Biocoal Production Research Articles

Accurate carbon structure for prediction of reaction pathway during bio-coal production using torrefaction

The structural parameters of carbon were accurately determined through correction by employing a linear correlation method. Further, the nuclear Overhauser effect (NOE) was reduced in solid 13C-nuclear magnetic resonance spectra using a solid cross-polarization/magic angle spinning (CP/MAS) probe and the total suppression of sidebands sequence (TOSS). The reaction pathway during torrefaction was inferred from analysis of the accurate bond behavior and product distribution. The results show that torrefaction has a significant influence on the structural evolution of biomass. After correction, the relative deviations in the H/C ratio and aromaticity of the carbon structure decreased below 20 %. During torrefaction, the aliphatic carbon bonds were cleaved and aromatic carbon bonds were formed by dehydration, deoxygenation, oligomerization, aromatization, and Diels-Alder reaction. Torrefaction of biomass is divided into three stages. The first stage occurs below 220 °C, with disruption of the hydrogen bonds, a decrease in the number of Cal-O bonds, and the release of some CO2, CO, and furaldehyde. The second stage proceeds in the 220–260 °C range, where β-O-α bonds and glycoside bonds are broken, with the generation of ketones, furan, phenols, CO, and CO2. In the third stage between 260 and 300 °C, Cal-O and Cal-Cal bonds are broken. Bio-coal is composed of monomers of C20H14O3 with two aromatic rings linked by one aromatic ring. This significant, fundamental study enables accurate calculation and simulations for optimizing the industrial utilization of biomass.

Regulation of energy properties and thermal behavior of bio-coal from lignocellulosic biomass using torrefaction

The energy properties in bio-coal, such as proximate analysis, element composition, high heat value, colour, thermal behavior are detailed elaborated. The results show bio-coal production processes from biomass can be divided into three stages which is close to coalification through the data in energy properties. The first stage called mild torrefaction (≤220 °C) seen as biomass to peat phase during coalification in the result of unstable oxygenated functional groups in hemicellulose are decomposed and Maillard reaction induces the colour modification. Second stage called moderate torrefaction (220–260 °C) seen as lignite formation process during coalification leads to degradation of celluloses. Biomass colour from brown to sepia due to the chromophoric groups. The heating value of maple sawdust (MS) increases to 30.02 MJ/kg of MS-260. Third stage called severe torrefaction (260–300 °C) considered as metamorphic episode of lignite to bituminous coal results of covalent bond cleavage, oxygenation of lignin and condensation of aromatic carbons. As functional groups decomposition during bio-coal production, three characteristic temperatures increase with the torrefied temperature increasing read from TG and DTG curves. The MS with the highest cellulose and aliphatic C–C bonds, is effective raw materials for bio-coal production by torrefaction with the close energy properties, thermal behavior to bituminous coals.

Production of Biocoal from Wastewater Sludge and Sugarcane Bagasse: A Review

The rising volume of wastewater sludge and sugarcane bagasse is becoming a prominent concern globally. Furthermore, the growing demand for fuel coupled with the depletion of fossil fuel reserves in South Africa demonstrates the need for alternative energy sources. To minimize the reliance on fossil-based energy sources, a renewable resource such as biomass can be optimized as an energy source. Wastewater sludge and bagasse have the energy potential to produce high-calorific-value biocoal; this will contribute to the supply of energy in South Africa. The synthesis of biocoal from wastewater sludge and bagasse through an artificial synthetic coal production process, i.e., hydrothermal carbonization (HTC), is preferred over other thermal conversion techniques as HTC is capable of handling feed having a high (75–90%) moisture content. This article focuses on the production of biocoal from wastewater sludge and sugarcane bagasse as an alternative to sustainable bioenergy supply and as one of the potential solutions for reducing net CO2 greenhouse gas (GHG) emissions from fossil-fuel power plants, and addresses the use of different thermochemical technologies, previous studies on the composition of wastewater sludge and bagasse, and the benefits of hydrothermal carbonization.

