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Dr Mark Walker


A techno-economic assessment of implementing power-to-gas systems based on biomethanation in an operating waste water treatment plant (2020)
Journal Article
Michailos, S., Walker, M., Moody, A., Poggio, D., & Pourkashanian, M. (2021). A techno-economic assessment of implementing power-to-gas systems based on biomethanation in an operating waste water treatment plant. Journal of Environmental Chemical Engineering, 9(1), Article 104735. https://doi.org/10.1016/j.jece.2020.104735

The aim of the present study is to assess the techno-economic viability of integrating biomethanation into power to gas systems in a real waste water treatment plant (WWTP). The research is the first attempt to assess the viability of several scenari... Read More about A techno-economic assessment of implementing power-to-gas systems based on biomethanation in an operating waste water treatment plant.

Biomethane production using an integrated anaerobic digestion, gasification and CO2 biomethanation process in a real waste water treatment plant: A techno-economic assessment (2020)
Journal Article
Michailos, S., Walker, M., Moody, A., Poggio, D., & Pourkashanian, M. (2020). Biomethane production using an integrated anaerobic digestion, gasification and CO2 biomethanation process in a real waste water treatment plant: A techno-economic assessment. Energy Conversion and Management, 209, Article 112663. https://doi.org/10.1016/j.enconman.2020.112663

The biomethanation of CO2 from anaerobic digestion within the power to gas concept has recently emerged as a promising technology to upgrade biogas, to decarbonise the domestic and industrial heat sector, provide long term energy storage and deliver... Read More about Biomethane production using an integrated anaerobic digestion, gasification and CO2 biomethanation process in a real waste water treatment plant: A techno-economic assessment.

Assessment of micro-scale anaerobic digestion for management of urban organic waste: A case study in London, UK (2017)
Journal Article
Walker, M., Theaker, H., Yaman, R., Poggio, D., Nimmo, W., Bywater, A., …Pourkashanian, M. (2017). Assessment of micro-scale anaerobic digestion for management of urban organic waste: A case study in London, UK. Waste Management, 61, 258-268. https://doi.org/10.1016/j.wasman.2017.01.036

This paper describes the analysis of an AD plant that is novel in that it is located in an urban environment, built on a micro-scale, fed on food and catering waste, and operates as a purposeful system. The plant was built in 2013 and continues to op... Read More about Assessment of micro-scale anaerobic digestion for management of urban organic waste: A case study in London, UK.

Modelling the anaerobic digestion of solid organic waste – Substrate characterisation method for ADM1 using a combined biochemical and kinetic parameter estimation approach (2016)
Journal Article
Poggio, D., Walker, M., Nimmo, W., Ma, L., & Pourkashanian, M. (2016). Modelling the anaerobic digestion of solid organic waste – Substrate characterisation method for ADM1 using a combined biochemical and kinetic parameter estimation approach. Waste Management, 53, 40-54. https://doi.org/10.1016/j.wasman.2016.04.024

This work proposes a novel and rigorous substrate characterisation methodology to be used with ADM1 to simulate the anaerobic digestion of solid organic waste. The proposed method uses data from both direct substrate analysis and the methane producti... Read More about Modelling the anaerobic digestion of solid organic waste – Substrate characterisation method for ADM1 using a combined biochemical and kinetic parameter estimation approach.

Assessment and parameter identification of simplified models to describe the kinetics of semi-continuous biomethane production from anaerobic digestion of green and food waste (2016)
Journal Article
Owhondah, R. O., Walker, M., Ma, L., Nimmo, B., Ingham, D. B., Poggio, D., & Pourkashanian, M. (2016). Assessment and parameter identification of simplified models to describe the kinetics of semi-continuous biomethane production from anaerobic digestion of green and food waste. Bioprocess and biosystems engineering, 39(6), 977-992. https://doi.org/10.1007/s00449-016-1577-x

Biochemical reactions occurring during anaerobic digestion have been modelled using reaction kinetic equations such as first-order, Contois and Monod which are then combined to form mechanistic models. This work considers models which include between... Read More about Assessment and parameter identification of simplified models to describe the kinetics of semi-continuous biomethane production from anaerobic digestion of green and food waste.

