Abstracts – Day 2

Day 2 – Thursday 23rd of March 2017

There are three parallel sessions on day 2 (please see below for info). The abstracts for these sessions can be found by clicking on the drop-down menu’s below.

Parallel session 4 – 9:00-11:00

  • Whole System (Auditorium)
  • Combustion and Emissions (Exchange Room 1)

Parallel session 5 – 12:00 – 1:30

  • Catalysis (Auditorium)
  • Policy (Exchange Room 1)

Parallel session 6 – 14:30 – 16:00

  • Gasification(Auditorium)
  • Socio-economics and development (Exchange Room 1)

The full conference agenda can be found by clicking here.

  • Combustion and Emissions

    Keynote:  Professor Jenny Jones (University of Leeds)

    • Optimizing the fuel properties of waste wood using pre-treatment methods (washing and torrefaction) : Bijal Gudka, University of Leeds
    • Self-heating and ignition behaviour of torrefied biomass and biochar: Francesco Restuccia, Imperial College London
    • The impact of biomass flue gas on the Performance of post combustion CO2 capture plant: Muhammad Akram, University of Sheffield
    • Additives and Coatings to Mitigate Slagging and Fouling in Biomass Combustion: Lee Roberts, University of Leeds
    • Predicting the ash deposition propensity of biomass combustion in a pilot-scale facility:  Xin Yang, University of Sheffield

  • 4.1.1: Optimizing the fuel properties of waste wood using pre-treatment methods (washing and torrefaction)

    Presenter: Bijal Gudka, University of Leeds

    Abstract: Waste to Energy is a very attractive concept for the generation of electricity and heat and has a high potential in the UK due to the generation of large amounts of wastes. In 2010, approximately 4.3 Mtons of waste wood (including municipal, commercial and industrial and construction and demolition)  was generated in the UK of which 2 Mtons was recycled. This wood is classified depending on the composition, chemical treatment, condition and the amount of non-lignocellulosic contamination as Grade A (clean) to Grade D (hazardous) according to the Waste Recyclers Association (WRAP). Waste wood has a high potential of being used as a power station fuel but it contains large amounts of alkali and alkaline earth metals, nitrogen, chlorine, sulphur and trace metals which when combusted cause slagging and fouling in boilers (which leads to downtime on the power plant) and are released as emissions of  SOx, NOx and particulate matter.

    Pre-treatment methods like washing and torrefaction help to improve the chemical and physical properties of the waste wood which makes it more attractive for combustion. This study seeks to assess the removal of the problematic species via water washing to reduce the ash related problems and emissions from burning the fuel.  In addition, torrefaction of both the raw and washed waste wood has been examined to determine whether further reduction of species occurs and also to increase the energy density and improve the grinding properties of the fuel.

    The ash content of the fuel is nearly halved after washing which directly impacts (positively) on the tendency of the fuel to cause slagging and fouling. The N, Cl and S contents of the fuel also decrease significantly thus reducing the NOx, HCl and SOx emissions respectively. Torrefaction improves the energy density and grinding properties of the fuel.

  • 4.1.2: Self-heating and ignition behaviour of torrefied biomass and biochar

    Presenter: Francesco Restuccia, Imperial College London

    Abstract:Over the past number of years, biomass has become an important part of the fuel mix for fossil fuel power plants, and its use is projected to grow significantly. At the same time, biochar is being used for soil amendment and atmospheric carbon sequestration. However, there are fire safety issues with these materials. Both biochar and torrefied biomass are produced from biomass through pyrolysis in a reactor under controlled conditions. Different reactor temperatures produce different pyrolyzed biomass, leading to materials with different properties and reactivity.  Pyrolyzed biomass like biochar and torrefied biomass are reactive porous media, and therefore can undergo self-heating. Self-heating is the tendency to spontaneously ignite under the right thermal and Oxygen conditions due to exothermic reactions via oxidation leading to smouldering or flaming fires. The more reactive the material, the more prone it is to self-heat. Fire risk is associated with production, transport, handling and storage of these materials. Spontaneous ignition of pyrolyzed biomass has already lead to accidental fires, for example biomass storage units at Tilbury Power Plant (UK) ignited in 2012 due to self-heating. Using basket tests in a thermostatically controlled laboratory oven we experimentally measured the different ignition temperatures of softwood pellets, rice husks and wheat straw pellets and their respective biochar produced at temperatures from 450 to 700 ᵒC. By investigating self-heating behaviour as a function of pyrolysis reactor temperatures we were able to quantify the different reactivities. This work improves the understanding of the fire risks posed by biomass pyrolysis and their impact on self-heating, providing insights necessary for successful and safe application of these products.

  • 4.1.3: The impact of biomass flue gas on the Performance of post combustion CO2 capture plant

    Presenter: Muhammad Akram, University of Sheffield

    Abstract:This paper presents results of an experimental campaign carried out at the Pilot Scale Advanced Capture Technology (PACT) facilities of the UK Carbon Capture and Storage Research Centre (UKCCSRC). A 0.25MW solid fuel Combustion Test Facility (CTF) is integrated with a post combustion carbon capture plant of 1TPD CO2 capture capacity. The CTF comprises of down-fired furnace fitted with a scaled version of a commercial low-NOx burner. The flue gas generated is drawn through a cyclone separator and a high temperature candle filter for fine particulate removal by an induced draught fan. A slip stream of the flue gas is taken by the capture plant for CO2 absorption using Monoethanolamine (30%) at varied flow rates. The absorption tower (8m x 0.3m) is packed with state of the art high performance Mellapak CC3 packing manufactured by Sulzer.  Pressurized hot water heated to a temperature in the range of 115–120°C was used for stripping CO2.

    The impact of the impurities such as K, Na, Ca, Mg, Zn, Hg, Cr, V, Fe, Cu, Cd etc.  in the biomass on the operational and environmental performance of the capture plant is evaluated. The performance of the capture plant in terms of reboiler duty, capture rate, rich and lean solvent loadings, loading capacity and liquid to gas ratio is evaluated at different operating conditions. Moreover, emissions of solvent and some of the degradation products (NH3, Formaldehyde etc.) measured by a 5 point measurement system at Flue Gas Desulphurisation (FGD) inlet, absorber inlet and outlet, wash column outlet and stripper outlet using FTIR are discussed in relation to the presence of impurities in the biomass flue gas. It has been observed that the presence of impurities in the biomass can have significant impact on the operational and environmental performance of the capture process.

