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The global food demand is projected to significantly increase. To maintain global food security in the future, protein production needs to become more efficient regarding the use of limited land and water resources. Protein-rich biomass can be produced via direct air capture of CO2 with the help of H2-oxidizing bacteria and renewable electricity in a closed, climate-independent system. This quantitative literature review conservatively estimated the direct land and water use of bacterial protein production relying on secondary data for the components of the technology and for the reference protein sources. A several times higher potential protein yield per land area can be achieved by this technology with approximately one-tenth of the water use compared to that required for soybean production.

The power sector is faced with strict requirements in reducing harmful emissions and substantially increasing the level of sustainability. Renewable energy (RE) in general and solar photovoltaic (PV) in particular can offer societally beneficial solutions. The LUT energy system transition model is used to simulate a cost-optimised transition pathway towards 100% RE in the power sector by 2050. The model is based on hourly resolution for an entire year, the world structured in 145 regions, high spatial resolution of the input RE resource data, and transition steps of 5-year periods. The global average solar PV electricity generation contribution is found to be about 69% in 2050, the highest ever reported. Detailed energy transition results are presented for representative countries in the world, namely, Poland, Britain and Ireland, Turkey, Saudi Arabia, Brazil, Ethiopia, and Indonesia. The global average energy system levelised cost of electricity gradually declines from 70 €/MWh in 2015 to 52 €/MWh in 2050 throughout the transition period, while deep decarbonisation of more than 95% around 2040, referenced to 2015, would be possible. The targets of the Paris Agreement can be well achieved in the power sector, while increasing societal welfare, given strong policy leadership.

Sugarcane biorefineries, despite their contribution to sustainable transportation fuels and mitigation of carbon emissions in the mobility sector, produce a large amount of carbon dioxide in their conversion processes. According to the Paris climate agreement, a carbon neutral energy system has to be launched in the years to come, and in this scenario, greenhouse gases emission free industrial processes and alternative carbon sources will be needed. Therefore, this paper presents the evaluation of carbon mass balance of a typical Brazilian ethanol mill to better understand its potential for energy and carbon yield improvement. Due to the fact that Brazilian sugarcane mills are evolving from first generation to integrated first and second generation plant, four different scenarios were analysed. For a first generation plant without (S-I) and with conversion of straw to electricity (S-II) and for the integrated plant (S-III), results of carbon mass balance showed that the harvested sugarcane carbon was mainly converted into CO2 and in a smaller proportion into ethanol. In the modelled cases S-I to S-III the conversion of sugarcane carbon into CO2 and ethanol ranged from 41% to 53% and 17%–22%, respectively. Because this carbon amount in the CO2 flows provides an interesting platform to both increase the bioenergy produced and the harvested carbon-to-fuels ratio, a fourth scenario (S-IV) that studies the integration of power-to-gas (PtG) technologies into the mill was also considered. PtG can increase the sugarcane fuels energy content from 9.3 kW/ha to 33.6 kW/ha using 1361.3 MWe of electricity, increasing the amount of sugarcane carbon transformed into sugarcane based fuels to 54% and converting CO2 into a high value added product.

The global energy system has to be transformed towards high levels of sustainability in order to comply with the COP21 agreement. Solar photovoltaic (PV) offers excellent characteristics to play a major role in this energy transition. The key objective of this work is to investigate the role of PV in the global energy transition based on respective scenarios and a newly introduced energy transition model developed by the authors. A progressive group of energy transition scenarios present results of a fast growth of installed PV capacities and a high energy supply share of solar energy to the total primary energy demand in the world in the decades to come. These progressive energy transition scenarios can be confirmed. For the very first time, a full hourly modelling for an entire year is performed for the world, subdivided in 145 sub-regions, which is required to reflect the intermittent character of the future energy system. The model derives total installed solar PV capacity requirements of 7.1–9.1 TWp for the electricity sector (as of the year 2015) and 27.4 TWp for the entire energy system in the mid-term. The long-term capacity is expected to be 42 TWp and, because of the ongoing cost reduction of PV and battery technologies, this value is found to be the lower limit for the installed capacities. Solar PV electricity is expected to be the largest, least cost and most relevant source of energy in the mid-term to long-term for the global energy supply. Copyright © 2017 John Wiley & Sons, Ltd.

In this study, a 100% renewable energy (RE) system for Brazil in 2030 was simulated using an hourly resolution model. The optimal sets of RE technologies, mix of capacities, operation modes and least cost energy supply were calculated and the role of storage technologies was analysed. The RE generated was not only able to fulfil the electricity demand of the power sector but also able to cover the 25% increase in total electricity demand due to water desalination and synthesis of natural gas for industrial use. The results for the power sector show that the total installed capacity is formed of 165 GW of solar photovoltaics (PV), 85 GW of hydro dams, 12 GW of hydro run-of-river, 8 GW of biogas, 12 GW of biomass and 8 GW of wind power. For solar PV and wind electricity storage, 243 GWh el of battery capacity is needed. According to the simulations the existing hydro dams will function similarly to batteries, being an essential electricity storage. 1 GWh of pumped hydro storage, 23 GWh of adiabatic compressed air storage and 1 GWh of heat storage are used as well. The small storage capacities can be explained by a high availability of RE sources with low seasonal variability and an existing electricity sector mainly based on hydro dams. Therefore, only 0.05 GW of PtG technologies are needed for seasonal storage in the electricity sector. When water desalination and industrial gas sectors’ electricity demand are integrated to the power sector, a reduction of 11% in both total cost and electric energy generation was achieved. The total system levelized cost of electricity decreased from 61 €/MWh to 53 €/MWh for the sector integration.

During biomass and waste combustion, high levels of alkali halides in the flue gas often lead to increased deposit formation and accelerated superheater corrosion. These problems can be reduced either by co-combustion or by the use of sulfur-containing additives. A measurement campaign was carried out in a 20 kWth bubbling fluidized bed (BFB) bench-scale reactor to characterize the sulfation behaviors of alkali chloride and alkali bromide. Spruce bark was used as the base fuel - serving as a source of alkali metals (mainly K). HCl and HBr gases were fed with the fluidization air to simulate co-firing of a halide-rich fuel with bark. SO2 and elemental S powder were used as additives to convert the alkali halide aerosols to less corrosive alkali sulfates. The sulfation behavior of alkali halides was evaluated by means of several measurements including: FTIR (flue gas measurement), a low-pressure impactor (particle size distribution and chemical composition of extracted aerosol particles) and deposit probe sampling (deposit growth rate and chemical composition of the windward, 90° side and leeward deposits). The results indicated a higher tendency for sulfation of alkali chloride than of alkali bromide.

