Evaluating Your Feedstock(s)
If your Project is focused on the digestion of a specific feedstock (or number of feedstocks) then we will focus our initial work on the detailed compositional analyses and
digestion (batch and continuous) experiments on these feedstocks.
We can suggest, based on these results, the most appropriate AD technology (e.g. UASB or CSTR) for your feedstock(s) and we can also look at addressing any issues
that may arise from the use of these feedstocks, for example feedstock toxicities and nutrient imbalances.
Choosing Feedstock(s) for Your TechnologyAlternatively, you may be open to using different feedstocks but fixed with regards to the technology and size of AD process that you will be developing. In that instance we can audit a range of different feedstocks that you have available within the catchment area and evaluate which of these would be most suitable for the selected process and would allow for optimal biomethane yields and/or project revenues. We can then undertake lab-scale experiments where the co-feeding of feedstocks, and the supplementation of nutrients and/or microbes, is optimised.
Technoeconomic Analyses (TEAs)Our TEAs can take places at several stages, and to varying levels of detail, during the project development process. We can explore various options (e.g. differing reactor sizes, variable levels of subsidies, feedstock supply curves) to investigate their relative impacts upon key project financial metrics (e.g. IRR, Payback Period etc.).We can also undertake Life Cycle Analyses to explore the carbon intensity of the process and we can examine how the project can fit under existing rgulatory and support frameworks (e.g. LCFS, D3 RINS, RED II etc.).
Risk EvaluationsBased on our expertise in biological consultations, biomass feedstocks, and process design, we can undertake an external review of your plans for your future AD facility with a target of identifiying areas in which the project can be improved and elements of the project that may be exposed to higher levels of risk. We then work on identifying and recommending risk-mitigation strategies.
Changes in FeedstockIf you are looking to change the feedstock(s) being processed in your AD plant, or just to modify the relative proportion each feedstock contributes to the total mix, we would strongly recommend that these changes are first tested at the lab-scale. This will allow for the effects of these adjustments, on biogas/biomethane yields and other important process parameters, to be understood and for approriate modifications to be made to the planned activities so that plant performance will not be negatively affected. Undertaking such modifications directly at the plant would mean that you run the risk of reducing digester yields or, potentially, of causing a digester crash.
Ensuring Stable Digester PerformanceIn an ideal world there would be no performance issues with digesters as they would always operate under stable conditions. This would avoid the revenue losses associated with reduced efficiencies and would also mean that there would be no risk of potentially catastrophic digester crashes. The regular collection of relevant process parameters can help significantly with regards to identifying warning-signs of imminent drops in reactor performance and so can allow for appropriate mitigation strategies to be employed. These strategies would result in the predicted drop in performance being avoided and would ensure that the digester remains stable.
AD Feedstock Mixture Optimisation ToolCelignis 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.
Continuous Digestions for Improved OLRCelignis carried out continuous digestion experiments, for a company that produces biogas from OFMSW (the organic fraction of municipal solid waste) and other waste streams, in order to determine the maximum achievable organic loading rate and optimum feedstock mixtures. These experiments also determined the minimum organic loading rate to maintain the health of the plant in the scenarios where feedstock availability was limited.
Stabilising Plant PerformanceA Germany-based biogas company that operates dozens of AD/RNG plants in Europe and the UK approached Celignis to support them in optimising their plant operations to allow for more consistent outputs and reduced downtime. As a result, Celignis provided Biological Consultancy support which involved us analysing the plant process data in terms of: feedstock loading (organic loading rate); recirculation strategies; biogas composition and yield; volatile fatty acids (VFAs); and alkalinity.
Feed Limits for New AD StreamsA biogas plant started underperforming when a new feedstock was used as co-feed to the plant. As the plant received an important gate-fee for this new feedstock, they did not want to discontinue its use but to instead use it in a controlled and scientifically-driven manner. Celignis was asked to provide support for: determining the toxic effects of the feedstock; the causes of it; and to provide feeding limits.
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.
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.
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.
Global Recognition as AD/RNG Experts
Specific Microbial Activity
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.
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.
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.
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.
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.