her biological expertise together with process engineering knowledge, she ensures that assumptions made in the simulations are meeting the real plant scenarios considering the limitations associated with bacterial and fungal systems such as product feedback inhibitions and substrate inhibitions. She is adept at developing multi-product processes from single feedstock or mix of feedstock and believes in AD not just for biogas, but AD for local decentralized biorefineries.

How we Can Help with TEA of Your AD/RNG Projects

Our techno-economic experts can work with you to evaluate the economic prospects of your technology or feedstock using the bench scale data. We apply accurate and realistic costing models to determine the CAPEX and OPEX of simulated and pilot scale processes which are then used to determine key economic indicators such as IRR, NPV and payback periods.
We provide comprehensive, objective and transparent results to help you obtain a good understanding of your process and its value chain as well as inform your budget and investment resource allocation. Our sensitivity analysis exposes the hotspots in the process flow as well as the main influencing parameters.

Case Study of a Celignis TEA Project

Celignis was approached by a large beverage production company to determine the feasibility of utilising their waste streams for biogas production and to determine the additional feedstock requirement to meet the full plant energy demand.

Celignis performed the required biological and chemical analysis of the facility's waste streams and developed a spreadsheet tool for feedstock mixtures design to allow the conversion of the sugar and acid rich waste stream to biogas and to meet the energy requirements of the company.

The tool considered seasonality of the locally-available feedstock that could be used as co-feed with the sugar rich waste streams. Also considered, while designing the feedstock mixtures, were Renewable Energy Directive (RED) II GHG emission targets and waste to energy crops ratio.

Greenhouse has (GHG) emission reductions and carbon dioxide that could be captured and the total revenue generation from biogas and CO2 were also estimated. The tool allowed the company to make informed decisions on the project and understand the biogas potential and feedstock requirements to meet the target power requirement.

Additional Information on Technoeconomic Analyses

Feel free to get in touch with us if you have any questions about our TEA services or if you are considering different technology and feedstock options for your AD/RNG facility. Relevant members of the Celignis anaerobic digestion team will be happy to assist. Those team members with the most experience with undertaking TEAs are listed below.

Lalitha Gottumukkala

Founder and Lead of Celignis AD, CIO of Celignis


Has a deep understanding of all biological and chemical aspects of anaerobic digestion. Has developed Celignis into a renowned provider of AD services to a global network of clients.

Kwame Donkor

AD Services Manager

BSc, MSc, Phd (yr 4)

His PhD focused on optimising AD conditions for Irish feedstocks such as grass. Kwame is now leading the Celignis AD team in the provision of analysis and bioprocess services.

Oscar Bedzo

Technoeconomic Analysis Lead


A dynamic, purpose-driven chemical engineer with expertise in bioprocess development, process design, simulation and techno-economic analysis over several years in the bioeconomy sector.

TEA Publications by the Celignis Team

Swart, L. J., Bedzo, O. K. K., van Rensburg, E., Gorgens, J. F. (2022) Pilot-scale xylooligosaccharide production through steam explosion of screw press-dried brewers spent grains, Biomass Conversion and Biorefinery 12: 1295-1309


Brewers spent grains (BSGs) represent the largest quantity of solid waste from brewing, while xylooligosaccharides (XOS) produced from BSG show promising applications in food, beverage and health products. Production of XOS from a Weiss and malt BSG was scaled-up in steam explosion hydrothermal treatment using process conditions from bench-scale liquid hot water optimisations in stirred batch reactors. Three levels of moisture (15, 25 and 32% dry matter) achieved by screw press dewatering were evaluated by varying the treatment temperatures and times. Results show the highest XOS yields (73.1%) were obtained, for both BSGs, at process condition selected (180 C, 10 min) with 25% initial dry matter content. These yields were higher than reported bench-scale optimisations (61%), but obtained using 60% less water; hence, initial dry matter content was an important variable affecting XOS yield. The pilot-scale steam explosion results provide a departing point for a cost-effective commercial production of XOS from BSG.