Feasibility of Bio-Coal Production from Hydrothermal Carbonization (HTC) Technology Using Food Waste in Malaysia

The alarming rise of food waste all over the world due to population and economic growth must be tackled with better waste management and treatment methods. The current practice of landfilling has been scientifically proven to adversely impact environmental and societal health. A relatively new technology called hydrothermal carbonization (HTC) has the potential to solve this problem. It takes in high-moisture-content material, like food waste, and converts it into bio-coal with a heating value similar to normal coal. The present study explored the feasibility of HTC technology and bio-coal production in Malaysia. An in-depth study via desk research was conducted by implementing Porter’s five forces analysis to evaluate the feasibility of the bio-coal production project. A survey involving 215 respondents from different households that represent the average demography of Malaysia was also conducted to understand the behaviors and attitudes of different households towards food waste. The present study found that a typical Malaysian household disposes mostly of meal leftovers, with an average of 926 g of food waste per day. In addition, the 3 highest food categories that were disposed of were rice or noodles or pasta (13.0%), vegetables (12.2%) and curry and soup (10.1%). Meal leftovers such as curry and soup are high in moisture content, which is suitable for HTC. The survey on household waste provided adequate information to support the availability of a sufficient quantity of food waste in the country to sustain the raw material for the bio-coal project in Malaysia. Furthermore, a consumer survey involving seven industrial firms was conducted to determine the potential buyers of bio-coal. The responses from the industrial firms show that a bio-alternative for coal is important, and they are willing to transition to greener technologies. However, five out of seven firms stated that the main hurdle in adopting bio-coal is the high cost of production and incompatibility with existing industrial processes. Finally, interviews were conducted with key players in the industry to evaluate the adoptability of bio-coal into the wider market. The findings from the desk research and the primary research show that the outlook for bio-coal in the market is quite positive. In the long run, HTC is certainly profitable, but for immediate benefits, adequate government support and policy in favour of the use of HTC bio-coal in power plants are required.

Techno-economic assessment for bio coal production from brewers spent grain

Tons of organic wastes are being generated from household, domestic and industrial waste. This waste if left untreated results in the emission of greenhouses gases such as methane and carbon dioxide, in overall resulting in climate change effects. On the other hand, the organic waste provides a valuable source of raw material for the production of bio coal, which is green and is renewable. In this study, brewery waste was converted to bio coal using the hydrothermal carbonization technology. Bio coal with a heating value of 26.1 MJ/kg was then produced. An economic assessment indicated that a total capital investment of USD 7.58 million is required for a plant that produces 69 tons/day. The production cost is USD 190.60 per tonne; the selling price was pegged at USD 200.00 which is less than the market value of fossil coal by USD10.00. The net present value of utilising brewery waste as a raw material in bio coal production was positive; with a payback period of 4.62 years and a 21.7% return on investment.

Effect of pyrolysis temperature and biomass particle size on the heating value of biocoal and optimization using response surface methodology

The effect of pyrolysis temperature (T) and biomass particle size (z) on the biocoal's heating value of Oak acorn shell (OA), deseeded carob pods (CP) and olive mill solid waste (OMSW) were investigated. The higher heating value (HHV) increased with T. The effect of the particle size differed according to the biomass. Response surface methodology (RSM) was used to optimise the biocoal production system from technical, end-user and socio-environmental perspectives. The maximum HHV, representing the technical objective, is achieved at maximum T and minimum z for OA biocoal; at maximum T and minimum z for OMSW and at maximum T and maximum z for CP. The highest lower heating value (LHV), corresponding to end-user, for OA biocoal is achieved when T is greater than 450 °C and z < 1000 μm. For OMSW, particle size was the most important factor with the best LHV achieved when z > 1750 μm. The maximum net energy return per kg of biomass processed and maximum GHG offset (socio-economic) is realised at the lowest T for all biomass and particle sizes. This study is relevant to policy makers as it highlights potential conflict between the optimal conditions to produce high quality biocoal characterised by its high LHV and the optimal conditions to achieve the maximum utility from the resource and in turn potentially higher socio-environmental return.