In the production of solid recovered fuel (SRF), certain waste components have excessive influence on the quality of product. The proportion of rubber, plastic (hard) and certain textiles was found to be critical as to the elemental quality of SRF. The mass flow of rubber, plastic (hard) and textiles (to certain extent, especially synthetic textile) components from input waste stream into the output streams of SRF production was found to play the decisive role in defining the elemental quality of SRF. This paper presents the mass flow of polluting and potentially toxic elements (PTEs) in SRF production. The SRF was produced from municipal solid waste (MSW) through mechanical treatment (MT). The results showed that of the total input chlorine content to process, 55% was found in the SRF and 30% in reject material. Of the total input arsenic content, 30% was found in the SRF and 45% in fine fraction. In case of cadmium, lead and mercury, of their total input content to the process, 62%, 38% and 30%, respectively, was found in the SRF. Among the components of MSW, rubber material was identified as potential source of chlorine, containing 8.0 wt.% of chlorine. Plastic (hard) and textile components contained 1.6 and 1.1. wt.% of chlorine, respectively. Plastic (hard) contained higher lead and cadmium content compared with other waste components, i.e. 500 mg kg−1 and 9.0 mg kg−1, respectively.

To meet the increasing volume of waste to be treated via energy recovery, high SRF-energy-share fuel is being fired in conventional waste-to-energy facilities. In this work, corrosion related risk during firing of 70 e-% share (target fuel) is studied and compared against the base case fuel containing 50 e-% share. Cl and S concentration is highest in the target fuel as a direct result of increasing the proportion of SRF in the fuel mixture. Br, Zn and Pb showed the same trend. Meanwhile, the concentration of Na, K, Al and Si are highly dependent on the type of the SRF fired. The corrosion risk of the base and target fuels are analyzed using the composition of the fine aerosol fraction and deposit samples measured near the vicinity of the superheater. Surprisingly aerosols for the target fuel are less risky – having less Cl and more S, than that of the base fuel. The effects of sulfur based additives – elemental sulfur and sulfate injection, and fuel substitution on the risk of superheater corrosion are likewise analyzed. All these strategies can reduce the concentration of Cl in the aerosols, however it is concluded that sulfate injection is considered as a robust strategy for mitigating alkali chloride formation. Sulfate injection is able to reduce Cl in the aerosols and deposits regardless of the quality of the fuel mixture. Robust strategies are important in ensuring the boiler performance during high SRF-energy share firing. An attempt of linking the quality of the deposits and the properties of the flue gas and aerosols around the superheater using partial least squares regression is also presented.

This is the third and final part of the three-part article written to describe the mass, energy and material balances of the solid recovered fuel production process produced from various types of waste streams through mechanical treatment. This article focused the production of solid recovered fuel from municipal solid waste. The stream of municipal solid waste used here as an input waste material to produce solid recovered fuel is energy waste collected from households of municipality. This article presents the mass, energy and material balances of the solid recovered fuel production process. These balances are based on the proximate as well as the ultimate analysis and the composition determination of various streams of material produced in a solid recovered fuel production plant. All the process streams are sampled and treated according to CEN standard methods for solid recovered fuel. The results of the mass balance of the solid recovered fuel production process showed that 72% of the input waste material was recovered in the form of solid recovered fuel; 2.6% as ferrous metal, 0.4% as non-ferrous metal, 11% was sorted as rejects material, 12% as fine faction and 2% as heavy fraction. The energy balance of the solid recovered fuel production process showed that 86% of the total input energy content of input waste material was recovered in the form of solid recovered fuel. The remaining percentage (14%) of the input energy was split into the streams of reject material, fine fraction and heavy fraction. The material balances of this process showed that mass fraction of paper and cardboard, plastic (soft) and wood recovered in the solid recovered fuel stream was 88%, 85% and 90%, respectively, of their input mass. A high mass fraction of rubber material, plastic (PVC-plastic) and inert (stone/rock and glass particles) was found in the reject material stream.

In order to study the mass flow of pollutant and potentially toxic elements (PTEs) in the output streams of solid recovered fuel (SRF) production process, the various streams produced in commercial scale SRF production process are characterized chemically and, the elemental balance of SRF production process is presented. The SRF is produced from commercial and industrial waste (C&IW) through mechanical treatment (MT). The elements investigated for their mass balance in SRF production process are chlorine (Cl), arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg). The results showed that of the total input chlorine 60% was found in the SRF stream and 35% in the reject material stream and rest of 5% was in fine fraction and heavy fraction streams. Of the total input arsenic content 42% was found in the reject material and 32% in the SRF stream and rest (i.e. 26%) was found in the fine fraction stream. In case of cadmium, lead and mercury of their total input content to the process 46%, 58% and 45% respectively was found in the SRF stream. Among the waste components of C&IW, rubber and plastic (hard) were measured to contain the highest content of chlorine i.e. 8.0 wt.% (dry basis) and 3.0 wt.% (dry basis) respectively. Rubber was also found to contain higher content of cadmium as compared to other waste components. Plastic (hard) was measured to contain higher content of lead (i.e. 400 mg/kg, dry basis) than other components of input waste stream. The distribution of waste components (mainly plastic (hard), rubber and to some extent textile) was found significantly more important than other components of input waste stream in defining the concentration of pollutant and potentially toxic elements in output streams of SRF production process.

Quality of solid recovered fuel (SRF) demands that the waste components containing pollutant and potentially toxic elements (PTEs) and inert components are sorted out into separate small streams and to concentrate the suitable components into a prepared depolluted combustible fraction stream of SRF. In the SRF production, mass flow of waste components’ type into the output streams determine the quality of SRF. This paper presents the mass flow of pollutant and potentially toxic elements in full-scale SRF production. The SRF was produced from construction and demolition waste (C&DW) through mechanical treatment (MT). The input and output streams of SRF production were chemically characterised for the concentration of inorganic elements in details. The results showed that of the total input chlorine content to the process, 34% was found in SRF and 48% in reject material. Mercury (Hg) and arsenic (As) were found concentrated in fine fraction i.e. of the total input content of mercury and arsenic, 64% and 42% respectively was found in fine fraction. Most of the lead (Pb) was found in reject material and fine fraction i.e. of the total input lead content, 45% and 44% was found in reject material and fine fraction respectively. In case of cadmium (Cd), of the total input content of cadmium, 68% was found in SRF. Among the components of C&D waste, rubber and plastic (hard) were measured to contain higher chlorine (Cl) content i.e. 7.6 wt.%, d. and 7.0 wt.%, d. respectively. Plastic (hard) was measured to contain 880 mg/kg, d. of lead (Pb) which was higher than measured in other components. Textile was measured to contain 12 mg/kg, d. of arsenic (As) which was higher than measured in other components.

