Updraft gasification of poultry litter at farm-scale--A case study

Comparison of Characteristics of Poultry Litter Pellets Obtained by the Processes of Dry and Wet Torrefaction

Torrefaction is a technology for the preliminary thermochemical treatment of biomass in order to improve its fuel characteristics. The aim of this work is to conduct comparative studies and select the optimal operating conditions of fluidized bed torrefaction for the processing of poultry litter (PL) into an environmentally friendly fuel. PL torrefaction was evaluated according to three different process configurations: (1) torrefaction of PL pellets in a fixed bed in a nitrogen medium at temperatures of 250 °C, 300 °C and 350 °C (NT1, NT2 and NT3); (2) torrefaction of PL pellets in a fluidized bed of quartz sand in a nitrogen medium at temperatures of 250 °C, 300 °C and 350 °C (NT4, NT5 and NT6); and (3) torrefaction of PL pellets in a fluidized bed of quartz sand in an environment of superheated steam at temperatures of 250 °C, 300 °C and 350 °C (ST1, ST2 and ST3). The duration of the torrefaction process in all experiments was determined by the time required for completion of CO2, CO, H2, and CH4 release from the treated biomass samples. The gas analyzer (Vario Plus Syngaz) was used to measure the concentration of these gases. The torrefaction process began from the moment of loading the PL sample into the reactor, which was heated to the required temperature. After the start of the torrefaction process, the concentration of CO2, CO, H2, and CH4 in the gases leaving the reactor initially increased and, subsequently, dropped sharply, indicating the completion of the torrefaction process. The chemical composition of the obtained biochar was studied, and it was found that the biochar contained approximately equal amounts of oxygen, carbon, nitrogen, hydrogen and ash, regardless of the torrefaction method. Furthermore, the biogas yield of the liquid condensate, obtained from the cooling of superheated steam used in the torrefaction process, was evaluated. The results highlight the efficiency of fluidized bed torrefaction, as well as the performance of superheated steam as a fluidization medium.

Moisture content and aeration control mineral nutrient solubility in poultry litter

Poultry litter waste is typically land-applied as a soil amendment but repeated application in the vicinity of poultry houses has led to phosphorus accumulation in soil. Such application can also lead to runoff that causes eutrophication. Most farmers store litter under dry conditions or compost the litter prior to land application, but it is not clear if these approaches are best from a nutrient management-perspective. The objective of this study was to investigate the effects of moisture content and active aeration on soluble mineral forms of nitrogen and phosphorus in poultry litter incubated for roughly one month. Mineral forms of nutrients are immediately plant-available upon field application and also most conducive to low-cost stripping and recovery methods. Litters were incubated at 50% and 70% moisture content with and without active aeration. Litter aeration led to significant ammonia losses and a consequent decline in litter pH but it had no effect on phosphate solubility. Moisture content during litter incubation governed the levels of plant-available phosphate and nitrification. High (70%) moisture led to 41%-78% higher plant-available phosphate (4.2-4.8 mg/g litter) compared to litters with 50% moisture content (2.7-3.0 mg/g litter). In contrast, the 50% moisture litters experienced 5-6 fold higher levels of nitrification (0.11-0.12 mg NO₃-N/g litter) than litters with 70% moisture content (0.02 mg NO₃-N/g litter), regardless of aeration. The implication is that lower-moisture litter storage is likely best for field application because phosphate is less soluble under neutral-alkaline conditions and therefore less likely to end up in runoff. In contrast, higher-moisture litter storage may be amenable to low-cost processes to leach and recover phosphate from litter.

Effects of biochar and ash outflow during updraft partial gasification on process parameters in a moving bed reactor

The present paper concerns the partial updraft gasification of wheat–rye straw pellets, using air as a gasification agent. The aim of this paper is to examine the impact of biochar and ash outflow during the updraft gasification process on the parameters of the latter. For this purpose, a series of five experiments with different parameters of biochar and ash outflow and a reference experiment were carried out with a constant amount of supplied air. The results of the research show that higher volumetric outflows of biochar and ash increase the calorific value (from 6.7 to 7.4 MJ/Nm3) and production (from 34.8 to 40.3 Nm3/h) of the producer gas, as well as the rate of fuel feed rate (from 30 to 43 kg/h). Reductions in the yield of gas (from 1.16 to 0.94 Nm3/kgfuel), equivalence ratio (from 0.125 to 0.087), and cold gas efficiency (from 44.7 to 40.2%) were observed. The content of gravimetric tar in producer gas was typical of updraft gasification and fluctuated within a range of 65‒125 g/Nm3.