Carbonization of microalgae for bio-coal production as a solid biofuel similar to bituminous coal

The carbonization of Nannochloropsis gaditana microalgae biomass was found to produce bio-coal that is similar to bituminous coal used in thermal power plants. Currently, microalgae that capture CO2 while they are in the growth stage are considered a source for the production of biofuels. The carbonization of biomass for producing bio-coal has received attention for its ability to improve the biomass quality for producing solid biofuels. The research was focused on optimizing a fixed carbon index (FCindex), which allows finding operational conditions of carbonization to favor the fixed carbon content without significantly affecting the bio-coal yield. The optimization carried out by response surface methodology in a thermogravimetric analyzer allowed the prediction of optimal carbonization conditions to achieve an FCindex of 191% at 403 °C, 71 °C/min, and 60 min of residence time. The bio-coal produced under optimized conditions was characterized by 59% of fixed carbon and 41% of volatiles on a dry and ash-free basis, which is similar to bituminous coal. The promising results of dry carbonization producing bio-coal similar to bituminous coal could promote this technology, avoiding the necessity of hydrothermal carbonization. Because a high ash content was detected in the final product, further studies using the optimized conditions and a washing step should be conducted.

Xylose production and the associated integration for biocoal production

Abstract Xylose is the second most abundantly available sugar in nature next to glucose. It is one of the hemicellulose based (C5) sugars and is often discarded during the conversion of lignocellulosic biomass to biofuels. Xylose recovery as a coproduct has a great potential to reduce the overall production cost of biofuels through increased revenue and efficient utilization of biomass. A low-energy non-conventional xylose production process from the University of Louisville (UofL) uses a boron capturing agent to esterify xylose, isolate it from aqueous hydrolyzate stream, and recover xylose as a dry product under ambient process conditions. Effective integration of this xylose production as a pre-step for processing biomass to biofuels such as biocoal has significant advantages in terms of enhanced product quality and improved economics. The xylose separation process yields modified biomass with stripped of hemicellulose and alkaline ash leading to reduced oxygen content and has higher energy density. TGA study showed that such modified biomass needs low energy input for carbonization during the torrefaction process. This modified biomass doubles up as a binder during the densification process to produce biocoal, thus significantly minimizing the cost of biocoal production. The preliminary techno-economic analysis for a biocoal plant based on wood chips indicate that xylose integration imparts greater viability of the plant even when the raw material costs are more than $40 per ton while significantly cutting down the payback time.

Converting beach wrack into a resource as a challenge for the Baltic Sea (an overview)

The paper distinguishes beach wrack, the marine generated organic part of beach cast, as a separate management object and discusses research questions related to its management and economically viable use. Based on experiences from the Baltic Sea and existing practices from countries with different management systems clear distinction between the management of natural and anthropogenic components of cast material is seen as an essential prerequisite for developing sustainable product chains that allow beach wrack to be used as a resource of commercial value. Presenting and discussing examples from Denmark (Køge Municipality), Germany (Kühlungsborn, Rügen and Poel Island), Poland (Gulf of Gdansk), Russia (Curonian and Vistula spits) and Sweden (Kalmar municipality and Öland), social, ecological, and economic consequences of beach wrack removal are analysed to improve the attractiveness of beaches for recreational purposes. It also includes potential contribution to Baltic Sea water restoration processes through the removal of the organic part of beach cast, where indeed more studies about the chemical (nutrients, metals) composition of beach wrack are required for reliable calculation of a depuration rate. For local economies within the Baltic Sea region, the organic part of beach cast (beach wrack and terrestrial debris) has reasonable economic prospects as a renewable natural resource, e.g. for soil improvement products, in fertilisers and bio-coal production, for landfill covers (contributing to climate change mitigation), biogas generation, and even for coastal protection by providing humus-like material for accelerated dune vegetation succession. For all these recycling options the development of cost-efficient technologies for collecting beach cast on sandy as well as stony beaches and also for separating the organic part from sand and anthropogenic litter (mainly plastic), is urgently required. Amendments of legal regulations, that better reflect the dualism of beach cast are also required. In essence, dualism results from the fact that beach wrack is a part of nature (or a natural resource) when it remains on a beach. However, beach wrack immediately becomes legally categorised as waste once humans collect it irrespective of its litter content. Another legal aspect being dealt with originates from the migration of the beach wrack between water and beach, whilst it is an object of ерleagl cleaning operations only at the beach it onto the beach, but not whilst in the water.