  • 4.1.4: Additives and Coatings to Mitigate Slagging and Fouling in Biomass Combustion

    Presenter: Lee Roberts, University of Leeds

    Abstract: Utilising biomass for combustion presents a number of challenges, one of which is an often increased rate of deposition. Biomass ash typically contains significantly higher alkali-based compounds, with lower initial melting points compared to those typically found in coal ash, which can become soft and even molten at high combustion temperatures. This softened ash can deposit upon boiler walls, where high radiant heat transfer is present (slagging), and can deposit upon heat transfer surfaces as it is transported away from the combustion zone to lower temperature regions of the boiler (fouling). These deposits differ in nature – slagging deposits often have partially or fully molten layers present, and are heavily influenced by viscosity, while fouling deposits consist of sintered fly ash and condensed volatiles. One approach to mitigate these issues is to use an additive, which transforms the composition of the ash to include higher melting-point compounds, which in turn produce weaker, easier to remove deposits. Another is to use coatings, which increase the contact angle of molten ash, reducing the force needed to remove deposits.

    The behaviour of biomass ash with and without the presence of an alumiunosilicate based additive is currently being investigated using a number of approaches to measure changes in ash deformation, ash sintering and impacts on deposition and ESP performance.  Laboratory methods have been developed to measure ash resistivity and ash sinter strength, as a function of temperature and results will be presented.   In addition, several novel and commercial coatings will be tested in a full-scale boiler to examine deposition.  The results will provide insight into the impact of aluminosilicate additives on biomass ash behavior in boilers.

  • 4.1.5: Predicting the ash deposition propensity of biomass combustion in a pilot-scale facility

    Presenter: Xin Yang, University of Sheffield

    Abstract: Due to the advantage of CO2-neutrality, biomass combustion is regarded as a significant method to help control CO2 emissions to meet stringent carbon budgets. When combined with oxy-firing technology, biomass combustion can even achieve net negative CO2 emissions. However, biomass has different inorganic components in the fuel than those in coals, which may cause uncertainties in the ash deposition behaviours. In addition, the changes in combustion conditions under oxy-firing (temperature, velocity, gas atmosphere, etc.) can further influence ash deposition behaviour. Ash deposition issues can reduce heat transfer to the tubes of the furnace walls and heat exchangers. Therefore, it is vital to investigate the ash deposition behaviour of biomass combustion in order to help the efficient utilisation of biomass.

    In the present study, a Computational Fluid Dynamics (CFD) based ash deposition model, which is based on inertial impaction, thermophoresis and the direct alkali vapour condensation and combined with chemical equilibrium method, is employed to predict the ash deposition behaviour of biomass combustion in a 250 kW cylindrical down-fired combustion test facility at PACT national facilities. Furthermore, ash chemistry and physical particle properties (particle size distribution) are investigated and compared among the original biomass particles, fly ash particles and the deposits. The information on fly ash particles (ash chemistry and particle size distribution) and the flue gas composition collected from the experimental data in the furnace are used to build the ash deposition model. This study enables us to better understand and predict the ash deposition behaviour of biomass combustion. In the current study, the ash deposition behaviour of a typical biomass fuel (pulverised wood) is investigated under air- and oxy-firing conditions. The next step will consider the ash deposition behaviour of the combustion of waste materials.

  • Whole Systems

    • Bioenergy role in a decarbonised future: implications of regional variability of biomass availability and costs: Paul Dodds, UCL Institute for Sustainable Resources
    • Emission and cost implications of preferential use of biomass in the residential sector vs transport and industry: Isabela Butnar, UCL Institute for Sustainable Resources, University College of London
    • South African sugarcane and bioenergy multi-level decision-making tool: strategic, tactical and operational supply chain optimisations : Koen H. van Dam, Department of Chemical Engineering, Imperial College London
    • A systems approach mapping in assessing  primary forest residues  as feedstock for sustainable  production of bioenergy in Malawi: Maxon Chitawo, Stellenbosch University
    • Biomethane from anaerobic digestion and bio-SNG via gasification – an integrated assessment of environmental balance, market status, and techno-economics: Paul Adams, University of Bath
    • UK bioenergy system assessment: quantifying the GHG benefits of biomass imports for a sustainable future: Miao Guo, Department of Chemical Engineering, Imperial College London

  • 4.2.1: Bioenergy role in a decarbonised future: implications of regional variability of biomass availability and costs

    Presenter: Paul Dodds, University College London

    Abstract: There is a high uncertainty around the amount, type and location of biomass resources potentially available for bioenergy purposes. Furthermore, it is difficult to connect biomass availability and its price in the future, as usually studies assessing biomass potential do not assess costs.  In this study we use a global energy system model, UCL-TIAM, to analyse the effects these uncertainties might have on future biomass trade and on the competitiveness of bioenergy relative to other low-carbon technologies, within scenarios in which the global temperature rise is limited to 2°C. For each of the 17 regions considered within the model, based on a literature review we identify ranges of biomass potential and costs, distinguishing between four types of biomass resources, i.e. solid biomass, energy crops, liquid biofuels, and wastes. Implementing these regionalised biomass potentials and costs in an energy system model brings new insights onto the role bioenergy could play globally, as previous studies assessed the variation of biomass potential at global level assuming constant regional biomass supply costs, and did not consider the variability of regional contribution to the global biomass potential at different points in time. Considering the trade patterns between the 17 regions under different scenarios of biomass availability and costs, we investigate the potential of global bioenergy, in terms of costs and contribution to GHG emission reductions, to the year 2100. Preliminary results show that in scenarios assuming high biomass availability at low costs, bioenergy with carbon capture and storage (BECCS) features strongly in least-cost decarbonisation solutions.  However, as regional biomass availability declines, or the cost of biomass supply increases, alternative decarbonisation options become more competitive in many regions.  Even if the competition food vs. fuel can be resolved, the bioenergy potential depends on the availability of biomass with low embedded emissions, at relatively low cost.