Swart, L. J., Bedzo, O. K. K., van Rensburg, E., Gorgens, J. F. (2021) Intensification of Xylo-oligosaccharides Production by Hydrothermal Treatment of Brewers Spent Grains: The Use of Extremely Low Acid Catalyst for Reduction of Degradation Products Associated with High Solid Loading, Applied Biochemistry and Biotechnology 193: 1979-2003


Brewers' spent grains (BSG) make up to 85% of a brewery's solid waste, and is either sent to landfill or sold as cheap animal feed supplement. Xylo-oligosaccharides (XOS) obtained from BSG are antioxidants and prebiotics that can be used in food formulations as low-calorie sweeteners and texturisers. The effect of extremely low acid (ELA) catalysis in liquid hot water (LHW) hydrothermal treatment (HTT) was assessed using BSG with dry matter contents of 15% and 25%, achieved by dewatering using a screw press. Batch experiments at low acid loadings of 5, 12.5 and 20 mg/g dry mass and temperatures of 120, 150 and 170 C significantly affected XOS yield at both levels of dry mass considered. Maximum XOS yields of 76.4% (16.6 g/l) and 65.5% (31.7 g/l) were achieved from raw BSG and screw pressed BSG respectively, both at 170 C and using 5 mg acid/g dry mass, after 15 min and 5 min, respectively. These XOS yields were obtained with BSG containing up to 63% less water and temperatures more than 20 C lower than that reported previously. The finding confirms that ELA dosing in LHW HTT allows lowering of the required temperature that can result in a reduction of degradation products, which is especially relevant under high solid conditions. This substantial XOS production intensification through higher solid loadings in HTT not only achieved high product yield, but also provided benefits such as increased product concentrations and decreased process heat requirements.

Swart, L. J., Peterson, A. M., Bedzo, O. K. K., Gorgens, J. F. (2021) Techno-economic analysis of the valorization of brewers spent grains: production of xylitol and xylo-oligosaccharides, Journal of Chemical Technology & Biotechnology 96(6): 1632-1644


Brewers spent grains (BSG) represents around 85% of a brewery's solid waste and common disposal to landfill is increasingly more difficult. Yet BSG is a food-grade by-product with potential economic valorization that can significantly improve resource efficiency and reduction in carbon emissions. This study investigated valorization of BSG through the application of novel high solids hydrothermal processing technology in a small-scale biorefinery, annexed to a brewery. It focused on three scenarios for the production of: (A) the sugar replacement xylitol; (B) prebiotic xylo-oligosaccharide (XOS); and (C) co-production of xylitol and XOS. Economic assessment was conducted by comparing the capital and operating expenditure from process simulations created in Aspen Plus. The process models developed were supplemented with experimental data to improve accuracy.
Internal rate of return (IRR) values obtained were greater than the hurdle rate of 9.7% for all scenarios when considering a conservative market price for xylitol and XOS as US$4500 t-1, yet dedicated production of XOS was economically more favourable with a minimum required selling price (MRSP) of US$2509 t-1 compared to US$4153 t-1 for xylitol. Additionally, the scenario for co-production of xylitol and XOS achieved the lowest MRSP of US$2182 t-1. By-products significantly contributed to 32.7%, 14.2% and 27.5% of the revenue generated in scenarios A, B and C, respectively.
These results provide a good platform from which to develop the cost-effective commercial production of XOS and xylitol from BSG.

Bedzo, O. K. K., van Rensburg, E. and Gorgens, J. F. (2021) Investigating the effect of different inulin-rich substrate preparations from Jerusalem artichoke (Helianthus tuberosus L.) tubers on efficient inulooligosaccharides production, Preparative Biochemistry and Biotechnology 51(5): 440-449


Commercial production of inulooligosaccharides (IOS) relies largely on chicory roots. However, Jerusalem artichoke (JA) tubers provide a suitable alternative due to their high inulin content and low cultivation requirements. In this study, three inulin-rich substrate preparations from JA were investigated to maximize IOS production, namely powder from dried JA tuber slices (Substrate 1), solid residues after extracting protein from the JA powder (Substrate 2) and an inulin-rich fraction extracted from protein extraction residues (Substrate 3). The preferred temperature, pH and inulin substrate concentration were determined after which enzyme dosage and extraction time were optimized to maximize IOS extraction from the three substrates, using pure chicory inulin as benchmark. Under the optimal conditions, Substrate 3 resulted in the highest IOS yield of 82.3% (w/winulin). However, IOS production from the Substrate 1 proved more efficient since it renders the highest overall IOS yield (mass of IOS per mass of the starting biomass). In the case of co-production of protein and IOS from the JA tuber in a biorefinery concept, IOS production from the Substrate 2 is preferred since it reduces the inulin losses incurred during substrate preparation. For all the inulin-rich substrates studied, an enzyme dosage of 14.8 U/ginulin was found to be optimal at reaction time less than 6 h. JA tuber exhibited excellent potential for commercial production of IOS with improved yield and the possible advantage of a reduced biomass cost.