High-Energy Solid Fuel Obtained from Carbonized Rice Starch

The paper describes the investigations of the physicochemical properties of biocoal, a solid fuel obtained following the carbonization of rice starch. The production of biocoal (carbonization) was completed at the temperature of 600 °C in the nitrogen atmosphere. As a result of the carbonization, amorphous carbon with high monodispersity was obtained, devoided of oxygen elements and was a very well developed BET specific surface—360 m2 g−1. The investigations of the technical parameters have confirmed a very high concentration of energy. The calorific value of 53.21 MJ kg−1 and the combustion heat of 54.92 MJ kg−1 are significantly higher than those of starch before carbonization (18.72 MJ kg−1 and 19.43 MJ kg−1, respectively) and these values for typical biomass fuels. These values are also greater than those of hard coal. Other advantageous features of the obtained fuel are low ash (0.84%) and moisture content. These features predispose this fuel for the application as an alternative to conventional fuels.

Energy Multiphase Model for Biocoal Conversion Systems by Means of a Nodal Network

The coal-producing territories in the world are facing the production of renewable energy in their thermal systems. The production of biocoal has emerged as one of the most promising thermo-energetic conversion technologies, intended as an alternative fuel to coal. The aim of this research is to assess how the model of biomass to biocoal conversion in mining areas is applied for thermal systems engineering. The Central Asturian Coal Basin (CACB; Spain) is the study area. The methodology used allows for the analysis of the resource as well as the thermo-energetic conversion and the management of the bioenergy throughout the different phases in a process of analytical hierarchy. This is carried out using a multiphase mathematical algorithm based on the availability of resources, the thermo-energetic conversion, and the energy management in the area of study. Based on the working conditions, this research highlights the potential of forest biomass as a raw material for biocoal production as well as for electrical and thermal purposes. The selected node operates through the bioenergy-match mode, which has yielded outputs of 23 MWe and 172 MWth, respectively.

Bio-coal: A renewable and massively producible fuel from lignocellulosic biomass.

Development of renewable energy is essential to mitigating the fossil fuel shortage and climate change issues. Here, we propose to produce a new type of energy, bio-coal, via a fast pyrolysis coupled with atmospheric distillation process. The high heating values of the as-prepared bio-coals from the representative biomass are within 25.4 to 28.2 MJ kg-1, which are comparable to that of the commercial coals. Life cycle assessment further shows that the bio-coal production process could achieve net positive energy, financial, and environmental benefits. By using available biomass wastes as feedstock, China is expected to have a total bio-coal production of 402 million tons of standard coal equivalent, which is equal to 13% of national coal consumption. It would grant China an opportunity to additionally cut 738 million tons of CO2 emission by substituting an equal amount of coal with bio-coal in 2030.

Production of Biocoal by the Pyrolysis of Biomass

Effective use of biomass has recently received special attention. Pyrolysis is of great interest among the biomass conversion processes. The pyrolysis technology allows the production of biocoal (biochar), which can replace fossil energy fuels. Biocoal can also be converted into liquid fuel for direct use in vehicles and for the replacement of petroleum products (gasoline, aviation kerosene, and diesel fuel). In recent years, biocoal has been increasingly used in the agricultural industry as a high-quality complex fertilizer with unique properties.