  • 4.2.2: Emission and cost implications of preferential use of biomass in the residential sector vs transport and industry

    Presenter: Isabela Butnar, Institute for Sustainable Resources, University College of London

    Abstract: Currently bioenergy covers about 10% of the primary energy supply, and it is primarily used for cooking and heating in developing countries. There are significant uncertainties around the future potential contribution of bioenergy to the global energy supply, under conditions of increased population and food demand, diversifying diets, national and global decarbonisation targets. In this work we use a global energy systems model, UCL-TIAM, to investigate scenarios of biomass resource use leading to the lowest overall energy system costs and GHG emissions. Specifically, we designed scenarios limiting the use of biomass in three main sectors, i.e. industrial, residential and transport, and analysed them under two constraints: (1) limiting the global temperature increase to 2 degrees by 2100, vs. (2) introducing a carbon tax to keep emissions down, so we could compare the effects of preferential use of biomass in the three sectors without the model forcing the structure of the energy system to keep under 2 degrees. Our preliminary results suggest that biomass availability is determinant for the contribution of bioenergy to the global primary energy mix, i.e. under high biomass availability the amount of bioenergy produced increases significantly, especially under a carbon tax regime. In terms of emissions, limiting biomass use in the residential sector leads to significant increase in emissions, in both low and high biomass availability scenarios, especially when the model cannot invest in new biomass technologies in the residential sector. This might be due to increased use of fossil energy, e.g. coal, when biomass is not available for cooking or heating, causing higher emissions even than switching the industrial sector off biomass, in conditions of the latter is the biggest user of biomass. This could be explained by a higher availability of alternative low-emission processes in the industrial sector as compared to the residential sector.

  • 4.2.3: South African sugarcane and bioenergy multi-level decision-making tool: strategic, tactical and operational supply chain optimisations

    Presenter: Koen H. van Dam, Department of Chemical Engineering, Imperial College London

    Abstract: The use of sugarcane residues for bioenergy can have a positive impact on the economy, society and environment in South Africa. However, there are key challenges in making this a reality as there is a gap between the high-level analyses and more specific and technical studies conducted. A link is lacking between these two levels for the stakeholders to get a better understanding of the sugarcane supply chain, which could also help policy makers in the implementation of policies for the development of bioenergy.

    In this work a supply chain optimisation model has been developed to improve the complexity and accuracy of the supply chain optimisation in terms of strategic, tactical and operational decisions, and to study the impacts of different parameters. The model can be used to optimise global revenues of the companies or to minimise their global carbon footprint. Demand in sugar was considered on a national level, while demands in electricity and fuel were calculated for the regions of KwaZulu-Natal and Mpumalanga. The impact of subsidies, carbon price, bagasse drying, blending ratio of ethanol in conventional fuel can be studied.

    Results show the production of sugar, biofuels and bioelectricity do not compete. Companies all chose to annex biorefineries to the existing sugar mills instead of building centralised ones in other places. Sensitivity analysis revealed that subsidising does not notably increase the production of bioenergy from the companies; however, high capital costs could discourage companies from investing in that sector. For that reason, incentives may be a good way of encouraging some commitment. It also appeared that as soon as a carbon tax is established, changing the price of carbon has no effect on the behaviour of the companies. On overall, diversifying the end-products could benefit sugar companies due to high potentials of production for bioelectricity and biofuels.

  • 4.2.4: A systems approach mapping in assessing primary forest residues as feedstock for sustainable production of bioenergy in Malawi

    Presenter: Maxon Chitawo, Stellenbosch University

    Abstract:   Provision of sustainable energy to rural and semi urban households is one of the main developmental  challenges in Malawi. Primary forest residues can contribute to provision of modern energy to the rural households in areas where the plantations are located. However, lack of synchronisation of replanting and harvesting of the timber can cause significant variations in  the availability of the residues for bioenergy production. Overtime, these variations in the supply chain have the potential to exacerbate  sustainability challenges in bioenergy production from the residues. Understanding the sources and causes of these variations can enable formulation of policy frameworks that can enhance availability  and steady supply of the residues for sustainable production of  bioenergy. This paper presents a systems approach mapping of primary forest residues in the  supply chain of Viphya forest plantations in northern Malawi to elucidate potential sources of variations overtime in the residues supply chain. Management and harvesting systems and technologies applied in the plantations, residues production, post harvesting handling and utilisation were assessed from plantations management reports and from onsite material balance of timber production processes. Over extraction of mature stand, delayed replanting, coupled with high death rate of replanted trees resulted in depletion of the plantations before maturity  of first stand of replanted trees, which in turn led to intermittent supply of the residues. Key sustainability challenges along the supply chain categorised as managerial, economic, environmental, social, technical logistics are presented in the paper.  Stakeholders analysis along the supply chain revealed the  power/influence, interests and concerns of the stakeholders in the value chain that provide opportunities for management innovations in the supply chain for sustainable production of bioenergy from the residues. An integrated forest plantations management and bioenergy production framework can allow sustainable harvesting of mature stand for both timber and bioenergy production.

  • 4.2.5: Biomethane from anaerobic digestion and bio-SNG via gasification – an integrated assessment of environmental balance, market status, and techno-economics

    Presenter: Paul Adams, University of Bath

    Abstract: Biomethane from anaerobic digestion (AD) is widely implemented across the UK producing nearly 3TWh of renewable gas each year from over 70 facilities  In contrast bio synthetic gas (bio-SNG) produced via gasification has not reached commercial status. Both biomass conversion pathways offer a way to decarbonise the gas supply and reduce dependency on fossil fuels. This study assesses the different facets of each technology including greenhouse gas (GHG) emissions, land use, feedstock availability, technical barriers, and an overview of the economics of individual facilities.

    Biomass sustainability criteria introduced in the UK apply to all biomethane facilities. Operators are required to report GHG emissions for each MJ of gas injected into the grid. Failure to meet the GHG criteria means that subsidies are withheld which puts the financial viability of the facility at risk. This study presents GHG emissions for different feedstock and operating parameters to assess expected compliance for producers. Data has been collected from feedstock suppliers and operating facilities to model the full life cycle GHG emissions for biomethane production. Results show that whilst many facilities meet GHG criteria several operators may not comply due to operating practices and external influences such as poor harvests.

    Land availability is important to the potential feedstock supply for biomethane and bio-SNG, therefore an analysis of land requirements is presented for crops and residues. The analysis shows the impacts of land use change when crop rotations are accounted for. Technical barriers have restricted the development of bio-SNG, an overview of the key issues for different conversion routes is provided.  Finally the economics of producing renewable gas are analysed including Capex, Opex, revenue streams, and subsidies that are required. Overall the results from several Supergen Bioenergy Hub projects are presented to provide an integrated assessment of both biomethane from AD, and bio-SNG via gasification.