Gasification of poultry litter in a lab-scale bubbling fluidised bed reactor: Impact of process parameters on gasifier performance and special focus on tar evolution

Poultry litter (PL) gasification was experimentally investigated using a lab-scale bubbling fluidised bed reactor. Characterisation of the gasification process was performed in terms of yields and compositions of both gas and tar, lower calorific value (LCV) of the product gas, cold gas efficiency (CGE) and carbon conversion efficiency (CCE). Experiments were carried out at different temperatures (700-750 °C) and equivalence ratios (ERs). The effect of gasifier temperature at a constant ER of 0.21 shows that an increase in temperature improved the gasification process performance whilst the total tar content decreased, implying that higher temperature enhances the conversion of biomass to product gas. The total gas yield increased from 0.93 to 1.24 N_2-free m³/kg_{feedstock-daf}, LCV increased from 3.38 MJ/m³ to 4.2 MJ/m³, while the tar content was reduced by 24% (5.6-4.25 g_tar/kg_{feedstock-daf}). The detailed analyses of tar compositions reveal that styrene and xylenes were the most abundant compounds in the secondary tar group. Moreover, naphthalene and 1, 2-methyl naphthalene were the dominant compounds found in tertiary polycyclic aromatic hydrocarbons (PAH) and alkyl tertiary groups, respectively. Furthermore, at the highest tested temperature of 750 °C and ER of 0.25, bed agglomeration took place causing the shutdown of the gasifier. The defluidisation of the bed occurred due to the high ash content of PL comprising of low melting temperature alkali compounds. The results obtained from this study showed the performance and potential challenges associated with gasifying PL in a fluidised bed reactor for the combined heat and power production at farm level.

Pyrolysis Process as a Sustainable Management Option of Poultry Manure: Characterization of the Derived Biochars and Assessment of their Nutrient Release Capacities

Raw poultry manure (RPM) and its derived biochars at temperatures of 400 (B400) and 600 °C (B600) were physico-chemically characterized, and their ability to release nutrients was assessed under static conditions. The experimental results showed that RPM pyrolysis operation significantly affects its morphology, surface charges, and area, as well as its functional groups contents, which in turn influences its nutrient release ability. The batch experiments indicated that nutrient release from the RPM as well as biochars attains a pseudo-equilibrium state after a contact time of about 48 h. RPM pyrolysis increased phosphorus stability in residual biochars and, in contrast, transformed potassium to a more leachable form. For instance, at this contact time, P- and K-released amounts passed from 5.1 and 25.6 mg g−1 for RPM to only 3.8 and more than 43.3 mg g−1 for B400, respectively. On the other hand, six successive leaching batch experiments with a duration of 48 h each showed that P and K release from the produced biochars was a very slow process since negligible amounts continued to be released even after a total duration of 12 days. All these results suggest that RPM-derived biochars have specific physico-chemical characteristics allowing them to be used in agriculture as low-cost and slow-release fertilizers.

Environmental and economic sustainability of poultry litter gasification for electricity and heat generation

This work aims to assess the environmental and economic sustainability of poultry litter gasification for heat and electricity generation. The results are compared with gasification of two other biomass feedstocks (Miscanthus and waste wood) and energy from fossil fuels. The findings suggest that poultry litter gasification can lead to significant reductions in 14 out of 16 impacts considered in the study in comparison with fossil-fuel alternatives. Compared to combined heat and power (CHP) from natural gas, most impacts from gasification of the litter are lower by more than 90%, including global warming potential. However, human toxicity and depletion of minerals are 25% and three times higher, respectively. Energy from poultry litter also has lower impacts than from waste woodchips and Miscanthus across all the categories, except for acidification. Owing to high capital costs, the unsubsidised cost of generating heat and electricity from poultry litter is similar to that of natural gas CHP but significantly cheaper than from other fossil-fuel alternatives. However, with the current subsidies in the UK, the payback time for poultry litter gasification is 13.5 years. It is estimated that 4.55 Mt of poultry litter is currently available in the UK, 2.73 Mt of which is suitable for conversion to energy. If this waste is utilised in gasification plants, it could potentially provide 0.6% of electricity and heat in the UK and save 1.7 Mt of GHG per year, equivalent to around 0.4% of UK's GHG emissions. However, the successful uptake of this technology will depend on a future reduction in capital costs.