Bedzo, O. K. K., Mandegari, M. and Gorgens, J. F. (2020) Techno-economic analysis of inulooligosaccharides, protein, and biofuel co-production from Jerusalem artichoke tubers: A biorefinery approach, Biofuels Bioproducts & Biorefining-Biofpr 14(4): 776-793


Jerusalem artichoke (JA) is a crop with excellent potential for application in biorefineries. It can resist drought, pests, and diseases and can thrive well in marginal lands with little fertilizer application. The JA tubers contain considerable quantities of inulin, which is suitable for the production of inulooligosaccharides (IOS), as a high-value prebiotic, dietary fiber. In this study, five JA tuber biorefinery scenarios were simulated in Aspen Plus and further evaluated by techno-economic and sensitivity analyses. Production of IOS, proteins and animal feed was studied in scenarios A and C, applying various biorefinery configurations. Scenario B explored the option of producing only IOS and the sale of residues as animal feed. Scenarios D and E investigated the economic potential of biofuel generation from residues after IOS and protein production by generation of biogas and ethanol respectively, from residues. Based on the chosen economic indicators, scenario B resulted in the lowest minimum selling price (MSP) of 3.91 US$ kg-1 (market price 5.0 US$ kg-1) with correspondingly reduced total capital investment (TCI) and total operating cost (TOC) per mass unit produced of IOS of 18.91 and 2.59 US$ kg-1 respectively, compared with other studied scenarios. Considering the set production scale, it is more profitable when the residues are sold as animal feed instead of being converted into biofuel, due to the capital-intensive nature of the biofuel production processes. The coproduction of protein had a negative impact on the economics of the process as the associated capital and operating expenditure outweighed the associated revenue.

Bedzo, O. K. K., Mandegari, M. and Gorgens, J. F. (2020) Comparison of immobilized and free enzyme systems in industrial production of short-chain fructooligosaccharides from sucrose using a techno-economic approach, Biofuels Bioproducts & Biorefining-Biofpr 14(4): 776-793


Short-chain fructooligosaccharides (scFOS) are nutraceuticals with numerous applications in the food and pharmaceutical industries. The production of scFOS using immobilized biocatalysts offers some functional and technical advantages over free enzyme counterparts. To investigate the economic potential of the immobilized enzyme system relative to the free enzyme system, a techno-economic comparison was conducted on three methods of scFOS production (powder and syrup forms) at a capacity of 2000?t per annum (tpa) by enzymatic synthesis from sucrose: the free enzyme (FE), calcium alginate immobilized enzyme (CAIE), and amberlite IRA 900 immobilized enzyme (AIE) systems. These processes were simulated in Aspen Plus to obtain the mass and energy balances and to estimate the operating and capital costs, followed by economic evaluation and sensitivity analysis. Profitability analysis showed that all three systems are economically viable as their associated minimum selling prices (MSP) were well below the scFOS market price of 5 $ kg-1. However, the FE system was the most profitable with the lowest MSP of 2.61 $ kg-1 because the savings on cost as a result of enzyme immobilization could not offset the additional costs associated with immobilization. Sensitivity analysis demonstrated that total operating cost, fixed capital investment, and internal rate of return (% IRR) have the greatest effects on the MSP. Furthermore, the syrup form of scFOS production leads to 29% less MSP, compared to powder form. In addition, the studied plant capacities of 5000 and 1000?tpa showed 10% and 16% reductions on MSP respectively.

Other Celignis Tests and Services for Anaerobic Digestion

Global Recognition as AD/RNG Experts

Celignis provides valued services to over 1000 clients. We understand how the focus of AD projects can differ between countries and have advised a global network of clients on their RNG projects. We also have customs-exemptions for samples sent to us allowing us to quickly get to work no matter where our clients are based.

Further Info...

Biomethane Potential

The biomethane potential (BMP) can be considered to be the experimental theoretical maximum amount of methane produced from a feedstock. In our laboratory, we have six BMP systems, comprising 90 reactors, that allow us to digest your samples and determine the biogas yield over periods of between 14 and 40 days.

Further Info...

Continuous Digestions

To help you evaluate how well your anaerobic digestion feedstocks will behave in real-world conditions we can undertake continuous digestion experiments. These operate at scales up to 12 litres and typically run for 3 months. We target maximum achievable organic loading rate (OLR) and biomethane potential.