  • 4.2.6: UK bioenergy system assessment: quantifying the GHG benefits of biomass imports for a sustainable future

    Presenter: Miao Guo, Department of Chemical Engineering, Imperial College London

    Abstract:Driven by the EU renewable energy binding targets (20% by 2020), imported biomass is making a substantial contribution to the EU and UK energy mix. Between 2011 and 2014 imports supplied over 95% of the wood pellets consumed by the main UK power stations (e.g. DRAX and IronBridge), which accounted for more than 22% of all renewable energy sources and 36% of bio-electricity generation in the UK [1]. With 4.8 million tonnes of wood pellets imported from global leading exporters (USA, Canada, Portugal, Latvia) in 2014, UK shared approximately 34% of world wood pellet trade [2].

    A significant barrier to further increasing bioenergy deployment is the need to better understand the net greenhouse gas (GHG) benefit of using bioenergy feedstocks. In particular, the temporal-spatial specific GHG profiles of imported biomass on UK bioenergy value chains. The wider system implications of changing key factors for overseas-sourced biomass e.g. cultivation and soil carbon counting strategies also need to be quantified and understood.

    To fill the knowledge gap above, a spatial-temporal mixed integer linear programming model ETI-BVCM (Energy Technologies Institute – Bioenergy Value Chain Model) [3-5] is adopted in this study. The extended ETI-BVCM model [6] is configured to account for the spatial variability, different field management strategies (e.g. land conversion/reversion), and soil carbon allocation methods for a range of imported biomass varieties. A case study approach is developed in our research to present the scientific insights into the effects of spatial/soil/management/crop specific GHG profiles of the imported biomass on UK bioenergy system-wide performance. Our research findings highlight the biomass trading opportunities for the UK over the coming decades and optimal value chain designs for imported biomass resources, identifying those which can best contribute to the UK climate change mitigation targets and bioenergy sector development needs.

  • Catalysis

    Keynote: Professor Christopher Hardacre, University of Manchester 

    • Valorisation of lignin by catalytic pyrolysis: Daniel Nowakowski, EBRI, Aston University, UK
    • Hydrogen enriched syngas production from catalytic biomass gasification: Chunfei Wu, University of Hull
    • Mechanism of catalytic hydrodeoxygenation for phenolic compounds over metal loaded HZSM-5 – A Density Functional Theory (DFT) study: Jiajun Zhang, Cranfield University
    • Photocatalytic conversion of cellulose into fermentable sugars:  Aakash Welgamage Don, Robert Gordon University, Scotland

  • 5.1.1: Valorisation of lignin by catalytic pyrolysis

    Presenter: Daniel Nowakowski, EBRI, Aston University, UK

    Abstract: Valorisation of residual lignin plays a key role in the development of cost-effective bio-refinery processes for biofuels and the production of bio-based materials and value-added chemicals from lignocellulosic biomass. Fast pyrolysis with upgrading of the pyrolysis vapours over zeolite catalysts offers the possibility to convert lignin to hydrocarbon products which can be used in the production of transportation fuels and valuable chemicals.

    Catalytic pyrolysis of lignin and lignin-rich materials (biomass acid hydrolysis residues) for the production of aromatic hydrocarbons was investigated to evaluate the performance of H-ZMS-5 zeolites with different loadings of cobalt (Co) and nickel (Ni) (5 and 10 wt.%). Catalysts were synthesised using as a commercially available support – ZSM-5 zeolite (Si/Al=40). Cobalt and nickel were incorporated to the supports by “ball-milling” (mechanochemical grinding). Characterisation of synthesised catalysts was focused on their acidic and textural properties. Lignin samples (ALM, ETEK, Organosolv, Alkali, pyrolytic lignin and acid hydrolysis residues) with and without catalyst were pyrolysed at 400-900°C using a CDS 5200 pyroprobe coupled to a Clarus 600 Series GC-MS/FID system. Experiments show that the selectivity to particular aromatic hydrocarbons varies with the composition and purity of the lignin for both catalysts. It was observed that the use of nickel-doped catalysts promoted with a higher efficiency production of saturated hydrocarbons such as ethylcyclohexane, benzene and 1-ethyl-2-methyl-benzene through the hydrogenation, dehydration and decarboxylation of oxygenated aromatic compounds.

  • 5.1.2: Hydrogen enriched syngas production from catalytic biomass gasification

    Presenter: Chunfei Wu, University of Hull, UK.

    Abstract: Biomass gasification is a promising technology to produce renewable hydrogen or hydrogen enriched syngas for a sustainable chemical industry. However, producing hydrogen from the biomass gasification process has several challenges such as low hydrogen production and high tar formation. Recently, biomass catalytic gasification has received great interest due to the increase of hydrogen yield and the decrease of tar formation. One significant challenge for catalytic gasification is to develop an efficient catalyst with high catalytic activity for hydrogen production and high catalyst stability in terms of coke deposition and metal sintering. In this work, Ni-based catalysts were investigated for hydrogen production from biomass gasification. The experimental results show that the highest hydrogen production (24.32 mmol g-1 biomass) was obtained with the Ni-Ce/Al2O3 catalyst, indicating the effective promotion of Ce metal. Fe-based catalysts produced a much higher molar ratio of H2/CO (2.87), while the Cu/Al2O3 catalyst only produced a gas with a H2/CO molar ratio of 0.89. The high concentration of CO2 and low concentration of CO produced from the Fe-based catalyst demonstrated that the catalyst might be effective for promoting water gas shift reaction. In addition, although the carbon deposition was low on the surface of the reacted Fe/Al2O3 catalyst, filamentous carbons could be easily identified, compared with other catalysts. From temperature programmed oxidation analysis of the reacted catalysts, reducing the injection of water into the process with the Fe-based catalyst, carbon deposition was shown to be significantly increased.