Comparative energy and techno-economic analyses of two different configurations for hydrothermal carbonization of yard waste

Hydrothermal carbonization (HTC) includes conversion of wet biomass to hydrochar, a coal-like product, eliminating the need for biomass pre-drying. There has been limited focus on the techno-economic assessment of the HTC process in the literature. In this study, techno-economic models were developed to assess the economics of bio-coal production from yard waste for two different HTC plant configurations. In configuration A, heat is recovered by steam using several flash separators while in configuration B special heat exchangers are used. Process models were developed for the two configurations and then further used to estimate bio-coal production costs. The bio-coal cost and the net energy ratio (NER, or ratio of energy output to the energy input in the system) indicate that configuration A is preferable in terms of energy (NER of 5.2 versus 1.4 for configuration B) but less desired economically because it costs 3.3 $/GJ more than configuration B.

ON THE REPLACEMENT OF FOSSIL COAL IN LOCAL SOLID FUEL BOILERS

The paper substantiates the need to replace fossil coal in local solid fuel boilers by biocoal produced from various types of agricultural waste. Selection of the best available technology for biocoal production should be based on an integrated assessment including economic, environmental and social aspects. It is noted that direct combustion of agricultural waste does not meet environmental safety standards and also requires significant costs for modernization of existing boiler equipment. It is proposed to produce biocoal from agricultural waste using modern methods of thermochemical treatment — torrefaction and carbonization. End-products of biomass torrefaction — biocoal pellets or briquettes — have high calorific value, low sulfur and heavy metal contents, and low nitrogen oxide emissions. Hydrothermal carbonization is currently the most advanced biomass processing technology. It completely prevents pollution and has a number of significant advantages over other methods of biomass treatment. These advantages make it possible to consider hydrothermal carbonization to be the best available technology for the production of biochar, liquid biofuel and other products from non-food biomass. Bibl. 15, Fig. 2, Tab. 1.

Potential for thermal conversion of brewer’s spent grain into biocoal via hydrothermal carbonization in Africa

Abstract Brewer’s spent grain (BSG) has the potential to contribute to the supply of energy in Africa, as concern for clean and sustainable energy grows. The synthesis of biocoal from BSG via an artificial coalification process, hydrothermal carbonization (HTC), is preferred amongst other thermal conversion techniques as HTC is capable of handling high moisture feed. BSG which consists of insoluble cereal residue that is separated from the mash before fermentation has been a major disposal problem in the brewing industry for decades. Considering the energy crises experienced in Africa, its use for energy is a more useful option. In this study, an estimate of BSG production, expected yield of biocoal and energy potential for African countries is given. Due to temporal variation and data uncertainty, a stochastic model supported by 50,000 Monte Carlo simulations was developed to carry out the assessment. The method involved the development of a mathematical model for estimating the yield of BSG-derived hydrochar. Probability distributions were applied to each independent variable based on historical datasets and published scientific literature. Monte Carlo simulations were conducted using commercially available software, Palisade’s @RISK, to give a probabilistic representation of the expected yield of hydrochar for each country. The total quantity of BSG generated in Africa has been estimated at 627,050 Mg/yr (514,177 - 739,914 Mg/yr at a 90% confidence level) since 2013 and the potential for biocoal production via hydrothermal carbonization annually is 309,140 Mg/yr (9.43 million GJ/yr) on average. Estimates at a country level are given and based on the evaluation, BSG-derived biocoal alone cannot make a significant contribution to meeting Africa’s demand for energy.