Further Info...

Toxicity Assays

The waste streams used in AD that arise from process industries may contain toxic or bacterial inhibitory compounds (e.g. antibiotics, polyelectrolytes, detergents). Our anaerobic toxicity assays can determine the presence of such toxicities and suggest the feeding limits for feedstocks.

Further Info...

Process Optimisations

There a many factors to consider when running an AD facility. We can design and experimentally-validate optimisations of these factors at the lab-scale prior to you implementing them at your AD facility. Such an approach allows for greater benefits and lower costs than optimising the process at the commercial scale.

Further Info...

Feedstock Analysis

Our analysts have characterised tens of thousands of biomass samples. We have dedicated analyses packages for the compositional parameters of most relevance to AD/RNG. Additionally, based on our detailed analyses we can recommend appropriate feedstock mixing proportions in co-digestion facilities.

Further Info...

Biological Consultations

We're experts in the biology of anaerobic digestion. We pour through operational data from biogas plants and identify correlations between process parameters and plant performance. This understanding on the specific biology of the digester allows for recommendations as to how peformance can be improved and made more stable.

Further Info...

Specific Microbial Activity

AD is a microbial process involving a sequence of stages (hydrolysis, acidogenesis, methanogenesis) to convert a complex feedstock to methane. We analyse samples collected from digesters and undertake tests to investigate how well they proceed with each of these stages of digestion.

Further Info...

Digestate Analysis

Digestate is the residue after the anaerobic digestion process. It can potentially have value as a soil fertiliser. We offer a range of detailed analysis packages for digestate, allowing you to fully assess this resource and to determine the best use for it. Our team can also assist in evaluating digestate valorisation options.

Further Info...

Project Development

The criteria for the development of a successful AD project are numerous and vary according to region, technology, and feedstock. We have a deep understanding of these regional, technical, and biological differences and have advised a global network of clients on effectively developing their AD projects.

Further Info...

Process Parameters

Celignis can undertake a range of key analyses for KPIs and advanced process monitoring. These include volatile fatty acids (VFAs); Alkalinity ratio (FOS/TAC); and redox potential. It is particularly imporant that these are monitored when undergoing changes of feedstock type, organic loading rate and hydraulic retention times.

Further Info...

Nutrient Supplementations

Nutrients are essential for maintaining stable microbial populations and for efficient anaerobic digestion. We can suggest optimal values for the presence of major and minor elements in the digester as well as upper and lower threshold values. This allows us to formulate a bespoke cocktail of additives according to the requirements of the digester.

Further Info...

Publications on Anaerobic Digestion By The Celignis Team

Ravindran, R., Donkor, K., Gottumukkala, L., Menon, A., Guneratnam, A. J., McMahon, H., Koopmans, S., Sanders, J. P. M., Gaffey, J. (2022) Biogas, biomethane and digestate potential of by-products from green biorefinery systems, Clean Technologies 4(1): 35-50



Global warming and climate change are imminent threats to the future of humankind. A shift from the current reliance on fossil fuels to renewable energy is key to mitigating the impacts of climate change. Biological raw materials and residues can play a key role in this transition through technologies such as anaerobic digestion. However, biological raw materials must also meet other existing food, feed and material needs. Green biorefinery is an innovative concept in which green biomass, such as grass, is processed to obtain a variety of protein products, value-added co-products and renewable energy, helping to meet many needs from a single source. In this study, an analysis has been conducted to understand the renewable energy potential of green biorefinery by-products and residues, including grass whey, de-FOS whey and press cake. Using anaerobic digestion, the biogas and biomethane potential of these samples have been analyzed. An analysis of the fertiliser potential of the resulting digestate by-products has also been undertaken. All the feedstocks tested were found to be suitable for biogas production with grass whey, the most suitable candidate with a biogas and biomethane production yield of 895.8 and 544.6 L/kg VS, respectively, followed by de-FOS whey and press cake (597.4/520.3 L/kg VS and 510.7/300.3 L/kg VS, respectively). The results show considerable potential for utilizing biorefinery by-products as a source for renewable energy production, even after several value-added products have been co-produced.

