Browsing by Author "Onabanjo, Tosin"

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    Conceptual energy and water recovery system for self-sustained nano membrane toilet
    (Energy Conservation and Management, 2016-08-12) Hanak, Dawid P.; Kolios, Athanasios; Onabanjo, Tosin; Wagland, Stuart Thomas; Patchigolla, Kumar; Fidalgo Fernandez, Beatriz; Manovic, Vasilije; McAdam, Ewan J.; Parker, Alison; Williams, Leon; Tyrrell, Sean; Cartmell, Elise
    With about 2.4 billion people worldwide without access to improved sanitation facilities, there is a strong incentive for development of novel sanitation systems to improve the quality of life and reduce mortality. The Nano Membrane Toilet is expected to provide a unique household-scale system that would produce electricity and recover water from human excrement and urine. This study was undertaken to evaluate the performance of the conceptual energy and water recovery system for the Nano Membrane Toilet designed for a household of ten people and to assess its self-sustainability. A process model of the entire system, including the thermochemical conversion island, a Stirling engine and a water recovery system was developed in Aspen Plus®. The energy and water recovery system for the Nano Membrane Toilet was characterised with the specific net power output of 23.1 Wh/kgsettledsolids and water recovery rate of 13.4 dm3/day in the nominal operating mode. Additionally, if no supernatant was processed, the specific net power output was increased to 69.2 Wh/kgsettledsolids. Such household-scale system would deliver the net power output (1.9–5.8 W). This was found to be enough to charge mobile phones or power clock radios, or provide light for the household using low-voltage LED bulbs.
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    Energy recovery from human faeces via gasification: A thermodynamic equilibrium modelling approach
    (Elsevier, 2016-04-01) Onabanjo, Tosin; Patchigolla, Kumar; Wagland, Stuart Thomas; Fidalgo Fernandez, Beatriz; Kolios, Athanasios; McAdam, Ewan J.; Parker, Alison; Williams, Leon; Tyrrel, Sean; Cartmell, Elise
    Non-sewered sanitary systems (NSS) are emerging as one of the solutions to poor sanitation because of the limitations of the conventional flush toilet. These new sanitary systems are expected to safely treat faecal waste and operate without external connections to a sewer, water supply or energy source. The Nano Membrane Toilet (NMT) is a unique domestic-scale sanitary solution currently being developed to treat human waste on-site. This toilet will employ a small-scale gasifier to convert human faeces into products of high energy value. This study investigated the suitability of human faeces as a feedstock for gasification. It quantified the recoverable exergy potential from human faeces and explored the optimal routes for thermal conversion, using a thermodynamic equilibrium model. Fresh human faeces were found to have approximately 70–82 wt.% moisture and 3–6 wt.% ash. Product gas resulting from a typical dry human faeces (0 wt.% moisture) had LHV and exergy values of 17.2 MJ/kg and 24 MJ/kg respectively at optimum equivalence ratio of 0.31, values that are comparable to wood biomass. For suitable conversion of moist faecal samples, near combustion operating conditions are required, if an external energy source is not supplied. This is however at 5% loss in the exergy value of the gas, provided both thermal heat and energy of the gas are recovered. This study shows that the maximum recoverable exergy potential from an average adult moist human faeces can be up to 15 MJ/kg, when the gasifier is operated at optimum equivalence ratio of 0.57, excluding heat losses, distribution or other losses that result from operational activities.
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    An experimental investigation of the combustion performance of human faeces
    (Elsevier, 2016-07-27) Onabanjo, Tosin; Kolios, Athanasios; Patchigolla, Kumar; Wagland, Stuart Thomas; Fidalgo Fernandez, Beatriz; Jurado Pontes, Nelia; Hanak, Dawid P.; Manovic, Vasilije; Parker, Alison; McAdam, Ewan J.; Williams, Leon; Tyrrel, Sean F.; Cartmell, Elise
    Poor sanitation is one of the major hindrances to the global sustainable development goals. The Reinvent the Toilet Challenge of the Bill and Melinda Gates Foundation is set to develop affordable, next-generation sanitary systems that can ensure safe treatment and wide accessibility without compromise on sustainable use of natural resources and the environment. Energy recovery from human excreta is likely to be a cornerstone of future sustainable sanitary systems. Faeces combustion was investigated using a bench-scale downdraft combustor test rig, alongside with wood biomass and simulant faeces. Parameters such as air flow rate, fuel pellet size, bed height, and fuel ignition mode were varied to establish the combustion operating range of the test rig and the optimum conditions for converting the faecal biomass to energy. The experimental results show that the dry human faeces had a higher energy content (∼25 MJ/kg) than wood biomass. At equivalence ratio between 0.86 and 1.12, the combustion temperature and fuel burn rate ranged from 431 to 558 °C and 1.53 to 2.30 g/min respectively. Preliminary results for the simulant faeces show that a minimum combustion bed temperature of 600 ± 10 °C can handle faeces up to 60 wt.% moisture at optimum air-to-fuel ratio. Further investigation is required to establish the appropriate trade-off limits for drying and energy recovery, considering different stool types, moisture content and drying characteristics. This is important for the design and further development of a self-sustained energy conversion and recovery systems for the NMT and similar sanitary solutions.
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    Techno-economic and environmental assessment of gas turbines utilizing biofuels
    (Cranfield University, 2015-03) Onabanjo, Tosin; Di Lorenzo, Giuseppina
    The continued global reliance on fossil fuels with impact on resource depletion, human health, atmospheric pollution and environmental degradation has necessitated a global drive to integrate renewable fuels such as biodiesels. Biodiesels are described as “fuels composed of fatty acid methyl or ethyl esters and obtained from vegetable oils or animal fats”. Their use in energy generation could diversify the world’s energy mix, reduce fossil fuel dependence, reduce emissions and energy cost to bring about other economic benefits, especially for developing economies and rural communities with lack of adequate access to modern energy. A techno-economic and environmental life cycle assessment is however required to ensure that these fuels are fit for use in engines and meet any regulatory standard and sustainability criteria. This thesis has evaluated the use of Jatropha- and microalgae-biodiesel for power generation in two industrial gas turbines with open and combined cycle configuration. This was achieved using a techno-economic and environmental life cycle impact assessment framework. Comparative fuel assessments have been carried out between biodiesels and fossil fuels. Furthermore, the concept of microbial fuel degradation was examined in gas turbines. The thesis have identified Jatropha biodiesel as a worthwhile substitute for conventional diesel fuel, because it has close performance and emission characteristics to conventional diesel fuel with added advantage of being renewable. The consequent displacement of conventional diesel fuel with Jatropha biodiesel has significant environmental benefits. For economic viability and sustainability of gas turbine operated power plants, energy producers require a minimum monetary amount to recover the added cost of operating 100% Jatropha biodiesel. Other integration mechanisms are also available for utilizing the fuel in engines without compromising on plant’s economic performance. In worst case scenarios, where there are no government incentives, local conditions such as high life cycle cost of electricity, open opportunities for distributed and independent power generation from renewable fuels like Jatropha-biodiesel. Furthermore, this thesis has identified salient energy conversion processes that occur in gas turbine fuels, especially with biodiesels and developed a bio-mathematical model, Bio-fAEG to simulate these processes in gas turbines. This platform is a first step in quantifiable assessment and could enable a better understanding of microbial initiated processes.