Increased use of biomass and waste fuels, and the consequent corrosion problem have led to an increased need to study and monitor the combustion processes. This study presents an extensive physical characterization of aerosol particles measured from a bubbling fluidized bed boiler with different fuel mixtures and optional ferric sulfate feeding. The fuel mixtures included bark, sludge, peat and solid recovered fuel. Previously, the characterization of the particles analyzed from a fluidized bed reactor has mainly focused on chemical off-line analysis of collected impactor samples, large coarse mode particles or laboratory-scale reactors. In this study, the focus is in the particle size range from 3 to 500 nm, where mobility size distributions, effective density, morphology and electric net charge of particles were measured and analyzed. In the boiler, the particle size distribution in the measurement range was unimodal. Gas phase species formed a second smaller particle mode in the dilution. The number concentration of the smaller mode, peaking around 20 nm, was mostly dominating but variations were seen with respect to measurement location, fuel mixture and additive feeding. The effective density of these particles was approximately 1.4 g/cm3. The larger mode, peaking around 80 nm, was found to be more stable and the effective density of these particles decreased as a function of particle size, being 3–4 g/cm3 at the maximum. The results of this work suggest that the cores of these particles already exist in the boiler and partly consist of heavier lead and zinc compounds. The ferric sulfate feeding decreased the number and mass concentration of the smaller mode particles, which are formed in the sampling and dilution processes mainly from the gas phase alkali chlorides. These condensable species were also linked to the negative net charge of particles. This study deepens the understanding of the combustion process and the sampling of aerosol particles with an aspect of on-line monitoring.

Levels of PCDD/F production in a 140 MW th bubbling fluidized bed boiler were measured. The boiler uses solid recovered fuel, bark and sludge. Homologue distribution patterns suggest the de novo mechanism is the main pathway for the generation of dioxin and furans in the post combustion zones of the boiler. Two modes of sulfur addition were tested to induce the deactivation of Cu which has been identified as the prime catalyst of this mechanism. First, S-pellet promoted Cu sulfation as supported by aerosol sampling data and resulted in a decrease in PCDD/F levels. The second approach was adding sulfur through peat; this resulted in an increase in PCDD/F concentration. Factors such as high Cu content in the SRF-peat-sludge fuel mixture and reduced volatilization of Cu may have contributed to the said increase. For all test cases, phase redistribution of PCDD/F was observed in the electrostatic precipitator favoring more gaseous PCDD/F at the outlet. The homologue distribution pattern did not change in the flue gas path, suggesting that further synthesis and/or chlorination in the stream were minimized. There is however evidence for subsequent reactions happening in the ESP fly ash. The homologue distribution pattern in the latter was different from that of the flue gas, and more highly chlorinated PCDD/Fs were present. Furthermore, the ratio of PCDD and PCDF was different from that of the samples in the flue gas path.

This paper presents the mass, energy and material balances of a solid recovered fuel (SRF) production process. The SRF is produced from commercial and industrial waste (C&IW) through mechanical treatment (MT). In this work various streams of material produced in SRF production process are analyzed for their proximate and ultimate analysis. Based on this analysis and composition of process streams their mass, energy and material balances are established for SRF production process. Here mass balance describes the overall mass flow of input waste material in the various output streams, whereas material balance describes the mass flow of components of input waste stream (such as paper and cardboard, wood, plastic (soft), plastic (hard), textile and rubber) in the various output streams of SRF production process. A commercial scale experimental campaign was conducted on an MT waste sorting plant to produce SRF from C&IW. All the process streams (input and output) produced in this MT plant were sampled and treated according to the CEN standard methods for SRF: EN 15442 and EN 15443. The results from the mass balance of SRF production process showed that of the total input C&IW material to MT waste sorting plant, 62% was recovered in the form of SRF, 4% as ferrous metal, 1% as non-ferrous metal and 21% was sorted out as reject material, 11.6% as fine fraction, and 0.4% as heavy fraction. The energy flow balance in various process streams of this SRF production process showed that of the total input energy content of C&IW to MT plant, 75% energy was recovered in the form of SRF, 20% belonged to the reject material stream and rest 5% belonged with the streams of fine fraction and heavy fraction. In the material balances, mass fractions of plastic (soft), plastic (hard), paper and cardboard and wood recovered in the SRF stream were 88%, 70%, 72% and 60% respectively of their input masses to MT plant. A high mass fraction of plastic (PVC), rubber material and non-combustibles (such as stone/rock and glass particles), was found in the reject material stream

A staged equilibrium process model was developed for a bubbling fluidized bed boiler firing SRF, bark and sludge. The model was used to study the influence of sulfur addition strategies (S-pellet additive and peat co-firing) on the behavior of copper, bromine, and alkalis. Aerosol samples collected from the backpass of the boiler were used to validate the chemistry predicted by the model. The model revealed that Cu existed as Cu 2 S (s3) in the reducing zone, and CuCl (g) (for all test cases) and CuO (s) (during peat co-firing) in the oxidation zones. CuBr 3(g) was also present after the introduction of tertiary air. However the model failed to predict the formation of CuSO 4 , an important passive species of Cu necessary for PCDD/F abatement. The modes of occurrence of Cu were classified as either active or passive with respect to de novo synthesis and an active/passive species molar ratio (APR) was introduced. APR showed high correlation with the PCDD/F production levels. Sensitivity analysis revealed that excessive Cu in the fuel mixture decreased the volatility of the element due to the formation of CuO (s) . Simulation for peat co-firing with low Cu content showed that PCDD/F concentration is decreased and is comparable to that of S-pellet addition. Sensitivity analysis revealed that increasing the energy share of sludge can likewise lower PCDD/F production.