  • 5.1.3: Mechanism of catalytic hydrodeoxygenation for phenolic compounds over metal loaded HZSM-5 – A Density Functional Theory (DFT) study

    Presenter: Jiajun Zhang, Cranfield University

    Abstract: Phenolic compounds abundantly exist in primary liquid products derived from fast pyrolysis of lignin, and their catalytic hydrodeoxygenation (HDO) as the key stage of the catalytic conversion is crucial for their upgrading to fuel additives (such as benzene, toluene, and xylene). It has been widely accepted that proton on Brønsted acid site plays key role in catalytic HDO reactions because it may launch electrophilic attack to phenolic compounds and form cations. However, the specific mechanism is still controversial. In this work, the HDO mechanism for phenolic compounds was investigated, and reaction energy barriers of HDO for three phenolic compounds over metal loaded HZSM-5 (HZ25) were calculated. All calculations were implemented within the Density Function Theory (DFT) in DMol3 module of Materials Studio 2016. Two possible HDO mechanisms were proposed based on proton’s electrophilic attack respect to the ortho carbon and oxygen atoms of a phenol molecule, termed as “carbonium reaction mechanism” and “hydroxyl oxidation mechanism”. Fukui analysis to a phenol molecule revealed that the most vulnerable site to electrophilic attack on phenol was the oxygen atom, indicating the cation might be generated based on the oxygen in catalytic reactions. Four possible cations were compared to confirm this hypothesis, showing the bond order of CSP2-O was the most weakened when the oxygen was under proton’s attack. Total energy calculation for each cation indicated that the cation formed under “hydroxyl oxidation mechanism” exhibited the lowest energy, confirming that hydroxyl oxidation was the most readily to happen. Catalytic HDO simulation revealed that active metals had significant effects in lowering energy barriers of the reactions for three phenolic compounds. The largest decrease in energy barrier for the HDO of phenol was observed in the case of Co-based HZ25. For o-cresol and p-cresol, the main reduction in the energy barrier was observed for Cu-based HZ25.

  • 5.1.4: Photocatalytic conversion of cellulose into fermentable sugars

    Presenter: Aakash Welgamage Don, Robert Gordon University, Scotland

    Abstract: Conversion of waste cellulosic biomass into liquid fuel provides a sustainable alternative for fossil fuel. Despite the advancement made in this field, direct low energy conversion of cellulose into fuel remains a significant challenge due to its water insolubility and rigid nature. Here we present the photocatalytic conversion of waste biomass into value added platform chemicals utilising α-cellulose as a model feedstock. A widely known catalyst; TiO2-P25 nanoparticles immobilised into ball milled α-cellulose were UV-irradiated with four low-power 36 W UV-A compact non-integrated fluorescent lamps housed in a bespoke light unit. Quadrupole time of flight mass spectroscopy analysis revealed the formation of multiple cellodextrins including glucose cellobiose as well as an array of C5 oligomers derived from photocatalysis of α-cellulose. Production of ethanol; a sustainable alternative liquid fuel was demonstrated using the yeast strains Saccharomyces cerevisiae and Candida wickerhamii fermenting cellulose degradation products as substrates. Catalysts applied here are of low cost, recoverable and can be activated by harvested natural light or augmented low power light emitting diodes (LEDs). Further studies are carried out to construct a test reactor composed of LEDs for photocatalysis as well as an in housed membrane separation system for efficient harvesting of fermentable sugars for ethanol production.

  • Policy

    Panel discussion:

    • Chair: Professor Patricia Thornley (SUPERGEN Bioenergy Hub Director/University of Manchester) Introduction from Raphael Slade, Imperial College London, UK. Panel discussion:
      • Avoiding the food-fuel-water-land nexus Richard Lord, University of Strathclyde, UK (Confirmed)
      • Environmental and financial analysis of biogas end-use options:  Jon McKenchie, University of Nottingham(Confirmed)
      • Analysing deployment strategies for liquid biofuels in the UK: An agent-based modelling approach: Koen H. van Dam, Department of Chemical Engineering, Imperial College London (Confirmed)
      • How policy makers learned to start worrying and fell out of love with bioenergy:  Paul Adams, University of Bath, UK (Confirmed)
      • More food than fuel: Mirjam Roeder, University of Manchester, UK (confirmed)

  • 5.2.1: Avoiding the food-fuel-water-land nexus: Can we reuse vacant and derelict brownfield land or former landfill sites for land-based renewables instead?

    Presenter: Richard Lord, University of Strathclyde, UK

    Abstract: Reusing vacant or derelict, non-agricultural land for land based renewables could avoid the need to use land which is required for food production, either now or in the future.  Research at the University of Strathclyde is considering the theoretical potential and practical issues of using a range of non-agricultural landbanks for renewables, including biomass for combustion or biogas feedstocks, ground source heat or solar PV.

    Using non-agricultural land for energy crops could deliver renewable energy that is secure, local and ethically acceptable, since brownfield sites, former landfills and other similar categories of peri-urban marginal land are potentially contaminated and so are unsuitable for food production.  A range of societal benefits can be expected from this sustainable approach, including aesthetic improvement and enhanced ecosystem service delivery.  For this activity to be both economically viable and environmentally benign, biomass productivity must be adequate, fuel quality sufficient and fuel contamination low enough to allow combustion without further environmental dispersion.   While many have suggested using marginal lands for bioenergy production, relatively few studies have confirmed the effectiveness of this approach in terms of the actual biomass yield that is achievable with actual field trials.

    Results are presented from 5 year extended monitoring of field scale trials of reed canarygrass first established on sites in NE England as part of the EU Life BioReGen Project (Biomass, Remediation, re-Generation: Reusing brownfield sites for renewable energy, LIFE05 ENV/UK/125).  The results indicate annual yields of 4-7 odt.ha-1 are achievable on previously developed land from the second growth season, equivalent to 97GJ.ha-1 at contamination levels acceptable for domestic pellets*.

    Current research is directed towards identifying the scale of the non-agricultural landbank for renewables in Scotland and the distribution of this potential resource compared to biomass markets, heat use patterns and fuel poverty.

    *Lord (2015).  Biomass & Bioenergy 78, 110-25.

  • 5.2.2: Environmental and financial analysis of biogas end-use options

    Presenter: Jon McKenchie, University of Nottingham

    Abstract: Biogas production is an option for valorising organic waste streams with applications in heat, electricity generation, and transport sectors. Meeting fuel specifications for different end uses requires varying costs and energy inputs to process raw biogas. As such, it is essential to understand the overall environmental and economic impacts of competing biogas utilisation scenarios.

    Biogas end-uses considered are combined heat and power, upgrading to biomethane for gas grid injection (natural gas displacement) or transport fuel (diesel displacement). Mass and energy balances are calculated and combined with upgrading costs (CAPEX, OPEX) to assess the environmental and financial impacts of three biogas utilisation scenarios: combustion in combined heat and power system; and upgrading to biomethane by water absorption or membrane system. Net present value (NPV) is used to measure relative financial performance of alternative biogas utilisation routes, accounting for current UK policy support. Life cycle greenhouse gas (GHG) emissions are quantified to assess environmental performance.