Assessment of the Energy Potential of Chicken Manure in Poland

Animal waste, including chicken manure, is a category of biomass considered for application in the energy industry. Poland is leading poultry producer in Europe, with a chicken population assessed at over 176 million animals. This paper aims to determine the theoretical and technical energy potential of chicken manure in Poland. The volume of chicken manure was assessed as 4.49 million tons per year considering three particular poultry rearing systems. The physicochemical properties of examined manure specimens indicate considerable conformity with the data reported in the literature. The results of proximate and ultimate analyses confirm a considerable effect of the rearing system on the energy parameters of the manure. The heating value of the chicken manure was calculated for the high moisture material in the condition as received from the farms. The value of annual theoretical energy potential in Poland was found to be equal to around 40.38 PJ. Annual technical potential of chicken biomass determined for four different energy conversion paths occurred significantly smaller then theoretical and has the value from 9.01 PJ to 27.3 PJ. The bigger energy degradation was found for heat and electricity production via anaerobic digestion path, while fluidized bed combustion occurred the most efficient scenario.

The influence of temperature on the physicochemical properties of products of pyrolysis of leather-tannery waste

The present paper examines the pyrolysis of waste from leather tanneries at 300-500 °C. These studies are important because of difficulties in the utilisation of this type of waste as well as its energy potential as fuel. The pyrolysis of tannery waste and data from the relevant literature showed that thermal degradation can be explained using tanned collagen as a reference. Moreover, the experimental results indicated that this process is highly non-linear, due to various mechanisms of heat transport which cause temperature differences in a laboratory pyrolysis reactor. Thermogravimetric analysis has shown that the greater part of mass loss is observed between 80 and 500 °C and that the most significant mass release occurs at 325 °C. Moreover, the proportions of CO₂ and CO decrease along with increasing temperatures. The paper presents characteristics of the composition of solid, liquid, and gaseous products of leather-waste pyrolysis at various temperatures. The maximum heating value of gaseous products at 500 °C was 9.54 MJ/Nm³. An increase from 300 to 500 °C results in the dominant position of condensation polymerisation; the maximum value of the liquid phase yield is reached at 400 °C (42%). HHV analysis of the resulting char showed a maximum value of 21.18 MJ/kg at 450 °C. The results of oxidised component analysis showed that the major oxidised component of char was chromium oxide (Cr₂O₃), with a content of approximately 8.5% at all pyrolysis temperatures.

Tar yield and composition from poultry litter gasification in a fluidised bed reactor: effects of equivalence ratio, temperature and limestone addition

Qualitative and quantitative measurements of tar from poultry litter gasification in an air-blown fluidised bed.

Energy from poultry waste: An Aspen Plus-based approach to the thermo-chemical processes

A particular approach to the task of energy conversion of a residual waste material was properly experienced during the implementation of the national funded Enerpoll project. This project is a case study developed in the estate of a poultry farm that is located in a rural area of central Italy (Umbria Region); such a farm was chosen for the research project since it is almost representative of many similar small-sized breeding realties of the Italian regional context. The purpose of the case study was the disposal of a waste material (i.e. poultry manure) and its energy recovery; this task is in agreement with the main objectives of the new Energy Union policy. Considering this background, an innovative gasification plant (300KW thermal power) was chosen and installed for the experimentation. The novelty of the investigated technology is the possibility to achieve the production of thermal energy burning just the produced syngas and not directly the solid residues. This aspect allows to reduce the quantity of nitrogen released in the atmosphere by the exhaust flue gases and conveying it into the solid residues (ashes). A critical aspect of the research program was the optimization of the pretreatment (reduction of the water content) and the dimensional homogenization of the poultry waste before its energy recovery. This physical pretreatment allowed the reduction of the complexity of the matrix to be energy enhanced. Further to the real scale plant monitoring, a complete Aspen Plus v.8.0 model was also elaborated for the prediction of the quality of the produced synthesis gas as a function of both the gasification temperature and the equivalence ratio (ER). The model is an ideal flowchart using as input material just the homogenized and dried material. On the basis of the real monitored thermal power (equal to about 200kW average value in an hour) the model was used for the estimation of the syngas energy content (i.e. LHV) that resulted in the range of 3-5MJ/m³ for an equivalence ratio (ER) equal to 0.2.

Characteristics and synergistic effects of co-combustion of carbonaceous wastes with coal

This study presents combustion behavior and emission results obtained for different fuels: poultry litter (PL) and its char (PLC), scrap tires (ST) and its char (STC) and blends of char/lignite (PLC/LIG and STC/LIG). The combustion parameters and emissions were investigated via a non-isothermal thermogravimetric method and experiments in a lab-scale reactor. Fuel indexes were used for the prediction of high temperature corrosion risks and slagging potentials of the fuels used. The addition of chars to lignite caused a lowering of the combustion reactivity (anti-synergistic effect). There was a linear correlation between the NO_x emissions and the N content of the fuel. The form of S and the concentrations of alkali metals in the fuel had a strong effect on the extent of SO₂ emissions. The use of PL and PLC in blends reduced SO₂ emissions and sulphur compounds in the fly ash. The 2S/Cl ratio in the fuel showed that only PLC and STC/PLC would show a risk of corrosion during combustion. The ratio of basic to acidic oxides in fuel indicated that ST, STC and STC/LIG have low slagging potential. The molar (Si+P+K)/(Ca+Mg) ratio, which was used for PL, PLC and PLC containing blends, showed that the ash melting temperatures of these fuels would be higher than 1000 °C.