In solid substances used as fuels, bromine originates mainly from flame retarded plastics and textiles, as well as from wastewater sludge. It has been indicated that bromine behaves in a similar way as chlorine with respect to ash forming matter, aerosol formation and high temperature corrosion in biomass and waste fired boilers. In this work, a measurement campaign was carried out in a 20 kW th bubbling fluidized bed (BFB) bench scale reactor to characterize the fate of Cl and Br in BFB combustion conditions. Spruce bark was used as the base fuel – serving as a source of alkali metals (mainly K, little Na). The gases HCl and HBr were fed with the fluidization air at different proportions into the BFB unit. In total, six experiments were done. The fate of bromine and chlorine was evaluated by means of several measurements including: FTIR (flue gas measurement), a low-pressure impactor (size distribution and chemical composition of aerosol particles) and deposit probe sampling (deposit growth rate and chemical composition of the windward, 90° side and leeward deposits). It was shown that the addition of HBr or HCl greatly increased the release of alkali metals (K, Na) from the original fuel (spruce bark) during combustion. The promoting effect of HBr was more obvious than that of HCl. HBr was found more reactive towards alkali metals than HCl.

In solid recovered fuel (SRF) production, type and nature of input waste stream influences the quality of fuel product. This paper presents the influence of input waste stream on SRF production in a mechanical treatment (MT) plant. The SRF was produced at industrial scale from three different types of waste streams: commercial and industrial waste (C&IW), construction and demolition waste (C&DW) and municipal solid waste (MSW). Here, the stream of MSW used for SRF production was energy waste collected from households. In the SRF production from MSW, higher yields of material were recovered in the form of SRF as compared with that of recovered from C&IW and C&DW. Of the input MSW to the MT plant, 72 wt% was recovered as SRF, equivalent to 86% energy recovery. The energy consumed to produce unit tonne of SRF from C&IW, C&DW and MSW was 1153 MJ, 1246 MJ and 1626 MJ, respectively. In the SRF production, removal of chlorine (Cl), lead (Pb) and mercury (Hg) from C&IW feedstock was worse than from C&DW and MSW feedstocks. In the SRF production from C&IW, of the input mass of chlorine, lead and mercury to the MT process 60%, 58% and 45%, respectively was found in the SRF. The SRF produced from C&DW contained the lowest mass fraction of the input chlorine, lead and mercury in comparison with the SRF produced from C&IW and MSW, namely 34%, 8% and 30%, respectively. Among the waste components rubber, plastic (hard) and textile (synthetic) were identified as potential sources of polluting and toxic elements, whereas wood, paper & cardboard and plastic (soft) were found to contain the lowest content of polluting and toxic elements. The pollutant and toxic elements investigated in this research work were chlorine, lead, cadmium, mercury and arsenic.

Power systems for South and Central America based on 100% renewable energy (RE) in the year 2030 were calculated for the first time using an hourly resolved energy model. The region was subdivided into 15 sub-regions. Four different scenarios were considered: three according to different high voltage direct current (HVDC) transmission grid development levels (region, country, area-wide) and one integrated scenario that considers water desalination and industrial gas demand supplied by synthetic natural gas via power-to-gas (PtG). RE is not only able to cover 1813 TWh of estimated electricity demand of the area in 2030 but also able to generate the electricity needed to fulfil 3.9 billion m3 of water desalination and 640 TWhLHV of synthetic natural gas demand. Existing hydro dams can be used as virtual batteries for solar and wind electricity storage, diminishing the role of storage technologies. The results for total levelized cost of electricity (LCOE) are decreased from 62 €/MWh for a highly decentralized to 56 €/MWh for a highly centralized grid scenario (currency value of the year 2015). For the integrated scenario, the levelized cost of gas (LCOG) and the levelized cost of water (LCOW) are 95 €/MWhLHV and 0.91€/m3 , respectively. A reduction of 8% in total cost and 5% in electricity generation was achieved when integrating desalination and power-to-gas into the system.

Analogously to chlorine, bromine has been shown to have a role in high temperature corrosion and dioxin/furan formation in combustion systems. This paper presents a review on the origin, content and modes of occurrence of bromine in solid substances used as fuels. In Part 1 the natural and in Part 2 the anthropogenic occurrence of bromine is discussed. The reader is provided with a comprehensive background to understand the factors influencing bromine sources and content in fuels as well as the implications of bromine on combustion systems. Bromine has both natural and anthropogenic sources depending upon the fuel type, the most important of which are the deposition of sea salts and the utilisation of brominated flame retardants (BFRs), respectively. Nor can the influence of various brominated chemicals such as biocides be disregarded. Bromine content exhibits large variation in fuels. The BFR treated plastics can contain several weight percentages of bromine whereas up to 500 mg kg −1 has been found in municipal solid waste (MSW) and Solid Recovered Fuel (SRF). Industrial and residential water treatment (sanitising, slime control) may involve the use of brominated biocides which results in bromine residuals in sludge – up to approximately 100 mg kg −1 . Bromine is applied in other selected uses such as colourants, rubber additives and in photographic paper which may be found in solid waste fuels, too.

In Part 1 of the work a measurement campaign was carried out to determine the occurrence of corrosive ash components in a bubbling fluidized bed (BFB) boiler combusting solid recovered fuel (SRF). It was found out that the main ash-forming elements that had been vaporized and subsequently condensed from the gas phase were Na, K, S and Cl together with minor amounts of Zn, Pb, Cu, and Br. Both, Cl and Br were found in the corrosion front of the waterwalls prior to the measurement campaign. In this work, the forms of ash forming elements in the combustion gases and in the waterwall deposits of the examined boiler were predicted by means of thermodynamic equilibrium modeling. Laboratory tests were also carried out to estimate the degree of corrosion of boiler steels under bromine containing deposits. A mixture of ZnBr2 and K2SO4 was selected for high temperature lab-scale corrosion testing since Zn, Br and K as well as sulfates were present in the deposit and it was possible to compare these results to previously published results with ZnCl2–K2SO4 mixtures. The comparison showed that more severe material degradation was caused by the ZnBr2 containing salt than by the corresponding chloride and corrosion was significant already at 400 °C.