    Upgrading biogas to biomethane, via membrane or water absorption systems, achieves the greatest GHG reduction when displacing diesel in transport applications (300 gCO2eq./kWhbiogas), but the smallest GHG benefit when displacing natural gas (185 gCO2eq./kWhbiogas).  Financial performance is particularly sensitive to policy support. Current policy support, through Feed in Tariffs and the Renewable Heat Incentive, directly subsidise heat, electricity and gas grid injection. The Renewable Transport Fuel Obligation provides certificates that may be traded on the open market rather than a fixed, direct subsidy, thus increasing uncertainty and risk surrounding biomethane for transport applications. For unsubsidised biogas utilisation, CHP and biomethane for transport return highest NPV. Our analysis identifies CHP and biomethane for transport as the two most promising options in terms of environmental and financial performance. However, significant infrastructure investment would be necessary to realise these opportunities (biomethane vehicles/fuelling stations; heat distribution networks).

  • 5.2.3: Analysing deployment strategies for liquid biofuels in the UK: An agent-based modelling approach

    Presenter: Koen H. van Dam, Department of Chemical Engineering, Imperial College London

    Abstract:The aim of this study is to investigate the influence and feasibility of different policy interventions supporting adoption of energy crops and investment in biofuels production capacity in the UK in the period 2015 – 2050. An agent-based modelling and simulation approach is used to provide insights relevant to infrastructure choices and efficient deployment strategies.

    The system to be analysed is the bioenergy system in the U.K with a focus on production and consumption of liquid biofuels in the period 2015s – 2050s. Bioenergy is expected to support the transition to a low carbon, secure and affordable energy system. However, there is a lack of understanding in how this system could evolve as the bioenergy system is overwhelmingly complex. The interaction of elements such as resource availability, geographical characteristics, uncertainties such as climate and fossil fuel prices, and competition between biomass producers/consumers sectors subject to different institutional conditions gives as a result the emergence of a complex adaptive system.

    Overall, current scientific literature has been focused on the long term optimal design of bioenergy systems. This literature has provided insights by identifying promising configurations for feedstock, technology, and energy vectors. However, an analysis of the effect of different deployment strategies for bioenergy systems development is still missing. It is not well understood what policy strategies might steer the bioenergy system in the direction pointed by the optimization studies. In fact, empirical research has shown that the application of formal institutions (e.g. policy interventions) in bioenergy systems might have side effects that are hard to predict because of the high interdependencies of the biomass and bioenergy markets. The splash and dash phenomenon in the US is one clear example.

    The work described in this paper has been undertaken as part of the EPSRC project SUPERGEN Bioenergy Value Chains (2013-2017).

  • 5.2.4: How policy makers learned to start worrying and fell out of love with bioenergy

    Presenter: Paul Adams, University of Bath

    Abstract: Bioenergy has come to be given a prominent role in national energy strategies in more than 60 countries around the world. The impetus for these policies draws on a range of motivations: improving energy security, diversifying agricultural production stimulating rural development, job creation, and reducing greenhouse gas (GHG) emissions.

    Arguably GHG reductions was never the main driver for bioenergy policy, yet controversy over the extent, timing and duration of carbon savings threatens to derail policy initiatives to drive up deployment. This paper analyses current controversies around bioenergy in the context of historic developments in the United States, Brazil or European Union. It addresses two key questions: “how did we end up in this policy mess?” And, “how do we get out of it?”

    Policy makers have faced three broad challenges to whether policies introduced to support bioenergy can genuinely contribute to GHG mitigation. The first is that carbon accounting frameworks misrepresent the carbon saving benefits of bioenergy, potentially leading policy makers to support policies that have unintended and undesirable consequences. The second is that increasing biomass production on agricultural land can directly, or indirectly, lead to increasing carbon emissions. The third challenge is that increased use of forest biomass does nothing to reduce emissions in the short term but can only reduce carbon emissions in the distant future.

    We examine the evidence around each of these challenges and critically evaluate the policy responses. We argue that the greatest risk lies in political loss of confidence and institutional paralysis. Whereas the greatest opportunity lies in the co-evolution of bioenergy production and governance systems, drawing on the collective judgment of stakeholders involved in experiential, interactive and deliberative decision making processes.

  • 5.2.5: More food than fuel

    Presenter: Mirjam Roeder, University of Manchester, UK

    Abstract: Anaerobic digestion (AD) is of growing importance within the UK as it can make an important contribution to the countries energy and climate change targets. With the growth of the sector, discussions about competing land uses are likely to increase. For a better understanding of the synergies between agricultural land, itsrole  and bioenergy the perception of the different stakeholders will play an important role. The perception of stakeholders related to AD, feedstock and energy crop production was investigated through interviews and a stakeholder workshop. The results indicated that from an AD operator and feedstock producer perspective, on-farm AD is more an additional activity integrated into existing agricultural systems than a renewable energy technology. The risk of a shift in agricultural practices and large areas to grow energy crops for AD is seen as low for the UK. Nonetheless, land use and related challenges need to be considered as the demand for AD feedstocks increases with the fast growth of the sector. Considering the synergies between bioenergy and agriculture as well as the motivations and benefits perceived by stakeholders will play an important role in a successful policy design to provide the required emission reduction in both sectors without subverting sustainability.

  • Socio-economics and Development

    • Cost-benefit analyses for small scale biogas systems development in Ethiopia: Richard Blanchard, Loughborough University, England, UK
    • How can we engage farmers in rice straw bioenergy development? Perspectives from India and the Philippines: Patricia Thornley, University of Manchester, England, UK
    • How should land be used? Bioenergy and responsible innovation in agricultural systems: Alison Mohr, University of Nottingham
    • Sweet energy – bioenergy integration pathways for sugarcane residues. A case study of Nkomazi, District of Mpumalanga, South Africa: Mirjam Roeder, University of Manchester, England, UK

  • 6.1.1: Cost-benefit analyses for small scale biogas systems development in Ethiopia