Donkor, K. O., Gottumukkala, L. D., Lin, R., Murphy, J. D. (2022) A perspective on the combination of alkali pre-treatment with bioaugmentation to improve biogas production from lignocellulose biomass, Bioresource Technology 351



Anaerobic digestion (AD) is a bioprocess technology that integrates into circular economy systems, which produce renewable energy and biofertilizer whilst reducing greenhouse gas emissions. However, improvements in biogas production efficiency are needed in dealing with lignocellulosic biomass. The state-of-the-art of AD technology is discussed, with emphasis on feedstock digestibility and operational difficulty. Solutions to these challenges including for pre-treatment and bioaugmentation are reviewed. This article proposes an innovative integrated system combining alkali pre-treatment, temperature-phased AD and bioaugmentation techniques. The integrated system as modelled has a targeted potential to achieve a biodegradability index of 90% while increasing methane production by 47% compared to conventional AD. The methane productivity may also be improved by a target reduction in retention time from 30 to 20 days. This, if realized has the potential to lower energy production cost and the levelized cost of abatement to facilitate an increased resource of sustainable commercially viable biomethane.

Donkor, K. O., Gottumukkala, L. D., Diedericks, D., Gorgens, J. F. (2021) An advanced approach towards sustainable paper industries through simultaneous recovery of energy and trapped water from paper sludge, Journal of Environmental Chemical Engineering 9(4): 105471


This study considered the possibility of reducing the environmental footprint of paper and pulp industry by producing bioenergy from paper sludge by using process wastewater instead of fresh water, and reclaiming water trapped in paper sludge. Experimental studies are conducted with streams from three different pulp and paper mills (virgin pulp mill (VP), corrugated recycling mill (CR), tissue printed recycling mill (TPR)) for sequential bioethanol and biogas production with simultaneous reclamation of water from paper sludge (PS). Total energy yields of 9215, 6387, 5278 MJ/tonne dry PS for VP, CR and TPR, respectively, were obtained for ethanol-biogas production. Virgin pulp paper sludge gave the highest yield for ethanol and biogas in stand-alone processes (275.4 kg and 67.7 kg per ton dry PS respectively) and also highest energy conversion efficiency (55%) in sequential process compared with CR and TPR. Energy and environmental case study conducted on virgin pulp mill has proven the possibility of using paper sludge bioenergy to reduce energy demand by 10%, while reclaiming 82% of the water from the PS, reducing greenhouse gas emissions (GHG) by 3 times and producing solids suitable for land spreading.

Gottumukka L.D, Haigh K, Collard F.X, Van Rensburg E, Gorgens J (2016) Opportunities and prospects of biorefinery-based valorisation of pulp and paper sludge, Bioresource technology 215: 37-49


The paper and pulp industry is one of the major industries that generate large amount of solid waste with high moisture content. Numerous opportunities exist for valorisation of waste paper sludge, although this review focuses on primary sludge with high cellulose content. The most mature options for paper sludge valorisation are fermentation, anaerobic digestion and pyrolysis. In this review, biochemical and thermal processes are considered individually and also as integrated biorefinery. The objective of integrated biorefinery is to reduce or avoid paper sludge disposal by landfilling, water reclamation and value addition. Assessment of selected processes for biorefinery varies from a detailed analysis of a single process to high level optimisation and integration of the processes, which allow the initial assessment and comparison of technologies. This data can be used to provide key stakeholders with a roadmap of technologies that can generate economic benefits, and reduce carbon wastage and pollution load.

Gottumukkala L.D, Parameswaran B, Valappil S.K, Pandey A (2014) Growth and butanol production by Clostridium sporogenes BE01 in rice straw hydrolysate: kinetics of inhibition by organic acids and the strategies for their removal, Biomass Conversion and Biorefinery 4(3): 277-283


Growth inhibition kinetics of a novel non-acetone forming butanol producer, Clostridium sporogenes BE01, was studied under varying concentrations of acetic and formic acids in rice straw hydrolysate medium. Both the organic acids were considered as inhibitors as they could inhibit the growth of the bacterium, and the inhibition constants were determined to be 1.6 and 0.76 g/L, respectively, for acetic acid and formic acid. Amberlite resins—XAD 4, XAD 7, XAD 16, and an anion exchange resin—Seralite 400 were tested for the efficient removal of these acidic inhibitors along with minimal adsorption of sugars and essential minerals present in the hydrolysate. Seralite 400 was an efficient adsorbent of acids, with minimal affinity towards minerals and sugars. Butanol production was evaluated to emphasize the effect of minerals loss and acids removal by the resins during detoxification.