Three alternative condensing mode power and combined heat and power (CHP) waste-to-energy concepts were compared in terms of their impacts on the greenhouse gas (GHG) emissions from a heat and power generation system. The concepts included (i) grate, (ii) bubbling fluidised bed (BFB) and (iii) circulating fluidised bed (CFB) combustion of waste. The BFB and CFB take advantage of advanced combustion technology which enabled them to reach electric efficiency up to 35% and 41% in condensing mode, respectively, whereas 28% (based on the lower heating value) was applied for the grate fired unit. A simple energy system model was applied in calculating the GHG emissions in different scenarios where coal or natural gas was substituted in power generation and mix of fuel oil and natural gas in heat generation by waste combustion. Landfilling and waste transportation were not considered in the model. GHG emissions were reduced significantly in all of the considered scenarios where the waste combustion concepts substituted coal based power generation. With the exception of condensing mode grate incinerator the different waste combustion scenarios resulted approximately in 1 Mton of fossil CO2-eq. emission reduction per 1 Mton of municipal solid waste (MSW) incinerated. When natural gas based power generation was substituted by electricity from the waste combustion significant GHG emission reductions were not achieved.

An experimental campaign was carried out with a circulating fluidised bed (CFB) pilot scale combustor to study the role of coal bound kaolin in the fate of solid recovered fuel (SRF) originated halide aerosols. A combustion experiment was carried out with SRF–Spruce Bark mixture as a reference. High kaolinite coal and paper pigment kaolin, one at a time, were mixed with the SRF–Bark in increasing proportions until dp < 1 μm fine particles were absent as measured from 780 °C combustion gases by means of a dilution probe and low pressure impactor (LPI). This fine particle mode was absent after mixing sufficiently either coal or kaolin with SRF–Bark and only traces of water soluble alkali metal salts were found in the CFB fly ash. These conditions were achieved when kaolin was mixed with the SRF–Bark for 52 times on a molar basis compared to the Na + K initially found in the aerosols. This proportioning was found to be the same for the additive kaolin and coal bound kaolinite. Na and K in the fly ash seem to be bound chemically to the kaolin as alkali aluminosilicates rather than in water soluble alkali sulphates. This is indicated by their solubility behaviour.

Combustion of two biomass fuels: demolition wood (DW) and pepper plant residue (PPR), was investigated from an emission viewpoint in a 20 kWth fluidized bubbling bed reactor and a 1 MWth fluidized bubbling bed test boiler. Fluidization velocity and boiler output were varied in the larger facility whereas they were kept constant in the smaller reactor. Traditional flue gases were analyzed. In addition, impactor measurements were carried out to determine the mass flow of the finest fly ash and toxic elements. These measurements were compared with EU emission directives for biomass co-incineration. It was possible to combust DW without operational problems. However, the DW was contaminated with lead, which tended to get strongly enriched in the fine fly ash. Pb tends to be adsorbed on the measurement line surfaces stronger than many other toxic elements and therefore proved difficult to collect and measure. Enrichment of Pb in the fine fly ash can be weakened by co-firing DW with PPR. Increasing the share of PPR up to 50% markedly reduces the toxic metal concentration in the finest fly ash. This, however, leads to increased mass flow of fine fly ash and increases the potential risks of operational problems such as bed agglomeration and fouling.

Firing or co-firing of biomass in efficient power plants can lead to high-temperature corrosion of superheaters due to condensation of alkali chlorides into superheater deposits. Corrosion can be prevented if a significant portion of the alkali chlorides present in the flue gases is destroyed before reaching the superheaters. The alkali capturing power of aluminium and ferric sulphates was determined in a pilot-scale fluidised bed (FB) reactor. The reagents were added in solution, through a spraying nozzle, to the upper part of the freeboard. Both reagents, at economical dosages, fast and effectively destroyed the alkali chlorides by producing sufficient SO3 for the sulphation. Both the mass flow rate and type of sulphate affected the sulphation ability. Thus, the cation, too, plays a role in the reaction. The required chemical dosage is not directly proportional to the Sreagent/Cl2fuel ratio because alkali chlorides must compete with calcium and magnesium oxides and probably also with alkali oxides for the available SO3.

In this chapter, technology options for solid biomass and waste fuel utilisation in large-scale combustion plants are presented with the focus on fuel flexible technologies allowing multi-fuel operation. Fuel flexibility (the ability to use various fuels) protects power plant investment from changes in competitiveness between different fuels, which can be caused, for example, by changes in legislation. In multi-fuel operation (burning various fuels at the same time), synergies between different types of fuels can be exploited allowing higher generation efficiency also from lower-quality fuels. The three main combustion technologies for solid fuels are grate, fluidised-bed and pulverised-fuel combustion. Grate boilers are adaptable to various fuels but are quite sensitive to changes in fuel quality and have limited multi-fuel operation capability. Fluidised-bed boilers provide the best fuel flexibility. With circulating fluidised-bed (CFB) boilers, biomass/waste fuels can be co-fired with coal on 0–100% share. Various technologies have been developed to enable co-firing biomass with coal in pulverised coal (PC) boilers as the enormous capacity of existing PC boilers offers huge potential for increasing biomass utilisation and economic benefits compared to new stand-alone biomass/waste plants. Capital costs are reduced markedly, and the high electrical efficiency of large PC boilers and the favourable properties of coal ash can be exploited. Three different routes can be taken to utilise co-firing in PC boilers: (1) direct co-firing, (2) indirect co-firing, and (3) parallel co-firing. In addition, a PC boiler can be converted into a bubbling fluidised-bed (BFB) boiler with attractive economics.

In this work, the fraction of construction and demolition waste (C&D waste) complicated and economically not feasible to sort out for recycling purposes is used to produce solid recovered fuel (SRF) through mechanical treatment (MT). The paper presents the mass, energy and material balances of this SRF production process. All the process streams (input and output) produced in MT waste sorting plant to produce SRF from C&D waste are sampled and treated according to CEN standard methods for SRF. Proximate and ultimate analysis of these streams is performed and their composition is determined. Based on this analysis and composition of process streams their mass, energy and material balances are established for SRF production process. By mass balance means the overall mass flow of input waste material stream in the various output streams and material balances mean the mass flow of components of input waste material stream (such as paper and cardboard, wood, plastic (soft), plastic (hard), textile and rubber) in the various output streams of SRF production process. The results from mass balance of SRF production process showed that of the total input C&D waste material to MT waste sorting plant, 44% was recovered in the form of SRF, 5% as ferrous metal, 1% as non-ferrous metal, and 28% was sorted out as fine fraction, 18% as reject material and 4% as heavy fraction. The energy balance of this SRF production process showed that of the total input energy content of C&D waste material to MT waste sorting plant, 74% was recovered in the form of SRF, 16% belonged to the reject material and rest 10% belonged to the streams of fine fraction and heavy fraction. From the material balances of this process, mass fractions of plastic (soft), paper and cardboard, wood and plastic (hard) recovered in the SRF stream were 84%, 82%, 72% and 68% respectively of their input masses to MT plant. A high mass fraction of plastic (PVC) and rubber material was found in the reject material stream. Streams of heavy fraction and fine fraction mainly contained non-combustible material (such as stone/rock, sand particles and gypsum material).