    Presenter: Richard Blanchard, Loughborough University, England, UK

    Abstract: In developing countries, anaerobic digestion to produce biogas offers a suitable solution to replace unsustainable utilization of traditional fuels. In the case of Ethiopia, the domestic energy situation is characterised by a very low per capita energy consumption combined with a dominant usage of traditional biomass fuel, with cooking taking the major share. Suitable biogas feedstocks, such as animal dung, are available in Ethiopia.  However, the full benefits can only be gained when the biogas system is fully functional, which requires adequate efforts on the supply and on the demand sides. The National Biogas Programme (NBP) in Ethiopia aims at developing a “commercially viable, market-oriented biogas sector in the country”. In this paper, the factors for success and failures for small scale biogas systems in Ethiopia are analysed. Costs-benefits analyses are carried out on the supply and demand sides with sensitivity analysis at household level considering two scenario (“potential” and “to date”). The analysis highlights the high potential in economic terms, but the need to address challenges that are specific to the Ethiopian context. The biodigesters are still relatively expensive for the households and not yet fully suited to the energy needs of end-users, and the digester constructors may not get sufficient benefits to remain actively involved in the sector. Biogas development is highly relevant in the Ethiopian context and these challenges are being addressed by the NBP, with adequate solutions being put in place, but a pure commercial market model may not easily work at this stage.

  • 6.1.2: How can we engage farmers in rice straw bioenergy development? Perspectives from India and the Philippines

    Presenter: Patricia Thornley, University of Manchester

    Abstract: Rice straw burning remains a key agricultural problem in the Philippines, where up to  95% or 10 Mt is burnt annually despite policies and farmers’ awareness of its negative impacts on health and pollution. Using rice straw as a feedstock for energy production provides an alternative to rice straw burning, with potential positive impacts on rural development and environment.

    However, introducing innovations—as in the case of sustainable rice straw bioenergy development—is not without social challenges, including  technology adoption, acceptance, and actor involvement. As such, this research seeks to identify and analyse the factors that might affect farmers’ engagement in bioenergy development.

    We compared the case of two provinces in the Philippines, Laguna and Nueva Ecija, which have different prevailing practices in rice straw management. Through in-depth interviews and participant observation, we explored farmers’ attitudes, values, and perceptions towards rice straw management and bioenergy development. Furthermore, we mapped out their information networks to identify the ‘decision-making influencers’ in their communities who could be significant actors in bioenergy technology diffusion.

    Our preliminary results show that farmers’ rice straw management practices are more motivated by social factors (i.e., through their farm activities and community relationships) rather than environmental (i.e., concern about pollution) or financial (i.e., time and money savings). This complements our results from network mapping, where other actors in the community, such as rice traders and buyers, lenders, and farm labourers were identified as important decision-making links. This opened up new ways of thinking about farmers’ roles in bioenergy development, while reinforcing the importance of their communities in technological adoption.

  • 6.1.3: How should land be used? Bioenergy and responsible innovation in agricultural systems

    Presenter: Alison Mohr, University of Nottingham

    Abstract: Two recent conservation reports – State of Nature and Rewilding Britain’s Reducing Flood Risk – have sparked intense public debate on the issue of how we should value and manage the ways in which we use land. The public debate highlights sensitivities and tensions between the different values people in the UK associate with land use for conservation or for agriculture that has important implications for bioenergy crops. Bioenergy has been positioned as both a problem and an innovative solution for land-use conflicts arising at the nexus between food security and environmental conservation (Tilman et al., 2010; Murphy et al., 2011).

    In this paper, we examine different valuations of land use and biomass that need to be considered when assessing bioenergy interventions. Drawing on research into controversies around bioenergy, we show that at stake in this debate are different ways of conceptualising the problem definition and innovation pathways. These arise from differences in the way people value the use of land for food, fuel or fodder, as well as in differences in the facts that are considered or excluded. Is land a global resource to be managed in accordance with universal targets and technological innovation for food production or nature conservation, or is it a place of lived experience where historical attachments, struggles and local needs ought to shape interventions? While much of the technical and policy literature on food security begins from the former position (a target-based approach), as social researchers we highlight the need to begin from the latter (a context-based approach). To do this, we draw on the concept of responsible innovation, which draws attention to the fact that there are multiple pathways for any technological interventions. We do so with reference to research undertaken in the UK and situate it in the global agricultural complex.

  • 6.1.4: Sweet energy – bioenergy integration pathways for sugarcane residues. A case study of Nkomazi, District of Mpumalanga, South Africa

    Presenter: Mirjam Roeder, University of Manchester

    Abstract:The South African sugar sector is making important contributions to the national economy in terms of income, employment, land reform and rural development. The sugar sector is challenged by fluctuating world market prices. At the same time sharp price increases for electricity and inconsistent electricity supply effect the South African society and economy and there is also a recognised need to switch to more sustainable, low carbon and renewable energy carriers. Sugarcane residues, currently burned before the cane harvest, are therefore of increasing interest as renewable energy feedstock. This paper investigates sustainability challenges of integrating bioenergy from sugarcane residues into the South African sugar value chain by identifying the key aspects that need to be assessed to ensure sustainable integration. During farm visits and stakeholder meetings, preliminary data was collected in Nkomazi, District of Mpumalanga, South Africa to scope agricultural, logistical and socio-economic opportunities and challenges. From these, four potential bioenergy integration pathways were developed. Their benefits, opportunities and challenges were qualitatively evaluated. While the pathway with centralised bioenergy generation can provide benefits to the overall national energy supply, local small-scale bioenergy integration can directly target the development and empowerment of communities and improve the energy security and livelihoods of these households. Assessing the opportunities and challenges and comparing the different pathways show that it is necessary to consider carefully: (1) what is the desired outcome of integrating bioenergy into the sugar value chain, (2) what are the trade-offs between different sustainability aspects, and (3) who will receive the actual benefits.

  • Gasification

    • The production and role of bio-hydrogen for delivering low carbon heat: Chris Manson-Whitton – Progressive Energy Ltd
    • BioSNG Demonstration Project: Results and Lessons Learned: Mike Cairns-Terry – Progressive Energy Ltd
    • Improving biomass gasification through tar detection and gasifier control: Zakir Khan, University of Glasgow
    • Pyrolysis Plasma-Catalytic gasification of biomass to produce high quality syngas: Mohamad Anas Nahil, University of Leeds

  • 6.2.1: The production and role of bio-hydrogen for delivering low carbon heat:

    Presenter: Chris Manson-Whitton – Progressive Energy Ltd

    Abstract:The UK has recently signed up to its fifth Carbon Budget as part of its ambitious carbon reduction plan. Heat contributes a third of the UK’s carbon emissions and whilst progress is being made to decarbonize electricity, decarbonising heat has proved challenging. The UK has a world class gas grid and gas dominates the heat supply curve, heating 83% of its buildings and providing most of its industrial heat. Decarbonisation through lowering the carbon intensity of gas through the use of hydrogen is receiving renewed interest. Compared with solutions such as heat pumps, this cost effectively capitalises on existing gas distribution assets which are designed to deliver peak heat, and importantly means that customers do not require disruptive and expensive changes in their homes. Hydrogen also has potential for applications in the transport sector, particularly for larger vehicles where battery solutions are less feasible.