Bio-coal production with agroforestry biomasses in Brazil

Pyrolysis is a promising technology for thermal conversion of lignocellulosic biomass into a higher added value fuel. The aim of this study was to analyze the potential of four agroforestry biomass to produce energy as a raw material or as a bio-coal. In this study, slow pyrolysis was conducted in three final temperatures to evaluate the bio-coal production of four agroforestry biomasses widely available in Brazil. The biomass used was sugarcane bagasse (Saccharum sp.), bamboo (Dendrocalamus giganteus), straw bean (Phaseolus vulgaris) and eucalypts wood chips (Eucalyptus sp.). In the first part was presented the raw biomasses proprieties, such as lignin, carbon, hydrogen and ash content. In the second part was showed the bio-coal proprieties, such as, gravimetric and fixed carbon yield, fixed carbon and ash content. These bio-coal results were showed as a function of final temperature of pyrolysis. The best energy indicators for bio-coal production, such as fixed carbon yield, high heating value, was found in the bamboo and eucalypts. The bagasse and straw bean biomasses possess high concentrations of ash and low lignin content when compared with the other biomasses assessed and are less suitable to produce bio-coal.

Life cycle assessment of a corn stover torrefaction plant integrated with a corn ethanol plant and a coal fired power plant

A life cycle assessment (LCA) study was conducted to understand and assess potential greenhouse gas (GHG) emissions reduction benefits of a biomass torrefaction business integrated with other industrial businesses for the use of the excess heat from the torrefaction off-gas volatiles and biocoal. A torrefaction plant processing 30.3 Mg h−1 of corn stover at 17% wet basis (w.b.) moisture content was modeled. The torrefaction plant produced 136,078 Mg y−1 of biocoal at 1.1% w.b. moisture content and 28.1 MW of excess heat energy in the torrefaction off-gas volatiles. At the torrefaction plant gate, the life-cycle GHG emission for the production of biocoal (including corn stover logistics emissions) is 11.35 g MJ−1 carbon dioxide equivalent (dry basis) (i.e., 229.5 kg Mg−1 carbon dioxide equivalent of biocoal at 1.1% w.b. moisture content). The excess heat from the torrefaction plant met 42.8% of the process steam needs of a U.S. Midwest dry-grind corn ethanol plant producing 0.38 hm3 y−1 of denatured ethanol, which results in about 40% reduction in life-cycle GHG emissions for corn ethanol compared to gasoline. Co-firing 10%, 20%, and 30% (energy basis) of biocoal at a coal-fired power plant reduced the life-cycle GHG emissions of electricity generated by 8.5%, 17.0%, and 25.6%, respectively, compared to 100% coal-fired electricity. A sensitivity analysis showed that adding a combined heat and power (CHP) system at the torrefaction plant to meet 100% electricity demand of the torrefaction plant (2.5 MW) could further reduce the GHG emissions for biocoal, corn ethanol, and co-fired electricity.

Bio-coal, torrefied lignocellulosic resources – Key properties for its use in co-firing with fossil coal – Their status

Abstract Bio-coal has received generous amounts of media attention because it potentially allows greater biomass co-firing rates and net CO2 emission reductions in pulverised-coal power plants. However, little scientific research has been published on the feasibility of full-scale commercial production of bio-coal. Despite this, several companies and research organisations worldwide have been developing patented bio-coal technologies. Are the expectations of bio-coal realistic and are they based on accepted scientific data? This paper examines strictly peer-reviewed scientific publications in order to find an answer. The findings to date on three key properties of torrefied biomass are presented and reviewed. These properties are: the mass and energy balance of torrefaction, the friability of the product and the equilibrium moisture content of torrefied biomass. It is these properties that will have a major influence on the feasibility of bio-coal production regardless of reactor technology employed in production. The presented results will be of use in modelling commercial production of bio-coal in terms of economics and green-house gas emission balance.

A decentralized approach for biocoal production in a mud kiln

The thermochemical conversion of waste biomass was studied in a 1-m 3 mud kiln. The yield of biocoal from the kiln ranged between 32 and 33%, depending upon the raw material used for carbonization. The physiochemical properties of the biomass and the biocoal, the composition of the flue gases, and the heating value of the fuel were determined, and a cost benefit analysis performed.