The main fine particle (dp < 1 μm) forming elements found in combustion gases of anthropogenic waste or biomass fired boilers are typically K, Na and Cl, possibly complemented with S. When these are excluded, in solid recovered fuel (SRF) combustion the main elements were found to be: Ba, Br, Cr, Cu, Fe, Pb, Sb, Sn and Zn. Fine particle composition is presented for 6 different furnace heights of a bubbling fluidized bed (BFB) boiler. As the fine particles are formed of vaporized ash species the experimental results are discussed with the support of thermodynamic equilibrium modeling for estimating the forms of the gaseous elements in the furnace. The occurrence of bromine was found to be similar to chlorine as the main forms of bromine in the furnace were estimated to be KBr(g) and NaBr(g) complemented with CuBr3(g). It is proposed that the trace elements mentioned originate mainly from plastics and rubber where they are used as production additives, stabilisers, dyes, colorants and flame retardants. Cr, Cu and Zn may originate to a large extent from alloys and other metallic impurities. SEM-EDS analyses carried out for the SRF supports the postulated origin of the elements.

In waste fired boilers high temperature corrosion has often been attributed to zinc and lead chlorides. In addition, bromine induced high temperature corrosion has been earlier observed in a bubbling fluidised bed (BFB) boiler co-firing solid recovered fuel (SRF) with bark and wastewater sludge. In Part 1 of this work a measurement campaign was undertaken to determine the occurrence of Cl, Br, Zn and Pb in the fuel, in the combustion gases as well as in the deposits on the boiler waterwalls. It was observed that Cl, Br, Zn and Pb originate to a large extent from the SRF, they are vaporised in the furnace, and may form waterwall deposits. This, complemented by fluctuations between oxidising and reducing atmosphere resulted in rapid corrosion of the waterwall tubes. Concentrations of Cl, Br, Zn and Pb in the fuel, in the furnace vapours and in the deposits are reported in this work. As there is lack of published data on the bromine induced high temperature corrosion, laboratory scale corrosion tests were carried out to determine the relative corrosiveness of chlorine and bromine and these results will be reported in Part 2 of this work. Furthermore, the forms of Cl, Br, Zn and Pb in the combustion gases as well as in the waterwall deposits were estimated by means of thermodynamic equilibrium modelling and these results will also be discussed in Part 2.

Aerosol and fly ash sampling was carried out at a 80MWth bubbling fluidised bed (BFB) boiler plant co-firing solid recovered fuel (SRF), spruce bark and paper mill wastewater sludge in two experimental conditions. The SRF-Bark ratio in the fuel mix was kept constant at 50%–50% on dry mass basis in both experiments but two sludge proportions were used: 15% and 4% on dry mass basis. Aerosol samples were collected from the superheater region of the boiler furnace and fly ash from the electrostatic precipitator (ESP). Na, K, Cl and S were found to be in mainly water soluble compounds in the aerosols sampled by means of a Dekati type Low Pressure Impactor (DLPI). Bromine was found in several weight percentages in aerosols and it was amongst the main elements in some of the samples collected. Bromine is assumed to mainly originate from flame retarded plastics and textiles in the SRF. According to the measurements, the fate of Br seems to be analogous to the other main halogen, Cl, and its conversion from fuel to aerosols was high, indicating a strong tendency to form bromine salts.

Costs of biofuel production from energy crops can be reduced by applying the crop residues in heat and power production. Perennial herbaceous crops like Cynara cardunculus L. are challenging fuels because they tend to have high ash and chlorine contents. Coals, however, are often rich in aluminium silicates and sulphur, and co-firing of these biofuels with coal could be expected to reduce operational problems. In addition, CO2 emissions are lower than during coal firing alone. Blends of Cynara and two coals, South African bituminous and Spanish sub-bituminous coal, were combusted in a 20 kW bubbling bed pilot reactor to ascertain the ability of the coals to reduce operational problems by alkali capture. The Cynara fuel sample contained almost 2 wt% chlorine. The South African coal was rich in kaolinite capable of capturing alkalies from chlorides to produce alkali aluminium silicate and HCl. The Spanish coal was rich in sulphur (mostly present as FeS2), and produced high concentrations of SO2 that partially oxidised to SO3. The SO3 can capture alkalies from chlorides by sulphation. Up to 30% Cynara, on energy basis, could be co-fired with Spanish coal without operational problems, whereas the same percentage of Cynara with South African coal led to strong Cl deposition. Co-firing of Cynara with both coals resulted in high HCl emissions (up to 1500 mg/Nm3 in 6% O2). In addition, co-firing of the Spanish coal led to very high SO2 emissions (up to about 16,000 mg/N m3 in 6% O2). Thus, a power plant capable of firing such blends must be equipped with flue gas cleaning equipment for effective SO2 and HCl capture in the flue gas channel after the superheaters, or else the quality of the Cynara must be markedly improved by changing the harvesting technology and fertilisers, which could be major sources of high ash and chlorine content in the fuel.

The co-combustion of fossil fuels with CO2 -neutral fuels is an attractive way both to decrease CO2 emissions in energy production and to use fuel synergies which decrease each other’s undesirable properties. This paper presents a new approach to understand and predict the chlorine deposition tendency in the co-combustion of coal with biomass and RDF. This novel approach combines the results from deposit analysis with flue gas emission measurement and advanced fuel characterization methods. The experiments were carried out in a 0.1 MW circulating fluidized bed reactor. Two different types of bituminous coal (South African and Polish) were co-fired with RDF, demolition wood and bark. The traditional way to predict risk for chlorine deposition, the fuel S/Cl molar ratio, and the safe limit molar ratio > 4 for biofuels were shown to be inadequate. The mineral kaolinite in coal ash was found to be able to capture alkalis and, in most cases, more effectively than sulphur compounds. The alkali capture capability of coal sulphur is quickly consumed due to reactions with calcium compounds. Furthermore, the ability of SO2 to sulfate alkali chlorides were found to be weaker than presented in the literature. Thus in many cases it is only kaolinite that keeps Cl away from the deposit. New index to predict chlorine deposition tendency were introduced: the reactive (Al+Si)/fuel Cl molar ratio. The results showed a good correlation between the chlorine concentration in the deposit and the new index. The reactive (Al+Si)/fuel Cl molar ratio higher than 8–10 was found to prevent chlorine to deposit. The new approach for better understanding and preventing of chlorine deposition promotes the co-combustion of coal with biomass and RDF by introducing new synergy benefits.Copyright © 2005 by ASME