Modelling an off-grid integrated renewable energy system for rural electrification in India using photovoltaics and anaerobic digestion (2014)
Journal Article
Castellanos, J., Walker, M., Poggio, D., Pourkashanian, M., & Nimmo, W. (2015). Modelling an off-grid integrated renewable energy system for rural electrification in India using photovoltaics and anaerobic digestion. Renewable energy, 74, 390-398. https://doi.org/10.1016/j.renene.2014.08.055

This work describes the design optimisation and techno-economic analysis of an off-grid Integrated Renewable Energy System (IRES) designed to meet the electrical demand of a rural village location in West Bengal – India with an overall electrical req... Read More about Modelling an off-grid integrated renewable energy system for rural electrification in India using photovoltaics and anaerobic digestion.

Modeling the Water Scrubbing Process and Energy Requirements for CO2 Capture to Upgrade Biogas to Biomethane (2014)
Journal Article
Nock, W. J., Walker, M., Kapoor, R., & Heaven, S. (2014). Modeling the Water Scrubbing Process and Energy Requirements for CO2 Capture to Upgrade Biogas to Biomethane. Industrial & engineering chemistry research, 53(32), 12783-12792. https://doi.org/10.1021/ie501280p

Water scrubbing is the most widely used technology for removing CO2 from biogas and landfill gas. This work developed a rate-based mass transfer model of the CO2–water system for upgrading biogas in a packed bed absorption column. The simulated resul... Read More about Modeling the Water Scrubbing Process and Energy Requirements for CO2 Capture to Upgrade Biogas to Biomethane.

Ammonia removal in anaerobic digestion by biogas stripping: An evaluation of process alternatives using a first order rate model based on experimental findings (2011)
Journal Article
Walker, M., Iyer, K., Heaven, S., & Banks, C. (2011). Ammonia removal in anaerobic digestion by biogas stripping: An evaluation of process alternatives using a first order rate model based on experimental findings. Chemical Engineering Journal, 178, 138-145. https://doi.org/10.1016/j.cej.2011.10.027

The feasibility of biogas stripping to remove ammonia in the anaerobic digestion of source segregated food waste was investigated. It was found in batch experiments that ammonia could be removed from digestate and that the removal followed 1st order... Read More about Ammonia removal in anaerobic digestion by biogas stripping: An evaluation of process alternatives using a first order rate model based on experimental findings.

Mass and energy balance for a rotating-drum composting plant (2011)
Journal Article
Eades, P., Banks, C., Heaven, S., & Walker, M. (2011). Mass and energy balance for a rotating-drum composting plant. Proceedings of the ICE - Waste and Resource Management, 164(3), 151-159. https://doi.org/10.1680/warm.2011.164.3.151

The Bioganix in-vessel composting system at Leominster, UK, received 33 515 t of waste from January 2006 to December 2007, of which 9200 t was source-segregated biodegradable municipal waste (BMW). The process operated with a nominal in-vessel retent... Read More about Mass and energy balance for a rotating-drum composting plant.

Preliminary trials of in situ ammonia stripping from source segregated domestic food waste digestate using biogas: Effect of temperature and flow rate (2010)
Journal Article
De la Rubia, M. Á., Walker, M., Heaven, S., Banks, C. J., & Borja, R. (2010). Preliminary trials of in situ ammonia stripping from source segregated domestic food waste digestate using biogas: Effect of temperature and flow rate. Bioresource technology : biomass, bioenergy, biowastes, conversion technologies, biotransformations, production technologies, 101(24), 9486-9492. https://doi.org/10.1016/j.biortech.2010.07.096

Batch experiments to remove ammonia from food waste digestate were set up, and preliminary runs undertaken. These experiments were based on gas stripping in a heated column reactor; the effects of different temperatures (35, 55 and 70 °C) and gas flo... Read More about Preliminary trials of in situ ammonia stripping from source segregated domestic food waste digestate using biogas: Effect of temperature and flow rate.