A critical review on sustainable biochar system through gasification: Energy and environmental applications

This review lays great emphasis on production and characteristics of biochar through gasification. Specifically, the physicochemical properties and yield of biochar through the diverse gasification conditions associated with various types of biomass were extensively evaluated. In addition, potential application scenarios of biochar through gasification were explored and their environmental implications were discussed. To qualitatively evaluate biochar sustainability through the gasification process, all gasification products (i.e., syngas and biochar) were evaluated via life cycle assessment (LCA). A concept of balancing syngas and biochar production for an economically and environmentally feasible gasification system was proposed and relevant challenges and solutions were suggested in this review.

An environmental friendly animal waste disposal process with ammonia recovery and energy production: Experimental study and economic analysis

Animal manure waste is considered as an environmental challenge especially in farming areas mainly because of gaseous emission and water pollution. Among all the pollutants emitted from manure waste, ammonia is of greatest concern as it could contribute to formation of aerosols in the air and could hardly be controlled by traditional disposal methods like landfill or composting. On the other hand, manure waste is also a renewable source for energy production. In this work, an environmental friendly animal waste disposal process with combined ammonia recovery and energy production was proposed and investigated both experimentally and economically. Lab-scale feasibility study results showed that 70% of ammonia in the manure waste could be converted to struvite as fertilizer, while solid manure waste was successfully gasified in a 10kW downdraft fixed-bed gasifier producing syngas with the higher heating value of 4.9MJ/(Nm³). Based on experimental results, economic study for the system was carried out using a cost-benefit analysis to investigate the financial feasibility based on a Singapore case study. In addition, for comparison, schemes of gasification without ammonia removal and incineration were also studied for manure waste disposal. The results showed that the proposed gasification-based manure waste treatment process integrated with ammonia recovery was most financially viable.

Hydrothermal carbonisation of poultry litter: Effects of initial pH on yields and chemical properties of hydrochars

In this study, hydrothermal carbonisation (HTC) of poultry litter (PL) was carried out to evaluate the impact of initial pH using acetic acid (CH₃COOH) or sulfuric acid (H₂SO₄) on the yields and properties of hydrochar (HC). The PL samples were treated by HTC at various initial pH and at 250°C for 2h. The HCs produced were characterized by ultimate, proximate and fibre analyses as well as heating value and surface area measurements. The results indicated that undertaking HTC in the presence of acids (CH₃COOH, H₂SO₄) significantly affects the yields and properties of HC. The C content and HHV of the HC increased with decreasing initial pH. In the presence of H₂SO₄, the hydrochar yield (HY) increased while the ash content was significantly reduced. The lowest ash content and the highest HY were measured in the HC produced from the suspension with an initial pH of 2 using H₂SO₄.

Evaluating stream sediment chemistry within an agricultural catchment of Lebanon, Northeastern USA

Recent arsenic pollution of drinking-water wells across Lebanon, northeastern USA has led to a growing concern about possible impact of agricultural activities on the hydrologic system. This study assessed the concentrations and distributions of arsenic and ten other elements (Al, Cd, Cr, Cu, Fe, K, Mn, P, Pb, and Zn) in stream sediments. The overall goal is to determine the extent of these elements within the fluvial systems, as well as overall sediment quality. A total of 65 stream sediments samples were collected, and analyzed for particle size distributions, organic matter contents, trace, and major elements concentrations. Results showed spatial variability in the concentrations of trace elements due to variation in sediments grain sizes, organic matter content, as well as land use activities within the study area. Calculation of sediment enrichment with respect to As, Cd, Cr, Cu, Mn, Pb, and Zn showed that about 48-52% of all the sampling locations are not enriched, nevertheless, approximately 2-11% of all the sampling locations are significantly enriched, an indication of anthropogenic input. However, results of ecological risk assessment showed no connection with sediment enrichment as most sampling locations have concentrations below the threshold probable effect concentration (PEC) value. Statistical analysis using principal component analysis (PCA) extracted three significant components explaining over 72% of total variance covering elements having origin in both natural and anthropogenic sources, thus suggesting that the concentrations and distribution of these elements within stream sediments are related to a combination of weathering processes on the bedrock geology, and anthropogenic activities.