Co-combustion of coal with biomass or firing biomass alone is increasingly used as a first step to meet the Finnish commitments under the Kyoto agreement. Fluidized bed combustors are commonly used when co-firing, however, even if FBC’s have a wide tolerance for different fuel qualities, co-combustion of biomass or firing biomass alone may lead to unwanted ash-related problems. A deposit measurement campaign was done, at the 550 MWth biofuelled CFB in Jakobstad, Finland. During the campaign a total of 16 different fuel blends were burned. The deposits were sampled with air-cooled probes with detachable rings. The deposits were sampled at two different locations, one where the flue gas temperature was about 730°C (probe surface temp. 540°C) and the second where the flue gas temperature was about 530°C (probe surface temp. 350°C). From every deposit sample three elemental analyses were done — one from the wind side, one from the lee side, and one from an angle of about 50° from the wind side. The analyses were done with a SEM/EDX analyzer. The fuels used during the measurement campaigns were sampled and analyzed. In addition to proximate and ultimate fuel analysis so called fuel fractionation was applied. The fractionation method is based on selective leaching by water, ammonium acetate, and hydrochloric acid, consecutively. After each leaching step the solutions are analyzed for the most important elements. The method can be used to determine how the elements are bound in the fuel and how they may behave during combustion. The analysis results from the measurement campaign and from the advanced fuel analysis were combined and are reported in this paper, with emphasis on the fate of chlorine.Copyright © 2005 by ASME

When co-firing biomass fuels with fossil fuels, following implications may be expected: increased rate of deposit formation, shorter sootblowing interval, bed material agglomeration, increased risk of corrosion, higher in-house power consumption etc. Deposit formation inhibits heat transfer and reduces boiler efficiency, additionally chlorine rich deposits induce hot corrosion of heat transfer surfaces. Due to this operating and maintenance costs can increase, but this can be diminished or even avoided with appropriate fuel blend and process control. Effect of different fuels on deposition and corrosion have been studied by deposit and material testing probes, both in VTT Processes' test facilities and in power plant boilers. To support plant operators in daily decision-making and in plant operation optimisation advanced methods for combining data from deposit formation monitoring and process calculations are being developed. These methods will help operators to achieve better boiler performance with improved fuel flexibility. Use of biomass fuels reduces emissions but may cause harmful forming of deposition. Depending on the boiler type, it is recommended to combust 10-20% of peat with wood fuels in order to reduce above mentioned operational problems. If wood fuels consist mainly of new tree growth, like logging residue, it is favourable to use even higher share of peat, 30-40%, as co-firing fuel.

VTT Processes has studied co-firing of peat and wood based fuels in several national and international research projects. Utilisation of solid biofuels sets new demands for fuel handling and feeding systems as well as for combustion technologies. Wood fuels differ from peat in many properties; moisture content, heating value, energy density, particle size, ash content and ash quality etc. All these factors effect greatly on fuel combustion behaviour. One of the most important differences between wood fuels and peat is ash behaviour during combustion. Typically wood fuels contain higher amount of weak acid soluble alkaline metals, potassium and sodium, when compared to peat. These alkaline metals exist in different forms of compounds (sulphates, chlorides, nitrates, etc.) or they are attached directly to organic matter in growing plants. Easily soluble alkalies are released during combustion into gas phase and cause risk for boiler bed material agglomeration, fouling of heat transfer surfaces and superheater corrosion. These phenomena have effect on power plant availability and production economics and thus they should be carefully recognised. Fouling inhibits heat transfer and reduces boiler efficiency, additionally; chlorine rich deposits induce hot corrosion of heat transfer surfaces. Effect of different fuels on deposition and corrosion have been studied by deposit and material testing probes, both in VTT's test facilities and in power plant boilers. Studies show that with co-firing peat with wood a great deal of benefits is achieved in controlling emissions and harmful forming of deposition. Depending on the boiler type, it is recommended to combust 10 - 20 % of peat with wood fuels in order to reduce above mentioned operational problems. If wood fuels consist mainly of new tree growth, like logging residue, it is favourable to use even higher share of peat, 30 - 40 %, as co-firing fuel.

To support power plant operators in daily decision-making and in plant operation optimisation, advanced methods for combining data from deposit formation monitoring and process calculations are being developed. These methods will help power plant operators to achieve better power plant performance with improved fuel flexibility. Correlation has been observed between temperature behaviour of VTT Prosesses' deposit monitoring probe and thermal efficiency of steam boilers. Based on the data provided by heat transfer monitoring probes, correlations have been developed to describe on-line changes in heat transfer rate and boiler efficiency. This gives basis for developing on-line methods for maximising boiler efficiency and quantifying the implications of applied fuel blend on boiler performance.

There is a growing international interest in utilising renewable fuels, also in multifuel applications. Main reasons for this are the objective to reduce CO2 emissions and meet emission limits for NOx and SO2. On one hand cofiring, defined as simultaneous combustion of different fuels in the same boiler, provides an alternative to achieve emission reductions. This is not only accomplished by replacing fossil fuel with biomass, but also as a result of the interaction of fuel reactants of different origin (e.g. biomass vs. coal). On the other hand, utilisation of solid biofuels and wastes sets new demands for process control and boiler design, as well as for combustion technologies, fuel blend control and fuel handling systems. In the case of wood-based fuels this is because of their high reactivity, high moisture content and combustion residues' high alkaline metal content. Combustion and cofiring properties of fuels have been studied both in VTT Processes' test facilities and in industrial-scale power plant boilers. The formation of alkaline and chlorine compounds in biomass combustion and their effect on boiler fouling and corrosion have been monitored by temperature controlled deposit formation and material monitoring probes. Deposit formation monitoring at full-scale boilers provides unique information on the rate of deposit formation, the effect of sootblowing and consequent changes in heat transfer. Additionally, the data from deposit formation monitoring has been shown to correlate with boiler performance, which gives basis for studying the interrelation of: fuel blend characteristics - deposit formation - boiler performance. If biomass fuels are blended with coal or peat, following implications may be expected: increased rate of deposit formation, shorter sootblowing interval, cleaning of heat transfer surfaces in revisions may be required, bed material agglomeration (in fluidised beds), increased risk of corrosion, higher in-house power consumption, higher flue gas temperature. These factors affect operating and maintenance costs, but their effect can be reduced or even avoided with appropriate fuel blend control. By the aid of the aforementioned means, optimum share of biomass fuel in different fuel blends can be defined.