    This requires sources of low carbon hydrogen, often considered to be primarily from electrolysis or longer term from fossil sources with CCS. The production of hydrogen from biomass-rich sources not only provides a low carbon solution in the short term, but the potential for negative emissions (known as BECCS) with the carbon captured and stored. Progressive Energy, along with National Grid Gas Distribution and Advanced Plasma Power are building on their BioSNG programme to develop the process for the production hydrogen from biomass rich waste sources via gasification.

    This paper will provide (a) an overview of the recent activities undertaken by the gas sector related to overcoming the barriers to hydrogen use for heat, such as HyDeploy and the Leeds City Gate H21 project, (b) the process requirements and challenges in conversion of biomass and waste materials through to consumer quality hydrogen, and (c) the expected technical, carbon and financial performance of such a facility.

  • 6.2.2: BioSNG Demonstration Project: Results and Lessons Learned

    Presenter: Mike Cairns-Terry – Progressive Energy Ltd

    Abstract: There is a well-established need to produce low-carbon replacements for fossil fuels.  While this is currently technically possible, doing so in a low-cost, low-emission way and at volume is a challenge which needs to be met.  Several potential solutions for thermal production of methane from biomass are under development, with promising results, but the range of biomass feedstocks that can be utilised is limited.   Meanwhile, the UK’s resource of residual waste is such that it exports millions of tonnes per year of Refuse Derived Fuel (RDF) to incineration plants in Europe.

    The BioSNG demonstration project, conceived and delivered by a consortium of Progressive Energy, National Grid Gas Distribution and Advanced Plasma Power, sought to demonstrate the technical and economic feasibility of thermal production of methane from RDF.  In order to successfully do this, the project addressed many technical challenges, including production of syngas at sufficient quality for a catalytic process, selecting appropriate catalysts and operating conditions, and upgrading the methanated syngas to a quality suitable for injection to the gas grid.

    In successfully demonstrating the production of methane from waste feedstocks, the project has laid the groundwork for commercial plants employing the technology, the first of which is under construction.  In addition, the environmental credentials of the process as a substitute for natural gas were firmly established.  By doing this, the project has unlocked the considerable resource of residual waste for renewable methane production, paving the way for it to provide up to a third of the UK’s domestic gas demand, and dramatically reducing the quantity of waste sent to landfill.

    This paper will detail key technical solutions and results, including plasma treatment of syngas, experimental work to establish reaction kinetics, and product gas refining, and will look briefly at the future development of the technology.

  • 6.2.3: Improving biomass gasification through tar detection and gasifier control

    Presenter: Zakir Khan, University of Glasgow

    Abstract: Gasification and the production of syngas can be traced back to as early as 1609.  The process was used to produce town gas for street lighting as early as 1801 and as a fuel to drive vehicles in the Second World War.  Recently, there has been resurgence in gasification, at least partly driven by finite fossil fuel reserves, the move away from coal, the potential advantages that gasification can bring to utilising the system’s exergy and ease of electricity production.  Gasification has the potential to alleviate energy poverty around the world, where 18% of the population lack access to electricity and 38% lack clean cooking facilities.  Syngas can be directly combusted and used to produce electricity from internal combustion engines (ICEs) or gas turbines.  Gas turbines require exceptionally clean syngas and ICEs are more forgiving.  Consequently, some form of gas clean up may be essential.  This could be e.g. filtration, cyclone or wet scrubbing or plasma.  Collaborative work at the Universities of Glasgow, Aston, Manchester and Aberystwyth, funded by EPSRC (SUPERGEN Bioenergy Challenge II) is seeking to identify methods of real time control of gasifiers to increase tolerance to biomass variety and reduce emissions.  To achieve this, novel tar detection systems are being built so that gasifier variables can be optimised to reduce tar in the syngas, reducing clean-up demand and costs.  Because of the potential wide spread use of gasification globally, the ethos behind this research is to produce inexpensive instrumentation systems that can be built using readily available components, develop control strategies that broaden the potential biomass feedstock range and develop novel gasifiers that operate on the minimum tar production point.  An overview of this research and current status will be given and how it critically addresses the bottlenecks to widespread adoption of gasification.

  • 6.2.4: Pyrolysis Plasma-Catalytic gasification of biomass to produce high quality syngas

    Presenter: Mohamad Anas Nahil, University of Leeds

    Abstract: Biomass gasification is considered a promising technology in order to develop a sustainable energy system and to decrease our current dependence on fossil fuels. Thus, biomass is converted into a syngas stream which can be combusted for power and heat generation but also used as raw material for production of fuels and chemicals. The main drawback of biomass gasification and its implementation at large scale is the formation of tar compounds together with the product syngas. The presence of tar makes the syngas problematic for applications such as the Fischer-Tropsch process for chemical production where syngas tar leads to serious coke deposition over the catalyst. The main objective of this study is to develop a low temperature plasma-catalytic process that can be used to produce a high quality syngas from the gasification of biomass.

    Wood pellets were used as a feedstock. Pyrolysis plasma-catalytic steam reforming of wood pellets was carried out in a two-stage pyrolysis fixed bed and plasma DBD reactors. Pyrolysis of the wood pellets occurred in the first reactor at 600 °C under nitrogen atmosphere, and the product pyrolysis volatiles were passed directly to the plasma DBD reactor, where plasma-catalytic reactions occurred. The plasma-catalyst reactor was externally heated to 250 ºC to avoid any condensation. Ni based catalysts were prepared by conventional wet preparation method and calcined at 750 ºC for 3 hours. The gaseous product produced from the process was collected by a Tedlar gas sample bag and analyzed by packed column gas chromatography (GC). The amount and nature of the coke deposited over the catalyst were analysed by TPO and SEM.

    The results showed that applying plasma with a catalyst produced the highest syngas yield and the lowest tar yield and carbon deposition over the catalyst compared to using the catalyst or plasma alone.