There is a growing interest in utilising renewable fuels in multifuel applications. Main reasons for this are environmental; reduction of CO2 emissions as well as NOx and SO2 emissions. The cofiring, defined as simultaneous combustion of different fuels in the same boiler, therefore provides an alternative to achieve lower emission in energy and power production. However, the utilisation of solid biofuels and wastes sets new demands for process control and boiler design, as well as for combustion technologies, fuel blend control and fuel handling systems. The ash behaviour in combustion of biomass-based fuel affects highly on it's combustion characteristics compared to peat and coal. Combustion and cofiring properties of fuels have been studied both in pilot scale testing at VTT and in industrial-scale power plant boilers. The formation of alkaline and chlorine compounds in biomass combustion and their effect on boiler fouling and corrosion have been monitored by temperature controlled deposit formation and material monitoring probes. Deposit formation monitoring at full-scale boilers provides unique information on the rate of deposit formation, the effect of soot blowing and consequent changes in heat transfer. Additionally, the data from deposit formation monitoring has been shown to correlate with boiler performance, which gives basis for studying the interrelation of: fuel blend characteristics - deposit formation - boiler performance. By the aid of the aforementioned means, optimum share of biomass fuel in different fuel blends can be defined.

Utilisation of solid biofuels and wastes sets new demands for fuel handling and feeding systems, as well as for boiler design and combustion technologies. Especially ash quality of wood fuels differs remarkably chemically from ashes of peat or coals and other fossil fuels. The alkaline metals, which are usually responsible for fouling of heat transfer surfaces, are abundant in wood and will be released during combustion easily in gas phase. The combustion and co-firing properties of fuels have been studied both in VTT's test facilities and in industrial-scale power plant boilers. The formation of alkaline and chlorine compounds and their effect on boiler fouling and corrosion have been monitored by cooled temperature controlled deposit and material probes. The experimental studies clearly showed that if sulphur existed in combustion environment, chlorine was released as HCl and did not drift into deposits. Fouling of the boiler effects on several factors at the plant. These factors, e.g. the increment of operating and maintenance costs caused by fouling of the boiler, can increase the energy production costs significantly. In addition to increased need for soot blowing and cleaning, as well as the possible renovation need of the super heaters, the efficiency of the boiler decreases as thermally insulating ash deposits on the heat transfer surfaces of the boiler. By the side of these factors costs are caused by more often replaced bed material, the increased need for power consumption of the plants, and storage costs of wood fuels

Power-to-gas (PtG) technology has received considerable attention in recent years. However, it has been rather difficult to find profitable business models and niche markets so far. PtG systems can be applied in a broad variety of input and output conditions, mainly determined by prices for electricity, hydrogen, oxygen, heat, natural gas, bio-methane, fossil CO 2 emissions, bio-CO 2 and grid services, but also full load hours and industrial scaling. Optimized business models are based on an integrated value chain approach for a most beneficial combination of input and output parameters. The financial success is evaluated by a standard annualized profit and loss calculation and a subsequent return on equity consideration. Two cases of PtG integration into an existing pulp mill as well as a nearby bio-diesel plant are taken into account. Commercially available PtG technology is found to be profitable in case of a flexible operation mode offering electricity grid services. Next generation technology, available at the end of the 2010s, in combination with renewables certificates for the transportation sector could generate a return on equity of up to 100% for optimized conditions in an integrated value chain approach. This outstanding high profitability clearly indicates the potential for major PtG markets to be developed rather in the transportation sector and chemical industry than in the electricity sector as seasonal storage option as often proposed.

Power-to-gas (P2G) technologies producing synthetic fuels have the potential to address the issue ofintermittency of electricity from solar and wind farms, and simultaneously contribute to lower CO2concentration in the atmosphere. However it requires, among others, judicious technical selection ofappropriate CO2 capture and delivery technologies. For example, compared to CCS, where the purity ofthe product CO2 gas is mostly dictated by transportation and subsequent storage requirements, in P2Gsystem producing SNG the catalyst to be used in the Sabatier conversion of CO2 to CH4 is sensitive totrace contents of S and metal impurities. This is also true for Fischer–Tropsch based synthesis of otherhydrocarbons.More than 100 technical articles were reviewed to understand CO2 capture technologies includingcapture from air that have received attention within the last decade. The goal is to determine theapplicability of these technologies to P2G systems producing synthetic fuels. The review includestechnologies such as absorption, adsorption, and low temperature CO2 capture. In addition, top sourcesof renewable CO2, such as biomass combustion, are also presented.An easy-to-understand visual summary on the energy requirements, recovery, CO2 product purity,hydrophobicity issues and technology development status is presented. More importantly, the quality ofthe product CO2 from the said technologies is assessed. From these properties an appropriate CO2capture and delivery technology is proposed for the production of synthetic fuel.

Combustion of biomass-based fuels and wastes may cause unexpected problems in power plant operation. In addition to operational disturbances in fuel pre-treatment and feeding systems, several observations have shown that alkali metal compounds in biomass cause hot corrosion of heat transfer surfaces - especially at low sulphur conditions. The behaviour of biomass fuel is influenced during combustion by existence of other fuels. It has been noticed in the previous studies that even small concentration of chlorine in logging residue chips will result in harmful formation of alkali and chlorine compounds on boiler heat transfer surfaces. This could be prevented by co-firing sulphur-containing fuel like peat. In this case vaporised alkali metals of wood ash are bound in sulphur, the amount of alkali chlorides in deposits is reduced or these are not formed at all, and chlorine is released as HCl into flue gases. The formation of alkali and chlorine compounds in biomass combustion and their contribution to boiler fouling and corrosion has been monitored by specific temperature controlled probes both at VTT Processes' test facilities and at full-scale power plant boilers. These studies have been supplemented by examining the availability and operation history of selected Finnish and Swedish wood-fired power plants. As a result of these studies, and in co-operation with steam boiler manufacturers and operators, VTT Processes has developed new methods for defining the optimum share of biomass fuels in different fuel blends and for improving power plant availability.